Cohen TJ, Goldner BG, Maccaro PC, Ardito AP, Trazzera S, Cohen MB, Dibs SR. A comparison of active compression-decompression cardiopulmonary resuscitation with standard cardiopulmonary resuscitation for cardiac arrests occurring in the hospital. N Engl J Med. 1993 Dec 23;329(26):1918-21. PubMed PMID: 8018138.

Ellinger K, Luiz T, Denz C, van Ackern K. [Randomized use of an active compression-decompression technique within the scope of preclinical
resuscitation]. Anasthesiol Intensivmed Notfallmed Schmerzther. 1994 Dec;29(8):492-500. German. PubMed PMID: 7841276.

The Cohen study is available as a free full text here: http://www.nejm.org/doi/pdf/10.1056/NEJM199312233292603

If you delve deeply into CPR research, you will find that almost everything fails – including interventions or devices that unequivocally improve perfusion and oxygenation. In fact, most of these interventions, such as CPR machines, show a worse outcome! So how is this possible if blood flow is better using the devices? Several answers have been proposed, but here are the most likely ones:

1) The application of any modality that requires a device almost invariable translates into either more time doing CPR, or interruptions in CPR to apply the device. You can’t put most mechanical CPR machines on the patient without, however briefly, interrupting CPR. That is a no, no! Even a 5 second interruption in CPR markedly negatively impacts outcome. This is one of the reasons that Gordon Ewy’s “new” compressions only “cardiopulmonary cerebral resuscitation CPR” is working – and forcing the American Heart Association into a very uncomfortable position of retreat.

Every time you interrupt CPR to give a breath, flow stops, and that is very injurious. What’s more, even if you give the breath while continuing CPR you are transiently raising the pressure inside the chest. CPR does not move blood primarily by squeezing the heart “between the breastbone and the backbone” as the lay literature says. Rather, it works using other mechanisms, primary something called the “thoracic pump” and possibly something called the “lung pump.” These mechanisms depend upon a negative pressure being created within the chest which in turns pulls or “sucks” blood into the great vessels of the thorax which is subsequently expelled during the down-stroke part of the CPR duty cycle. When you give a breath in CPR you are giving a positive pressure breath. That is unphysiologic, because if you think about it, every time you inhale normally, you are creating a negative pressure (relative vacuum) inside the chest by pulling your diaphragm downwards. Each positive pressure breath prevents or actively expels blood from the chest – effectively cutting into cardiac output.

The vast majority of people who are going to survive cardiac arrest do so as a result of early defibrillation, not CPR. Mostly, CPR doesn’t work, and the proof of this is the proliferation of all these expensive automatic external defibrillators (AEDs) in airports, shopping malls, and the like. And that brings us to reason #2:

2) Patients who get “devices” to assist with CPR are usually those who have failed the first round of AED. That is a very, very bad prognosis, because every minute you spend absent spontaneous circulation is pretty much ischemic time, and by the time the new device is brought into the picture, your 4-6 minute of cerebral salvage-ability has likely clocked out.

3) There is a shallow learning curve to using all of these devices. I know, I’ve used them. It takes lots of continued practice to apply even the the easiest to apply of these devices without losing time to no flow. In fact, you wouldn’t believe how much effort is required – and it is ongoing, because if you don’t keep drilling, you lose speed. Paramedics HATE CPR machines and don’t much like CPR adjuncts, either. It is hard to describe the degree of their contempt. It seems to be largely an artifact of their belief that they are better than any machine. This doesn’t make it easy to get good compliance during clinical trials. And CPR isn’t that commonplace – who is going to spend time drilling with a noisy, clunky machine 2x a week…?

4) The CardioPump and other active decompression CPR devices really only work well if you close the airway during upstroke! Since you are trying to create a relative vacuum in the chest during upstroke by pulling on the chest wall with a suction cup, it hardly makes sense to allow air to rush into the lungs 100 time/min, and defeat this process. It also results in over-ventilation, which is very bad in CPR. So, a resuscitation researcher named Keith Lurie invented the airway impedance valve, or as it now called, an “impedance threshold device (ITD)”. This device closes the airway during upstroke and allows for breaths to be given using positive pressure ventilation, as needed. A couple of the papers below are full text and will explain the mechanics of the ITD:

Plaisance P, Soleil C, Lurie KG, Vicaut E, Ducros L, Payen D. Use of an inspiratory impedance threshold device on a face mask and endotracheal tube to reduce intrathoracic pressures during the decompression phase of active compression-decompression cardiopulmonary resuscitation. Crit Care Med. 2005 May;33(5):990-4. PubMed PMID: 15891326.

Lurie KG, Barnes TA, Zielinski TM, McKnite SH. Evaluation of a prototypic inspiratory impedance threshold valve designed to enhance the efficiency of cardiopulmonary resuscitation. Respir Care. 2003 Jan;48(1):52-7. PubMed PMID:12556262.
http://www.rcjournal.com/contents/01.03/01.03.0052.pdf

Lurie K, Zielinski T, McKnite S, Sukhum P. Improving the efficiency of cardiopulmonary resuscitation with an inspiratory impedance threshold valve. Crit Care Med. 2000 Nov;28(11 Suppl):N207-9. PubMed PMID: 11098948.

Lurie K, Voelckel W, Plaisance P, Zielinski T, McKnite S, Kor D, Sugiyama A, Sukhum P. Use of an inspiratory impedance threshold valve during cardiopulmonary resuscitation: a progress report. Resuscitation. 2000 May;44(3):219-30. Review. PubMed PMID: 10825624.

Plaisance P, Lurie KG, Payen D. Inspiratory impedance during active compression-decompression cardiopulmonary resuscitation: a randomized evaluation in patients in cardiac arrest. Circulation. 2000 Mar 7;101(9):989-94. PubMed PMID: 10704165. http://circ.ahajournals.org/cgi/reprint/101/9/989

This work resulted in a clinically available FDA approved device called the ResQPod, and there is a very nice series of animated teaching modules showing how it works here:

http://www.advancedcirculatory.com/resqpod/product_overview.htm

Addition info can be had here:

http://www.mypatrioteducation.com/classes/resqpod/ResQPOD_FAQs.pdf

But, to return to the CardioPump. Since the device failed its clinical trials it not allowed, however, a mechanical CPR device called the LUCAS, which uses the CardioPump suction cup is FDA approved and can be purchased in the US. You can watch an instructional video for the LUCAS here:

http://www.youtube.com/watch?v=3M96sFP-0Xc&NR=1

The LUCAS + ITD is the most effective CPR available, bar none, and I am hearing first-hand reports of patients being conscious on LUCAS support absent a spontaneous heartbeat more and more, almost by the month, from physicians using it in Europe. It is rapidly becoming the standard of care in the Netherlands. LUCAS recently came out with an electrically powered unit (an artifact of LiPO battery technology) which eliminates the need for a bulky and difficult to transport oxygen tanks. — Mike Darwin

Is this device legal in the U.S.? If not, what regulatory hurtles must be overcome to make it available for use in the U.S.?