I sat with him, the oxygen cylinder that the flight attendant had also brought him between my legs, for the next several hours -- so much for getting any sleep. I coaxed him to drink water since I couldn't give him fluids intravenously while checking his blood pressure repeatedly. It was still low but stable. I was afraid that I might have to perform CPR on him if his blood pressure dropped further. How would we get him out of his seat and flat on the floor if it came to that? I asked the flight crew to have an ambulance waiting for us at the gate. As we prepared for landing, a flight attendant took back the oxygen tank. I protested, but she told me that it would be unsafe to leave it with us during the landing. Once on the ground, the flight crew allowed the other passengers to deplane first, even after I reminded them that their passenger might have a life threatening illness. By the time I helped the man off the aircraft, there were still no medical personnel at the gate to receive us. I was appalled.

***

Over the past seven years, I have responded to five in-flight medical events, three of which were true emergencies. It's estimated that a medical event of some sort occurs once for every 10,000 to 40,000 passengers on intercontinental flights. Information about these incidents is limited by underreporting, variable data quality, and the inability to determine what happens to patient-passengers when they leave the plane. In the United States, an airline is only required to report an incident to the Federal Aviation Administration (FAA) when a passenger dies or if the plane is diverted due to a death or medical emergency.

What we do know is that more Americans are flying than ever before: U. S. airlines alone transported 732 million passengers last year and by 2024 that number is expected to increase to 1 billion. At the same time an aging population means many passengers are taking to the skies with more medical problems. The result is an increase in in-flight medical incidents -- an upward trend that raises new questions about what ought to happen when a passenger falls ill while in transit.

Flying is stressful on the body. We carry heavy luggage over long distances between terminals, rushing to make our flights. We cross time zones, which may complicate our medication schedules. Some of us are afraid of flying or just see it as an opportunity to tune out the world and relax, and so drink alcohol or take sedatives.

While most medical emergencies occur due to pre-existing medical conditions or an acute illness, the aircraft itself can contribute to health problems. The cabin environment, which is pressurized to the equivalent of 6,000 to 8,000 feet above sea level, causes a 10 percent drop in blood oxygen saturation in the average traveler. Doctors generally advise healthy patients who are traveling to high-altitude destinations to allow at least a day at 8,000 feet to acclimatize before ascending further. Unfortunately many physicians aren't fully aware of the risks of flying, especially for their patients with chronic diseases. (If you can walk fifty yards at a normal pace or climb one flight of stairs without chest pain or significant shortness of breath, you are probably okay to fly without supplemental oxygen.)