Review of:Bobrow BJ, Ewy GA, Clark L, et al. Passive Oxygen Insufflation Is Superior to Bag-Valve-Mask Ventilation for Witnessed Ventricular Fibrillation Out-of-Hospital Cardiac Arrest. Ann Emerg Med. 2009:54(5):656 662.
This retrospective study, conducted from January 2005 to September 2008, compared the effect of what the authors term "passive oxygen insufflation" to traditional bag-valve mask (BVM) ventilation during cardiac arrest management. Passive oxygen insufflation (PV) is accomplished by opening the victim's airway and applying a non-rebreather mask.
The goal was to determine if passive insufflation was superior to BVM ventilation by looking at the primary outcome of neurologically intact survival. The authors also examined return of spontaneous circulation (ROSC) rates, hospital admission and survival to discharge. The study captured 1,019 adult out-of-hospital cardiac arrests, 459 of whom received passive ventilation and 560 who received BVM ventilation. Of those who experienced a witnessed V-Fib/V-Tach (VF/VT) arrest, the neurologically intact survival rate was 39 of 102 (38.2%) with PV and 31 of 120 (25.8%) with BVM ventilation.
With unwitnessed VF/VT and non-shockable rhythms, the authors reported no statistical difference between PV and BVM ventilation as it relates to survival to discharge or neurologically outcome. The authors conclude passive insufflation is the superior treatment for witnessed VF/VT cardiac arrests due to increased survivability and increased positive neurological outcomes.
In both arms of the study, the cardiac arrest protocol was 200 compressions, rhythm analysis and shock if indicated, followed by 200 compressions before pulse check. Intubation was withheld until after the third series of compressions/analysis. Intraosseous or IV access was established early, and epinephrine administration was encouraged.
Dr. Wesley and Medic Marshall discuss this new methodology and mindset of cardiac arrest management. While the doctor delves into the research, Medic Marshall discusses cardiac arrest management from the standpoint of a medic.
Doc Wesley:I completely agree with the authors that minimally interrupted CPR isone of the fundamentals to cardiac arrest survival. However, their obsession with the potential role of passive ventilations neglects the overwhelming amount of literature supporting some degree of ventilation during the vast majority of cardiac arrest and totally disregards the extremely strong evidence for the use of the ResQPod to enhance blood return to the heart.
It's generally accepted that cardiac arrest has three phases. The first is electrical, during which immediate defibrillation is indicated. The second phase is perfusion, during which there's evidence to support aggressive minimally interrupted CPR to prime the heart with oxygenated blood. The third phase is metabolic, during which severe acidosis exists and for which there is evidence to withhold defibrillation until some unknown amount of CPR, oxygenation/ventilation, and premedication occurs.
This study concentrated its analysis only on the witnessed VF/VT patients, which I believe may be somewhat closer to Phase 1 than Phase 2. Another problem with this study is that there was no control for the rate of ventilation in the BVM group. In fact ventilation rates were not measured. Although it has been demonstrated that hyperventilation can and does occur with BVM, this is not reason enough to discard the procedure. Rather, it's reason to instead attempt to better control it with adjuncts.
The ResQPOD, when applied with a face-mask and BVM, significantly enhances cardiac preload, coronary and cerebral perfusion. Newer automated external defibrillators (AEDs) incorporate verbal and auditory prompts to encourage proper ventilation rate. Additionally, there are BVMs that prevent excessive tidal volumes and pressures.
Finally, as stated by the authors, they only showed benefit to the witnessed VF/VT victims. However, their data showed a higher ROSC for the patient with asystole/PEA (pulseless electrical activity) who received BVM ventilation. The incidence of witnessed VF/VT is dropping, and to suggest that we would need to adopt different ventilation strategies depending on the presenting rhythm is logistically problematic. We need to make arrest management simpler and find the technique that provides the most benefit for the most common conditions.
So for me, my protocol is high performance CPR, early ResQPOD used with a BVM and insertion of the King LT following the second analysis.
Medic Marshall:I think the Doc summed this one up pretty well; I have to agree with him that minimally interrupted chest compressions are the key to survival. We as EMS providers need to start being cognizant of that. But the Doc touched on something that I would like to go into further, cardiac arrest management.
Having worked a number of cardiac arrests in my tenure, I've had my share of bad ones, great ones, goofy ones. They rarely, if ever, go by the book. The difficult thing about cardiac arrest management is the constantly changing protocol. They can include everything from aggressive airway management and changes in chest compression to aggressive pharmacological management, such as new or different drugs. Why not keep things as simple as possible, right? This is what I try to accomplish. Not only does it make running an arrest smoother, but gives you a stronger sense of control -- which in turn provides you with confidence to manage a chaotic situation.
I have the privilege of having Dr. Wesley as my medical director, and I can attest to his philosophy of high-performance CPR, early ResQPOD use with BVM and a King airway. Anecdotally, I've seen an increase in the number of patients who get ROSC in the field following this mindset. If your system allows it, I encourage you to do the same.