03. July 2009 · Comments Off on CPR: new standards; new needs · Categories: Cryonics · Tags: , , , ,

In 2005 the American heart association revised its standards for CPR increasing the number of compressions from 80 cpm to 100 cpm, eliminating pauses for ventilation, and urging that focus be shifted to compressions (perfusion) rather than ventilation. This latter change is more profound than it might seem at first glance. In the past, a central focus (many would argue the central focus) of early ACLS was securing the airway by endotracheal intubation. Intubation is a demanding and skill-intensive task and it tends to absorb not only most of the focus of the rescue effort, but also the attention of the most skilled and experienced personnel on the scene.

As Gordon Ewy has demonstrated, minute ventilation with chest compressions in the presence of an open airway is usually adequate to provide for sufficient gas exchange for the first 6 to 10 minutes of CPR. [1,2]  Indeed, the limiting factor is not a failure of oxygen delivery resulting from the 100 tiny breaths a minute produced by the new AHA standard chest compressions, but rather hypercarbia from progressive accumulation of CO2 due to inadequate alveolar ventilation. This change in the guidelines has meant a refocusing of paramedical attention on perfusion – on chest compressions – and on the way chest compressions are carried out. The new AHA standards call for square wave compressions and emphasize the importance of delivering compressions of adequate force, depth and frequency. [3]

Anyone who has had sustained contact with paramedics (at least in the US) will know that if there is anything paramedics are more enamored of than badges and certifications, it is gadgets. Paramedics (and rightly so) are great users of equipment that makes their work faster, more effective and safer. In a profession where every second counts, anything that can improve speed or efficiency has the potential to translate into additional lives saved. To this end, Zoll (Philips and Laerdal) has introduced the Q-CPR, the first device designed to improve the quality of CPR by providing transducer derived surrogate data which is processed and transformed into verbal instructions which the device gives the EMS personnel.

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In other words, the Q-CPR measures chest compressions and provides real time verbal feedback during cardiopulmonary resuscitation. This is accomplished using a compression sensor which is placed between the rescuer’s hands and the patient’s sternum where it measures motion and force. Compression rate and depth are presented as a waveform on the monitor and if either the depth or rate drifts outside the target range established by AHA, the Q-CPR provides audible feedback. The sensor tells the EMS personnel to “press harder” or give compressions “more frequently” through verbal commands. Data on the frequency and adequacy of ventilation are collected and analyzed using impedance technology employing sensors built into the adhesive pads placed to deliver the defibrillating shock.  Changes in thoracic impedance are interpreted and displayed as lung volume and ventilation rate on the monitor screen. The Q-CPR is pictured above. As a standalone, this device would likely not have been launched. However, it is available as a ‘value added’ option to Phillips defibrillators and, as such, it has the advantage of being part of the first device, indeed the only definitive device, currently available to restore adequate perfusion and ventilation; the defibrillator. In this case the Phillips HeartStart MRx defibrillator.

Still, this technology does not come cheaply; the Q-CPR add-on retails for $3800. The latest models of the Q-CPR have a miniature LCD screen embedded in the chest sensor enabling the rescuer to see the ‘adequacy’ of his compressions continuously and without interruption.  Preliminary studies indicate that the Q-CPR improves retention of CPR skills via the ongoing verbal feedback the device provides.  Arguably just as importantly, the Q-CPR captures an enormous amount of data about each case, including how well CPR was performed and what courses of treatment are effective. The device not only stores CPR data, but also the complete ECG record and, obviously, a record of all defibrillation attempts. These data are useful not only for post-event debriefing, but will hopefully help to guide the development of more effective treatments, as well.  The Q-CPR weighs about 200 g, adding virtually no weight to the HeartStart MRx.  The module was cleared by FDA earlier this year and is now available for purchase in the U.S.

A useful video review of the Q-CPR system can be seen at:

http://www.youtube.com/watch?v=mZDxZYBneNU&feature=related

As a grimly humorous aside; only a few of us are still alive who hail from the beginnings of ‘practical’ cryonics in the late 1960s. The first HLR used in cryonics was the Westinghouse Iron Heart.

Robert Ettinger with the Iron Heart in 1964

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The second heart-lung resuscitator used in cryonics (after the Westinghouse Iron Heart) was the Brunswick HLR-50-90 which used a strap-on piston to provide chest compressions. While there are more of us left alive from those days, few of us are still active in cryonics.

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The HLR-50-90 is shown on Youtube in action with the Q-CPR in a clip entitled ‘Vintage Ambulance Equipment – HLR with MRx.”

http://www.youtube.com/watch?v=FXaFCRr-1ss&feature=related

I should also note that the Brunswick  HLR 50-90 is still being manufactured and sold and is still much cheaper to purchase than competing HLRs. It has been updated by the manufacturer to deliver 2005 AHA compliant CPR, including ventilations: http://www.brunswick-biomedical.com/

Vintage, indeed.

REFERENCES

1. Ewy GA, Kern KB. Recent advances in cardiopulmonary resuscitation: cardiocerebral resuscitation. J Am Coll Cardiol 2009; 53: 149–57.

2. Davis, DP, Cardiocerebral resuscitation: a broader perspective. Journal of the American College of Cardiology 2009; 53: 158-59.

3.2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2005; 112: IV-12 – IV-18.