Patent Publication Number: US-2023157925-A1

Title: Cameras for Emergency Rescue

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/363,117 filed Jun. 30, 2022, which is a continuation of U.S. patent application Ser. No. 16/856,590, filed Apr. 23, 2020, which issued as U.S. Pat. No. 11,077,017, which is a continuation of U.S. patent application Ser. No. 15/215,891, filed Jul. 21, 2016, which issued as U.S. Pat. No. 10,667,988, which is a continuation of U.S. patent application Ser. No. 14/075,741, filed Nov. 8, 2013, which issued as U.S. Pat. No. 10,420,701, and is a continuation-in-part of U.S. patent application Ser. No. 13/897,318, filed May 17, 2013, which is a continuation-in-part of U.S. patent application Ser. No. 13/474,269, filed May 17, 2012, which issued as U.S. Pat. No. 9,522,096, the entire contents of each of which are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     This document relates to cardiac resuscitation, and in particular to systems and techniques for assisting rescuers in performing and reviewing cardiopulmonary resuscitation (CPR). 
     BACKGROUND 
     CPR is a process by which one or more rescuers may provide chest compressions and ventilation to a victim who has suffered an adverse cardiac event—by popular terms, a heart attack. Chest compressions are considered to be the most important element of CPR during the first five to eight minutes after CPR efforts begin, because chest compressions help maintain circulation through the body and in the heart itself, which is the organ that can sustain the most damage from an adverse cardiac event. Generally, American Heart Association CPR Guidelines define protocols by which a rescuer is to apply the chest compressions in coordination with ventilations. For example, current 2010 AHA Guidelines specify a ratio of 30:2 for compressions to ventilations—i.e., thirty compressions for every two breaths. And compressions are to be performed at a rate of around 100 per minute. 
     CPR may be performed by a team of one or more rescuers, particularly when the rescuers are professionals such as emergency medical technicians (EMTs) on an ambulance crew. One rescuer can provide the chest compressions and another can time their ventilations of the victim to match the chest compressions according to the appropriate CPR protocol. When professionals such as EMTs provide the care, ventilation is more likely to be provided via a ventilation bag that a rescuer squeezes, than by mouth-to-mouth. The CPR can be performed in conjunction with providing shocks to the patient from an external defibrillator, including from an automatic external defibrillator (AED) that is designed to be used by laypeople. Such AEDs often provide audible information to rescuers such as “push harder” (when the rescuer is not performing chest compressions forcefully enough), “stop CPR,” “stand back” (because a shock is about to be delivered), and the like. In determining how chest compressions are being performed, certain defibrillators may obtain information from one or more accelerometers (such as in the CPR D PADZ, CPR STAT PADZ, and ONE STEP pads made by ZOLL MEDICAL of Chelmsford, Mass.) that can be used to compute depths of chest compression, e.g., to determine that the compressions are too shallow to be effective and thus to cause the verbal cue “push header” to be spoken by the defibrillator. 
     High quality interactions within a team of rescuers can help to improve treatment outcomes. Approaches to assessing and evaluating team performance can enable measurement and monitoring of the effectiveness of teams of rescuers and the results of training rescuers in both medical and teamwork skills. Watching rescuers delivering treatment to a victim can be used to evaluate team performance. For instance, such monitoring allows a reviewer to notice subtle performance indicators, such as team interactions and communications, utterances by a rescuer, body language cues, or minor errors, and thus can be helpful in identifying unsafe acts by rescuers, the occurrence of pre-cursor events, opportunities for accidents, and various types of performance failures. Analysis of one or more rescue scenes can help pinpoint problem areas that can be addressed by additional focused training. 
     SUMMARY 
     This document describes systems and techniques that may be used to help manage the work by teams of rescuers who are responding to a victim, or person in need of emergency assistance. For example, typically such teams include a pair of rescuers, where a first of the rescuers performs CPR chest compressions on the victim and the other performs ventilations, either by mouth-to-mouth techniques or using a flexible ventilator bag. Frequently such teams are made up of an EMT or ambulance crew. Also frequently, a good heartbeat cannot be established quickly for the victim, so that CPR must be carried out for many minutes in order to maintain perfusion of blood in the victim. In such situations, rescuers can tire after only a minute or two of providing chest compressions, so that certain protocols call for the rescuers to switch roles periodically. The systems and techniques discussed here are implemented with a recognition that different people have different levels of skill, strength, and stamina for performing chest compressions and other components of CPR such as ventilating a victim or administering drugs to the victim. As a result, the techniques discussed here monitor the quality of certain components of CPR as it is being performed, such as by monitoring the depth and rate of chest compressions being performed, and they tell the rescuers to switch out when a component indicates that the performance of the chest compressions or other CPR component is inadequate, and might be, or would be, performed better by the other rescuer who is presumably more “fresh.” 
     Alternatively, or in addition, cameras may be provided on a victim, on rescuers, and/or on vehicles driven by the rescuers or equipment used by the rescuers. For example, each rescuer may be provided with glasses or other wearable components that include forward-facing cameras for capturing generally what is in the field of view of each respective rescuer as they work. Similarly, the rescuers may mount a camera to the victim, such as by adhering a patch with an attached camera to the victim&#39;s forehead or another relatively stationary location that has a broad field of view. Cameras on vehicles may obtain a higher and broader view of a scene, such as by viewing downward toward the rescuers. Such cameras may capture 360 degree panoramas (e.g., via cameras similar to those used with Google StreetView implementations, where images from adjacent cameras may be stitched together to form a 360 degree image so that the camera is in effect a 360 degree camera) and/or may be aimed toward the rescuers using signals from beacons worn by the rescuers or their medical equipment (e.g., monitors and defibrillators). In some implementations, the cameras may include multiple 360 degree cameras and/or light field cameras whose focus distance may be adjusted with software post-capture—in such a way, objects at different distances from the camera may be made to be the focus by people or software that is analyzing the images remote from the emergency, either at the time of the rescue or a later time. 
     The images captured by the cameras (which may be captured every few seconds, every second, or multiple times per second up to video speeds) may be used for a variety of purposes. For example, the images may be used to identify the rate and depth of chest compression that are performed on a patient in the field of view of one or more of the cameras. Also, experts may use the images to conduct a code review to determine the effectiveness of the rescuers during a rescue. Also, the images may be used manually or automatically in combination with the techniques for switching rescuers in particular roles, in order to determine which rescuer is performing in each role at any particular period of time, and not merely that a change has occurred. To that end, near field communications chips may be worn by the rescuers (e.g., in wristbands) to further identify the locations of particular rescuers, such as when the NFC chip is near a reader or chip in a CPR puck on a victim&#39;s torso. The captured images may also be combined into a single larger image or panorama to provide a complete and immersive images of a rescue scene, such as for later review or for an offsite person to more fully experience the situation at the rescue site. The composite view may be provided to a remote location for review, such as by virtual reality techniques. 
     In certain implementations, such systems and technique may provide one or more advantages. For example, a patient may be provided with the best care that is available from the rescue team throughout a rescue episode. For example, a rescuer with greater stamina may be left performing chest compressions longer than another rescuer with less stamina, whereas they might have been allowed to perform for equal time periods, with substandard performance, using techniques other than those described here. Also, the terms of each cycle may change as the rescue continues—e.g., by shortening the cycles as each of the rescuers gets more tired. Such adjustments may be dynamic and need not rely on a static timed schedule. Also, the system may identify erosion in performance even when the rescuers themselves do not recognize that their performance has eroded. Such identification may occur by measures external to the rescuer, such as their rate and depth of providing chest compressions, or measures internal to the rescuer, such as by measuring their blood oxygen level and pulse rate. The instructions to switch may also be provided in a clear and simple manner (and in a variety of manners, such as audibly or on a visual display next to the hands of the rescuer performing chest compressions), so that even rescuers in a high-stress environment can get the message (and the instructions can be provided at an increasing severity level if the system determines that the rescuers are not responding to the original instructions). 
     Moreover, in certain implementations, such techniques can be used on teams of two, three, or more rescuers. In addition, in certain implementations, the techniques described here can be implemented as part of an automatic external defibrillator (AED) or a professional defibrillator, or in a dual-mode defibrillator. As a result, the clinical performance of a rescuing team can be increased, and patient outcomes improved. Also, cameras may be used to capture images of a scene for later review of the performance of a rescue, or to be transmitted to a remote site in real time for review (e.g., by disaster management personnel for large-scale accidents, or by a physician who is monitoring a particular EMT rescue operation). 
     This description also discusses systems and techniques for generating a three-dimensional (3D) representation of a rescue scene based on images received from one or more cameras at the rescue scene. The 3D representation provides an animated 3D view of the people, objects, and activity at the rescue scene. The 3D representation can be anonymized, e.g., by removing identifying features from the images of the people at the rescue scene, to preserve the privacy and confidentiality of the involved parties. Real time analysis of the 3D representation can yield information associated with the resuscitation of the victim that can be provided to rescuers, e.g., to inform their treatment of the victim. Analysis of the 3D representation after the resuscitation of the victim is completed can provide insight into the efficiency and accuracy of the rescuers&#39; treatment of the victim, thus helping to improve future performance. 
     The techniques described here can have one or more of the following advantages. Analysis of a 3D representation of a rescue scene can provide information that can be used to monitor and enhance the performance of rescuers in real time or following treatment of a victim. For instance, relevant information can be identified that can be used by a rescuer to inform his treatment of the victim. The rescuer can be provided with only that information that is pertinent to his particular task, thus preventing the rescuer from being overwhelmed with excess information. Following treatment, analysis of the 3D representation can provide insight into the efficiency and accuracy of rescuers&#39; performance, thus helping to improve the future performance of teams of rescuers. The analysis of the 3D representation can be at least partially automated, thus providing for rapid and accurate outputs of the analysis. Identifying information, such as facial features, can be removed from the 3D representation, yielding an anonymized representation of the rescue scene that protects the privacy and confidentiality of both the victim and the rescuers. 
     In a general aspect, a system includes a processor coupled to a memory. The processor and memory are configured to receive, from one or more cameras, multiple images of a victim undergoing a resuscitation event at a rescue scene; generate a representation of the rescue scene based on the received images; and determine a characteristic associated with the resuscitation event based on an analysis of the of the rescue scene. 
     Embodiments can include one or more of the following features. 
     The representation of the rescue scene is a three-dimensional representation. 
     Generating the representation of the rescue scene includes removing information sufficient to identify the victim from the representation. In some cases, removing information sufficient to identify the victim includes one or more of blurring facial features associated with the victim, removing facial features associated with the victim, and replacing a portion of a face associated with the victim with an anonymous representation of the victim. 
     The processor and the memory are configured to detect a face of the victim based on at least one of an analysis of the images and an analysis of the representation of the rescue scene. 
     The processor and the memory are configured to identify one or more objects at the rescue scene based on at least one of an analysis of one or more of the images and an analysis of the representation of the rescue scene. 
     The representation includes an animated representation of the rescue scene. 
     The processor and the memory are configured to determine a message for a rescuer based on the determined the characteristic associated with the resuscitation event. In some cases, the message includes information indicative of at least one of a medical status of the victim and a performance of one or more of the rescuers. In some cases, the message includes at least one of a visual message and an audio message. 
     Determining a characteristic associated with the resuscitation event includes determining a task associated with each of multiple rescuers. In some cases, the processor and the memory are configured to determine a message for a particular one of the rescuers based on the determined task associated with the particular one of the rescuers. 
     Determining a characteristic associated with the resuscitation event includes determining the characteristic while the victim is undergoing the resuscitation event. 
     Determining a characteristic associated with the resuscitation event includes determining a characteristic after the resuscitation event is finished. 
     Determining a characteristic associated with the resuscitation event includes determining a relative position of the victim and one of the rescuers at the rescue scene. 
     Determining a characteristic associated with the resuscitation event includes determining at least one of a rate and a depth of compressions delivered to the victim by a rescuer. 
     Determining a characteristic associated with the resuscitation event includes determining a metric indicative of at least one of an accuracy and an efficiency of a rescuer at the rescue scene. 
     At least one of the one or more cameras is mounted on a rescuer at the rescue scene. 
     The system includes a wearable computing device that includes at least one of the one or more cameras. 
     At least one of the one or more cameras is mounted on a medical device at the rescue scene. 
     In a general aspect, a method includes receiving, from one or more cameras, multiple images of a victim undergoing a resuscitation event at a rescue scene; generating a representation of the rescue scene based on the received images; and determining a characteristic associated with the resuscitation event based on an analysis of the of the rescue scene. 
     Embodiments can include one or more of the following features. 
     The representation of the rescue scene is a three-dimensional representation. 
     Generating the representation of the rescue scene includes removing information sufficient to identify the victim from the representation. In some cases, removing information sufficient to identify the victim includes one or more of blurring facial features associated with the victim, removing facial features associated with the victim, and replacing a portion of a face associated with the victim with an anonymous representation of the victim. 
     Determining a characteristic associated with the resuscitation event includes determining a task associated with each of multiple rescuers. In some cases, the method includes determining a message for a particular one of the rescuers based on the determined task associated with the particular one of the rescuers. 
     Determining a characteristic associated with the resuscitation event includes determining a relative position of the victim and one of the rescuers at the rescue scene. 
     Determining a characteristic associated with the resuscitation event includes determining at least one of a rate and a depth of compressions delivered to the victim by a rescuer. 
     Determining a characteristic associated with the resuscitation event includes determining a metric indicative of at least one of an accuracy and an efficiency of a rescuer at the rescue scene. 
     In a general aspect, a computer readable medium stores instructions for causing a computing device to receive, from one or more cameras, multiple images of a victim undergoing a resuscitation event at a rescue scene; generate a representation of the rescue scene based on the received images; and determine a characteristic associated with the resuscitation event based on an analysis of the of the rescue scene. 
     In one implementation, a method for managing cardiopulmonary resuscitation (CPR) treatment to a person in need of emergency assistance is disclosed. The method includes monitoring, with an electronic medical device, a parameter that indicates a quality level of a CPR component being provided to the person by a user; determining, with the electronic medical device, that the parameter indicates that the quality level of CPR being provided is inadequate; and providing, to one or more rescuers of the person, an audible, visual, or tactile indication that a different person should perform the CPR component. The method may also comprise repeating cyclically the actions of monitoring, determining, and providing, while multiple different people are instructed to perform the CPR component. The CPR component can comprise chest compressions, and the parameter comprises depth of compression, rate of compression, or both. In some aspects, the method also comprises generating a chest compression quality score from a combination of chest compression rate and chest compression depth, and providing the indication in response to the quality score falling outside a determined acceptable range. 
     In certain particular aspects, the method further comprises providing information about a target chest compression depth with the electronic medical device, or providing periodic feedback to the user by displaying on a graphical display screen of the electronic medical device, an indication of values for depths of one or more of a plurality of chest compressions and an indication of a target compression depth. Providing the periodic feedback can also comprise displaying on a graphical display screen of a defibrillator, a graphical representation of the depths of one or more of the plurality of the chest compressions and an indication of the target compression depth. Separately, providing the periodic feedback can further comprise displaying on a graphical display screen of a defibrillator, a graph having a visual indicia representing the target compression depth and visual indicia representing the values for the depths of one or more of the plurality of the chest compression displayed above or below the visual indicia representing the target compression depth. 
     In yet other aspects, the method can also comprise displaying, on a first electronic display located on a thorax of the person in need of emergency assistance, information that provides instructions for performing CPR to one of the rescuers. And display may be made, on a second electronic display and to another of the rescuers, of information that provides instructions for performing CPR to one of the rescuers, the information provided on the first electronic display differing from the information provided on the second electronic display. The electronic device can also be connected to a defibrillation electrode on the person in need of emergency assistance. Moreover, the method can include providing, to a first of the one or more rescuers, an indication about the quality of chest compressions given to the patient, the indication about the quality chest compressions differing from the indication that a different person should perform the CPR component. Yet in other implementations, the method comprises identifying a protocol for CPR being performed by the rescuers, and coordinating the providing of the indication that a different person should perform the CPR component with stored parameters that define the protocol, wherein the identified protocol is select from among multiple protocols stored on the electronic medical device. 
     In another implementation, a system is disclosed for managing cardiopulmonary resuscitation (CPR) treatment to a person in need of emergency assistance. The system comprises an electronic patient monitor; a sensor interface on the monitor arranged to receive input from one or more sensors that sense one or more that indicate a quality level of one or more CPR components being provided to the person in need of emergency assistance; a CPR monitor in the electronic patient monitor programmed to use the input from the sensors to identify a quality parameter and to generate a signal to switch rescuers performing CPR when the quality parameter meets a determined criterion; and an output interface in communication with the CPR monitor and arranged to provide rescuers using the electronic patient monitor with an indication to switch rescuers, in response to receiving the generated signal from the CPR monitor. The electronic patient monitor can be part of an external patient defibrillator, and the output interface can comprise an electronic display attached to a connector that also is attached to defibrillator electrodes for connection to the external patient defibrillator. Moreover the electronic display can be attached to one of the defibrillator electrodes and arranged so as to rest adjacent a rescuer&#39;s hands when the electrode is properly placed on the person in need of emergency assistance, and the rescuer&#39;s hands are placed for performing CPR chest compressions. In some aspects, the CPR monitor comprises a microprocessor connected to electronic memory that stores instructions that when executed perform a process of identifying a quality parameter and generating a signal to switch rescuers performing CPR when the quality parameter meets a determined criterion. 
     In some other aspects, the system also comprises a sensor arranged to sense a quality level of chest compressions performed on the person is need of emergency assistance. The CPR monitor can also be further programmed to repeat cyclically actions of identifying the quality parameter, determining whether the quality parameter indicates a need to switch rescuers, and generating a signal to switch rescuers when the quality parameter indicates a need. And the quality parameter can reflect a depth of chest compressions, rate of compression, or both, of chest compressions performed on the person in need of emergency assistance. The system can also comprise a display arranged to provide feedback to a rescuer indicating a way to improve the one or more CPR components. Moreover, the output interface can comprise a wireless transmitter arranged to communicate data regarding the one or more CPR components to a rescuer of the person in need of emergency assistance. In addition, the first interface can be arranged to communicate with a first display device for use by a first rescuer, and further comprising a second interface arranged to communicate with a second display device for use by a second rescuer, the second display device to communicate information about a CPR component that is different than information about a CPR component that is displayed on the first display device. Finally, the system can further comprise identifying a protocol for CPR being performed by the rescuers, and coordinating the providing of the indication that a different person should perform the CPR component with stored parameters that define the protocol, wherein the identified protocol is select from among multiple protocols stored on the electronic medical device. 
     In yet other implementations, a computer-implemented method for managing cardiopulmonary resuscitation (CPR) treatment to a person in need of emergency assistance is disclosed. The method comprises capturing one or more images at a scene where the person in need of medical assistance is being treated using one or more cameras at the scene; performing automatic computer-based analysis of the images to identify a quality of treatment provided to the person in need of medical assistance; and using analysis of the images to direct rescuers at the scene of the person in need of medical assistance in performing care for the person in need of medical assistance. The method can also comprises monitoring, with an electronic medical device, a parameter that indicates a quality level of a CPR component being provided to the person by a user; determining, with the electronic medical device, that the parameter indicates that the quality level of CPR being provided is inadequate; and providing, to one or more rescuers of the person, an audible, visual, or tactile indication that a different person should perform the CPR component. In addition, the method can comprise repeating cyclically the actions of monitoring, determining, and providing, while multiple different people are instructed to perform the CPR component. Providing the indication that a different person should perform the CPR component can comprise using the analysis of the images. Moreover, the CPR component can comprise chest compressions, and the parameter can comprise depth of compression, rate of compression, or both. 
     In some aspects of this method, the one or more cameras include a light field camera, and using the analysis of the images to direct rescuers comprises detecting compression quality parameters from images from the light field camera. The one or more cameras can alternatively include a light field camera, and the method can further comprise providing to a location remote from the scene a three-dimensional view using image data form the light field camera. At least one of the one or more cameras can have been attached to the person in need of medical assistance by one of the rescuers. The method can also include identifying locations of the rescuers using near-field communication devices worn by the rescuers. 
     In yet other aspects, this method further comprises identifying locations of the rescuers using indoor GPS devices. The method can also include displaying a real-time presentation of the scene to a remote viewer. The real-time presentation of the scene can be annotated with icons or text that identifies one or more of the rescuers, and/or with information that indicates a condition of the person in need of medical assistance. This method can further comprise enabling an automatic audio communication between the remote viewer and one or more of the rescuers. In some aspects, at least one of the one or more cameras is mounted to a rescue vehicle or a portable medic device and is configured to automatically locate, in a potential field of view, treatment being provided to the person in need of medical assistance. Also, at least one of the one or more cameras can be a 360 degree camera. The method can further comprise identifying presence of multiple people in need of medical assistance at the scene, and in response to input received from the remote viewer, displaying information about different ones of the people in need of medical assistance. 
     In yet another implementation, a computer-implemented method comprises providing a rescue vehicle at a scene of an emergency, the rescue vehicle having mounted to it one or more cameras for capturing images from the scene of the emergency; capturing images of the scene of the emergency in coordination with the emergency vehicle traversing through the scene of the emergency; and automatically transmitting the captured images to a remote location for immediate viewing of the scene of the emergency by personnel at the remote location. The one or more cameras mounted to the rescue vehicle can include a 360 degree camera, and the system can include a geographic location determination device to correlate geographic locations of the rescue vehicle with images captured at corresponding ones of the geographic locations. The method can also include initiating the capturing of the images in response to a selection by an occupant of the rescue vehicle. Moreover, the method can include initiating the transmission in response to a selection by an occupant of the rescue vehicle. In addition, the method can comprise correlating a plurality of images captured at different locations at the scene with particular ones of the different locations at the scene at which particular ones of the images were captured. The correlated plurality of images can form a continuous display of views along a route traversed by the emergency vehicle. 
     In some aspects, the method also comprises displaying the transmitted images in a virtual reality system at the remote location. This method can also comprise annotating the displayed images with icons, textual information or both that describes items at the scene, and displaying particular ones of the icons or textual information in locations with corresponding items in the displayed images that are determined to correspond to the icons or textual information. The method can also comprise identifying motion of a user of the virtual reality system and changing images displayed by the virtual reality system in coordination with a direction of the identified motion determined by the virtual reality system. 
     In yet another implementation, a computer-implemented system is disclosed that comprises one or more cameras configured to be mounted to a person in need of medical assistance, rescuers of the person in need of medical assistance, or both; an image processing sub-system to combine image information from multiple ones of the one or more cameras; and an analysis sub-system programmed to identify a quality level of a CPR component being provided to the person by a user using an analysis of the combined image information. The system can also include a CPR evaluation sub-system associated with a portable medical device and programmed to: determine that a sensed parameter of CPR provided by a component of CPR applied to the person in need of medical assistance indicates that the quality level of CPR being provided is inadequate; and provide, to one or more rescuers of the person, an audible, visual, or tactile indication that a different person should perform the CPR component. The CPR evaluation sub-system can be programmed to repeatedly cycle the actions determining and providing while multiple different people are instructed to perform the CPR component. Also, providing the indication that a different person should perform the CPR component can comprise using the analysis of the image information. In addition, the CPR component can comprise chest compressions, and the parameter comprises depth of compression, rate of compression, or both. 
     In certain aspect, the one or more cameras include a light field camera, and using the analysis of the images to direct rescuers comprises detecting compression quality parameters from images from the light field camera. Also, the one or more cameras can include a light field camera, and the system can be further arranged to provide to a location remote from the scene a three-dimensional view using image data form the light field camera. At least one of the one or more cameras can be attachable to the person in need of medical assistance by one of the rescuers. The system can be further arranged to identify locations of the rescuers using near-field communication devices worn by the rescuers. In addition, the system can be further arranged to identify locations of the rescuers using indoor GPS devices, and/or to display a real-time presentation of the scene to a remote viewer. The real-time presentation of the scene can be annotated with icons or text that identifies one or more of the rescuers and/or with information that indicates a condition of the person in need of medical assistance. Also, the system can be further arranged to enable an automatic audio communication between the remote viewer and one or more of the rescuers. At least one of the one or more cameras can be mounted to a rescue vehicle or a portable medic device and is configured to automatically locate, in a potential field of view, treatment being provided to the person in need of medical assistance. And at least one of the one or more cameras can be a 360 degree camera. 
     The techniques described herein can have one or more of the following advantages. 
     The analysis of a representation of a rescue scene, such as a three-dimensional (3D) animated representation of the rescue scene, yields information that can be valuable in understanding what is occurring or did occur at the rescue scene. Multiple observers (including the rescuers themselves) can review a video representation of the rescue scene, and the video can be reviewed multiple times, thus enabling those observers to make a precise and detailed analysis of the rescue scene. Analysis of a video representation can supplement existing quality assurance approaches, thus allowing further assessment of team performance during a rescue. The automation of video analysis described here can make the analysis more efficient and less time- and labor-intensive, thus allowing more information to be extracted from a video representation with less time and effort. In addition, the anonymization of the video representation can preserve privacy and confidentiality of the parties at the rescue scene, including the rescuers and the victim. 
     Other features and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG.  1 A  is an overhead view of rescuers performing CPR on a victim using an electronic system that instructs them in performance of the CPR. 
         FIG.  1 B  show the view of  FIG.  1 A , with focus on the positioning of cameras around a rescue scene. 
         FIG.  1 C  is a block diagram. 
         FIGS.  2 A and  2 B  show a portable defibrillator and ancillary components arranged to provide feedback and instruction to rescuers. 
         FIGS.  2 C- 2 E  show chest compression pucks that can capture information from a rescuer. 
         FIG.  3    shows example chest compression inputs and mechanisms for analyzing the inputs to determine whether a different person should provide chest compressions. 
         FIG.  4 A  is a flowchart of a process for monitoring CPR performance and providing feedback for improvement of the performance. 
         FIGS.  4 B and  4 C  are flowcharts of processes for capturing and using images form a rescue site. 
         FIGS.  5 A and  5 B  illustrate a defibrillator showing certain types of information that can be displayed to a rescuer. 
         FIGS.  6 A- 6 C  show screenshots of a defibrillator display that provides feedback concerning chest compressions performed on a victim. 
         FIGS.  7 A and  7 B  show screenshots providing feedback regarding a perfusion index created form chest compressions. 
         FIGS.  8 A and  8 B  show screenshots with gradiated scales indicating target chest compression depths. 
         FIG.  9    is a flowchart. 
         FIG.  10    shows a general computer system that can provide interactivity with a user of a medical device, such as feedback to a user in the performance of CPR. 
     
    
    
     DETAILED DESCRIPTION 
     This description discusses systems and techniques for guiding the provision of care to a patient, such as the provision of CPR to a victim of cardiac arrest. For example, a portable electronic defibrillator may be provided to rescuers and may include common features for delivering defibrillating energy (a shock) to a victim of cardiac arrest through electrodes that may be placed on the torso of the victim. The defibrillator may also be provided with a mechanism for sensing the manner in which CPR chest compressions are performed on the victim, such as a puck or similar item that includes an accelerometer and may be placed under the hands of the person performing chest compressions and on top of the sternum of the victim. The defibrillator may use information from such an item to identify the depth and rate of chest compressions that are being performed by a rescuer, and may identify when such information indicates that the rescuer is tiring, such as when the depth of compressions is inadequate for a time period, and the rate of compressions begins to slow. Also, the system may look to internal factors of the rescuer such as pulse and blood oxygen level, in making the determination. When the defibrillator makes a determination that the chest compressions are inadequate due to fatigue on the part of the rescuer, the defibrillator may provide an indication to that rescuer that he or she should step away and allow another rescuer to perform chest compressions for a time. For example, where there are two rescuers, the other rescuer may have been providing ventilation to the victim using a ventilation bag, and may be simultaneously prompted to turn and provide chest compressions, while the first rescuer takes over operation of the bag. 
     This description also discusses systems and techniques for generating a graphical representation, such as a three-dimensional (3D) graphical representation, of a rescue scene based on images received from one or more cameras at the rescue scene. The representation may provide an animated two-dimensional (2D) or 3D view of the people, objects, and activity at the rescue scene. The representation can be anonymized, e.g., by removing identifying features from the images of the people at the rescue scene, to preserve the privacy and confidentiality of the involved parties. Real time analysis of the representation can yield information associated with the resuscitation of the victim that can be provided to rescuers, e.g., to inform their treatment of the victim. Analysis of the representation after the resuscitation of the victim is completed can provide insight into the efficiency and accuracy of the rescuers&#39; treatment of the victim, thus helping to improve future performance. 
       FIG.  1 A  is an overhead view of rescuers  104 ,  106  performing CPR on a victim  102  at a rescue scene  100  using an electronic system that instructs them in performance of the CPR. The rescue scene  100  can be a scene at which the victim is undergoing a resuscitation event, such as a victim undergoing cardiac arrest, ventilatory arrest, or trauma (e.g., from an injury such as a gunshot wound). In this example, rescuers  104 ,  106  are already in position and providing care to the victim  102 , with rescuer  104  in position and providing chest compressions to the torso of the victim  102 , and rescuer  106  providing ventilation using ventilation bag  112 . The rescuers  104 ,  106  may be lay rescuers who were in the vicinity of the victim  102  when the victim  102  required care, or may be trained medical personnel, such as emergency medical technicians (EMTs). Although two rescuers are shown here for purposes of explanation, additional rescuers may also care for the victim  102 , and may be included in a rotation of rescuers providing particular components of care to the victim  102 , where the components may include chest compressions, ventilation, administration of drugs, and other provision of care. 
     In some examples, one or more therapeutic delivery devices (not shown) can automatically deliver the appropriate therapy to the patient. The therapeutic delivery devices can be, for example, a portable automatic chest compression device (e.g., with a belt that wraps around the victim&#39;s chest), a drug infusion device, an automatic ventilator and/or a device that includes multiple therapies such as defibrillation, chest compression, ventilation, and drug infusion. The therapeutic delivery devices are physically separate from the defibrillator  108 , and control of the therapeutic delivery devices may be accomplished by a communications link from the defibrillator  108  that may be wired, wireless, or both. 
     In other examples, control and coordination for the overall resuscitation event and the delivery of the various therapies may be accomplished by a device or processing element that is external to the defibrillator  108 , such as by use of a tablet-based computer that is controlled by one of the rescuers. For instance, the device may download and process ECG data from the defibrillator  108 ; analyze the ECG signals, perform relevant determinations like those discussed above and below based on the analysis, and control the other therapeutic devices. In other examples, the defibrillator  108  may perform all the processing of the ECG, including analyzing the ECG signals, and may transmit to a separate device only the final determination of the appropriate therapy, whereupon the separate device can perform the control actions on the other linked devices. 
     An electrode assembly  110  is shown in position on the victim  102  in a normal position. The electrode assembly  110 , in this example, is an assembly that combines an electrode positioned high on the right side of the victim&#39;s torso and an electrode positioned low on the left side of the victim&#39;s torso, along with a sensor package located over the victim&#39;s sternum. The sensor package, which is obscured in the figure by the hands of rescuer  104  in this example, may include an accelerometer or similar sensor package that may be used in cooperation with a computer in the defibrillator  108  to generate an overall quality score for the chest compression, and the quality score may indicate instantaneous quality or average quality across a time. 
     The score may indicate when and how the rescuer  104  is performing chest compressions on the victim  102 , based on signals from the sensor package. For example, as a simplified description, signals from an accelerometer may be double integrated to identify a vertical displacement of the sensor package, and in turn of the sternum of the victim  102 , to identify how deep each chest compression is. The time between receiving such input from the sensor package may be used to identify the pace at which chest compressions are being applied to the victim  102 . 
     The defibrillator  108  in this example is connected to the electrode package  10  and may operate in a familiar manner, e.g., to provide defibrillating shocks to the electrode package  110 . As such, the defibrillator may take a generally common form, and may be a professional style defibrillator, such as the R-SERIES, M-SERIES, or E-SERIES from ZOLL Medical Corporation of Chelmsford, Mass., or an automated external defibrillator (AED), including the AED PLUS, or AED PRO from ZOLL Medical Corporation. The defibrillator is shown in one position relative to the rescuers  104 ,  106  here, but may be placed in other locations to better present information to them, such as in the form of lights, displays, vibrators, or audible sound generators on a chest-mounted component such as an electrode or via an addressable earpiece for each of the rescuers. Such feedback, as discussed more fully below, may be on units that are separate from the main housing of the defibrillator, and that may communication information about the victim  102  and performance of CPR to the defibrillator  108  or may receive feedback information from the defibrillator  108 , through either wired or wireless connects that are made directly with the defibrillator  108  or indirectly through another device or devices. 
     For illustrative purposes, two particular examples of feedback are shown here on a display of the defibrillator  108 . First, a power arrow  114  provides feedback to the rescuer  104  regarding the depth of compression that the rescuer  104  is applying in each compression cycle to the victim  102 . In this example, power arrow  114  is pointing upward, and thus indicating to rescuer  104 , that rescuer  104  needs to apply more vigorous input to create deeper chest compressions. Such feedback may be only provided visually for performing chest compressions, in order to minimize the amount of information that the rescuer  104  must deal with in a stressful situation. For example, an arrow indicating to apply less compression may not be shown under an assumption that very few rescuers will apply too much compression, and thus the user need only respond to indications to apply more pressure. The particular type of feedback to be provided can be determined by a designer of the defibrillator  108  and may vary to match particular situations. 
     Separately, the rescuer  104  may be provided with additional limited feedback, such as feedback for performing chest compressions at an appropriate rate. As one example, the defibrillator  108  may emit a sound through speaker  118  in the form of a metronome to guide the rescuer  104  in the proper rate of applying CPR. A visual representation may also indicate rates for performing compressions, such as a blinking of the display on defibrillator  108 . In addition, or as an alternative output mechanism that is designed to avoid distracting rescuer  106 , haptic feedback may be provided to rescuer  104  through electrode assembly  110 . For example, a puck or other item on which the rescuer  104  places her hands may be provided with mechanisms for vibrating the puck similar to mechanisms provided for vibrating portable communication devices (e.g., when an incoming telephone call is received on a smartphone). Such vibrating may be provided so as to minimize the amount of information that can distract other rescuers in the area, and may also more directly be used by the rescuer  104  to synchronize her chest compression activities with the output. For example, the vibrations may be periodic (approximate 100 times per minute) at the rate of performing chest compressions when the rescuer  104  should be performing compressions and may stop or be vibrated constantly when the rescuer  104  is to stop and switch positions with another rescuer, such as rescuer  106 . With feedback provided at the rescuer&#39;s hands, and because the rescuer  104  is providing the chest compressions with her hands directly, input by the system into her hands may be more directly applied with respect to the rescuer  104  keeping an appropriate pace. Such haptic feedback may also relieve the rescuer  104  of having to turn her head to view the display on defibrillator  108 . Thus, a first type of feedback, such as pulsed visual, audible, or tactile feedback may be provided to guide a user in performing CPR, and that type of feedback may be interrupted and replaced with a different type of feedback such as constant sound or vibration to indicate that a rescuer is to stop performing the particular component of CPR and let someone else take over. 
     Cycling arrows  116  are shown separately on the display of the defibrillator  108 . Such arrows may indicate to the rescuer  104  and to the rescuer  106  that it is time for them to switch tasks, such that rescuer  104  begins operating the ventilation bag  112  (as shown by the arrow superimposed over the legs of rescuer  104  to indicate that she would slide upward toward the victim&#39;s head, rotate the bag 180 degrees and begin operating it), and rescuer  106  begins providing chest compressions on electrode assembly  110 . Where there are three or more rescuers, the third rescuer may have been resting, and may take over chest compressions for rescuer  104  when a rescuer change is directed by the system, and the rescuer  104  may then the rest or may take the bag while rescuer  106  rests or does something else. For example, the rescuers may readily determine that rescuer  106  does not have the strength to provide consistent chest compressions on the victim  102 , and may determine that rescuer  106  should constantly provide ventilation using ventilation bag  112 , while other rescuers switch out in providing chest compressions. Thus, when the arrows  116  are displayed, rescuer  106  may stay in place while two other rescuers switch places with respect to delivering chest compressions. In the examples, discussed here, the system may be programmed to be indifferent to the manner in which rescuers decide to rotate, and the rotation may change during a rescue (e.g., rescuer  106  may initially provide chest compressions as part of a 3-person rotation and may then bow out and just provide ventilation while the other 2 rescuers rotate on chest compressions). 
     The defibrillator  108  may cause the cycling arrows  116  to be displayed based on the occurrence of various events. In one example, the cycling arrows  116  may be displayed after a set time period has elapsed since rescuer  104  began applying chest compressions. For example, a particular CPR protocol may require switching of rescuers at certain predefined periodic intervals (e.g., every 2 minutes). As described below in more detail, the cycling arrows  116  or a similar cycling signal, may alternatively be generated according to determinations made by the defibrillator  108  regarding the quality of chest compressions being provided to the victim  102  by rescuer  104 , including by monitoring past compression parameters (e.g., rate over several compressions and depth) and monitoring the rescuer directly (e.g., by determining a pulse and blood oxygen level of a rescuer). Such an analysis may recognize that rescuers tire progressively over time as they are providing chest compressions, so that the depth of chest compressions is likely to fall over time, and the rate of chest compressions may also fall or become more erratic over time. 
     The defibrillator  108  may thus be programmed to identify when such factors indicate that the chest compression ability of the rescuer  104  has fallen, or is about to fall, below a level that is of adequate effectiveness. As discussed below, for example, a score may be generated for the depth of compression based on how far from optimal compression each of the rescuer&#39;s  104  compressions are. Another score may be generated based on how far from optimal the rate of compressions are, and the two scores (depth and rate) may be combined to generate an overall quality score for each compression. A third score may indicate the rescuer&#39;s  104  physical state (e.g., via pulse measurement) and that score may also be combined. A running quality score may then be computed to indicate the quality of compressions over a period of time, such as over the last several compressions made by the user, so as to better indicate a trend in the quality of chest compressions being provided (in the past, the near future, or both). When the quality score falls below a threshold, the defibrillator  108  may then generate an indication that the current rescuer  104  should stop performing chest compressions and allow someone else to take over, such as by displaying cycling arrows  116 . 
     Similarly, the quality of ventilation may be monitored. For example, providers of ventilation may tire and forget that they are squeezing a ventilation bag too frequently—at too high a rate. They may be reminded initially, such as by a beeping metronome tied to the proper rate, or an LED on the bag that blinks at the proper rate. As with reminders for chest compression, such a reminder may be provided constantly, whether the user is performing properly or not, or can be triggered to start when the user is initially identified as performing in a substandard fashion. Subsequently, if the substandard performance continues for a predetermined time period or deteriorates to a second threshold level; the performance trends in a manner that indicates the user is not likely to improve the performance; or the performance otherwise indicates that the provider of ventilation should be switched out, a switching indication may be generated. Also, whether for compression or ventilation, different colors of lights may be used to indicate different types of feedback, such as a green light for good work, a yellow light to indicate a temporary deviation from good work, and a red light or even a blinking red light to indicate that the rescuer should switch out with someone else. 
     Where the providers of chest compressions and of ventilation are both being monitored in such a manner, a signal to switch may be generated when the first provider hits a substandard level. Alternatively, if chest compressions are considered more important than is ventilation, the level at which ventilation will trigger a switch can be set much more below a level considered to be satisfactory as compared to a level for chest compressions. In other words, a system may be biased to let the “weak” rescuer continue performing ventilation, rather than switching to a situation in which a somewhat fresh, but nonetheless tired with respect to squeezing a bag, and weak rescuer is placed in the most important position over another rescuer who may be more tired but is overall stronger at performing chest compressions. Various mechanisms may be used to balance the multiple factors, which include the relative important of each component to patient outcomes, the relative strength of each rescuer, the current performance and trending of performance for each rescuer, and knowledge or performance and trending for each rescuer from prior rescues (e.g., if the rescuers  104 ,  106  are part of an EMT team that uses the same defibrillator multiple times, or who have their data from multiple rescues uploaded to a central system for analysis) or prior cycles in the same rescue. 
     The process of observing the quality of a component of the CPR, such as the quality of chest compressions, may then continue recursively as long as care is being provided to the victim  102 . For example, after the defibrillator  108  generates an indication to switch providers of chest compression, the defibrillator  108  may sense through the electrode package  110  that chest compressions stopped for a period, thus indicating that users have switched as suggested by the defibrillator  108 . Once chest compressions then start again, the defibrillator  108  may again begin determining a quality score for chest compressions provided by the new rescuer, and may indicate that rescuers should switch again when the quality falls. In certain instances, an indication to switch may be blocked from being generated for a certain period after a new user begins performing compressions, under the assumption that the user might not be tired, but is merely trying to establish a rhythm in performing the chest compressions. Also, trends in the quality of the particular CPR component may be tracked rather than absolute values of the performance, so that the defibrillator  108  can distinguish situations in which a rescuer is giving a poor chest compressions because he or she was trying to find the appropriate rhythm or was distracted by a temporary problem, from situations in which the user truly is tiring and should be replaced. 
     In certain instances, the defibrillator  108  may be adaptable to different CPR protocols. For example, the defibrillator  108  may be programmed according to a protocol that, among other parameters, calls for each rescuer to provide chest compressions for a preset period of time. In such a situation, the defibrillator  108  may use pauses in the provision of chest compressions to determine when users have switched providing chest compressions, and may start a timer based on such observation. When the timer hits the preset period, the defibrillator  108  may then provide an indication that the rescuer giving chest compressions is to change. The timer may then be reset once a next rescuer is identified as having started giving chest compressions, such as by recognizing a pause in the provision of chest compressions. 
     Other protocols may be more flexible and may allow switches in rescuers to be dependent on the performance of the rescuers in addition to a predefined time interval. For example, the defibrillator  108  may be programmed to indicate that rescuers should change when it senses that performance has fallen below an acceptable level, and may also indicate the need for change when a maximum preset time has occurred even if the current rescuer appears to be performed well. In such a protocol, the time interval may be substantially longer than an interval for a protocol that requires changing based only upon elapsed time, and not upon degraded performance by the rescuer. Various different protocols may call for changing of rescuers based on different levels in performance, or upon different elapsed time periods, or a combination of the two. In particular, AHA protocols are generally just guidelines, and a particular medical director may alter such guidelines to fit their particular needs or professional judgment. (Indeed, revisions to AHA guidelines typically come from forward-thinking people who make modifications to prior guidelines and find the modifications to be effective.) 
     In such a situation, the defibrillator  108  may be programmed with the parameters for each of the protocols, and an operator of the defibrillator  108  may select a protocol to be executed by the defibrillator  108  (or the protocol may have been selected by a medical director). Such a selection may occur at the time of a rescue, or at a prior time. For example, the ability to select of a protocol may be limited to someone who logs onto the defibrillator  108  or configuration software separate from defibrillator  108  using administrator privileges, such as a person who runs an EMT service (e.g., a medical director of appropriate training and certification to make such a determination). That person may select the protocol to be followed on each of the machines operated by the service, and other users may be prevented from making such changes. In this manner, the defibrillator  108  may be caused to match its performance to whatever protocol its users have been trained to. 
     Thus, using the techniques described here, the defibrillator  108  may, in addition to providing defibrillation shocks, ECG analysis, and other features traditionally provided by a defibrillator, also provide indications to switch rescuers between various components of providing CPR and other care to a patient. The defibrillator may be deployed in the same manner as are existing defibrillators, but may provide additional functionality in a manner that can be easily understood by trained and untrained rescuers. 
       FIG.  1 B  shows the rescue scene  100  of  FIG.  1 A , with focus on the positioning of cameras around the rescue scene  100 . The other medical equipment would typically be used in combination with the cameras, but has been removed here to permit greater visual focus on the use and positioning of the cameras. A camera  124  can be adhered to the forehead of victim  102 , as positioned, for example, by one of rescuers  104 ,  106 , Camera  124  may be battery-operated and may communicate with a central controller such as a controller in defibrillator  108  (see  FIG.  1 A ). This camera may be directional and may be aimed over the torso of the victim  102  so as to continuously capture what is occurred with respect to treatment of the victim  102 . For example, camera  124  may show who is currently providing ventilation to victim  102  and who is providing chest compressions. Camera  124  may also be a 360 degree camera that captures images through a dome in a familiar manner. One or more cameras (not shown) may also be included in pieces of medical equipment. For example, defibrillator  108  may be provided with a camera in its face, where the camera has a field of view of substantial the entire areas in front of the defibrillator  108 . In some examples, the defibrillator  108  can be aimed toward a rescuer who wants to see a screen of the defibrillator  108 , and thus will have a front field of view that includes the victim and the rescuers. 
     One or more cameras  119 ,  120 ,  122  are integrated into or mounted on devices  121 ,  123  worn by rescuers  104  and  106 , respectively. The devices  121 ,  123  can be, e.g., a wearable computing device such as computing glasses or a watch that include an integrated camera component (e.g., Google Glass™), a headpiece or helmet or other type of wearable item on which the camera and other components (e.g., a display screen) are mounted, or another type of device. For instance, in the example shown, two cameras  119 ,  120  are integrated into the wearable computing device  121  and a single camera  122  is integrated into the wearable computing device  123 ; other numbers of cameras are also possible. The cameras  119 ,  120 ,  122  may be forward facing so as to have a field of view that approximates a field of view of the respective rescuer, e.g., such that the cameras  119 ,  120 ,  122  can capture images of the victim  102  undergoing the resuscitation event. 
       FIG.  1 C  shows a block diagram that represents the wearable computing device  121  and an image processing system  150 . The wearable computing device  123  can also be configured as shown for the wearable computing device  121 . In the example shown, the image processing system  150  is implemented by a processor and a memory in a local computing device  151  at the rescue scene  100 ; in some examples, the image processing system  150  can be implemented by a processor and memory of one or both of the wearable computing devices  121 ,  123  and/or by a processor and memory in a remote server, such as a computing device at an emergency response center (e.g., a 911 call center, a police dispatch, an ambulance dispatch, a fire department, or another emergency response center). 
     Still and/or video images of the rescue scene  100  captured by the cameras  119 ,  120 ,  122  are transmitted (e.g., as streaming data or as a batch from a local memory on the wearable computing devices  121 ,  123 ) to the image processing system  150 . For instance, the images can be transmitted by a wired or wireless Internet connection, such as a local area network (LAN) connection between the wearable computing devices  121 ,  123  and the local computing device  151 ; a Bluetooth™ connection; a 3G or 4G cellular connection, or by another type of connection. In some examples, e.g., when the image processing system  150  is hosted on a remote server, the images can be transmitted as described in U.S. patent application Ser. No. 13/538,031, the contents of which are incorporated herein by reference in their entirety. 
     One or both of the wearable computing devices  121 ,  123  can have a microphone  154  integrated into the device or mounted on the device by which a rescuer may communicate with other rescuers at the rescue scene  100 , with a dispatcher, with a remotely located physician who is going to receive the victim  102  when the rescuers get to a hospital emergency room, or with other personnel. The wearable computing devices  121 ,  123  may also, for example, provide heads-up displays (e.g., on a display interface  156 ) that appear to be in front of the respective rescuer and that show vital signs about the victim  102 , information that is also displayed on a visual display of the defibrillator  108 , instructions for treating the victim obtained from a remote database, and other such information that includes real-time status information about the victim. 
     Referring to  FIGS.  1 A- 1 C , using the still and/or video images received from one or more of the cameras  119 ,  120 ,  122 , a still, animated, etc. representation of the resuscitation event undergone by the victim  102  at the rescue scene  100  can be generated by a representation module  155  of the image processing system  150 . For instance, in some examples, a three-dimensional (3D) representation can be generated. A 3D representation can be considered a 3D model that is created from a set of 2D images (e.g., the images from one or more of the cameras  119 ,  120 ,  122 ). For instance, the 3D representation of the rescue scene  100  can be an animated (e.g., cartoon-like) overhead view of the rescue scene  100  such that a viewer of the 3D representation can have an unobstructed view of the activity occurring at the rescue scene  100 . In some examples, the animated representation can be synchronized with medical data associated with the victim  102 , such as the victim&#39;s ECG and/or other physiological waveforms or stored event data, such as drug delivery data, defibrillation shock data, and/or other types of medical data. The representation (and the synchronized medical data, if available) can be viewed on review software such as RescueNet Code Review™ (ZOLL Medical, Chelmsford, Mass.). 
     In some examples, the representation can be generated by the representation module  155  and analyzed by an analysis module  158  in real time, e.g., as the victim  102  is undergoing the resuscitation event at the rescue scene  100  (e.g., while the rescuer  104 ,  106  are treating the victim  102  at the rescue scene  100 ). The real time representation can be analyzed automatically and/or by a person, such as a rescuer, an emergency medical director, an analyst, or another person, to extract real time characteristics associated with the resuscitation event, such as real time medical data associated with the victim  102 , information associated with the performance of one or more of the rescuers  104 ,  106 , or other types of real time information. For instance, in some examples, the real time representation can be analyzed automatically by a computing device at the rescue scene  100 , such as by the defibrillator, by a mobile device such as a tablet operated by a rescuer, by a computing device in an ambulance at the rescue scene, or by another local device. 
     In some examples, the representation can be generated and/or analyzed after the resuscitation event is finished (e.g., after the rescuers  104 ,  106  have completed treatment of the victim  102  at the rescue scene). The post-event representation can be analyzed automatically and/or by a person to conduct a review of activities at the rescue scene  100  and to extract characteristics associated with the resuscitation event, such as information about the rescuers&#39; efficiency or accuracy. For instance, in some examples, the post-event representation can be analyzed automatically by a computing device remote from the rescue scene  100 , such as a computing device at a central emergency response center or a computing device at a hospital or other medical facility. 
     The analysis module  158  can detect and identify faces of the people at the rescues scene  100 , such as the victim  102  and/or one or more of the rescuers  104 ,  106 . For instance, the analysis module  158  can implement a facial detection algorithm (e.g., such as the facial detection algorithm described below) that analyzes the images from one or more of the cameras  119 ,  120 ,  122  and/or the representation to automatically detect and identify faces at the rescue scene  100 . The identified faces can be labeled in the representation, e.g., with a generic identifier (e.g., “victim,” “rescuer #1,” “rescuer #2,” etc.). 
     In some examples, the wearable computing devices  121 ,  123  can include an orientation sensor  125 , such as a magnetic sensor, compass, or gyroscope that provides information about the angular orientation of the cameras  119 ,  121 ,  123  worn by the rescuers  104 ,  106 . The victim  102  and/or the rescuers  104 ,  106  can be identified based on their relative positions and/or orientations, e.g., as determined by the analysis module  158  based on data from the orientation sensors  125 . For instance, a face that is oriented horizontally in an image from one of the cameras  119 ,  120 ,  122  can be identified as the victim  102 , because the victim  102  is likely to be lying in a prone position when undergoing a resuscitation event. Similarly, a face that is oriented vertically can be identified as one of the rescuers  104 ,  106 . 
     In some examples, the analysis module  158  automatically anonymizes one or more of the detected faces (e.g., the face of the victim  102  and/or the faces of one or more of the rescuers  104 ,  106 ) in the representation, e.g., to preserve the victim&#39;s privacy and/or to preserve confidentiality for all people involved at the rescue scene. For instance, a detected face can be anonymized by blurring facial features, removing identifying facial features, removing all facial features, replacing the face or person in the representation with a generic cartoon image or a cartoon image that shares a general characteristic with the person whom the cartoon represents (e.g., a weight, build, gender, hair color, hair length, etc.), and/or anonymized in another way. The position and motions of the people are preserved in the anonymized representation. The degree to which the people are anonymized can depend on factors such as preferences of the rescuers  104 ,  106 , decisions by regulatory personnel regarding which personal features are considered confidential, and/or other factors. In some examples, only anonymized data is stored in the memory  153 . 
     The analysis module  158  can detect and identify objects at the rescue scene  100 . For instance, the analysis module  158  can implement an object detection algorithm that analyzes the images from one or more of the cameras  119 ,  120 ,  122  and/or the representation to automatically detect and identify objects, such as medical devices, body parts, and/or anatomical features. For instance, the analysis module  158  can detect and identify objects based on features such as shape, color, size, location, and/or other features. In one example, certain types of defibrillator pads manufactured by ZOLL Medical are round and white and include a CPR depth sensor marked with a red “X”; these pads can be detected and identified based on one or more of the shape, the color, the presence of the “X,” the position on the chest of the victim  102 , and/or other features. In one example, certain types of AEDs manufactured by ZOLL Medical are bright green with an angular box-like shape; these AEDs can be detected and identified based on one or more of the shape, the color, and/or other features. The identified objects can be labeled in the representation, e.g., with a generic identifier (e.g., “pads,” “AED,” “victim arm,” etc.). 
     In some examples, a beacon  130  can be placed on one or more objects or people at the rescue scene  100 , such as on the defibrillator  108 , the victim  102  (shown), one or more of the rescuers  104 ,  106 , and/or other objects. The beacons  130  can include light emitting diodes (LEDs) that emit light that is visible or invisible (e.g., infrared LEDs) to the human eye. Each beacon  130  can be uniquely coded, e.g., by color, by time domain pulsing, or by another approach, such that each object that is tagged with a beacon  130  can be distinguished and identified, thus simplifying the facial and object detection and identification tasks carried out by the analysis module  158 . That is, for instance, the analysis module  158  can be configured to recognize that a beacon emitting light at 850 nm is positioned on the hands of the rescuer delivering compressions to the victim  102 . 
     The analysis module  158  can analyze the representation of the rescue scene  100  to determine characteristics associated with the resuscitation event. For instance, the analysis module  158  can determine the relative positions of the victim  102  and one or more of the rescuers  104 ,  106  or an object at the rescue scene; the motion of the victim  102  and/or one or more of the rescuers  104 ,  106 ; a metric associated with compressions delivered to the victim  102 ; a task associated with each rescuer  104 ,  106 ; and/or other characteristics associated with the resuscitation event. 
     In some examples, the analysis module  158  can estimate the distance between people and/or objects at the rescue scene based on information from images received from multiple cameras. For instance, the analysis module  158  can conduct a stereoscopic analysis of the images from multiple cameras worn by a single rescuer (e.g., cameras  119 ,  120  worn by rescuer  104 ) to estimate the distance of the victim  102  from the rescuer  104 . When both rescuers are wearing a camera, the images from those cameras (e.g., cameras  119  and  120  worn by rescuer  104  and camera  122  worn by rescuer  106 ) can be analyzed to estimate the distance between the victim  102  and each of the rescuers  104 ,  106 . 
     In some examples, one or both of the wearable computing devices  121 ,  123  include a motion-sensitive component  162 , such as a 3-axis accelerometer, a gyroscope (e.g., InvenSense™ MPU-6000), and/or another motion-sensitive device that can enable inertial motion tracking of the rescuer  104 ,  106  wearing the wearable computing device  121 ,  123 . The analysis module  158  can determine information about the motions of one or more of the rescuers  104  based on an analysis of the images from one or more of the cameras  119 ,  120 ,  122  and/or an analysis of data from the motion-sensitive component. For instance, the analysis module  158  can track the hand motion of the rescuer delivering chest compressions based on the position of the victim  102  and the rescuer&#39;s hands (detected in the images from one or more of the cameras  119 ,  120 ,  122 ), the angle of the rescuer&#39;s head (e.g., determined from data from the orientation sensor  125 ), and the motion of the rescuer&#39;s body (e.g., determined from data from the motion-sensitive component). The analysis module  158  can use the tracked hand motion to generate a dynamic 3D representation of the positions of the rescuer  104  and the victim  102  during chest compressions. From this dynamic 3D representation, measures of the quality of the chest compressions can be obtained, such as the depth of the chest compressions, the position of the rescuer&#39;s hands, the degree to which the rescuer releases his hands from the victim&#39;s chest on the upstroke of each compression, and/or other quality measures. 
     In some cases, motions in the 3D representation, such as a rescuer&#39;s hand motions, can be analyzed using robot kinematics, which applies geometry to the study of the movement of multi-degree of freedom kinematic chains that form the structure of robotic systems. Robot kinematics studies the relationship between the dimensions and connectivity of kinematic chains and the position, velocity, and acceleration of each of the links, where the links are modeled as rigid bodies and its joints are assumed to provide pure rotation or translation. 
     In some examples, one or more of the cameras  119 ,  120 ,  122  can implement image stabilization capabilities. For instance, a camera can recognize one or more features in its field of view and use those one or more features as landmarks for stabilization. 
     In some examples, one or more of the cameras  119 ,  120 ,  122 , and/or a camera attached to a relatively stable item such as the patient, a medical device, or an ambulance, may have self-aiming mechanisms provided with the cameras. In particular, the cameras may scan either electronically through a field of view or mechanically to capture a new field of view, until a processor receiving data form a particular camera senses motion or items indicative of a victim being treated. Software receiving the images may be programmed to scan until an image is captured that matches a signature of a patient being treated, such as a horizontal patient at ground level and moving items (rescuers) around the horizontal object. Similarly, a camera mount at the back of an ambulance may scan an area for items and motion indicative of rescue operations on a victim. Such scanning can also be performed in combination with other location techniques, such as using triangulation to roughly identify where rescuers are located, and using image and motion recognition to more finely identify the rescuers. 
     In some examples, one or more of the cameras  119 ,  120 ,  122  can automatically track a feature in its image, for instance, to keep a feature in the center of its field of view. For instance, a camera can automatically change its direction in order to keep a feature, such as a beacon, in its field of view long enough for an object detection or facial recognition algorithm to be completed. 
     A messaging module  159  can provide messages to one or more of the rescuers  104 ,  106 . For instance, a visual message can be provided for display on the display interface  156 , an audio message can be provided through a speaker  160 , or another type of message can be provided. The messages can be based on the results of the real time analysis of the representation and/or on real time medical data associated with the victim  102 . Example messages can include, e.g., a message to alert the rescuer  104  that the speed of the compressions he is delivering is low, a message to provide a view of a portion of the victim&#39;s ECG, a message to prompt the rescuer  104  to adjust the positioning of the electrode assembly  110 , and/or other types of messages. For instance, messaging can be administered as described in U.S. patent application Ser. No. 13/474,269, filed May 17, 2012, the contents of which are incorporated herein by reference in their entirety. 
     In one example, the messaging module  159  provides a message to alert one or more of the rescuers  104 ,  106  that an object or person is positioned incorrectly at the rescue scene. For instance, the analysis module  158  can compare the actual position of a detected object or person with stored information indicative of the proper position for the detected object or person (e.g., the proper distance between the center of the electrode assembly  110  and one or more anatomical features of the victim  102 , such as the victim&#39;s face, arms, torso, shoulders, etc., or the proper position along the victim&#39;s torso of a rescuer providing ventilation treatment). If the actual position of the object or person differs from the proper position of the object or person, the analysis module  158  can cause the messaging module to provide a message alerting one or more of the rescuers to the misplaced object. 
     In some examples, the messaging module  159  can provide customized messages to each of the rescuers  104 ,  106 , such as messages that are specific to the types of tasks each rescuer  104 ,  106  is performing at the rescue scene  100 . For instance, a message such as “slow down ventilations” can be sent to a rescuer performing ventilator tasks, a message such as “stronger compressions” can be sent to a rescuer performing compression tasks, a message such as “move toward victim&#39;s head” can be sent to a rescuer performing infusion tasks, etc. 
     In some cases, the messaging module  159  can be manually configured to provide the appropriate type of message to each rescuer  104 ,  106 . For instance, a medical director at the rescue scene  100  or elsewhere, one or more of the rescuers  104 ,  106 , or another person can input information indicative of which types of task each rescuer is performing. In some cases, the analysis module  158  automatically infers which type of task each rescuer  104 ,  106  is performing, e.g., based on the detected position of each rescuer relative to the victim  102 , and can provide the inferred type of task for each rescuer to the messaging module  159 . For instance, the analysis module  158  can infer that a rescuer at the head of the victim  102  is performing ventilator tasks, a rescuer to the left of the victim  102  is performing compression tasks, and a rescuer to the right of the victim  102  is performing infusion tasks. The analysis module  158  can detect when rescuers change positions (e.g., to switch tasks) and can provide the messaging module  159  with a new type of task for each newly positioned rescuer. 
     Referring to  FIG.  9   , in an example approach to generating and analyzing a representation of a rescue scene in real time, still and/or video images of a victim undergoing a resuscitation event at a rescue scene are received from one or more cameras, such as cameras worn by one or more of the rescuers at the rescue scene ( 900 ). For instance, the images can be received at a computing device located at the rescue scene, such as a mobile computing device (e.g., a laptop, tablet, or another type of mobile computing device). 
     A representation (e.g., a 3D representation) of the rescue scene is generated based on the received images ( 902 ), for instance, using the approach described below. 
     Faces of one or more of the people at the rescue scene (e.g., the victim and/or the rescuers) are detected and identified using a facial recognition algorithm ( 904 ). For instance, in one example, facial recognition can be performed using an algorithm that implements face detection as a specific case of object-class detection. In general, object-class detection aims to find the locations and sizes of all objects in an image that belong to a given class of objects, such as upper torsos, pedestrians, cars, or other objects. Face detection in particular aims to find the locations and sizes of an unknown number of faces in an image. Such facial detection techniques may implement one or more processes, methodologies, etc. For example, a principal component analysis (PCA) based technique may be employed that uses orthogonal transformation to convert a set of observations of relatively correlated variables (e.g., such as facial features) into a set of variable referred to as principal components. In some arrangements, representations (e.g., captured images) of various types of facial features may be used for PCA, for example, naturally occurring facial features (e.g., eye brows, wrinkles, etc.), artificial features (e.g., one or more markers, make-up, etc. applied to the face), combinations of natural and artificial features, etc. Techniques such as PCA, may also assist with compressing data representing facial expressions for later retrieval and analysis such as scene reconstruction. 
     Some examples of face detection algorithms focus on the detection of frontal human faces. Some examples of face detection algorithms attempt to solve the more general problem of multi-view face detection, which is the detection of faces that are rotated along the axis from the face to the observer (in-plane rotation) and/or rotated along the vertical or left-right axis (out-of-plane rotation). These latter face detection algorithms can take into account variations in images or video resulting from factors such as facial appearance, lighting, pose, and/or other factors. 
     Information sufficient to identify the victim  102  and/or one or more of the rescuers  104 ,  106  is removed from the representation ( 906 ), e.g., to preserve the victim&#39;s privacy and/or to preserve confidentiality for all people involved at the rescue scene. For instance, a detected face can be anonymized by blurring facial features, removing identifying facial features, removing all facial features, replacing the face or person in the representation with a generic cartoon image or a cartoon image that shares a general characteristic with the person whom the cartoon represents (e.g., a weight, build, gender, hair color, hair length, etc.), and/or anonymized in another way. The position and motions of the people are preserved in the anonymized representation. 
     Objects at the rescue scene are detected and identified ( 908 ), e.g., using an object detection algorithm. For instance, objects can be detected and identified based on features such as shape, color, size, location, and/or other features. 
     A characteristic associated with the resuscitation event is determined based on an analysis of the representation of the rescue scene ( 910 ). For instance, the analysis module  158  can determine the relative positions of the victim  102  and one or more of the rescuers  104 ,  106  or an object at the rescue scene; the motion of the victim  102  and/or one or more of the rescuers  104 ,  106 ; a metric associated with compressions delivered to the victim  102 ; a task associated with each rescuer  104 ,  106 ; and/or other characteristics associated with the resuscitation event. 
     A message, such as an audio or a visual message, is determined for one or more of the rescuers based on the determined characteristic associated with the resuscitation event ( 912 ). For instance, a customized message can be determined for a particular rescuer based on a task that is associated with that rescuer. 
     In general, a 3D representation of the rescue scene creates a 3D model of the rescue scene from a set of one or more two-dimensional (2D) images. A 2D image is, in general, a projection of a 3D scene onto a 2D plane, which results in the loss of depth in the 2D image. The 3D point corresponding to a specific image point is constrained in the 2D image to be on the line of sight of the 2D image. Thus, from a single 2D image, it is impossible to determine which point on the line of sight corresponds to that specific 3D image point. 
     If multiple 2D images are available, then the position of a 3D image point can be found, for example, as the intersection of the projection rays for the multiple 2D images. This process is referred to as triangulation. Triangulation can be used to identify the position of a 3D image point provided the multiple 2D images are related in some way, such as that the multiple 2D images contain structure that is related to the position and/or calibration of the camera(s) acquiring the images. 
     To convert multiple 2D images into a 3D representation, the camera(s) acquiring the images are calibrated. Camera calibration includes intrinsic and extrinsic parameters. Depth determination is performed to calculate a depth for one or more image points in one or more of the images acquired by the cameras. To determine depth, correspondences between two images are identified. The positions of matched elements in the two images are triangulated in 3D space to determine a depth map. 
     Multiple depth maps are registered by calculating depth and projecting out of the camera to create a final mesh. Camera calibration can be used to identify where the many meshes created by the depth maps can be combined together into one or more larger meshes, thus providing more than one view of the 3D scene. Materials are applied to the complete 3D mesh, such as the colors from the original 2D images. In some examples, one or more of the 2D images can be projected onto the mesh randomly to apply color from the projected 2D images onto the mesh. In some examples, the textures of one or more of the 2D images can be combined for super resolution. In some examples, the mesh can be segmented by material, such as specula and/or diffuse properties. 
     In one example, 3D representation is performed for a group of 3D points viewed by N cameras with matrices 
       { P   i } i=1 . . . N′   (1)
 
     The homogeneous coordinates of the projection of the j th  point onto the i th  camera are defined as 
         m   j   i   ≅P   i ω j .  (2)
 
     The representation problem can be changed as follows: Given the group of pixel coordinates, find the corresponding set of camera matrices and the scene structure such that 
         m   j   i   ≅P   i ω j .  (3)
 
     Generally, without further restrictions, a projective representation can be obtained. If {P i } and {ω j } satisfy Eq. (3), then {P i T} and {T −1 ω j } will satisfy Eq. (3) with any 4×4 nonsingular matrix T. That is, a projective representation can be calculated by point correspondence only, without any a priori information. 
     In one approach, an autocalibration is performed (also referred to as a self-calibration), in which camera motion and parameters are recovered first, using rigidity. From the camera motion and parameters, structure can be calculated. Two example approaches to autocalibration include the Kruppa equations and the Mendonga and Cipolla approach. For instance, using the Kruppa equations, with a minimum of three displacements, the internal parameters of the camera can be obtained using a system of polynomial equations (the Kruppa equations). The Kruppa equations are derived from a geometric interpretation of the rigidity constraint. The matrix, referred to as the Kruppa matrix, is unknown in the Kruppa equations. With K and by the method of Cholesky factorization, the intrinsic parameters of K can be found as: 
     
       
         
           
             
               
                 
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     In some examples, 3D representation can be achieved using a stratification approach. A projective structure, which can be calculated from correspondences only, can be upgraded to a Euclidean representation by making use of available constraints. In some cases, it may not be possible to use the full 3D structure of Euclidean space for analysis of a representation problem. In these cases, a simpler structure can be used to analyze the representation problem, such as a projective structure or an affine structure. The concept of stratification is closely related to a series of transformations that can be carried out on geometric entities: the projective stratum includes a series of projective transformations (a homography), the affine stratum includes a series of affine transformations, and the Euclidean stratum includes a series of Euclidean transformations. 
     Suppose that a fixed scene is captured by two or more perspective cameras and the correspondences between visible points in different images are already given. In practice, this matching can be challenging to achieve. For instance, suppose that n 3D points are observed by m cameras with projection matrices. Neither the positions of the points nor the projections of the cameras are known; only the projections of the i th  point in the j th  image are known. By projective representation, simple counting indicates that there are 2 nm independent measurements and only 11 m+3n unknowns, so the representation problem is solvable with sufficient points and images. The equations in homogeneous coordinates can be represented as: 
         a   ij   ˜P   j   A   i   ,i= 1, . . . , n,j= 1, . . . , m.   (5)
 
     A nonsingular 4×4 transformation H can be applied to projections and world points. Hence, without further constraints, representation is only an unknown projective deformation of the 3D world. 
     An affine representation can be implemented by computing the location of the plane at infinity Π − ∞, for instance, by exploiting knowledge that the lines in the scene are parallel or that a point is one third of the way between two other points.| 
     To implement a Euclidean representation, the projective representation can be mapped to a representation that satisfies a group of redundant Euclidean constraints. This mapping results in the projective transformation H described above. These equations are highly nonlinear and involve the use of a good initial guess for the structure, which can be obtained by assuming a linear projection or a parallel projection. 
     In some examples, a 3D reconstruction can be generated from images from a single camera that is in motion about the rescue scene. To generate a 3D reconstruction from images from a single camera, the position, orientation, and distance of the camera relative to a fixed object at the scene are detected. Multiple 2D images from the single camera are then fitted together based on the detected position, orientation, and distance of the camera to generate the 3D reconstruction. 
     The capture of images and other data form a scene may be coordinated between and among the various devices on a scene so that all of the data may be combined in a manner that aligns it all time-wise with each other. For example, if the system is determined to have minimum latency, each of the devices may simply stream data in real-time to a central system (e.g., a computer system in a nearby ambulance) and that system may assemble the parts into an overall data transcript of an event. Alternatively, each device may keep a coordinated timeline with the data it collects, so that even if there is delay in transmitting the data to a common hub, that common hub can assemble all of the disparate pieces of data from different devices using the timeline as a base for aligning data. The coordination may occur, for example, by a central unit periodically transmitting a coordination signal that all other devices listen to, or by a mesh approach in which each device communicates with a nearby device so as to coordinate timing information that may be used to align events in a single event log that captures all data from the event. 
     As noted above, one or more of the cameras may have a 360 degree field of view and/or may be a light field camera that permits post-capture identification of a focus distance for an image (which may be a single image or a sequence of images, such as a video). The light field cameras may permit humans or software that are reviewing the captured video to “zoom in” so-to-speak on particular items in the field of view of the camera. For example, if text is identified in an image, the focus may be applied to that text after the image is captured so as to make the text clearer and to enable superior optical character recognition of the text. Alternatively, when two rescuers are located at two substantial different distances form the camera, the post-processing may be used to focus on one or the other of the rescuers. Such post-focusing may be performed manually in response to inputs from a user reviewing the images (e.g., watching a video or a rescue) or automatically, such as software identifying something of interest in the image and then focusing to that item. 
     Locations of items in a scene (e.g., a patient, rescuers, and other items) may be identified at least in part by performing differential focus analysis on light field camera images. In particular, the characteristics of a light field camera may be known, and the distance of an item from the camera can be determined by identifying when it is in or out of focus under different post-processing settings of the software for analyzing light field captured images. Such information may be combined, for example, with laser capture data of a scene (where the laser source is in or with one or more of the cameras or a separate location such as a high point on a rescue vehicle, where the laser scans an area, and a 3D model of the area can be created by such scanning. Also, the data can be combined with analysis of images taken from different angles, and the positions of rescuers may even be identified by the relationship of the images they are capturing as compared to the images captured by other cameras. 
     The light field camera may also be used to measure the depth and rate of compressions and be used to assess the performance of rescuers and initiate a switch of rescuer performing compressions, in manners like those discussed above. As one example, the light field camera may be used to measure the patient&#39;s chest size and use the data to adjust compression quality goals. The light field camera may also be used to analyze the movement of the rescuer and that data may be used to give more specific instructions to rescuers for example “release compressions fully” or “keep arms straight.” The light field camera may also be used to identify the position of individual rescuers and equipment, and the image data collected can be used to create three dimensional views of the rescue. 
     Standard sensor packages like those found in smartphones may also be arranged to move with each of the cameras. For example, a sensor pack may include an accelerometer, an inclinometer, a magnetometer, and the like. Such sensors may be used to identify the orientation and position of each camera, and to thereby better identify what the camera is showing. For example, if the patient camera  224  is set with no incline (and is showing human movement in its field of view), it might be inferred that the camera is pointing horizontally straight down the torso of the lying victim  102 . 
     The image data may also be used in other ways, including in coordination with the switching techniques described here. For example, it may be determined that rescuers move their shoulders more or less when they are getting tired compared to when they are fresh. Such information may be identified from video taken by the victim-mounted camera  124  or by movement of the image in cameras  120 ,  122  or movement sense by sensor packs in the cameras  120 ,  122 .  FIGS.  2 A and  2 B  show a portable defibrillator and ancillary components arranged to provide feedback and instruction to rescuers. Each of the figures shows an example in which visual feedback can be provided to a rescuer from a location that is away from the defibrillator unit, and more immediately in the line of sight and focus of attention of a rescuer, such as a rescuer who is providing CPR chest compressions. 
     Referring to  FIG.  2 A , a system  200  is shown in which a defibrillator  202 , which takes a standard form, but is provided with additional user feedback functionality, is connected to an electrode assembly by way of a wiring harness  204 . The wiring harness  204  may include a number of wire leads that are connected together by a common plastic shroud that may surround the wires or may have been integrally formed around the wires such as through an extrusion process, and may be connected to the defibrillator  202  by way of a single plug. For example, the defibrillator  202  may be provided with a female or male connection, and the plug may be provided with a corresponding connection in a manner that is well known in the art. The wires may carry power from the defibrillator  202 , such as current to provide a shock to a victim who is being provided with emergency care, or to the defibrillator  202 , such as in the form of signals for generating ECG information, accelerometer information, and measurements of trans-thoracic impedance of a victim. 
     The electrode assembly in this example includes a first electrode  206 , a second electrode  208 , and a chest compression assembly  210 . The first electrode  206  may be configured to be placed above the victim&#39;s right breast, while the second electrode  208  may be configured to be placed below the victim&#39;s left breast. During a rescue operation, printed insignia on one or both of the electrodes  206 ,  208  may indicate to a rescuer how to deploy the electrodes  206 ,  208 , and where each of them should be placed. In addition, the defibrillator  202  may display such instructions on a graphical display and may also provide verbal instructions to supplement was is shown in the visual instructions, such as instructions for the sequential operation of the defibrillator. 
     The chest compression assembly  210 , in this example, includes a detector  212  and a display  214 . The detector  212  may include a plastic housing within which is mounted an accelerator assembly. The accelerator assembly may move with the housing as chest compressions are performed on a victim so that motion of the accelerometer matches motion of the victim&#39;s sternum. The detector  212  is shown in the figure as having an “X” printed on its top surface to indicate to the rescuer where to place his or her hands when delivering chest compressions to a victim. The accelerator in the housing may be connected to pass signals through harness  204  to defibrillator  202  (or may include a wireless transceiver for passing the information wirelessly), which may be provided with circuitry and or software for converting such signals into the indications about the rate and depth of compressions being performed on the victim, in manners such as those described below. 
     The display  214  may provide feedback that is directed to the rescuer who is performing chest compressions. In this example, the feedback comprises symbols similar to those shown on the display of defibrillator  108  in  FIG.  1 A , in particular, an arrow indicating when the user is to perform chest compressions more vigorously, and circular cycling arrows indicating when rescuers are to switch in performing chest compressions. The particular symbols used may be selected also to be independent of the orientation from which they are viewed (as the cycling arrows are here), so that the symbols may have the same meaning to a rescuer who is on the right side of the victim as to a rescuer who is on the left side of the victim. In that manner, the system  200  does not need to determine where the rescuer is positioned. Also, a haptic vibrating mechanism may be provided at the assembly  210 , so as to provide tactile beats or metronomes for a user to follow in providing chest compressions. In certain instances, when the unit indicates that rescuers are to switch, such haptic or tactile feedback may be turned off or provided as a constant vibration so as to provide an additional indication to the rescuer that they should no longer be performing chest compressions. In some examples, the feedback is based at least in part on an analysis of the 3D representation of the rescue scene. 
       FIG.  2 B  shows a slightly different arrangement in a system  216  that includes a defibrillator  218  that is the same as defibrillator  202 . In actual implementation also, the same defibrillator could be used with two different types of electrode assemblies like those shown here in  FIGS.  2 A and  2 B . With specific reference to  FIG.  2 B , a wiring harness  220  in this example may be the same as wiring harness  204  in  FIG.  2 A , though here it connects defibrillator  218  to an electrode  224 , and an assembly  226 . The electrode  224  may simply be a single electrode that is connected to receive energy from the defibrillator  218 , and is arranged to be placed in a conventional manner above a victim&#39;s right breast. The electrode  224  may also include mechanisms for sensing an ECG reading from a victim, and for communicating sensed parameters back to the defibrillator  218 . 
     The assembly  226  may take a slightly L-shaped form, with one leg comprising an electrode designed to be placed below a victim&#39;s left breast, and another leg arranged to lie in a line with the victim&#39;s sternum. The assembly may be mounted on a flexible foam later that includes a gel layer on the bottom of the electrode for conducting a shocking pulse to a victim, but no gel under the sensor portion. However, the sensor portion may have a form of adhesive on its bottom side so that the accelerometer does not bounced and separate from the victim during chest compressions, and thus give an inaccurate reading to the defibrillator  218 . 
     In this example, the hypothetical victim is shown in dotted lines to indicate how the electrode  224  and the assembly  226  may be positioned in actual use. Before they are deployed, however, the various electrodes and assemblies may be stored in a sealed packet, and the wires may be coiled to reduce needed space, in conventional manners. At the time of an emergency, the wires may have already been plugged into the defibrillator (e.g., via the wires extending through a sealed hole out of a packet in which the electrodes are stored to keep their gels moist). A rescuer can then open the package, plug the wires in if they are not already plugged in, and if necessary, read instructions on the back sides of the electrodes regarding the proper manner to apply the electrodes—e.g., with graphics that show the peeling off of covers over the electrode gels and also show images of the proper placement of the electrodes on a line-drawn victim. 
     In additional to electrodes, the assembly  226  may include a sensor assembly  228  and a display  230 , similar to the sensor assembly  212  and display  214  in  FIG.  2 A . In addition, the components that provide functionality of the assembly  228  and display  230  may be the same as those described above for assembly  212  and display  214  in  FIG.  2 A . In this example, though, the assembly  228  and display  230  are connected directly to the electrode  226  by flexible structures that are arranged and sized so as to place the electrode and sensors in appropriate locations for a victim (under a left breast and aligned over the top of the sternum). Such an arrangement allows the system  216  to have fewer components that need to be applied to a victim then the system  200 , while still having the flexibility to space the two electrodes relative to each other depending on the size of the victim—i.e., because the electrodes are separate from each other, it may be easier to position them both on small victims and very tall/long victims. 
     In both of the systems  200 ,  216 , the placement of a display near the hands of a rescuer may provide one of more benefits in certain implementations. For example, a rescuer is typically looking at his or her hands when applying chest compressions, both because it is most natural to look forward, and as a mechanism to obtain feedback on how deep the chest compressions are and how the victim is doing. Thus, the rescuer can see the feedback without having to look around, and can constantly receive the feedback even while performing chest compressions. Also, the components can be provided in such locations conveniently and with relatively low cost, since the electrodes and accelerometers will already be provided, and a display need simply be added to one of these existing components (though in other implementations, the display may be located elsewhere). The feedback device also is naturally positioned to provide haptic feedback, which might be more directly processed by a rescuer. And by using visual feedback that is in the field of view of a particular rescuer and using haptic feedback, the system can reduce “attention pollution” at a scene, in that is lessens the level of noise and other distractions that other rescuers have to deal with in a very stressful environment. In some cases, the feedback displayed to a particular rescuer is specific to the task carried out by that rescuer, e.g., as determined from an analysis of the 3D representation of the rescue scene. 
     Feedback devices away from the main medical device may also take other forms. For example, an LED may simply be provide in the top surface of one of the electrodes or near a puck, and the LED may blink to indicate a rate of chest compressions to be performed, and stay solid on to indicate that rescuers should switch positions. Also, an LED or graphical display may be provided on the ventilation bag  212 , such as to blink to indicate a rate at which the bag is to be squeezed, and may be made solid in coordination with a display for the person performing chest compressions being made solid. In other words, the same signal can be provided to each of the rescuers to switch places, though on the respective sub-system that they are currently operating. As a result, the rescuers will only need to know a single “change” signal and will be able to react more intuitively and more quickly. 
       FIGS.  2 C- 2 E  show chest compression pucks that can capture information from a rescuer. In general, typical pulse oximetry sensor components may be integrated into a device on or in which a rescuer places his or her fingers, and can be used to provide a connected (wired or wirelessly) medical device such as a defibrillator, with indications of the blood oxygen level and pulse rate of a rescuer holding the device, which in these examples can be referred to as a CPR puck. The pucks shown here may be provided as part of the systems also shown in  FIGS.  2 A and  2 B , such as by integrating the components for sensing rescuer condition into the components in those other figures. 
     Referring now specifically to  FIG.  2 C , there is shown an assembly  232  made up of a puck housing  336  and substrate  234 . The substrate  234  may have on its lower side a gel-based adhesive so that the assembly  232  adheres to the chest of a victim on which it is placed. The housing  336  may in turn be solidly adhere to the top of the substrate  234  do that the housing  336  moves with a victim&#39;s sternum when a rescuer places his or her hands on top of the “X” shown on the top surface of the housing  236  and performs chest compressions. Connected to the substrate  234  and/or housing  336  by wire is a pulse oximeter  238 . The pulse oximeter may report a blood oxygen level and pulse rate through the wire from which hit is attached into the remainder of the assembly  232 , from which it may be reported to a defibrillator or other medical device, either wirelessly or by wired connection. 
     In operation, when a rescuer begins performing chest compressions, he or she may be instructed to slip a fingertip into the pulse oximeter  238  before placing his or her palms on top of the housing  336 . The wire may permit movement of the rescuer&#39;s fingertip as they perform chest compressions, while measuring the relevant values. Such values may then be used, as discussed above, along with other factors such as rate and depth of compressions, to determine when the rescuer should be instructed to stop performing chest compressions and yield to another rescuer. Also, the assembly  232  may be provided as a stand-alone unit separate from a defibrillator or other medical, so as to provide more general feedback to a rescuer, where the feedback integrates consideration of rescuer blood oxygen level, pulse, or both. 
     Referring to  FIGS.  2 D and  2 E , there is shown a top and side section view of an assembly  240  that is similar to assembly  232  in  FIG.  2 C , but integrates sensing functionality for the rescuer into the puck housing. 
     Again, the housing is shown on top of an adhesive substrate  242 , but in this example, the housing is provided with depressions  244   a ,  244   b  into which a rescuer can slide his or her fingertips while performing chest compressions, as shown by the hand in  FIG.  2 E . The housing is provided here with depressions  244   a ,  244   b  on opposed sides, so that rescuers on both sides of a victim may use the assembly  240  and take advantage of its rescuer monitoring functionality. Also, as shown, sensors  250  can be provided at multiple locations, including four different locations to reflect rescuers who may be on either side of the victim and may places fingers from their right or left hands into the depressions  244   a ,  244   b.    
     The assembly may simply send signals back to a medical device such as a defibrillator. Separately, the assembly  240  may modify or analyze the signals right on the assembly  240  in the housing. Thus, for example, a oximeter processor  248  is shown inside the housing and may receive signals from the sensors  250  and convert them partially or fully into blood oxygen and pulse rate values that can then be displayed or further processed on the assembly  240  (e.g., to identify that the rescuer is becoming fatigued). Similarly, an accelerometer pack  246  may be provided inside the housing in a position so as to sense proper motion of the victim&#39;s sternum. The pack  246  may, for example, compute depths of compressions and rates of compressions, and may also be connected to an output mechanism on the assembly  240  or connected to a medical device that is separate from the assembly  240  so as to provide chest compression feedback in manners like those discussed above and below. 
       FIG.  3    shows example chest compression inputs and mechanisms for analyzing the inputs to determine whether a different rescuer should provide chest compressions. In general, the example here shows a series of eighteen chest compressions  300  that have been graphed along a horizontal time axis, along with a variety of numbers that represent parameters of how the chest compressions were performed. Such sensed compression data and derived numbers may then be used to determine when the quality of the chest compressions indicates that the rescuer is getting fatigued, and the system should indicate to the rescuer that they should switch with another, fresher rescuer. 
     Referring more specifically to the graphed compressions, a dashed line  302  represents a target chest compression depth and each of the spikes  304  here indicate a distance level of downward compression (y axis), graphed according to time (x axis). In particular, the compressions are sharp motions followed by pauses, with the overall pattern repeated eighteen times during the time (which may be a fraction of a minute when the rescuer is performing about 100 compressions per minute). Such compressions may be sensed by an accelerometer assembly that is between the hands of the rescuer performing chest compressions and the sternum of the victim. Sensed signals may then be passed through a wiring harness to circuitry and software in a defibrillator or other medical device that can analyze the signals to identified compression depths and timing of the chest compressions. 
     As can be seen, the initial chest compressions are at an appropriate level and an appropriate rate, but began to dip at the fourth and fifth compressions. The compressions then pick up and hit the dashed line  302 , perhaps because the fall in compressions caused a defibrillator to indicate to a rescuer that they should compress harder, and the user followed such direction. The depth of compressions over time then falls again at compressions  11 ,  12  and  13 , but then picks up at  14  and falls yet again near the end, indicating that the user has become fatigued. 
     Below the graph are shown numbers that, for this example, indicate values that may be computed by a defibrillator that is connected to a system for determining when to signal that a provider of chest compressions to a victim should be changed by the system. The top row shows a score that may be given to a user to rate the quality of the depth of the chest compressions. Such a score may be given a baseline of 100 around a depth that approximates the desired line of  302 . The score may fall the further one gets from line  302 , though the score may fall more quickly for deviations on the under-compression side than the over-compression side, e.g., if a determination is made that under-compression is a more serious error than over-compression. Thus, for example, the fifth compression falls below line  302  by an amount less than the sixth compression falls above the line, but the fifth compression receives a lower score than does the sixth compression. 
     In this example, the depth of compression factor is provided 70% of a weighting in determining an overall score for the quality of the chest compression. The other 30% of the score is driven by the rate at which the user provides the compressions. Thus, for example, one can see fairly even spacing for compressions two through eight, but a slight delay for compression nine, so that the ninth compression receives a score of 90 instead of a score of 100. In addition, one can see lengthening delays between compressions at the end of the period. The rate scores reflect, in each instance, how far a compression was performed from the time at which it was supposed to be performed according to protocol. Again, the scores are scaled to a maximum of 100 for ease of explanation, but could take other forms also. 
     The third line in the numbers indicates an overall score for each of the compressions, where the overall score is simply the combined weighted value of the two component scores for depth and rate, respectively. Finally, the fourth line shows a running score that is a running average of the current score and the two previous scores. By using a running average, singular deviations from a perfect compression may be ignored, while lingering deviations can be captured so that continual failure by a user, which indicates fatigue of the user, can result in the generation of a signal to switch users in performing chest compressions. Thus, for example, compression number five is a bad compression, but the running score is relatively high because the previous two compressions were better. 
     In this example, the trigger for generating an indication that users should change position is a running score at or below 85. Thus, although the running score in the example rises and falls as a user has periodic problems with performing compressions, it does not fall to the triggering level until compression eighteen, after there had been three weak compressions in a row that were also spaced too far apart—so that the running average score really fell. In actual implementation, software may monitor the value as a user provides compressions, may periodically update the value (e.g., once for each compression or on another basis), and may cause a defibrillator, such as defibrillator  108 , to emit output to one or more rescuers to indicate the need for a change, such as the indication shown in the prior figures above. 
     While the particular running average scoring technique described here is provided for its simplicity and ease of understanding, different approaches may be used to identify when a user is likely becoming too fatigued to maintain quality chest compressions or other components of CPR. For example, various inputs may be subjected to derivations in order to determine rates of change of those inputs. An indication to change rescuers may be generated when the rate of change in the quality of performance exceeds a preset amount in a negative direction. Also, models may be generated to represent fatigued users, and actual inputs may be compared to such models to indicate when fatigue is setting in for a real user and to cause an alert to be generated. 
     In certain instances, such as when the number of rescuers is known, data may be stored across multiple cycles of chest compression sessions for each of the users. For example, the system may identify in early cycles of a rescue that one of the rescuers has a sudden drop-off in chest compression performance but then recovers, and may store such understanding and use it in subsequent cycles so as to not trigger an indication to change rescuers simply because the particular rescuer is having momentary problems. Another rescuer may be seen to have a slower drop in performance but may be more erratic in his provision of chest compressions, so that a system may permit more variability before it triggers an indication to switch rescuers, since variability by that user may not indicate fatigue, but may simply be normal variability in the manner in which the user performs chest compressions. Other factors may also be taken into account in addition to depth and rate of providing chest compressions. For example, a heart rate monitor may be applied to a rescuer and an increase in heart rate may indicate fatigue by the rescuer, and may be used to generate a signal to switch rescuers. Also, the shape of a compression profile may be used, such that a jerky or sharp profile may indicate fatigue by a user, and also contribute to the triggering of a signal to switch rescuers. 
       FIG.  4 A  is a flowchart of a process for monitoring CPR performance and providing feedback for improvement of the performance. Generally, the process involves automatic monitoring of the performance of a component of CPR, such as the provision of chest compressions to a victim, and the indication to a provider of such component when they should stop performing the component and allow another rescuer to perform the component. 
     The process begins at box  402 , where the process monitors, using an accelerometer puck, chest compressions that are performed on a victim. The process may have been started after rescuers arrived at the scene of a victim and deployed electrodes and the puck onto the torso of the victim. The rescuers may have then turned on a defibrillator connected to the electrodes and puck, and the defibrillator may have begun performing relevant functions for the rescue, while the rescuers performed their manual functions. For example, the defibrillator may have initially began taking an ECG reading from the victim and displaying it to the rescuers on a graphical display, and may have analyzed the victim&#39;s heart rhythms to determine whether a shockable rhythm existed so that a defibrillating shock could be applied to the victim. Other relevant analysis and processing may also have been performed, and continue to be performed by the defibrillator. 
     At the same time, one rescuer may have applied the electrodes and the puck and have begun performing chest compressions on the victim. Such compressions may cause the puck to move and accelerate up and down, so that an accelerometer in the puck generates signals indicative of such acceleration. The defibrillator may receive such signals and convert them into indications of the quality of the chest compression, such as indications of how deep each test compression is, and the pace at which particular ones of the chest compressions are occurring. The other rescuer may separately have applied a ventilation bag to the victim&#39;s mouth and began squeezing the bag in coordination with the chest compressions according to a predetermined protocol. 
     Before the monitoring begins, the process may have gathered certain data to aid in the monitoring. For example, as a rescuer sets up a defibrillator and hooks it to a victim, the defibrillator may ask the rescuer (on a display or via a spoken request) whether the rescuer is alone or is being aided, and might also ask how many additional rescuers are available. If the rescuer indicates that he or she is alone, then the system may follow a branch of programming that does not recommend switching of rescuers, but might more aggressively provide feedback in order to overcome the extra fatigue a solo rescuer will face. If the rescuer is accompanied, then the system may subsequently indicate when rescuers are to switch roles. The system may also assign a label to each rescuer, such as “Rescuer  1 ” and “Rescuer  2 ” or the actual names of the rescuers (which could have been programmed previously, such as for EMTs who use the system frequently, or could be obtained, such as by lay rescuers speaking their names into the device in response to prompts from the device). If there are three or more rescuers, instructions for rotating may be more complex—i.e., involving more than simply an instruction to switch positions, but instead telling each rescuer what component of CPR they should be performing for any particular time period. 
     A determination about the number of rescuers may also be made inferentially. For example, a ventilation bag may include electronics that report to a defibrillator or other box, and the box may sense that the bag is being deployed or used, or is being used simultaneous with chest compressions being performed, in order to infer that there are at least two rescuers. The defibrillator may adjust its operation accordingly in the manners discussed above in such a situation (e.g. by enabling prompts for rescuers to switch roles). 
     At box  404 , the process generates a chest compression quality score based on the observed prior chest compressions. For example, the quality score may be computed as a function of the depth and rate of one or more chest compressions that have been observed from the accelerometer puck. One such mechanism for computing a quality score is shown with respect to  FIG.  3    above. 
     At box  406 , external information is incorporated into the quality score, meaning that the information is external to the parameters that are indicating the current quality with which a particular component of CPR is being performed. With respect to chest compressions, the external components may include a pulse rate or respiration rate of a rescuer, indications about how that rescuer&#39;s performance degraded in prior sessions, predetermined time limits for the performance of chest compressions that may trump even adequate performance by a rescuer, and other such factors. Such an external factors may override the generated quality score, or may be incorporated into the quality score, such as to push it upward or downward depending on what the external factor is. For example, if the rescuer&#39;s pulse is abnormally high, the process may indicate that a new rescuer should take over chest compressions in response to an observed decrease in performance, in a manner that is more speedy than if the rescuer were observed to be calmer. 
     At box  408 , a determination is made with regard to whether the quality of the performance of the CPR component is adequate or not. With respect to chest compressions, adequate quality may largely be a function of the depth of chest compression and also a function of the rate of compression (though to a lesser degree). Other CPR component may have their quality determined using other factors and parameters. The overall quality level may be expressed as a threshold number, a threshold rate of change, or other appropriate threshold, which need not be a constant threshold, but could instead be a threshold that changes over time also. 
     If the quality is determined to be adequate, the process returns back to box  402  and continues monitoring the chest compressions using the accelerometer puck and determining the quality of such compressions. 
     If the quality is determined to not be adequate, at box  410 , the process provides an indication to the rescuer, and perhaps to others, than a provider of care should change. For example, the defibrillator may beep multiple times to indicate that a change in rescuers should occur between the tasks or components of chest compressions and operating the ventilation bag. Alternatively or in addition, visual indications may be given on a display of a defibrillator or may be displayed on a device mounted closer to the location where the rescuer is performing the particular component of CPR, such as adjacent to the hands of the rescuer when the hands are pressing on the sternum of a victim. In addition, haptic feedback may be provided to the rescuer, such as switching from periodic (metronomic) vibration in a unit under the rescuer&#39;s hands, to continuous vibration under the rescuer&#39;s hands, or another change in haptic feedback that differs from the feedback given when no change is to be made. 
     Using such a process, then, a system may adjust to the capabilities of various caregivers and maintain caregivers in a position to provide a particular component of care as long as they are able to provide for it. As a result, the system need not be stuck to preset time limits that might not reflect the actual standard of care that can be provided, but can instead vary based on the actual standard of care that is being given by a particular rescuer team in a particular situation. The process could result in better outcomes for victims tended to by such rescuers, and in a better experience for the rescuers themselves. 
     In certain circumstances, prompts for performing CPR may change the way in which CPR is to be performed in response to indications that there has been a degradation in performance. In particular, prompting of CPR at a sub-optimal level may be provided, as long as that sub-optimal level is better than wholly fatiguing a rescuer. For example, hemodynamics data indicates that depth of chest compressions may be more important to victim well-being than is rate of compressions—i.e., it may essentially not matter how fast you are performing compressions if none of those compressions is truly effective. As a result, the system may slow a rate (e.g., a metronome) of prompting compressions and may monitor how the depth of compressions changes in response to the prompted change in rate. Using stores hemodynamic data correlating depths and rates to effectiveness, the system may identify a most-preferred rate that maximizes the hemodynamic effect for a particular rescuer (using, e.g., the well-known Windkessel model or other approach). While such modifications may be made only after sensing that a particular rescuer is fatiguing, they can also be initiated at other points and in response to other criteria, including by making such adjustments throughout a rescue cycle (e.g., the rate of a metronome may be adjusted slightly and essentially continuously, and the combination of depth and rate that is measured from the rescuer may be input in real-time to a formula for computing hemodynamic effect, with subsequent changes in the rate of the metronome being made in an attempt to increase the hemodynamic effect within bounds of safety). 
       FIGS.  4 B and  4 C  are flowcharts of processes for capturing and using images form a rescue site. In particular,  FIG.  4 B  shows uses that may be made of image data acquired from cameras mounted to people or medical equipment.  FIG.  4 C  shows uses that may be made of images captured with cameras mounted to rescue vehicles. 
     Referring now to  FIG.  4 B , the process begins at box  412 , where cameras are mounted on objects at a rescue scene. For example, EMTs may don electronic glasses that perform a number of different data gathering and presentation operations, including capturing video of areas in front of the particular EMT. Also, a camera may be placed by an EMT onto part of a victim, such as by adhering a small, wireless communicating, battery-operated cameras to a victim&#39;s forehead. 
     At box  414 , images from the mounted cameras are captured. For example, at some point in a rescue, such as when a defibrillator or monitor is deployed, a signal may be sent to the cameras to cause them to begin capturing images. The images may be captured continuously, e.g., as motion video, or less continuously, e.g., as periodic fixed images capture every second or less frequently. The captured images may be stored at the devices to which the respective cameras are mounted and then transferred at a later time, such as after EMTs who are wearing cameras return to their ambulance. Alternatively, the images may be passed essentially in real time, e.g., to a mobile computing device operated by a rescuer, to a computing device in an ambulance, to a computing device in a piece of medical equipment such as a defibrillator or monitor. 
     At box  416 , the positions of the cameras are identified. For example, each camera may be provided with a sensor package that may identify an orientation (compass direction) that the camera is aimed and an inclination of the camera. In certain implementations an absolute position of each camera in 3D space may also be identified. Such positioning may be by beacon and triangulation, by indoor positioning system (IPS) using anchors on an ambulance and certain medical equipment (e.g., using the patient or a defibrillator as an anchor), GPS, and other such technologies. Alternatively, the locations of camera may be identified by cross-correlating information in images obtained by each of the cameras. For example, if three different cameras are capturing a common item simultaneously and the item is moving, the relative motion of the item in each captured stream of images may be used to identify the relative position of each camera to the other cameras. 
     At box  418 , objects in the field of view of each camera are identified, as are the positions of those objects. In particular, for example, the positions of identified rescuers may be identified, and their motions may also be identified. As one example, reciprocating up and down motion of a portion of one rescuer may be used to automatically identify that such rescuer is currently applying chest compressions to the victim. That rescuer may then be identified using facial recognition or near field communication mechanisms worn by the rescuer and included in a puck against which the rescuer performs the CPR, among other methods of identifying the position and location of the rescuer. 
     The location and identity of items at a rescue scene may be performed with additional sensors or alternative sensors. For example, laser scanning of an area may be used to identify the locations of items, and scanning over time may be used to identify the movement of those items, though laser scanning may have more difficulties with identifying items other than items having a particular shape. Separately or in combination, laser scanning may be performed on patterned codes, like bar codes, which may permit identification of an item though without locating the item (other than knowing it is within a scanning area). Also, ultrasound systems (along with the other systems described here, alone or in combination with each other) may similarly be used for locating items at the scene and for generating information to report such locations for immediate use by off-site. Also, as described, various objects attached to medical devices, rescuers, victims or other objects, such as magnetic sensors and magnets, near-field communication (NFC) devices, and the like may further be used to determine the locations of items relative to each other—such as to determine what actions are being performed by which rescuer at any given time. 
     At box  420 , the image data from multiple cameras may be combined. For example, various known multi-image fusion techniques may be employed to form a single larger images from portions made up of the images captured from different locations by different cameras. The Microsoft Image Composite Editor is one example of a system that performs such image combination. 
     At box  422 , a review of the rescue is provided using the image and other data. Such review may occur in real-time, such as by mass disaster personnel receiving a feed of the data during a disaster. The review may also occur later, such as by the rescuers and supervisors reviewing their rescuers&#39; performance and identifying places where improvement could be made. For example, wearing the same glasses that captured the images and assisted them with patient data during the rescue, the rescuers may be played video of the rescue that is overlaid with data about the rescuer, such as data like that discussed elsewhere in this disclosure that indicates fatiguing of rescuers. As a result, a rescuer may recognize actions that he or she takes as he or she starts to tire, and may adapt for such actions in future rescues. 
       FIG.  4 C  shows a process by which a camera on a rescue vehicle may capture images at a rescue scene. Such capture may occur as an alternative to, or in addition to, the capture discussed with respect to  FIG.  4 B . 
     The process begins at box  430 , where cameras are mounted on rescue vehicles. For example, a fleet of vehicles for a municipality may have 360 degree cameras, like those used with GOOGLE STREET VIEW™ cars, attached to their roofs or hoods. In particular, first responder vehicles may be so outfitted. 
     At box  432 , the occurrence of a rescue event is identified. As one example, a dispatcher may receive a call about an automotive accident or mass disaster (e.g., chemical release) and may call to multiple first responders to identify a vehicle to investigate the call. 
     At box  434 , the particular vehicle that first responds drives through the event site while capturing images. For example, the 360 degree camera may not be programmed to run continuously, but instead a dash-mounted button may activate the camera. When a first responder arrives on the scene, he or she may be trained to push the button and drive from one end of the scene to the other while the camera captures images and position data for the camera (box  436 ), in a manner like GOOGLE STREET VIEW™ cameras capture such data under non-emergency situations. 
     At box  438 , the captured images and associated data are transmitted to a remote site for review. For example, an emergency management center may receive such data where personnel are located for coordinating a large-scale response to emergencies. Thus, at box  440 , an application is used at such a site to navigate the area of the rescue event. Thus a desktop application with functionality like STREETVIEW may be employed while one or more emergency response personnel view the images to ascertain the situation on-site so as to identify additional resources that need to be sent to the site. For example, such analysis may identify the presence of a number of wounded people or certain infrastructure damage. Such images may be used by response personnel at a central planning center to deploy more ambulances to a site, to identify personnel capable of repairing the infrastructure damage (e.g., a broken pipeline), or assist in other ways. 
     The described method thus provides a very quick and convenient way for a first responder to capture comprehensive imaging of an emergency site without substantially delaying that first responder&#39;s ability to immediately begin caring for injured victims at the site. Central responders may then have a more complete understanding of the on-site situation than could be delivered by the first responder verbally or with basic photos taken manually by the first responder. Also, a virtual reality or other navigation application may be used to more fully immerse the remote workers in the site so that they more fully understand the situation on-site and can better coordinate a response to it. 
       FIG.  5 A  shows a defibrillator showing certain types of information that can be displayed to a rescuer. In the figure, a defibrillation device  500  with a display portion  502  provides information about patient status and CPR administration quality during the use of the defibrillator device. As shown on display  502 , during the administration of chest compressions, the device  500  displays information about the chest compressions in box  514  on the same display as is displayed a filtered ECG waveform  510  and a CO2 waveform  512  (alternatively, an SpO2 waveform can be displayed). 
     During chest compressions, the ECG waveform is generated by gathering ECG data points and accelerometer readings, and filtering the motion-induced (e.g., CPR-induced) noise out of the ECG waveform. Measurement of velocity or acceleration of chest compression during chest compressions can be performed according to the techniques taught by U.S. Pat. No. 7,220,235, titled “Method and Apparatus for Enhancement of Chest Compressions During Chest Compressions,” the contents of which are hereby incorporated by reference in their entirety. Displaying the filtered ECG waveform helps a rescuer reduce interruptions in CPR because the displayed waveform is easier for the rescuer to decipher. If the ECG waveform is not filtered, artifacts from manual chest compressions can make it difficult to discern the presence of an organized heart rhythm unless compressions are halted. Filtering out these artifacts can allow rescuers to view the underlying rhythm without stopping chest compressions. 
     The CPR information in box  514  is automatically displayed when compressions are detected by a defibrillator. The information about the chest compressions that is displayed in box  514  includes rate  518  (e.g., number of compressions per minute) and depth  516  (e.g., depth of compressions in inches or millimeters). The rate and depth of compressions can be determined by analyzing accelerometer readings. Displaying the actual rate and depth data (in addition to, or instead of, an indication of whether the values are within or outside of an acceptable range) can also provide useful feedback to the rescuer. For example, if an acceptable range for chest compression depth is 1.5 to 2 inches, providing the rescuer with an indication that his/her compressions are only 0.5 inches can allow the rescuer to determine how to correctly modify his/her administration of the chest compressions (e.g., he or she can know how much to increase effort, and not merely that effort should be increased some unknown amount). 
     The information about the chest compressions that is displayed in box  514  also includes a perfusion performance indicator (PPI)  520 . The PPI  520  is a shape (e.g., a diamond) with the amount of fill that is in the shape differing over time to provide feedback about both the rate and depth of the compressions. When CPR is being performed adequately, for example, at a rate of about 100 compressions per minute (CPM) with the depth of each compression greater than 1.5 inches, the entire indicator will be filled. As the rate and/or depth decreases below acceptable limits, the amount of fill lessens. The PPI  520  provides a visual indication of the quality of the CPR such that the rescuer can aim to keep the PPI  520  completely filled. 
     As shown in display  500 , the filtered ECG waveform  510  is a full-length waveform that fills the entire span of the display device, while the second waveform (e.g., the CO2 waveform  512 ) is a partial-length waveform and fills only a portion of the display. A portion of the display beside the second waveform provides the CPR information in box  514 . For example, the display splits the horizontal area for the second waveform in half, displaying waveform  512  on left, and CPR information on the right in box  514 . 
     The data displayed to the rescuer can change based on the actions of the rescuer. For example, the data displayed can change based on whether the rescuer is currently administering CPR chest compressions to the patient. Additionally, the ECG data displayed to the user can change based on the detection of CPR chest compressions. For example, an adaptive filter can automatically turn ON or OFF based on detection of whether CPR is currently being performed. When the filter is on (during chest compressions), the filtered ECG data is displayed and when the filter is off (during periods when chest compressions are not being administered), unfiltered ECG data is displayed. An indication of whether the filtered or unfiltered ECG data is displayed can be included with the waveform. 
     Also shown on the display is a reminder  521  regarding “release” in performing chest compression. Specifically, a fatigued rescuer may begin leaning forward on the chest of a victim and not release pressure on the sternum of the victim at the top of each compression. This can reduce the perfusion and circulation accomplished by the chest compressions. The reminder  521  can be displayed when the system recognizes that release is not being achieved (e.g., signals from an accelerometer show an “end” to the compression cycle that is flat and thus indicates that the rescuer is staying on the sternum to an unnecessary degree). Such a reminder can be coordinated with other feedback as well, and can be presented in an appropriate manner to get the rescuer&#39;s attention. The visual indication may be accompanied by additional visual feedback near the rescuer&#39;s hands, and by a spoken or tonal audible feedback, including a sound that differs sufficiently from other audible feedback so that the rescuer will understand that release (or more specifically, lack of release) is the target of the feedback. 
       FIG.  5 B  shows the same defibrillator, but when performance of chest compressions has fallen below a determined quality standard. In this example, an alert box  522  is now shown across the bottom half of the display and over the top of information that was previously displayed to provide feedback to cause the rescuer to improve their administration of chest compressions. While the user can continue to perform chest compressions, the blockage of feedback information may further induce the fatigued user to stop performing chest compressions, and the information is more likely to be observed quickly by the rescuer since it is placed in an area on the display where the rescuer will already be looking for feedback. 
       FIGS.  6 A- 6 C  show example screens that may be displayed to a rescuer on a defibrillator. Each of the displays may be supplemented with a display like box  522  in  FIG.  5 B  when the defibrillator determines that rescuers providing a certain component of care (e.g., chest compressions) should be changed. 
       FIG.  6 A  shows exemplary information displayed during the administration of CPR chest compressions, while  FIGS.  6 B and  6 C  show exemplary information displayed when CPR chest compressions are not being sensed by the defibrillator. The defibrillator automatically switches the information presented based on whether chest compressions are detected. An exemplary modification of the information presented on the display can include automatically switching one or more waveforms that the defibrillator displays. In one example, the type of measurement displayed can be modified based on the presence or absence of chest compressions. For example, CO2 or depth of chest compressions may be displayed (e.g., a CO2 waveform  620  is displayed in  FIG.  6 A ) during CPR administration, and upon detection of the cessation of chest compressions, the waveform can be switched to display an SpO2 or pulse waveform (e.g., an SpO2 waveform  622  is displayed in  FIG.  6 B ). 
     Another exemplary modification of the information presented on the display can include automatically adding/removing the CPR information from the display upon detection of the presence or absence of chest compressions. As shown in  FIG.  6 A , when chest compressions are detected, a portion  624  of the display includes information about the CPR such as depth  626 , rate  628 , and PPI  630 . As shown in  FIG.  6 B , when CPR is halted and the system detects the absence of CPR chest compressions, the defibrillator changes the CPR information in the portion  624  of the display, to include an indication  632  that the rescuer should resume CPR, and an indication  634  of the idle time since chest compressions were last detected. In a similar manner, when the defibrillator determines that rescuers should change, the label  632  can change to a message such as “Change Who is Administering CPR.” In other examples, as shown in  FIG.  6 C , when CPR is halted, the defibrillation device can remove the portion of the display  624  previously showing CPR data and can display a full view of the second waveform. Additionally, information about the idle time  636  can be presented on another portion of the display. 
       FIGS.  7 A and  7 B  show defibrillator displays that indicate to a rescuer levels of perfusion being obtained by chest compressions that the rescuer is performing.  FIG.  7 A  shows exemplary data displayed during the administration of CPR chest compressions when the CPR quality is within acceptable ranges, while  FIG.  7 B  shows modifications to the display when the CPR quality is outside of the acceptable range. 
     In the example shown in  FIG.  7 B , the rate of chest compressions has dropped from 154 compressions per minute ( FIG.  7 A ) to 88 compressions per minute. The defibrillator device determines that the compression rate of 88 compressions per minute is below the acceptable range of greater than 100 compressions per minute. In order to alert the user that the compression rate has fallen below the acceptable range, the defibrillator device provides a visual indication  718  to emphasize the rate information. In this example, the visual indication  718  is a highlighting of the rate information. Similar visual indications can be provided based on depth measurements when the depth of the compressions is shallower or deeper than an acceptable range of depths. Also, when the change in rate or depth indicates that a rescuer is becoming fatigued, the system may display a message to switch who is performing the chest compressions, and may also emit aural or haptic feedback to the same effect. 
     In the examples shown in  FIGS.  7 A and  7 B , a perfusion performance indicator (PPI)  716  provides additional information about the quality of chest compressions during CPR. The PPI  716  includes a shape (e.g., a diamond) with the amount of fill in the shape differing based on the measured rate and depth of the compressions. In  FIG.  7 A , the depth and rate fall within the acceptable ranges (e.g., at least 100 compressions/minute (CPM) and the depth of each compression is greater than 1.5 inches) so the PPI indicator  716   a  shows a fully filled shape. In contrast, in  FIG.  7 B , when the rate has fallen below the acceptable range, the amount of fill in the indicator  716   b  is lessened such that only a portion of the indicator is filled. The partially filled PPI  716   b  provides a visual indication of the quality of the CPR is below an acceptable range. 
     As noted above with respect to  FIG.  5 A , in addition to measuring information about the rate and depth of CPR chest compressions, in some examples the defibrillator provides information about whether the rescuer is fully releasing his/her hands at the end of a chest compression. For example, as a rescuer tires, the rescuer may begin leaning on the victim between chest compressions such that the chest cavity is not able to fully expand at the end of a compression. If the rescuer does not fully release between chest compressions the quality of the CPR can diminish. As such, providing a visual or audio indication to the user when the user does not fully release can be beneficial. In addition, such factors may be included in a determination of whether the rescuer&#39;s performance has deteriorated to a level that the rescuer should be instructed to permit someone else perform the chest compressions, and such information may be conveyed in the various manners discussed above. 
     As shown in  FIG.  8 A , a visual representation of CPR quality can include an indicator of CPR compression depth such as a CPR depth meter  820 . The CPR depth meter  820  can be automatically displayed upon detection of CPR chest compressions. 
     On the CPR depth meter  820 , depth bars  828  visually indicate the depth of the administered CPR compressions relative to a target depth  824 . As such, the relative location of the depth bars  828  in relation to the target depth  824  can serve as a guide to a rescuer for controlling the depth of CPR compressions. For example, depth bars  828  located in a region  822  above the target depth bar  824  indicate that the compressions were shallower than the target depth, and depth bars  828  located in a region  826  below the target depth bar  824  indicate that the compressions were deeper than the target depth. Again, then depth is inadequate (along with perhaps other factors) for a sufficient time to indicate that the rescuer is fatiguing, an indicator to switch rescuers may be provided in the manners discussed above. 
     While the example shown in  FIG.  8 A  displayed the target depth  824  as a single bar, in some additional examples, the target depth can be displayed as a range of preferred depths. For example, two bars  829   a  and  829   b  can be included on the depth meter  820  providing an acceptable range of compression depths (e.g., as shown in  FIG.  8 B ). Additionally, in some examples, compressions that have depths outside of an acceptable range can be highlighted in a different color than compressions that have depths within the acceptable range of compression depths. 
     The depth bars  828  displayed on the CPR depth meter  820  can represent the compression depths of the most recent CPR compressions administered by the rescuer. For example, the CPR depth meter  820  can display depth bars  828  for the most recent 10-20 CPR compressions (e.g., the most recent 10 CPR compressions, the most recent 15 compressions, the most recent 20 CPR compressions). In another example, CPR depth meter  820  can display depth bars  828  for CPR compressions administered during a particular time interval (e.g., the previous 10 seconds, the previous 20 seconds). 
     In some additional embodiments, physiological information (e.g., physiological information such as end-tidal CO2 information, arterial pressure information, volumetric CO2, pulse oximetry (presence of amplitude of waveform possibly), and carotid blood flow (measured by Doppler) can be used to provide feedback on the effectiveness of the CPR delivered at a particular target depth. Based on the physiological information, the system can automatically determine a target CPR compression depth (e.g., calculate or look-up a new CPR compression target depth) and provide feedback to a rescuer to increase or decrease the depth of the CPR compressions. Thus, the system can provide both feedback related to how consistently a rescuer is administering CPR compressions at a target depth, and feedback related to whether the target depth should be adjusted based on measured physiological parameters. If the rescuers does not respond to such feedback and continues performed sub-optimal CPR, the system may then display an additional message to switch out the person performing CPR chest compressions. 
     In some examples, the system regularly monitors and adjusts the target CPR compression depth. In order to determine a desirable target depth, the system makes minor adjustments to the target CPR compression depth and observes how the change in compression depth affects the observed physiological parameters before determining whether to make further adjustments to the target compression depth. More particularly, the system can determine an adjustment in the target compression depth that is a fraction of an inch and prompt the rescuer to increase or decrease the compression depth by the determined amount. For example, the system can adjust the target compression depth by 0.1-0.25 inches (e.g., 0.1 inches to 0.15 inches, 0.15 to 0.25 inches, about 0.2 inches) and provide feedback to the rescuer about the observed compression depth based on the adjusted target compression depth. Then, over a set period of time, the system can observe the physiological parameters and, based on trends in the physiological parameters without making further adjustments to the target compression depth and at the end of the set time period, may determine whether to make further adjustments to the target compression depth. 
     And again, the actual performance of the rescuer against the revised target may be continually monitored to determine when the rescuer&#39;s performance has fallen below an acceptable level, so that the rescuer and perhaps others may be notified to change who is performing the chest compressions. Also, each of the relevant parameters of patient condition discussed above with respect to the various screenshots may be made one of multiple inputs to a process for determining when rescuers who are performing one component of a rescue technique should be switched out with another rescuer, such as for reasons of apparent fatigue on the part of the first rescuer. 
     While at least some of the embodiments described above describe techniques and displays used during manual human-delivered chest compressions, similar techniques and displays can be used with automated chest compression devices such as the AUTOPULSE device manufactured by ZOLL Medical, Mass. 
     The particular techniques described here may be assisted by the use of a computer-implemented device, such as a defibrillator or other computing device that includes computing capability. Such defibrillator or other device is shown in  FIG.  10   , and may communicate with and/or incorporate a computer system  800  in performing the operations discussed above, including operations for computing the quality of one or more components of CPR provided to a victim and generating feedback to rescuers, including feedback to change rescuers who are performing certain components of the CPR. The system  1000  may be implemented in various forms of digital computers, including computerized defibrillators laptops, personal digital assistants, tablets, and other appropriate computers. Additionally the system can include portable storage media, such as, Universal Serial Bus (USB) flash drives. For example, the USB flash drives may store operating systems and other applications. The USB flash drives can include input/output components, such as a wireless transmitter or USB connector that may be inserted into a USB port of another computing device. 
     The system  1000  includes a processor  1010 , a memory  1020 , a storage device  1030 , and an input/output device  1040 . Each of the components  1010 ,  1020 ,  1030 , and  1040  are interconnected using a system bus  1050 . The processor  1010  is capable of processing instructions for execution within the system  1000 . The processor may be designed using any of a number of architectures. For example, the processor  1010  may be a CISC (Complex Instruction Set Computers) processor, a RISC (Reduced Instruction Set Computer) processor, or a MISC (Minimal Instruction Set Computer) processor. 
     In one implementation, the processor  1010  is a single-threaded processor. In another implementation, the processor  1010  is a multi-threaded processor. The processor  1010  is capable of processing instructions stored in the memory  1020  or on the storage device  1030  to display graphical information for a user interface on the input/output device  1040 . 
     The memory  1020  stores information within the system  1000 . In one implementation, the memory  1020  is a computer-readable medium. In one implementation, the memory  1020  is a volatile memory unit. In another implementation, the memory  1020  is a non-volatile memory unit. 
     The storage device  1030  is capable of providing mass storage for the system  1000 . In one implementation, the storage device  1030  is a computer-readable medium. In various different implementations, the storage device  1030  may be a floppy disk device, a hard disk device, an optical disk device, or a tape device. 
     The input/output device  1040  provides input/output operations for the system  1000 . In one implementation, the input/output device  1040  includes a keyboard and/or pointing device. In another implementation, the input/output device  1040  includes a display unit for displaying graphical user interfaces. 
     The features described can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. The apparatus can be implemented in a computer program product tangibly embodied in an information carrier, e.g., in a machine-readable storage device for execution by a programmable processor; and method steps can be performed by a programmable processor executing a program of instructions to perform functions of the described implementations by operating on input data and generating output. The described features can be implemented advantageously in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. A computer program is a set of instructions that can be used, directly or indirectly, in a computer to perform a certain activity or bring about a certain result. A computer program can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. 
     Suitable processors for the execution of a program of instructions include, by way of example, both general and special purpose microprocessors, and the sole processor or one of multiple processors of any kind of computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. The essential elements of a computer are a processor for executing instructions and one or more memories for storing instructions and data. Generally, a computer will also include, or be operatively coupled to communicate with, one or more mass storage devices for storing data files; such devices include magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, ASICs (application-specific integrated circuits). 
     To provide for interaction with a user, the features can be implemented on a computer having an LCD (liquid crystal display) or LED display for displaying information to the user and a keyboard and a pointing device such as a mouse or a trackball by which the user can provide input to the computer. 
     The features can be implemented in a computer system that includes a back-end component, such as a data server, or that includes a middleware component, such as an application server or an Internet server, or that includes a front-end component, such as a client computer having a graphical user interface or an Internet browser, or any combination of them. The components of the system can be connected by any form or medium of digital data communication such as a communication network. Examples of communication networks include a local area network (“LAN”), a wide area network (“WAN”), peer-to-peer networks (having ad-hoc or static members), grid computing infrastructures, and the Internet. 
     The computer system can include clients and servers. A client and server are generally remote from each other and typically interact through a network, such as the described one. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. 
     Many other implementations other than those described may be employed, and may be encompassed by the following claims.