CPR chest compression machine performing prolonged chest compression

Various types of chest compressions may be performed on a patient during a single resuscitation event. In embodiments one or more compression time parameters may be changed during the event, potentially optimizing blood flow for one side of the patient's heart, then the other. In some embodiments the event includes one or more prolonged compressions interposed between other compressions, potentially enabling the blood to reach to more remote locations than otherwise. In embodiments, a CPR chest compression machine includes a compression mechanism configured to perform successive compressions to the patient's chest, and a driver configured to drive the compression mechanism accordingly. In embodiments, a CPR metronome issues prompts for compressions accordingly.

BACKGROUND

In certain types of medical emergencies a patient's heart stops working. This stops the blood flow, without which the patient may die. Cardio Pulmonary Resuscitation (CPR) can forestall the risk of death. CPR includes performing repeated chest compressions to the chest of the patient so as to cause their blood to circulate some. CPR also includes delivering rescue breaths to the patient. CPR is intended to merely maintain the patient until a more definite therapy is made available, such as defibrillation. Defibrillation is an electrical shock deliberately delivered to a person in the hope of correcting their heart rhythm.

The repeated chest compressions of CPR are actually compressions alternating with releases. They cause the blood to circulate some, which can prevent damage to organs like the brain. For making this blood circulation effective, guidelines by medical experts such as the American Heart Association dictate suggested parameters for chest compressions, such as the frequency, the depth reached, fully releasing after a compression, and so on. The releases are also called decompressions.

Traditionally, CPR has been performed manually. A number of people have been trained in CPR, including some who are not in the medical professions just in case. However, manual CPR might be ineffective, and being ineffective it may lead to irreversible damage to the patient's vital organs, such as the brain and the heart. The rescuer at the moment might not be able to recall their training, especially under the stress of the moment. And even the best trained rescuer can become quickly fatigued from performing chest compressions, at which point their performance might be degraded. Indeed, chest compressions that are not frequent enough, not deep enough, or not followed by a full decompression may fail to maintain blood circulation.

The risk of ineffective chest compressions has been addressed with CPR chest compression machines. Such machines have been known by a number of names, for example CPR chest compression machines, mechanical CPR devices, cardiac compressors and so on.

CPR chest compression machines repeatedly compress and release the chest of the patient. Such machines can be programmed so that they will automatically compress and release at the recommended rate or frequency, and can reach a specific depth within the recommended range. Some of these machines can even exert force upwards during decompressions.

At present, most CPR chest compression machines repeat the same pattern of compressions over and over, maintaining a constant rate of compressions and a constant compression wave shape. This precise consistency is non-physiologic and may miss an opportunity to better move blood through each part of the patient's circulatory systems.

BRIEF SUMMARY

The present description gives instances of time-varying chest compressions, the performing of which may help overcome problems and limitations of the prior art. Various types of chest compressions may be performed on a patient during a single resuscitation event. In embodiments one or more compression time parameters may be changed during the event. In some embodiments the event includes one or more prolonged compressions interposed between other compressions.

In some embodiments a CPR chest compression machine includes a compression mechanism configured to perform successive compressions to the patient's chest, and a driver configured to drive the compression mechanism accordingly. In some embodiments a CPR metronomes instructs to perform such compressions accordingly.

An advantage over the prior art can be improved blood flow and thus improved CPR patient outcomes. For example, blood flow may be optimized for one side of the patient's heart, then the other. For another example, one or more prolonged compressions may permit blood may be able to reach to more remote locations than otherwise.

These and other features and advantages of this description will become more readily apparent from the Detailed Description, which proceeds with reference to the associated drawings in which:

DETAILED DESCRIPTION

As has been mentioned, the present description is about CPR chest compression machines, software and methods. Embodiments are now described in more detail.

FIG. 1is a diagram of components100of an abstracted CPR chest compression machine according to embodiments. Components100include an abstracted retention structure140of a CPR chest compression machine. A patient182is placed within retention structure140. Retention structure140retains the patient's body, and may be implemented in any number of ways. Good embodiments are disclosed in U.S. Pat. No. 7,569,021 to Jolife AB which is incorporated by reference, and are being sold by Physio-Control, Inc. under the trademark LUCAS®. In other embodiments retention structure140includes a belt that can be placed around the patient's chest. While retention structure140typically reaches the chest and the back of patient182, it does not reach the head183.

Components100also include a compression mechanism148configured to perform successive compressions to a chest of the patient, and a driver141configured to drive compression mechanism148so as to cause compression mechanism148to perform successive compressions to the patient's chest. Compression mechanism148and driver141may be implemented in combination with retention structure140in any number of ways. In the above mentioned example of U.S. Pat. No. 7,569,021 compression mechanism148includes a piston, and driver141includes a rack-and-pinion mechanism. In embodiments where retention structure140includes a belt, compression mechanism148may include a spool for collecting and releasing the belt so as to squeeze and release the patient's chest, and driver141can include a motor for driving the spool.

Driver141may be controlled by a controller110according to embodiments. Controller110may be coupled with a User Interface114, for receiving user instructions, and for outputting data.

Controller110may include a processor120. Processor120can be implemented in any number of ways, such as with a microprocessor, Application Specific Integration Circuits, programmable logic circuits, general processors, etc. While a specific use is described for processor120, it will be understood that processor120can either be standalone for this specific use, or also perform other acts.

In some embodiments controller110additionally includes a memory130coupled with processor120. Memory130can be implemented by one or more memory chips. Memory130can be a non-transitory storage medium that stores instructions132in the form of programs. Instructions132can be configured to be read by processor120, and executed upon reading. Executing is performed by physical manipulations of physical quantities, and may result in functions, processes, actions and/or methods to be performed, and/or processor120to cause other devices or components to perform such functions, processes, actions and/or methods. Often, for the sake of convenience only, it is preferred to implement and describe a program as various interconnected distinct software modules or features, individually and collectively also known as software. This is not necessary, however, and there may be cases where modules are equivalently aggregated into a single program, even with unclear boundaries. In some instances, software is combined with hardware in a mix called firmware. While one or more specific uses are described for memory130, it will be understood that memory130can further hold additional data, such as event data, patient data, and so on.

Controller110can be configured to control driver141according to embodiments. Controlling is indicated by arrow118, and can be implemented by wired or wireless signals and so on. Accordingly, compressions can be performed on the chest of patient182as controlled by controller110. In embodiments, the compressions are performed automatically in one or more series, and perhaps with pauses between them as described below, as controlled by controller110. A single resuscitation event can be a single series for the same patient, or a number of series thus performed sequentially.

Controller110may be implemented together with retention structure140, in a single CPR chest compression machine. In such embodiments, arrow118is internal to such a CPR chest compression machine. Alternately, controller110may be hosted by a different machine, which communicates with the CPR chest compression machine that uses retention structure140. Such communication can be wired or wireless. The different machine can be any kind of device, such as a medical device. One such example is described in U.S. Pat. No. 7,308,304, titled “COOPERATING DEFIBRILLATORS AND EXTERNAL CHEST COMPRESSION MACHINES”, only the description of which is incorporated by reference. Similarly, User Interface114may be implemented on the CPR chest compression machine, or on a host device.

FIG. 2is a diagram of a sample CPR chest compression machine200made according to embodiments, which is being used on a patient282. Machine200appears similar to the physical structure in the above mentioned example of U.S. Pat. No. 7,569,021. In addition, it has stored instructions232that can be similar to what is described for instructions132.

FIG. 3is a diagram of a state machine300for a CPR chest compression machine according to embodiments. While state machine300is described for a CPR chest compression machine, a similar state machine can also be implemented for a metronome as will be seen below.

State machine300is a representation of different modes in which a CPR chest machine can perform chest compressions. State machine300includes a state310during which chest compressions are performed according to a mode M1, a state320during which chest compressions are performed according to a mode M2, optionally a state330during which chest compressions are performed according to a mode M3, and so on. Modes M1, M2, M3can be different in that one or more of the chest compressions performed during these modes can have a chest compression time parameter of a different value. As will be seen in more detail below, examples of the chest compression time parameter include the frequency or rate, the duty ratio, the time waveform of individual compressions and/or decompressions, and so on. The waveform of compression can be characterized as plunger depth versus time, or compressive force versus time.

So, according to state machine300, operations of a CPR chest compression machine according to embodiments can include a first series of compressions according to mode M1, then a second series of compressions according to mode M2, then a third series of compressions according to mode M3and so on. In some embodiments where there are only two states310,320, execution may alternate between them. When there are three or more states, execution may or may not return to state310. When execution alternates or transitions between two modes, it can do so with or without a pause.

In many embodiments, one or more of the modes can be adjusted for optimizing blood flow into one or more of the different parts of the patient's circulatory system. More particularly, the patient's circulatory system has two main parts, namely the pulmonary vasculature396and the systemic arterial circulatory system397. The heart385of a patient is shown with a dot-dash line dividing it into the right side386(“right heart386”) and the left side387(“left heart387”). Right heart386pumps blood into pulmonary vasculature396, where it becomes oxygenated by the lungs while carbon dioxide is removed. The oxygenated blood is then received back in heart385. Left heart387then pumps the oxygenated blood into systemic arterial circulatory system397via the arteries. The blood is then received back in the heart via the veins. The two parts of the patient's circulatory system are mechanically different, and therefore have different hemodynamics for the purpose of pumping. For example, pulmonary vasculature396is more distensible than systemic arterial circulatory system397. Moreover, the operations of each part of the patient's circulatory system are different.

In these embodiments, as further indicated by large arrows inFIG. 3, mode M1of chest compressions may be optimized to assist the pumping operation of left heart387, while mode M2may be optimized to assist the pumping operation of right heart386. In some of these embodiments, state machine300dwells on state320for some time so that, due to the compressions being according to mode M2, the blood will preferentially accumulate in the lungs where it can become more thoroughly oxygenated, and then state machine300can return to state310for some time so that, due to the compressions being according to mode M1, the blood will preferentially be pumped into systemic arterial circulatory system397. This approach may improve CPR blood flow and/or its life-sustaining effects above what either type of compression would provide by itself. The left atrium, which is fairly distensible/compliant, can also potentially serve as a reservoir to accumulate blood during times when the mode favors pumping blood out of the right side of the heart. And then when switching to the mode favoring ejection of blood out of the left heart into the systemic circulation, the left side of the heart is primed full of blood to be pushed out to the systemic circulation.

The invention addresses the fact that, for CPR to successfully sustain a patient in arrest and ultimately lead to return of the patient to neuro-intact life, we believe that CPR must provide at least some minimal amount of blood flow to the brain and also to the heart itself (via the coronary arteries). The properties of the vasculatures in those two organs differ, and there is no particular reason to think that the same CPR pattern would lead to optimal flow to both organs. Therefore, embodiments alternate between modes, which may result in each organ receiving a burst of good blood flow periodically.

As mentioned above, modes M1, M2, . . . can be different in that one or more of the chest compressions performed during these modes can have a chest compression time parameter of a different value. Or more than one chest compression time parameter could change.

In embodiments, a driver of a CPR machine is configured to drive the compression mechanism so as to cause the compression mechanism to perform to the patient's chest a first series of successive compressions characterized by a compression time parameter having a first value, then a second series of successive compressions characterized by the compression time parameter having a second value at least 10% larger than the first value, and then a third series of successive compressions characterized by the compression time parameter having a third value at least 10% smaller than the second value. These can be according to the modes described above.

FIG. 4is a time diagram of selected chest compressions during a single resuscitation event for a patient. The shown compressions are at different modes at time ranges410,420,430. The modes are different because the value of at least one time parameter of these chest compressions changes, as shown by waveform segments415,425,435. In the example ofFIG. 4, during time range410a first series of successive compressions is being performed that is characterized by the compression time parameter having a first value V1. Then, during time range420a second series of successive compressions is being performed that is characterized by the compression time parameter having a second value V2. Value V2can be larger than value V1, e.g. by 10%, 20% or more. Then, during time range430a third series of successive compressions is being performed that is characterized by the compression time parameter having a third value V3. Value V3can be smaller than value V2, e.g. by 10%, 20% or more.

In the example ofFIG. 4the value changes between the first, second and third series of successive chest compressions. The value can change abruptly or gradually. There can be a pause between the different series or not.

In the example ofFIG. 4there are at least three modes, as characterized by the different parameter values. Where there are only two modes, third value V3can instead be substantially equal to first value V1, and so on.

In the example ofFIG. 4one can observe the time evolution of the value of a single compression time parameter. In embodiments, more than one of the possible time parameters may change. Some individual examples are now described about the frequency or rate and the duty ratio.

FIG. 5is a time diagram of selected chest compressions during a single resuscitation event according to embodiments. The shown compressions are an example of a first, a second and a third series515,525,535of certain successive chest compressions selected out of a longer series of chest compressions during the resuscitation event. First, second and third series515,525,535take place at time ranges510,520,530respectively. Time ranges510,520,530could be time ranges410,420,430ofFIG. 4.

It will be appreciated that the shown certain compressions of first series515, second series525and third series535are performed substantially periodically, i.e. each has its own frequency or rate. The frequency during time ranges510and530is F1. The frequency during time range520is F2, where F2is larger than F1by at least 10%. In other words, in the embodiment ofFIG. 5the compression time parameter includes a frequency of the shown compressions, and its value changes with time from F1to F2and then back to F1. This also can correspond to a state machine that has only two states and thus only two modes.

In one embodiment, the compression rate could alternate between a standard rate (for example 100 compressions per minute) and a higher rate (say 125 compressions per minute). After a run of standard rate compressions, the rate would be increased for a period of time, for example for 10 seconds, and then returned to standard rate for a period of time, for example 10 seconds. In another embodiment, the rate could alternate between periods of a low rate (for example, 80 compressions per minute) and a high rate (for example 120 compressions per minute. Experiments would be needed to figure out the optimal timing and rates. These rates could be better informed, for example, according to a time pattern of R-wave timing seen in a healthy individual, in other words, for embodiments to mimic the variation of heart rate observed in healthy individuals. More particularly, the chest compression rate could be informed by what is known about the heart rate variability (HRV) of a healthy person. More specifically, it is known that the heart rate of a healthy individual varies from moment to moment, and in fact that lack of this variability is one indicator of an unhealthy state. As the autonomic system becomes less effective, the heart rate variability decreases. One way to vary compressions during administration of CPR would be for embodiments to mimic the variation of heart rate observed in healthy individuals. That is, the chest compression device (or CPR coaching metronome) could be programmed to deliver compressions whose rate varies over time

FIG. 6is a time diagram of selected chest compressions during a single resuscitation event according to embodiments. The shown compressions are an example of a first, a second and a third series615,625,635of certain successive chest compressions selected out of a longer series of chest compressions during the resuscitation event. First, second and third series615,625,635take place at time ranges610,620,630respectively. Time ranges610,620,630could be time ranges410,420,430ofFIG. 4.

As can be seen, the shown certain compressions of first series615, second series625and third series635include first periods during which the chest is compressed alternating with second periods during which the chest is not compressed. This is now illustrated by magnification.

FIG. 7shows two time diagrams715,725. Time diagrams715,725show segments of the repeating portions of sessions615,625respectively. The segment of time diagram715includes a first period716during which the chest is compressed alternating with a second period717during which the chest is not compressed. The duty ratio is the ratio of the duration of first period716over the duration of second period717. These two latter durations being approximately equal, the duty ratio for the segment of time diagram715is about 1:1=1. The segment of time diagram725includes a first period726during which the chest is compressed alternating with a second period727during which the chest is not compressed. The duty ratio is the ratio of the duration of first period726over the duration of second period727, which is approximately equal to 2.5:1=2.5.

There are alternate ways of defining the duty ratio, but the result is the same. For example, the duty ratio can be defined as the ratio of the duration of the first period over the sum of the durations of the first period and the first period. For diagrams715,725, these sums are respectively durations718,728. As such, in these alternate definitions the duty ratio will be always less than one, and thus can be expressed as a percentage, and can also be called duty cycle. For example, in scholarly publications on CPR, the duty cycle is the percentage of the cycle during which the compression mechanism is down, squeezing the chest.

Returning toFIG. 6, then, it will be appreciated that the shown certain compressions in each of first series615, second series625and third series635have their own duty ratios. The duty ratios during time ranges610and630are 1. The duty ratios during time range,620are 2.5. In other words, in the embodiment ofFIG. 6the compression time parameter of the shown compressions includes a duty ratio of a duration of one or more of the first periods over a duration of one or more the second periods, and its value changes with time from 1 to 2.5 and then back to 1. This also corresponds to a state machine that has only two states and thus only two modes.

The devices and/or systems made according to embodiments perform functions, processes and/or methods, as described in this document. These functions, processes and/or methods may be implemented by one or more devices that include logic circuitry, such as was described for controller110.

Moreover, methods and algorithms are described below. This detailed description also includes flowcharts, display images, algorithms, and symbolic representations of program operations within at least one computer readable medium. An economy is achieved in that a single set of flowcharts is used to describe both programs, and also methods. So, while flowcharts describe methods in terms of boxes, they also concurrently describe programs.

Methods are now described.

FIG. 8shows a flowchart800for describing methods according to embodiments. The methods of flowchart800may also be practiced by embodiments described elsewhere in this document.

According to an operation810, a first series of successive compressions is performed. This first series can be characterized by a compression time parameter having a first value.

According to another operation820, a second series of successive compressions is performed. This second series can be characterized by the compression time parameter having a second value. The second value can be larger than the first value by 10%, 20% or more.

According to another operation830, a third series of successive compressions is performed. The third series can be characterized by the compression time parameter having a third value. The third value can be smaller than the second value by 10%, 20% or more.

In some embodiments a prolonged compression is interposed between other compressions, such as series of regular successive compressions. For example, a driver of a CPR machine can be configured to drive the compression mechanism so as to cause the compression mechanism to perform to the patient's chest a first series of successive compressions at a frequency of at least 70 bpm, and then a prolonged compression during which the compression mechanism compresses the chest for at least 1 sec. Examples are now described.

FIG. 9is a time diagram of selected chest compressions during a single resuscitation event according to embodiments. The shown compressions are an example of a first and a second series915,925of certain successive chest compressions selected out of a longer series of chest compressions during the resuscitation event. First and second series915,925can be thought of as “regular”, in that they are at a frequency of at least 70 beats per minute (“bpm”), and often faster, such as 100 bpm and even 120 bpm, as recently recommended by the American Heart Association.

As can be seen, a single prolonged compression922is interposed between series915,925according to embodiments. Compression922is prolonged in that it lasts for 1, 2, 3 full seconds or even longer, a duration which is substantially longer—at least percentage wise—than the duration of a typical compression performed at 70 bpm or faster. Indeed, an individual compression performed at even the slow rate of 70 bpm, with a high duty cycle of 50% corresponds to a time period of no more than 0.43 sec, followed by a similar release time, as can be seen for example inFIG. 7. However, prolonged compression922lasts definitely longer, and may give the blood the opportunity to reach more of its hoped-for destinations that are farther from the compression point, thus improving clinical outcome.

While shown inFIG. 9as an example, it is not required that both series915,925take place in all embodiments. The compressions ofFIG. 9may include compressions beyond series915or925, such as single compressions, additional prolonged compressions, one or more pauses, and so on.

FIG. 10is a time diagram of selected chest compressions during a single resuscitation event according to embodiments. The shown compressions are an example of a first and a second series1015,1025of certain successive chest compressions selected out of a longer series of chest compressions during the resuscitation event. First and second series1015,1025can be thought of as “regular”, in that they are at a frequency of at least 70 beats per minute (“bpm”), and often faster, such as 100 bpm and even 120 bpm. A prolonged compression1022is interposed between series1015,1025according to embodiments. Compression1022is prolonged in that it lasts for 2 sec, 3 sec, or even longer. Of course, while the compressions of series1015are shown as similar to those of series1025, they could be different, and so on.

FIG. 11shows a flowchart1100for describing methods according to embodiments. The methods of flowchart1100may also be practiced by embodiments described elsewhere in this document.

According to an operation1115, a first series of successive compressions is performed at a frequency of at least 70 bpm.

According to another operation1122, a prolonged compression is performed, during which the compression mechanism compresses the chest for at least 2 sec.

According to another, optional operation1125, a second series of successive compressions is performed at a frequency of at least 70 bpm. Of course, this pattern can be accompanied with other patterns, for example execution could then return to operation1115.

Returning toFIG. 1, components100can be augmented with a sensor (not shown) for sensing a physiological parameter of patient182. The physiological parameter can be an Arterial Systolic Blood Pressure (ABSP), a blood oxygen saturation (SpO2), a ventilation measured as End-Tidal CO2 (ETCO2), a temperature, a detected pulse, etc. In addition, this parameter can be what is detected by defibrillator electrodes that may be attached to patient182, such as ECG and impedance. The sensor can be implemented either on the same device as controller110or not, and so on.

Upon sensing the physiological parameter, a value of it can be transmitted to controller110, as is suggested via arrow119. Transmission can be wired or wireless.

Controller110may further optionally aggregate resuscitation data, for transmission to a post processing module190. The resuscitation data can include what is learned via arrow119, time data, etc. Transmission can be performed in many ways, as will be known to a person skilled in the art. In addition, controller110can transmit status data of the CPR chest compression machine that includes retention structure140.

Additionally, embodiments may be able to adapt, according to the sensed physiological parameter, the time parameter of the compressions or the duration of the prolonged compressions.

FIG. 12is a diagram of a sample CPR metronome1200made according to embodiments. In embodiments, CPR metronome1200is configured to guide a rescuer to perform Cardio-Pulmonary Resuscitation (“CPR”) chest compressions on a patient. CPR metronome1200is stand-alone, or may be provided in a host device1240such as a defibrillator, a medical monitor, a CPR feedback device, a smartphone, and so on.

CPR metronome1200includes a metronome controller1210. Metronome controller1210can be configured to generate prompt signals, which can be predetermined, if metronome controller1210is not programmable.

CPR metronome1200additionally includes a speaker1220. Speaker1220is configured to issue audible prompts1225responsive to the prompt signals generated by metronome controller1210. Prompts1225are intended to guide the rescuer to perform the chest compressions to the patient's chest. The chest compressions can be as described above. Implementing prompts1225as musical cues may be helpful in enabling the rescuer to follow rhythm, other than a constant pattern of compressions.

In the methods described above, each operation can be performed as an affirmative step of doing, or causing to happen, what is written that can take place. Such doing or causing to happen can be by the whole system or device, or just one or more components of it. In addition, the order of operations is not constrained to what is shown, and different orders may be possible according to different embodiments. Moreover, in certain embodiments, new operations may be added, or individual operations may be modified or deleted. The added operations can be, for example, from what is mentioned while primarily describing a different system, apparatus, device or method.

A person skilled in the art will be able to practice the present invention in view of this description, which is to be taken as a whole. Details have been included to provide a thorough understanding. In other instances, well-known aspects have not been described, in order to not obscure unnecessarily the present invention. Plus, any reference to any prior art in this description is not, and should not be taken as, an acknowledgement or any form of suggestion that this prior art forms parts of the common general knowledge in any country.

This description includes one or more examples, but that does not limit how the invention may be practiced. Indeed, examples or embodiments of the invention may be practiced according to what is described, or yet differently, and also in conjunction with other present or future technologies. Other embodiments include combinations and sub-combinations of features described herein, including for example, embodiments that are equivalent to: providing or applying a feature in a different order than in a described embodiment; extracting an individual feature from one embodiment and inserting such feature into another embodiment; removing one or more features from an embodiment; or both removing a feature from an embodiment and adding a feature extracted from another embodiment, while providing the features incorporated in such combinations and sub-combinations.

In this document, the phrases “constructed to” and/or “configured to” denote one or more actual states of construction and/or configuration that is fundamentally tied to physical characteristics of the element or feature preceding these phrases. This element or feature can be implemented in any number of ways, as will be apparent to a person skilled in the art after reviewing the present disclosure, beyond any examples shown in this example.

The following claims define certain combinations and subcombinations of elements, features and steps or operations, which are regarded as novel and non-obvious. Additional claims for other such combinations and subcombinations may be presented in this or a related document. When used in the claims, the phrases “constructed to” and/or “configured to” reach well beyond merely describing an intended use, since such claims actively recite an actual state of construction and/or configuration based upon described and claimed structure.