Synchronization of Repetitive Therapeutic Interventions

Abstract

A medical device of the type used for assisting a user in manually delivering repetitive therapy to a patient (e.g., chest compressions or ventilations in cardiac resuscitation), the device comprising a feedback device configured to generate feedback cues to assist the user in timing the delivery of the repetitive therapy, at least one sensor or circuit element configured to detect actual delivery times, at which the user actually delivers the repetitive therapy, and a processor, memory, and associated circuitry configured to compare the actual delivery times to information representative of desired delivery times to determine cue times at which the feedback cues are generated by the feedback device.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional application of and claims priority to U.S. application Ser. No. 12 / 639,133, filed on Dec. 16, 2009, which application is a divisional application of and claims priority to U.S. application Ser. No. 11 / 227,968, filed on Sep. 14, 2005. These applications are hereby incorporated by reference.TECHNICAL FIELD[0002]This invention relates to the field of medical devices for assisting in delivery of repetitive therapy, such as assisting rescuers in performing cardio-pulmonary resuscitation (CPR).BACKGROUND[0003]Resuscitation treatments for patients suffering from cardiac arrest generally include clearing and opening the patient's airway, providing rescue breathing for the patient, and applying chest compressions to provide blood flow to the victim's heart, brain and other vital organs. If the patient has a shockable heart rhythm, resuscitation also may include defibrillation therapy. The term basic life support (B...

AI Technical Summary

Benefits of technology

[0044]Because the heart is in the early stages of recovery after a defibrillation shock, often with rhythmic electrical activity but degraded mechanical output, cardiac recovery is enhanced by the invention, for chest compressions are synchronized with the normal, if low level, mechanical activity of the recovering heart. The invention may help provide effective CPR for patients in non-perfusing, fibrillatory rhythms as well as for patients in hemodynamically unstable or ineffective rhythms such as PEA.

[0045]The invention's ability to synchronize chest compression to the activity of a damaged heart may improve perfusion. Without the invention, chest compressions may occur during ventricular filling, and thus be less effective, as the volume of blood in the heart is small and little or no blood is ejected in to the aorta and coronary arteries. A compression during this time may increase intrathoracic and / or diastolic pressures and further slow ventricular filling.

[0046]The invention may improve effectiveness of CPR during PEA because the compressions can be timed to occur during specific phases of systole such as isovolumetric contraction.

[0047]Asystolic rhythms may convert spontaneously to PEA during the course of CPR, and asynchronous delivery of chest compressions during PEA, as is typically currently performed, is substantially suboptimal with regard to circulatory hemodynamics. In these early stages of recovery, such as during post-shock PEA, the heart is actually contracting to some degree and asynchronous compression phasing may inflict additional stress on the myocardium as well as lower ejection fractions. The invention provides detection of the change of the heart from one rhythm state to the next and may provide feedback to the rescuer that synchronizes (entrains) the phase of the rescuer's CPR activities such as ventilation and chest compressions to the underlying electrical and mechanical activity of the heart and lungs. This has the advantages both of reducing the need for interruptions of chest compressions as well as improving hemodynamics.

[0048]The invention may provide feedback to a rescuer on a compression by compression basis, thus monitoring the quality of CPR (e.g. depth of compressions) as well as looking at the specific effects of the compression on the patient's heart. CPR guidelines necessarily cover the general population, and individual parameters such as depth or rate of compressions may not be optimal for individual victims. Assessment of individual compressions may be beneficial to the rescuer both in providing more effective CPR as well as conserving energy by not compressing the chest with more force or speed than required.

Problems solved by technology

There are also several abnormal ECG rhythms that do not result in significant cardiac output but are still considered non-shockable, since defibrillation treatment is usually ineffective under these conditions.

Although a patient cannot remain alive with these non-viable, non-shockable rhythms, applying shocks will not help convert the rhythm.

Lay caregivers rarely have opportunities to defibrillate or deliver CPR, and thus they can be easily intimidated by an AED during a medical emergency.

Consequently, such lay providers may be reluctant to purchase or use AEDs when needed, or might tend to wait for an ambulance to arrive rather than use an available AED, out of concern that the lay provider might do something wrong.

Some trained medical providers, e.g., specialists such as obstetricians, dermatologists, and family care practitioners, also rarely have the opportunity to perform CPR and / or defibrillate, and thus may be uneasy about doing so.

Concerns about competence are exacerbated if training is infrequent, leading the caregiver to worry that he or she may not be able to remember all of the recommended resuscitation protocol steps and / or their correct sequence.

Similarly, both medical and lay caregivers may be hesitant to provide CPR and rescue breathing, or may be unsure when these steps should be performed, particularly if their training is infrequent and they rarely have the opportunity to use it.

It is well known to those skilled in the art, and has been shown in a number of studies, that CPR is a complex task with both poor initial learning as well as poor skill retention, with trainees often losing 80% of their initial skills within 6-9 months.

Further, less than 10% of the test subjects were able to sustain the recommended 100 compressions per minute for at least one minutes' duration.

Further, this study was performed using well-trained rescuers, including nurses and physicians, indicating that the problem of poor compression rates is widespread.

In some cases, this approach may be helpful, but because the compression tone rate is asynchronous with the rescuer's compressions, the tones may occur out of phase with the rescuer compression rate, and may actually act to confuse the rescuer and momentarily slow them down.

AEDs have also been solely focused on defibrillation, which, while it provides the best treatment for ventricular fibrillation and certain tachycardias, is of no therapeutic benefit for the 60% of the cardiac arrest patients presenting in pulseless electrical activity (PEA) or asystole.

As AEDs are becoming more prevalent in the home, there are also a host of other health problems that occur such as first aid as well as incidents related to chronic conditions such as asthma, diabetes or cardiac-related conditions for which the AED is of no benefit.

PEA is a condition where the heart is functioning electrically, but does not have enough healthy muscle fibers to contract effectively.

Many studies have reported that the discontinuation of chest compressions, such as is commonly done for ECG analysis, can significantly reduce the recovery rate of spontaneous circulation and 24-hour survival rate.

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