The NTSB yesterday asked the FAA to impose stricter requirements on all emergency medical services (EMS) flights, based on a study of 55 EMS accidents between January 2002 and January 2005. "The very essence of the EMS mission is saving lives. Operating an EMS flight in an unsafe environment just makes no sense," said NTSB Acting Chairman Mark Rosenker. The NTSB's study found that most accidents occur during flights with no patients on board, which operate under Part 91. To improve safety, all EMS flights should adhere to Part 135 rules, the NTSB said. Also this week, a study by a group of medical researchers found that for helicopter EMS operations, darkness more than triples the risk of fatalities, and bad weather increases the risk eight-fold. The Johns Hopkins study also found that post-crash fires are a risk, killing some victims who survived the crash. Military helicopters have stricter fuel-system requirements that reduce the fire hazard, the researchers said. Improving crashworthiness of helicopters and reducing trips during hazardous conditions can decrease EMS helicopter fatality rates, the study concluded. "Crashes of EMS helicopters have increased in recent years, raising concern for patients, as well as pilots, paramedics and flight nurses," said researcher Susan Baker. "Helicopter EMS programs should recognize these risky conditions and transport patients by air only when the benefit clearly exceeds the risk of the flight." The study authors examined NTSB records of EMS helicopter crashes between January 1, 1983, and April 30, 2005. During the 22-year study period, 184 occupants died in 182 EMS helicopter crashes. The study was recently published by Annals of Emergency Medicine.