Dr. Michael Nirenberg had been on an American Airlines flight from Reno, Nevada to Chicago last week when a passenger in his mid-60s fell unconscious.

As a podiatrist—a doctor that specializes in the foot and ankle—Nirenberg was one of the only medically-trained passengers on board the flight.

Aided by a retired nurse, Nirenberg leapt into action and rushed to help the unresponsive patient. Upon appraising the passenger's health, he and the nurse spent the next 40 minutes giving the man CPR and monitoring his vitals on a portable EKG while the plane changed course for an emergency landing in Denver.