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Review of: Havel C, Schreiber W, Riedmuller E, et al. "Quality of closed chest compression in ambulance vehicles, flying helicopters and at the scene." Resuscitation. 73(2):264-270, 2007.
The Science
This study from the Medical University of Vienna examined the quality of chest compression applied to a manikin. They compared CPR provided at the scene (the control group) with that provided during an eight-minute flight in an EC 135 air medical helicopter and an eight-minute transport in a Volkswagen LT 35 ambulance. The manikin was ventilated with an automatic ventilator and no defibrillation or medications were administered.
The researchers measured the number of total compressions delivered and the depth of compression as well as the frequency of improper hand placement. Participants in the study were trained in the 2000 AHA guidelines for CPR performance.
They found no statistical difference between the quality of CPR in the ambulance, in the helicopter and on scene. There conclusion is that quality CPR is possible in both the ambulance and helicopter. However, they go on to state that one should consider helicopter use for prolonged transports.
The Street
This study has much to be criticized. First of all, there was no attempt to make this a real-life scenario. It only examined one component of the cardiac arrest event -- CPR -- during transport. One has to wonder what the data would have shown had the authors compared 30 minutes of scene resuscitation with eight minutes of scene resuscitation followed by loading the patient into an ambulance and traveling 22 minutes by ambulance and 15 minutes by helicopter.
We all recognize that once we decide to transport the patient, interruptions in chest compression are inevitable while we move them to the cot and load them in the ambulance or helicopter. Do these delays vary for different modes of transport? This study could have answered that question. And, why did they only measure performance for eight minutes? Studies have shown the effects of fatigue on quality of CPR performance. Is the effect of fatigue greater or lesser in the ambulance and helicopter? How do you change positions for chest compression in the ambulance and helicopter? And, was the ambulance traveling code 3? We don't know because it was not measured or described.
Although the paper states the ALS providers were blinded to the results, we all know that due to the Hawthorne effect they knew what was being measured. This is going to cause them to attempt to provide the best chest compressions possible. It would take an enormous number of real patients collect sufficient data to make the comparison, but another way to eliminate observer effect would be to not have all patients be in cardiac arrest during the study. You could randomly determine who starts out in arrest, goes into arrest during transport, or never arrests at all. You could have both medical and trauma scenarios. In this manner, the ALS providers wouldn't know for sure which facet of their delivery was being measured.
I'm sorry. I respect the efforts of the authors to examine a very important issue, but one would be ill advised to use this study to validate the performance of CPR in a moving ambulance or helicopter.
