By Dr. Brian McDonough, Medical Editor

PHILADELPHIA (CBS) – Have you ever wondered about medical emergencies occurring on flights? Probably not, but as a physician it always crosses my mind because you just never know.

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Last week there was a report in the New England Journal of Medicine which found for every 604 flights, there’s 1 in-flight medical emergency. The scientists looked at five commercial airlines and reviewed almost 12,000 flights.

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Just in case you are wondering, the most common medical problems were fainting or near fainting, breathing problems, and nausea/vomiting. Seven percent of flights on which there was an emergency had to undergo an emergency landing.

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By the way as far as helping out on a plane with a medical emergency, there is no legal obligation to intervene, but health care providers have a moral and professional obligation to act as good samaritans, and are covered by the 1998 aviation medical assistance act, which includes a good samaritan provision.