Cassidy, a physician, and another doctor helped a man in his 50s who lost consciousness on their flight.
Cassidy told the newspaper they couldn’t find the passenger’s pulse and discovered his blood pressure was low.
They took off the man’s shirt, laid him across several plane seats and helped him regain consciousness, the report said.
Cassidy told The Times-Picayune the passenger identified himself as a conservative, but didn’t say how he’d vote in November.
Paramedics met the flight when it landed in Baltimore, and the man was taken to a nearby hospital.
The congressman was on his way back to Washington for two House vote on Monday evening.
Cassidy has worked as an associate professor of medicine at Louisiana State University and provided care to uninsured patients and trained doctors at a Baton Rouge-area hospital for the last 20 years.
He has served in Congress since 2009.