If you are severely injured, a helicopter flight to a top-level trauma center will boost your chance of survival over ground transport. That's the conclusion of a rigorous, national comparison of the effectiveness of helicopter versus ground emergency medical services, published in the April 18, 2012, issue of the Journal of the American Medical Association.

Survival after trauma has increased in recent years with improvements in emergency medical services coupled with the rapid transportation of trauma patients to centers capable of providing the most advanced care.

What has not been clear until this study, is the effectiveness of helicopter emergency medical services (HEMS), a limited and expensive resource, compared to its alternative, ground emergency medical services (GEMS).

"We looked at the sickest patients with the most severe injuries and applied sophisticated statistical analyses to the largest aggregation of trauma data in the world," says the study's principal investigator, Samuel M. Galvagno Jr., D.O., Ph.D., assistant professor, Department of Anesthesiology, Divisions of Trauma Anesthesiology and Critical Care Medicine, University of Maryland School of Medicine.

"We were careful at every step to balance all the potential other factors that could explain any benefit of the helicopter. After all that, the survival advantage of helicopters remained," says Galvagno.

Dr. Galvagno is on the staff of the R Adams Cowley Shock Trauma Center at the University of Maryland Medical Center, where many of the life-saving practices in modern trauma medicine were pioneered. The Shock Trauma Center was the first fully integrated trauma center in the world, and remains the epicenter for trauma research and training both nationally and internationally today.

"The use of helicopter emergency medical services in the United States has been a controversial subject over the last decade or so, centering on the costs and the potential for crashes, says Thomas M. Scalea, M.D., the Francis X. Kelly Professor of Trauma in the Department of Surgery; director of the Program in Trauma, University of Maryland School of Medicine; and physician-in-chief at the R Adams Cowley Shock Trauma Center.

"Previous studies have found a survival benefit by using helicopters, but the studies were small and left some doubt. This study in JAMA is very robust," says Dr. Scalea.

"Dr. Galvagno's research demonstrates how statistics and technology can be used to help researchers mine huge databases for useful information to help determine best care for patients and appropriate utilization of limited health care funds," says E. Albert Reece, M.D., Ph.D., M.B.A., vice president for medical affairs, University of Maryland; the John Z. and Akiko K. Bowers Distinguished Professor; and dean, University of Maryland School of Medicine.

"Advances in the emerging science of comparative effectiveness, coupled with the expertise of physician researchers who have direct patient care experience, will deliver data that clinicians, policy-makers and ultimately the public can use to make informed decisions."

For this study, Dr. Galvagno developed the most rigorous comparison of helicopter and ground transport to date. He and his team tracked patients meeting certain criteria who were listed in the 2007-2009 version of the American College of Surgeons (ACS) National Trauma Data Bank (NTDB). The NTDB contains more than 1.8 million patient records from more than 900 centers in the United States.

To meet the study's criteria, patients had to be adults (over age 15) who sustained blunt or penetrating trauma with an injury severity score greater than 15 (critically injured). They had to be taken to either an ACS Level I or Level II trauma center in the United States (centers that meet certain high standards of care, with Level I the highest). The main outcome measure was survival to discharge from the hospital.

"Dr. Galvagno is an anesthesiologist whose specialties include intraoperative care of people who have suffered trauma and the care of critically ill patients. He not only treats patients but also has major research interests in the improvement of patient safety and care," says Peter Rock, M.D., M.B.A., the Dr. Martin A. Helrich Professor and chair of the Department of Anesthesiology at the School of Medicine.

"His experience as a former paramedic and now in the Air Force Reserve where he assists in the evacuation of wounded warriors has taught him that saving lives is a combination of quality care both in the field and on the way to a trauma center, coupled with rapid transport and expertise at the hospital. All of those factors come together in this study."

A total of 223,475 adult patients met the criteria: ground transport accounted for 161,566, while 61,909 patients were flown in helicopters. Overall, 7,813 (12.6 percent) HEMS patients died compared to 17,775 (11 percent) transported by GEMS.

This raw data shows a significant difference, but Dr. Galvagno says the odds for helicopter transport improved when statistical models were applied to the numbers to factor in so-called "confounding" factors that could lead to a misinterpretation of the data. These include injury severity, age, vital signs, type of injury, gender and trauma center.

The researchers also developed statistical models to account for missing data in the NTDB, including travel time and distance to trauma centers, key bits of information that could impact survival.

Dr. Galvagno and his team conclude that the helicopter is associated with a 16 percent increased rate of survival for the 156,511 patients transported to Level I trauma centers. That percentage means 65 patients must be transported to save one life. The 64,964 patients who went by chopper to Level II trauma centers had a 15 percent survival advantage, meaning 69 must be transported to save one life.

Dr. Galvagno says the study raises many questions that need to be explored further. "The benefits of the helicopter, we believe, are related to multiple factors. Certainly time and crew expertise play a role. Beyond that, we're not sure. More study is warranted," says Dr. Galvagno.

Galvagno SM, Haut ER, Zafar SN, Millin MC, Efron DT, Koenig, Jr. GJ, Baker SP, Bowman SM, Pronovost PJ, Haider AH.. "Association between helicopter vs. ground emergency medical services and survival for adults with major trauma." JAMA. 2012;307[15]:1602-1610