The study, unveiled Tuesday, is the latest in a body of often conflicting research into whether medevac helicopters get patients to hospitals faster, provide better care and increase the chances of saving lives.
Decades' worth of studies have been used to support one side of the issue or the other. The Hopkins study found that patients transported by helicopter are 16 percent more likely to survive than those taken by land.
The study is one of the most extensive looks to date at the issue, examining records from more than 223,000 patients across the country using the National Trauma Data Bank. The data bank is the largest repository of trauma statistics in the world with information from more than 900 trauma centers. Researchers used software to crunch the numbers and adjust for factors such as patient age and severity of injury that otherwise might have skewed findings.
In fact, a higher percentage of patients in the study transported by helicopter died than those moved by ambulance. Those taken by air typically are more severely injured.
The results are to be published today in the peer-reviewed Journal of the American Medical Association.
"We hope that this paper really advances the scientific evidence for use of helicopters," said Dr. Samuel M. Galvagno Jr., a lead researcher on the study and an assistant professor at the University of Maryland School of Medicine. Galvagno was on the Hopkins faculty when the study was conducted.
The patients, who were transported during a two-year period beginning in 2007, sustained injuries that were at least moderately severe and needed to be taken to trauma centers. The researchers compared more than 161,500 patients transported by ambulance to nearly 62,000 taken by helicopter.
Despite the costs and risks associated with helicopter transport, the issue should be examined further because the technique saves lives, said Dr. Adil Haider, a senior researcher on the study and an associate professor of surgery, anesthesiology and critical care medicine at Hopkins' School of Medicine.
The study found that one in 65 significantly injured patients brought to a Level I trauma center by helicopter would die if ground transportation was the only option.
Haider said the next step in the research is to develop standards to help paramedics decide who should be transported by helicopter. Less severe cases still could go by ambulance.
"We need to help our EMS providers by giving them better tools to improve their ability to triage patients," Haider said. "They don't have all the information."
Maryland emergency management officials said the Hopkins data proves what their own tracking of helicopter transport has shown. Their analysis found that if a severely injured patient is farther than 30 minutes by ambulance from a trauma center, helicopter transport is better in most cases, said Dr. Robert R. Bass, executive director of the Maryland Institute for Emergency Medical Services Systems.
"Those who know the subject matter will believe helicopters are helpful," Bass said. "If you do the risk-adjusted study, you have a better chance of surviving if you travel by helicopter."
The state reduced the number of patients it transports by Medevac after re-examining its system in the wake of a 2008 crash in Prince George's County that killed four people. The helicopter was ordered because the damage to the vehicle was so severe. Guidelines at the time said a 12-inch dent in a car could mean the occupants had injuries that could not be immediately detected. In this case, though, the victims were awake and alert after the crash.
The state adopted new guidelines that required emergency workers to speak with doctors to help decide whether certain cases require a helicopter. That has reduced by more than half the number of helicopter transports from a peak of about 5,300 in 2005 to more than 2,200 last year, Bass said.
The Hopkins researchers noted other studies that found the annual cost of helicopter transportation ranged from $114,777 to $4.5 million per institution that used them. There's little debate that they are an expensive way to move patients. Maryland has a state-run system in which the average cost of helicopter transport is $5,000. For every 65 patients transported in Maryland, about $325,000 would have to be spent to save one life, the Hopkins analysis found.
Over the years, studies about helicopter transport have come to varying conclusions. One found that it made no difference for patients with severe injuries. Another found that patients arrived at the hospital later than those who went by ambulance, though they might have gotten more initial care.
Dr. Bryan E. Bledsoe, a University of Nevada emergency medicine specialist, conducted a study in 2006 that found that many patients transported by helicopter did not have life-threatening injuries and therefore did not need to fly.
"I think they are still vastly overused," Bledsoe said in a phone interview Tuesday.
Dr. Mark Gestring, medical director of the Kessler Trauma Center at the University of Rochester in New York, has done research that, like the Hopkins study, found improved outcomes from helicopter transport.
Gestring said the more recent studies are more precise and prove that there is more of a benefit to helicopter transport and that they are not overused. Past studies, he said, used smaller populations from single institutions or regions.
"The next generation of research will be who needs to fly and who doesn't," he said.