Helicopter EMS is Associated with Improved Survival – Review of Limitations
I wrote the other day about the recently released JAMA article detailing the improved survival of major trauma patients transported by air ambulance versus ground ambulance. As I stated in that post, I have some concerns about several limitations of the study that I thought warranted their own post.
The authors did a good job of controlling a variety of variables usually associated with these types of studies. They were able to show that there was a number of patients that needed to be transported to save the life of one patient. When looking at level I trauma centers that number was 65 and for level II trauma centers, that number was 69. Using that figure, they calculated that $325,000 would have to be spent on air transport to save one life. They admit, though, that
…this figure does not account for the number needed to treat to prevent disability or other health-related quality-of-life outcomes. 
As experienced medical providers realize, merely surviving a traumatic incident is just the beginning. Cardiac arrest research has changed focus from ROSC to neurologically intact discharge. Why would the study authors not take a similar step and determine the number of patients needed to treat to maintain functionality for one patient?
Additionally, and through no fault of their own, the authors were unable to use “total prehospital time” to determine if EMS time had any effect on patient survivability. Evidently the time data is flawed in the National Trauma Database during the time period studied. Though the concept of the “Golden Hour” has been shown to be faulty, it is reasonable to assume that trauma patients still benefit from timely care. As such, prehospital times are a vital part of patient outcomes and are clearly missing from this study.
Finally, the study authors were not able to analyze distance transported and crew configuration of transport aircraft. These data were not available in the Trauma Database but just as time may be a factor, distance is also important to include before inferring causation.
Crew configuration is extremely different from one system to the next. This paper cites a study that was unable to link presence of a physician on scene to survival or quality-of-life. However, this study also states that many of the previous air ambulance studies are flawed so inclusion of crew configuration in a study this large may have produced interesting results.
That last limitation gave me the most pause, however. The study regarding presence of a physician evidently included a measurement for quality-of-life for air ambulance patients. The authors of the JAMA study knew that not including quality-of-life was a limitation but did not correct for it even though they cited a study which had calculated it previously. That’s a pretty big miss in my mind.
Though there are limitations, the important thing to take home is that this IS a well-designed study. No research will ever be flawless and it appears that these authors went to great lengths to get useful, unbiased results. Readers should be cautioned, however, against merely reading the abstract of this article and accepting it as gospel. Many EMS and outside news outlets are citing this study as definitive proof of the usefulness of air ambulances. While this study starts to paint the picture, further research needs to be performed by any such statements can be made.
So what do you think, am I totally off base? Are the study authors right? Wrong? Let me know in the comments.
 Galvagno Jr, SM et. Al. Association Between Helicopter vs Ground Emergency Medical Services and Survival for Adults With Major Trauma. JAMA. 2012;307(15):1602-10.