Patent Description:
A tracheal tube is a catheter that is inserted into the trachea to establish and maintain a subject's airway. Tracheal tubes are frequently used for airway management in settings of general anesthesia, critical care, mechanical ventilation and emergency medicine. Tracheal tubes can be used to ensure an adequate exchange of oxygen and carbon dioxide, to deliver oxygen in higher concentrations than found in air, or to administer gases to a subject.

An endotracheal tube is a specific type of tracheal tube that is usually inserted through the mouth or nose. It is a breathing conduit designed to be placed into the airway of critically injured, ill or anesthetized subjects in order to perform positive pressure ventilation of the lungs and to prevent the possibility of aspiration or airway obstruction.

Intubation generally refers to the placement of a tracheal tube into the trachea of a subject to maintain an open airway, provide ventilatory assistance, or to serve as a conduit through which to administer certain drugs. Intubation is generally performed in critically injured, ill or anesthetized subjects to facilitate ventilation of the lungs and to prevent the possibility of asphyxiation or airway obstruction.

Methods to confirm proper tracheal tube placement include direct visualization during insertion as the tip of the tracheal tube passes through the glottis or indirect visualization of the tracheal tube within the trachea using a device such as a bronchoscope. If a tracheal tube is properly placed, equal bilateral breath sounds may be heard when listening to the chest of a subject with a stethoscope. This technique may be referred to as an auscultation of the chest. Further, equal bilateral rise and fall of the chest wall will be apparent with ventilatory excursions when the tracheal tube is properly placed into the trachea. If breath sounds are heard when listening to the area over a subject's stomach, this may indicate an improper placement of the tracheal tube into the esophagus. When the tube is properly placed, a small amount of water vapor may be evident within the lumen of the tracheal tube with each exhalation and there should be no gastric contents in the tracheal tube at any time.

Capnography has emerged as an important tool for confirmation of proper tube placement within the trachea. Other methods to detect tracheal tube placement using instruments include the use of a colorimetric end-tidal carbon dioxide detector and transthoracic impedance detection. Document <CIT> describes an automated interpretive medical care system with an extensive amount of variants used in different environments such as doctors' offices, ambulances and hospitals. In particular, a system for use in an on scene environment, such as a patient's home for detecting presence and severity of bronchospasm after a patient called an emergency service, is disclosed with reference to <FIG> and <FIG>. The system includes a plurality of sensors and, in particular, a capnograph, which are connected to a computer. Depending on various measurement results, which are provided to the computer, according to certain processing rules, various display messages are output by the computer, including an allowed message to check for tube dislodgement of an intubation tube. Document <CIT> describes a medical system comprising a manual patient ventilation unit and at least one sensor to be positioned in the airflow path of a patient, which is capable of sensing a presence of ventilation air flow, measuring a gas flow rate in the airflow path and sensing gas pressure in the airflow path. Based on the measurements, gas flow value is calculated and ventilation quality parameters comprising spirometric information are determined. On the basis of the determined ventilation quality parameters, feedback is given to a user. In embodiments, transthoracic impedance measurements can be performed, for example, for determining dislodgement of an endotracheal tube. Further, in embodiments, the system may comprise an accelerometer which can be used for detecting a dislocation of the endotracheal tube such as in view of movements or vibrations during transport. Document <CIT>describes a device for indication of the percentage of carbon dioxide in a person's exhaled air when breathing occurs through a means conducting the airflow. In particular, detection and evaluation of the parameter "end-tidal carbon dioxide" (ETCO<NUM>) are discussed. A particular aspect concerns proper placement of an endotracheal tube, i.e. in the proper part of the throat. The article "<NPL> describes capnography as a means for determining correct placement of an endotracheal tube (correctly in the trachea or accidentally in the esophagus) and comes to the conclusion that neither capnography nor any other methods taken alone can confirm correct placement with sufficient reliability. Inter alia, the technique of auscultation of breath sounds is discussed.

The present invention is a ventilation monitoring system for assisting in proper placement of an endotracheal tube in a subject as it is defined in claim <NUM> and a method for monitoring placement of an endotracheal tube in a trachea of a subject as defined in claim <NUM>.

Embodiments of the ventilation monitoring system are defined in the dependent claims.

<FIG> is a diagram showing ventilation monitoring device <NUM> and subject <NUM> intubated with an endotracheal tube <NUM> according to an example. A tracheal tube is a catheter that is inserted into the trachea of subject <NUM> to establish and maintain an open airway and to ensure adequate exchange of oxygen and carbon dioxide. An endotracheal tube such as endotracheal tube <NUM> is a specific type of tracheal tube that is usually inserted through the subject's mouth or nose. Many types of tracheal tubes such as endotracheal tube <NUM> may be used with embodiments of the present technology. For example, airway management tubes from King Systems of Noblesville, Indiana such as the King LT(S)-D airway tube or the Combitube ™ from Covidien of Mansfield, Massachusetts may be used.

Ventilation bag <NUM> coupled with the ventilation bag connector <NUM>, capnography sensor <NUM> and endotracheal tube <NUM> allows air to be forced into the subject's lungs as ventilation bag <NUM> is squeezed. Ventilation bag <NUM> may be equipped with a valve to allow the subject's exhalation gases to be released into the air without the possibility of backflow into ventilation bag <NUM>. The assembly permits gases exchanged with the subject's lungs to flow through and be monitored by capnography sensor <NUM>.

A capnography sensor such as capnography sensor <NUM> monitors the concentration or partial pressure of carbon dioxide (CO<NUM>) in the respiratory gases of the subject. Capnography sensor <NUM> communicates information related to the subject's respiratory gases such as CO<NUM> concentration in mm HG, end-tidal CO<NUM>, inspired CO<NUM> and respiratory rate to ventilation monitoring device <NUM> through communication cable <NUM>. Many capnography sensors on the market today may be used with embodiments of the present technology including but not limited to the Capnostat ® <NUM> or Capnostat ® <NUM> Mainstream CO<NUM> Sensors manufactured by Respironics, Inc. of Murrysville, Pennsylvania.

Communication cable <NUM> may be any type of communication cable or set of wires, which allows data to be exchanged between ventilation monitoring device <NUM> and capnography sensor <NUM> such as but not limited to an RS-<NUM> cable, Universal Serial Bus (USB) cable or Ethernet cable. Communication between ventilation monitoring device <NUM> and capnography sensor <NUM> may be a wireless communication channel such as but not limited to IEEE <NUM> wireless local area network (WLAN) or low-power radio frequency (RF) communication such as Bluetooth.

Examples of the present technology utilize principles as described in <CIT>. Electrodes 135a and 135b are electrically coupled with ventilation monitoring device <NUM> using cables <NUM> and <NUM>, respectively, as shown in <FIG>. Electrodes 135a and 135b are positioned across the subject's thoracic cavity and attached to the subject, one electrode anterior and the other electrode posterior, for example. In the embodiment, electrodes 135a and 135b are electro-cardiogram (ECG) signal pickup electrodes, but electrodes 135a and 135b may be any type of suitable electrodes capable of measuring a thoracic impedance of a subject. The ventilation monitoring device <NUM> is configured with electrodes 135a and 135b to monitor changes in the transthoracic impedance of subject <NUM>. If endotracheal tube <NUM> is properly placed in the subject's trachea and the subject's lungs are ventilated using ventilation bag <NUM>, ventilation monitoring device <NUM> will detect a change in impedance across the subject's thorax between electrodes 135a and 135b. If the endotracheal tube <NUM> has not been properly placed, for example, it was placed in the subject's esophagus, or has become dislodged, ventilation monitoring device <NUM> will not measure any significant impedance change across the subject's thorax and a corresponding indication may be conveyed to the user.

<FIG> is a block diagram of system <NUM> comprising ventilation monitoring device <NUM>, capnography sensor <NUM> and electrodes 135a and 135b according to an example. In an embodiment, ventilation monitoring device <NUM> is a dedicated ventilation monitor comprising examples of the present technology for at least the purpose of determining whether a subject's tracheal tube is properly placed. In another embodiment, ventilation monitoring device <NUM> is a part of a medical monitor and/or defibrillator such as the Zoll E-Series Monitor Defibrillator manufactured by Zoll Medical Corporation of Chelmsford, Massachusetts, which further comprises examples of the present technology.

In the embodiment, ventilation monitoring device <NUM> comprises at least one processor such as processor <NUM> and at least one memory such as volatile memory <NUM> or a non-volatile memory <NUM> including computer program code, which is configured to determine whether a subject's tracheal tube is properly placed. Volatile memory <NUM> and/or a non-volatile memory <NUM> may be removable by a user.

Volatile memory <NUM> may comprise a cache area for the temporary storage of data. Non-volatile memory <NUM> may further comprise an electrically erasable programmable read only memory (EEPROM), flash memory, and/or the like. In an embodiment, ventilation monitoring device <NUM> may use memory to store information and/or data including computer program code to implement one or more features of ventilation monitoring device <NUM> including but not limited to computer program code for determining whether an intubated subject's tracheal tube is properly placed.

Ventilation monitoring device <NUM> may comprise at least one processor such as processor <NUM> and at least one other processing component. Processor <NUM> may comprise circuitry for implementing medical monitoring features such as determining whether an intubated subject's tracheal tube is properly placed as well as other medical monitor functionality. For example, the at least one processor <NUM> may comprise a digital signal processor device, a microprocessor device, a digital to analog converter, other support circuits, and/or the like. Further, the processor <NUM> may comprise features to operate one or more software programs. In an embodiment, the processor <NUM> may be capable of operating at least one software program to implement functionality for determining whether an intubated subject's tracheal tube is properly placed. For example, the at least one software program may comprise a connectivity program to allow the ventilation monitoring device <NUM> to transmit and receive Internet and/or cellular data over a wired or wireless medium, such as but not limited to voice, text, email messages, location-based content, web page content, fax content and/or the like.

In an embodiment, the ventilation monitoring device <NUM> comprises at least one antenna <NUM> to communicate with a transmitter <NUM> and a receiver <NUM>. Transmitter <NUM> and/or receiver <NUM> are coupled with a network interface <NUM> for transmitting and receiving data with devices such as other medical equipment or emergency medical services centers. Processor <NUM> may be configured to provide at least one signal to the transmitter <NUM> and receive at least one signal from receiver <NUM>. Further, transmitter <NUM> and/or receiver <NUM> coupled with network interface <NUM> may be configured to transmit and receive analog and/or digital voice communications such as with emergency medical personnel.

The ventilation monitoring device <NUM> may further comprise an identifier, such as international mobile equipment identification (IMEI) code, capable of uniquely identifying itself. For example, the processor <NUM>, using the stored instructions, may determine an identity, e.g., using cell identification information.

Ventilation monitoring device <NUM> further comprises a user interface <NUM>, which may include at least one input and/or output device coupled with processor <NUM> such as but not limited to a display such as display <NUM>, touch screen, keyboard, keypad, mouse and/or the like. In an embodiment, display <NUM> shown in <FIG> and <FIG> coupled with processor <NUM> is capable of displaying at least one of an indication of a subject's breath, a representation of a subject's breathing pattern and information related to a determination of whether an intubated subject's tracheal tube is properly placed. In an embodiment, a keypad, keyboard, buttons and/or other input features such as soft keys <NUM> of <FIG> enables a user to configure ventilation monitoring device <NUM> to perform functions such as confirming whether a breath has been detected during an auscultation. Further, the keypad or keyboard may enable a user to compose text-based messages and communicate with other users such as emergency medical personnel.

In an embodiment, ventilation monitoring device <NUM> further comprises a speaker <NUM> and/or a microphone <NUM>. Speaker <NUM>, for example, may enable the ventilation monitoring device to provide voice instructions to a user. Microphone <NUM>, for example, may enable a user to speak with emergency medical personnel via network interface <NUM> at an emergency response facility.

In an embodiment, ventilation monitoring device <NUM> is a medical monitoring device further comprising features such as electrocardiogram (ECG) monitoring and/or defibrillation. For example, ventilation monitoring device <NUM> may comprise ECG monitoring unit <NUM> and/or defibrillation unit <NUM>. In an embodiment, ventilation monitoring device <NUM> further comprises at least one power supply such as battery <NUM> for providing power to ventilation monitoring device <NUM> and/or for charging defibrillation unit <NUM>. Ventilation monitoring device <NUM> may further comprise a location determining unit <NUM>. Location determining unit <NUM> may comprise a global positioning system (GPS) receiver <NUM> for receiving a geographic location of ventilation monitoring device <NUM>. Location determining unit <NUM> may use cell identification information, for example, to determine a geographic location for ventilation monitoring device <NUM>. Ventilation monitoring device <NUM> may further comprise programmable timer <NUM> for determining intervals of time such as a time period between indications of a subject's breath.

System <NUM> may comprise a capnography sensor <NUM> and/or electrodes 135a and 135b. In some embodiments, either a capnography sensor or electrodes configured with system <NUM> to determine transthoracic impedance may be used to detect a subject's breath. In some embodiments, both a capnography sensor and electrodes may be used simultaneously with system <NUM> to detect a subject's breath. Using both a capnography sensor and electrodes together may increase the reliability of breath detection. For example, if a capnography sensor such as capnography sensor <NUM> becomes dislodged from the subject tracheal or malfunctions, electrodes 135a and 135b may be used as a fallback or redundant means to detect a subject's breath. Likewise, if either electrodes 135a or 135b become disconnected from the subject, capnography sensor <NUM> may be used as a fallback or redundant means to detect a subject's breathe.

When capnography sensor <NUM> is used with system <NUM>, processor <NUM> may configure and/or calibrate capnography sensor <NUM> for use with ventilation monitoring device <NUM>. In an embodiment, processor <NUM> is configured with at least one memory such as non-volatile memory <NUM> to detect at least one indication of a subject's breath by receiving information related to the subject's respiratory gases such as CO<NUM> concentration, end-tidal CO<NUM>, inspired CO<NUM> and respiratory rate from capnography sensor <NUM>. In the embodiment, ventilation monitoring device <NUM> may comprise a capnography sensor interface <NUM>, which may include a device driver configured with processor <NUM> to read one or more memory locations from capnography sensor <NUM> in order to receive at least one indication of the subject's breath.

When electrodes 135a and 135b are used with system <NUM> to measure transthoracic impedance, processor <NUM> may initially configure and/or calibrate electrodes 135a and 135b for use with ventilation monitoring device <NUM>. In an embodiment, processor <NUM> is configured with at least one memory to detect at least one indication of a subject's breath by receiving impedance information from electrode 135a and 135b via electrodes interface <NUM> using principles described in <CIT>.

In some embodiments of the present invention, an indication from capnography sensor <NUM> of a subject's breath alone is sufficient evidence for processor <NUM> to determine that an intubated subject's tracheal tube is properly placed. In some embodiments, an indication via electrodes 135a and 135b of a subject's breath alone is sufficient evidence for processor <NUM> to determine that an intubated subject's tracheal tube is properly placed. In some embodiments, an indication of a subject's breath from both capnography sensor <NUM> and via electrodes 135a and 135b is required for processor <NUM> to determine that an intubated subject's tracheal tube is properly placed. In some embodiments, an indication from at least one of capnography sensor <NUM> and electrodes 135a and 135b along with a confirmation from a user of a positive result of at least one auscultation is required for processor <NUM> to determine that an intubation subject's tracheal tube is properly placed.

In some embodiments, the term "auscultation" as used herein means manual auscultation performed by a medical professional in the conventional sense. In some embodiments, acoustic cardiography performed by a device such as an Audicor ® manufactured by Inovise Medical, Inc. of Portland, Oregon may be used in place of manual auscultation to determine breath sounds or in some cases, a lack thereof. As such, "auscultation" as used herein may mean utilizing a device such as an Audicor® to perform a diagnostic technique such as cardiography on a subject to record and algorithmically interpret acoustical data to determine evidence of breath sounds or a lack thereof.

In an embodiment of the present invention, ventilation monitoring device <NUM> comprises at least one accelerometer such as accelerometer <NUM> coupled with processor <NUM> for detecting movement of the ventilation monitoring device <NUM>. In an embodiment of the present invention, system <NUM> comprises an accelerometer such as accelerometer <NUM>, which is external to but communicatively coupled with ventilation monitoring device <NUM> capable of detecting movement of subject <NUM>. For example, accelerometer <NUM> may be coupled with capnography sensor <NUM>, tracheal tube <NUM>, subject <NUM>, the subject's stretcher or bed or other locations on or near subject <NUM>. In an embodiment of the present invention, the at least one processor <NUM> and at least one memory <NUM> including computer program code are configured to receive a value from accelerometer <NUM> and/or accelerometer <NUM> related to motion of ventilation monitoring device <NUM> and/or subject <NUM>, respectively, and provide a prompt to a user when the value exceeds a predetermined threshold. For example, a value from an accelerometer which exceeds a predetermined threshold may indicate that subject <NUM> and/or ventilation monitoring device <NUM> received one or more mechanical shocks, for example, if ventilation monitoring device <NUM> or a stretcher carrying subject <NUM> was bumped against a wall during emergency transportation of subject <NUM>. In the embodiment, a user may be prompted to inspect the subject's tracheal tube or execute ventilation monitor testing using ventilation monitoring device <NUM> to be sure the tracheal tube did not become dislodged.

<FIG> shows an initial screen <NUM> of the ventilation monitoring device <NUM> of <FIG> according to an example. If ventilation monitoring device <NUM> is a dedicated ventilation monitor comprising examples of the present technology, an initial screen such as initial screen <NUM> may be displayed after ventilation monitoring device <NUM> is powered-up and completes a self-test. Alternatively, if ventilation monitoring device <NUM> is a part of a medical monitor and/or defibrillator which further comprises examples of the present technology, an initial screen such as initial screen <NUM> may be displayed at any point when the user selects the ventilation monitor feature on the device.

An initial screen of ventilation monitoring device <NUM> may comprise, for example, instructions to be performed by a user, user interface configurable parameters, status and/or the like. In an embodiment, initial screen <NUM> comprises instructions informing a user of ventilation monitoring device <NUM> to (<NUM>) prepare the subject and ventilation monitoring system, (<NUM>) test and confirm that the subject was intubated properly and (<NUM>) monitor ventilations.

In an embodiment, initial screen <NUM> further comprises a set of menu options "start ventilations", "Settings" and "Exit", which correspond to buttons <NUM>, <NUM> and <NUM>, respectively. Buttons <NUM>, <NUM> and <NUM> may be known as "soft keys" in the art since each key may correspond to multiple functions such that the present function of each key is related to the screen the user is presently viewing. The present function of a soft key such as soft key <NUM> is indicated by the description such as "Settings", which is located adjacent to the button.

In the embodiment, the user presses "Start Ventilations" soft key <NUM> once the subject has been intubated and ventilation monitoring is to begin. A user may press the "Exit" soft key <NUM> to end ventilation monitoring.

<FIG> is a diagram of a settings screen <NUM> of a ventilation monitoring device <NUM> according to an example. In a settings screen such as settings screen <NUM>, a user may modify one or more parameters related to the configuration of ventilation monitoring device <NUM>. In the embodiment, soft key <NUM> corresponding to the configurable parameter, "Source" enables a user to specify whether a capnography sensor, electrodes or both a capnography sensor and electrodes will be used with ventilation monitor. Further, "Source" may enable a user to specify that "either" the capnography sensor or electrodes may determine that a breath has been detected.

In the embodiment, soft key <NUM> corresponding to the configurable parameter, "Mode", may be used to set the ventilation monitor device <NUM> to a manual mode or automatic mode. In a manual mode, a user must press a "confirm" soft key for each auscultation performed on the subject, which indicates a positive result. In an automatic mode, a user may press a "confirm" soft key only once when all auscultations are performed on the subject and corresponding breaths were detected during each auscultation.

In the embodiment, soft key <NUM> enables a user to set the number of auscultations, which will be performed to <NUM> or <NUM>. If a user chooses <NUM> auscultations, then ventilation monitor device <NUM> will prompt the user to auscultate the subject's left lung, right lung and abdomen. If a user chooses <NUM> auscultations, then ventilation monitor device <NUM> will prompt the user to auscultate the subject's left lung, left axillary right lung, right axillary and abdomen.

In the embodiment, soft key <NUM> configures a timer for all tests performed. In the embodiment, timer such as timer <NUM> of <FIG> may be set to <NUM>, <NUM>, <NUM>, <NUM> or <NUM> seconds. In the embodiment, all of the tests being performed on the subject must be completed within the configured time limit or else a failure status for the testing will be reported. In another embodiment, each one of the tests being performed on the subject must be completed within the configured time limit or else a failure status for the testing will be reported. In this embodiment, the timer may be reset after each successful test. A user may press the "Exit" soft key <NUM> to exit the settings screen.

<FIG> is a diagram of a testing screen <NUM> of ventilation monitoring device <NUM> showing testing in progress, ventilation monitoring device <NUM> configured in a manual mode for use with capnography sensor <NUM> and a protocol comprising three auscultations according to an example. In the embodiment, the source is configured to "CO<NUM>" using soft key <NUM>, which means that only the capnography sensor <NUM> of <FIG> and <FIG> will be used as an automated means to detect the subject's breath. Manual mode, which requires the user to confirm a positive result of each auscultation performed using soft key <NUM>, is configured by the user using soft key <NUM>. The <NUM>-auscultation protocol, which includes user auscultations of the left lung, right lung and abdomen, is configured by the user using soft key <NUM>. At any point, the testing may be canceled by using soft key <NUM>.

In the embodiment, since the capnography sensor <NUM> is being used with ventilation monitoring device <NUM>, capnograph <NUM> is displayed on testing screen <NUM>. If a capnography sensor was not being used, i.e., "Source" corresponding to soft key <NUM> was configured to "Electrodes", then a capnograph would not be displayed and a transthoracic impedance graph would be displayed instead. If both the capnography sensor <NUM> and electrodes 135a and 135b were being used i.e. "Source:" was configured to "both", then both the capnograph and transthoracic impedance graph may be displayed on screen <NUM>.

According to testing screen <NUM>, the present status <NUM> of the testing indicates "Waiting for ventilation", which means that ventilation monitoring device <NUM> is waiting for capnography sensor <NUM> to detect a positive air flow from ventilation bag <NUM> of <FIG>. The results of Test <NUM><NUM> indicate that the test passed. The results of Test <NUM><NUM> further show that a confirmation was provided by the user that subject's left lung was auscultated and <NUM> breaths were detected by capnography sensor <NUM>.

Further, according to testing screen <NUM>, the result of Test <NUM><NUM> indicates that capnography sensor <NUM> detected <NUM> breath, however, since the user has not confirmed a breath from auscultation of the right lung, test <NUM> has not completed. Test timer <NUM>, which was originally set to <NUM> seconds using soft key <NUM>, indicates that there are <NUM> seconds left in the overall testing period including the time to complete Test <NUM> and Test <NUM>. If Test <NUM> and Test <NUM> are not completed within the time period left, which is <NUM> seconds, then the overall testing will fail and Status <NUM> will report "Failed" and the reasons for the failure.

<FIG> is a diagram of a testing screen <NUM> on ventilation monitoring device <NUM> showing the testing has passed, the ventilation monitoring device <NUM> configured in a manual mode for use with capnography sensor <NUM> and a protocol comprising three auscultations according to an example. In the embodiment, screen <NUM> shows a continuation of the testing as shown in screen <NUM> of <FIG>. According to screen <NUM>, the results of Test <NUM><NUM> indicate that the user has confirmed with soft key <NUM> that the subject's right lung has been auscultated and at least one breath was detected. Further, since capnography sensor <NUM> has detected at least one breath, <NUM> breaths in this case, Test <NUM> has passed.

In the embodiment, the results of Test <NUM><NUM> indicate that the user has confirmed with soft key <NUM> that the subject's abdomen has been auscultated and no breathing was detected. Further, since capnography sensor <NUM> has detected at least one breath, <NUM> breaths in this case, Test <NUM> has passed. Since each of Test <NUM>, Test <NUM> and Test <NUM> have passed; overall status <NUM> indicates that the testing has passed. In an embodiment, the results of the overall testing including the results of each of the Tests, e.g. Test <NUM>, Test <NUM> and Test <NUM>, are saved in memory, for example, in a FLASH memory such as non-volatile memory <NUM> of <FIG>. At this point, the user may exit the Ventilation Monitor Testing by pressing soft key <NUM>.

<FIG> is a diagram of a testing screen <NUM> on ventilation monitoring device <NUM> showing that the testing has failed, the ventilation monitoring device <NUM> configured in a manual mode for use with capnography sensor <NUM> and a protocol comprising three auscultations according to an example. In the embodiment, screen <NUM> shows a continuation of the testing as shown in screen <NUM> of <FIG>.

In the embodiment, the results of Test <NUM><NUM> indicate that the test has failed, which has caused the overall testing Status <NUM> to indicate failure. Although the capnography sensor <NUM> detected <NUM> breaths of the subject, the user did not confirm a positive result of the subject's abdominal auscultation in Test <NUM> using soft key <NUM> within the timer period. As a result, test timer <NUM> counted down to <NUM> as indicated at <NUM> and the overall testing failed. Reasons for the failure of the overall testing <NUM> indicate that the timer expired and that a confirmation in Test <NUM> was not received.

<FIG> is a diagram of a testing screen <NUM> on ventilation monitoring device <NUM> showing that the testing has failed, the ventilation monitoring device <NUM> configured in a manual mode for use with capnography sensor <NUM> and a protocol comprising five auscultations according to an example In the embodiment, screen <NUM> shows that a user configured the ventilation monitor testing using soft key <NUM> to require <NUM> auscultations to be performed on the subject including auscultations of the subject's left lung, right lung, abdomen, left axillary and right axillary.

Testing screen <NUM> shows that Tests <NUM> through <NUM> have passed, however, Test <NUM> has failed. In Test <NUM><NUM>, although the user confirmed that at least one breath was detected during auscultation of the subject's right axillary, capnography sensor <NUM> did not detect at least one breath. Screen <NUM> shows the results of Test <NUM><NUM>, which indicate that the subject's breath count did not increment (remained at <NUM>) and Test <NUM> failed as a result. The failure of a capnography sensor to detect a breath may be due to a number of reasons such as endotracheal tube <NUM> of <FIG> becoming dislodged from the subject's trachea or the subject may have stopped breathing. As ventilation monitoring device <NUM> was waiting for capnography sensor <NUM> to detect a breath from subject <NUM>, test timer <NUM> counted down to <NUM> as indicated at <NUM> and triggered a failure of the overall testing <NUM>. Screen <NUM> further indicates that reasons <NUM> for the failure of the overall testing was that the timer expired and no breath was detected in Test <NUM>.

<FIG> is a diagram of a testing screen <NUM> on ventilation monitoring device <NUM> showing that the testing has failed, the ventilation monitoring device <NUM> configured in a manual mode for use with capnography sensor <NUM>, electrodes 135a and 135b, and a protocol comprising five auscultations according to an example. In the embodiment, screen <NUM> shows that a user configured the ventilation monitor testing using soft key <NUM> to require <NUM> auscultations to be performed on the subject including auscultations of the subject's left lung, right lung, abdomen, left axillary and right axillary. Further, screen <NUM> shows that the user configured the source <NUM> to be both the capnography sensor <NUM> and electrodes 135a and 135b of <FIG>. As a result, both a capnograph <NUM> and transthoracic impedance waveform <NUM> are shown in screen <NUM>.

Testing screen <NUM> shows that Tests <NUM> through <NUM> have passed, however, Test <NUM> has failed. In Test <NUM>, although the user confirmed that at least one breath was detected during auscultation of the subject's left axillary, system <NUM> configured with capnography sensor <NUM> and electrodes 135a and 135b indicted a failure to detect a breath from subject <NUM>. Since source <NUM> is set to "both", the system <NUM> must detect a breath from both capnography sensor <NUM> and electrodes 135a and 135b. Screen <NUM> shows the results of Test <NUM><NUM>, which indicate that the subject's breath count did not increment (remained at <NUM>) and Test <NUM> failed as a result. Screen <NUM> further indicates that reasons <NUM> for the failure of the overall testing was that the timer expired and no breath was detected in Test <NUM> with respect to the transthoracic impedance testing using electrode 135a and 135b. Since source <NUM> was set to "both", even though system <NUM> may have detected a breath using capnography sensor <NUM>, the overall testing failed since no breath was detected with respect to the transthoracic impedance testing.

The failure of the transthoracic impedance to detect a breath may be due to a number of reasons such as electrode 135a or electrode 135b becoming disconnected from the subject's chest or back or the subject may be in repertory distress. As ventilation monitoring device <NUM> was waiting for the transthoracic impedance testing using electrodes 135a and 135b to detect a breath from subject <NUM>, test timer <NUM> counted down to <NUM> and triggered a failure of the overall testing indicated at <NUM>.

In another embodiment, if source <NUM> was set to "either" for example, a test such as Test <NUM> could pass providing that system <NUM> detected a breath using either capnography sensor <NUM> or transthoracic impedance testing and the user confirmed the presence of a breath by auscultation.

<FIG> is a diagram of a testing screen <NUM> on ventilation monitoring device <NUM> showing that the testing has passed, the ventilation monitoring device <NUM> configured in an automatic mode for use with capnography sensor <NUM>, electrodes 135a and 135b, and a protocol comprising five auscultations according to an example.

Screen <NUM> shows that the user configured the mode to be automatic using soft key <NUM>. As a result, the user may confirm a positive result for each of the auscultations performed by pressing confirm soft key <NUM> once when the auscultations are completed but before the expiration of test timer <NUM> at indicated at <NUM>. For example, according to screen <NUM> the user confirmed a positive result for each of the auscultations as indicated in result of Test <NUM><NUM>. Testing screen <NUM> shows that each of Tests <NUM> through <NUM> has passed and the status <NUM> for the testing indicates "Passed".

<FIG> is a flow diagram depicting a method <NUM> according to an example. Method <NUM> begins at <NUM>. At <NUM>, a timer is set. In an embodiment, the timer is a programmable timer such as programmable timer <NUM> of <FIG>. In the embodiment, the timer may be set to expire in a range between <NUM> and <NUM> seconds, however, other time periods are possible.

At <NUM>, a determination is made whether an indication of a subject's breath has been received from at least one sensor. The determination may be made by a computer or medical monitor such as system <NUM> of <FIG> configured with a capnography sensor such as capnographic sensor <NUM> of <FIG> or by determining a transthoracic impedance of the subject using, for example, electrodes 135a and 135b of <FIG> configured with system <NUM>. In some embodiments, system <NUM> may require indications of a subject's breath to be received from both the capnography sensor and electrodes 135a and 135b for the determination of the subject's breath to be made. In other embodiments, an indication of the subject's breath from one sensor only is necessary for system <NUM> to make the determination.

At <NUM>, if an indication of a subject's breath has not been received, then the flow proceeds to <NUM>. At <NUM>, if the timer has expired then the test has failed as indicated at <NUM>. At <NUM>, if the timer has not expired, then flow proceeds back to <NUM>.

At <NUM>, if an indication of a subject's breath has been received, then flow proceeds to <NUM>. At <NUM>, a determination is made whether a user has confirmed a positive result of an auscultation of the subject. For example, a user may auscultate a subject's left lung, right lung, left axillary or right axillary listening for an indication of the subject's breath. If a breath sound is heard during these auscultations, the subject's tracheal tube may be inserted correctly and the user may at this point confirm a positive result of the auscultation using system <NUM>, for example. If the user auscultates a subject's abdomen, then a positive result of the auscultation would be that no breath sounds are heard in the abdomen. Hearing breath sounds during auscultation of the abdomen may indicate that the tracheal tube has been inserted incorrectly, for example, into the subject's esophagus. If a positive result of an auscultation has not been confirmed, flow proceeds to <NUM>.

At <NUM>, if the timer has expired then the test has failed as indicated at <NUM>. At <NUM>, if the timer has not expired, then flow proceeds back to <NUM>. At <NUM>, if an indication of a subject's breath has been received, then the test has passed as indicated at <NUM> and the test ends at <NUM>.

Without in any way limiting the scope, interpretation, or application of the claims appearing below, a technical effect of one or more of the example embodiments disclosed herein is to provide a system for monitoring ventilation of a subject and determining whether a tracheal tube such as an endotracheal tube has been properly inserted in a subject's trachea. Examples of the present technology may be implemented in software, firmware, hardware, application logic or a combination of software, hardware and application logic. The software, firmware, application logic and/or hardware may reside on at least one system such as system <NUM> of <FIG>. In an embodiment, the application logic, software or an instruction set is maintained on any one of various conventional computer-readable media. In the context of this document, a "computer-readable medium" may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer, with one example of a computer, system <NUM>, described and depicted in <FIG>. A computer-readable medium may comprise a computer-readable storage medium that may be any media or means that can contain or store the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as in system <NUM> of <FIG>.

Claim 1:
A ventilation monitoring system (<NUM>), comprising:
a capnography sensor (<NUM>) configured to provide information representative of a breath of a subject (<NUM>); and
at least one processor (<NUM>) in communication with the capnography sensor (<NUM>), the at least one processor (<NUM>) configured to:
receive and process signals from the capnography sensor (<NUM>) representative of the subject's breath while an endotracheal tube (<NUM>) is positioned in a trachea of the subject (<NUM>),
monitor the received and processed signals to identify one or more indications of the subject's breath; and
provide a prompt for a user to inspect the endotracheal tube (<NUM>) to determine if the endotracheal tube (<NUM>) has become dislodged based on the identified one or more indications of the subject's breath;
characterized by
further comprising at least one accelerometer (<NUM>, <NUM>) in communication with the at least one processor (<NUM>) configured to detect movement of the at least one endotracheal tube (<NUM>), the capnography sensor (<NUM>), or the subject (<NUM>); and in that
the at least one processor (<NUM>) is further configured to
receive and process signals from the at least one accelerometer (<NUM>, <NUM>);
determine a value representative of movement of the endotracheal tube (<NUM>), the capnography sensor (<NUM>), or the subject (<NUM>) based on the received and processed signals from the at least one accelerometer (<NUM>, <NUM>); and
provide the prompt for the user to inspect the endotracheal tube (<NUM>) when the determined value representative of movement is greater than a predetermined threshold value.