When Liz Madigan boarded her red-eye flight back to the U.S. shortly before midnight Saturday, her six-day trip to Colombia was winding down. But things were about to get lively for the Frances Payne Bolton School of Nursing professor.

About four and a half hours into her six-hour flight from Bogota, Colombia—where she’d given the keynote address at a homecare nursing conference—to New York City, a flight attendant came onto the public address system asking for assistance from any doctors or nurses on the flight.

Less than a minute later, Madigan was in the first-class cabin checking on a passenger who had existing hypertension and had passed out after a dizzy spell. Madigan quickly got to work, putting on the oxygen and checking his blood pressure and pulse—stabilizing him until she felt comfortable with his progress.

Half an hour later, the flight crew returned to Madigan’s seat for assistance, as the passenger’s state had dwindled: His pulse had dropped and he had lost much of his color, Madigan remembered. Again, she stabilized him, but this time she stayed close until they arrived at the gate in New York City, where paramedics were waiting to assist.

The passenger—who at that point looked markedly better—thanked Madigan as she left the flight.

But, Madigan insists, she was just doing her job. “Any healthcare provider would do what I did,” she said.

Madigan also was quick to point out just how common situations such as this are. “The combination of altitude and dehydration, especially for those on blood pressure medications, can have this kind of effect. That’s why they always tell you on long flights to drink plenty of water,” she noted.

It’s so common, in fact, that this is not the first time Madigan has come to the rescue on an international flight. In 2005, she was on a flight to Taiwan when a similar situation arose due to the combination of altitude, dehydration and medication.

“On that flight, we were over the middle of the ocean and I didn’t know where we’d land if we needed to. This time, if we needed to land someplace, we could. This one,” she said, “was easy.”