In 2002, there were about 400 dedicated EMS helicopters, but that number rose to more than 800 in 2008, according to the association. The number of hours logged for medical helicopters more than doubled between 1991 and 2005 to 300,000 hours in-flight a year.
Most of these rescue missions aren't the ones citizens watch at an accident scene or see on a televised broadcast from a remote mountain trail. In fact, roughly 70 percent of medical emergency helicopter flights now run between hospitals, says Blair Beggan, communications and marketing manager of the Association of Air Medical Services in Alexandria, Va.
Beggan explains that hospitals are increasingly specializing in their care, such as cardiac or orthopedic treatment. Although every hospital keeps an open emergency room, it's not unusual for staff to send serious cases to the nearest specialty hospital.
"Medical helicopters are one of the most important medical service that we have in the US, especially as our roads get more and more crowded," Nance said. "They do make the difference between life and death."
A recent beneficiary of this service was Sen. Ted Kennedy, who took such a flight from the Cape Cod Hospital in Hyannis, Mass., to the Massachusetts General Hospital in Boston last month.
"The health care industry is rapidly changing," says Christopher Eastlee, government relations manager for the Association of Air Medical Services. "There's a misconception that when you get hurt, the hospital nearest you is the best equipped to take care of you.
"A lot of what we find is, you have these hospitals that are outlying the suburbs or exurbs or rural areas that are not equipped to handle some of these patients," he said.
With the two-pronged increase in flights to the scene of accidents as well as between hospitals, the NTSB might reasonably expect to see a relative increase in accidents.
But the number of crashes has outpaced the increased flight numbers. The NTSB reports that since 1991, the rate of helicopter accidents increased from 3.53 for every 100,000 flight hours to 4.56 accidents for 100,000 flight hours.
The problem of extracting what keeps going wrong in these crashes — and why — becomes compounded by the fact that no single entity governs medical flight helicopter services.
"Air medicine is a unique combination of two distinct industries — aviation and health care," Beggan says. "Each service is independent, or could be part of a group of similar programs."
However, all helicopters, medical or not, are governed by safety rules under the Federal Aviation Administration. By examining 50 example crashes, Guzzetti and his colleagues at the NTSB found five common causes in the majority of medical helicopter accidents.
Primarily, the NTSB found helicopter crews could have followed the more rigorous FAA safety standards set for flights with patients, even if only the medical staff are onboard while on the way to the accident scene.
The NTSB also found a lack of systematic weather safety checks before takeoff and a lack of consistent dispatch procedures for helicopters. New technologies to improve "terrain awareness" and night vision would also keep the medical flights safer.
Even with the medical airlift industry's shortcomings, patients with serious situations that warrant a medical flight — such as heart conditions, potential brain injuries or strokes — are better off in the air.