Even as emergency medical officials in Maryland consider stricter criteria for flying patients, in the wake of last weekend's fatal medevac helicopter crash in Prince George's County, some trauma specialists think they should be exploring a more fundamental question:

Should accident victims be transported by helicopter at all, especially in urban areas?

The idea borders on heresy in Baltimore, a city whose pioneering trauma center became a global model and where Dr. R Adams Cowley coined the phrase "golden hour," defining how quickly a patient should get to a hospital to have the best chance of survival. "Whenever someone says they want to ratchet it back," says Dr. Thomas M. Scalea, physician in chief at Shock Trauma, "I tell them 'OK, how many people can die next year to make that worthwhile?'"

Yet with more than 500,000 medical transport flights now being operated in the United States each year, and eight fatal accidents in the past year, some trauma specialists question how often they are used.

Skeptics, including a few of the nation's top trauma surgeons, cite studies that cast doubt on some of medevac's basic assumptions - that helicopters get patients to a hospital faster than ambulances, or that they increase a trauma patient's chance of survival.

One study, for example, found that helicopter transport made no difference for patients with severe injuries. Another found that while helicopter patients got initial treatment more quickly, they arrived at a hospital later than patients transported by ground ambulance.

If hospitals and emergency medical systems assessed the research objectively, the skeptics argue, many systems would limit helicopter use to rural emergencies or extreme situations such as high-rise evacuation and offshore rescue.

"In Maryland there's a culture that you ought to use a helicopter and you have to go to Shock Trauma," said Dr. Kenneth L. Mattox, chief of surgery at Ben Taub General Hospital in Houston. "But why? The little data we have says ground ambulances are superior."

Added Dr. Norman E. McSwain Jr., director of trauma at Tulane University and chief of surgery at the trauma center in New Orleans, "There is just too much flying of helicopters for non-medical reasons or for reasons that really have nothing to do with patient care. It's the kind of thing that we have got to get under control."

Questions about medevac safety are inevitably raised after every accident but are often tamped down by emotional anecdotes of high-speed rescues and lives saved.

Numerous medical studies validate one of the main tenets of Baltimore's vaunted trauma system - that critically injured patients fare better when they are treated in a dedicated, well-equipped and well-staffed trauma center like Shock Trauma.

The best way to get the patients there, however, is far from clear.

A detailed study in Phoenix in the 1980s found that helicopter transport didn't make a difference for patients with severe injuries. A similar study in London a decade later indicated helicopter transport might be harmful to patients with minor injuries.

A 2002 study of 16,699 cases in Boston came to a more complex conclusion: Trauma patients transported by helicopter were three times more likely to die than those transported by ambulance, though statistically they fared better when the increased severity of their injuries was taken into account.

Maryland officials are unswayed by the research, which they say is evolving and unclear.

"If it's my family or my patients, and there's no definitive research, then I want to have a paramedic and a helicopter available," said Dr. Robert R. Bass, director of the Maryland Institute for Emergency Medical Services Systems.

Scalea, of Shock Trauma, said he has no doubt that use of helicopters saves lives. There were about 4,500 medevac flights in Maryland last year.

"The accident victim who's staggering and slurring his words: Is he drunk or does he have a brain injury? If the pre-hospital guys had X-ray vision, then they could diagnose every injury at the scene. But as a medical community, and as a country, we've made the decision that over-triage is preferable to the alternative," he said.

"We know injury is a time-related disease."