A polio survivor known as the "man in the iron lung" has died aged 78, according to his family and a fundraising website.

Paul Alexander of Dallas, Texas contracted polio at the age of six, leaving him paralyzed from the neck down and reliant on a mechanical respirator to breathe for much of the time.

Though often confined to his submarine-like cylinder, he excelled in his studies, earned a law degree, worked in the legal field and wrote a book.

"With a heavy heart I need to say my brother passed last night," Philip Alexander posted on Facebook early Wednesday. "It was an honor to be part of someone's life who was as admired as he was."

Christopher Ulmer, a disability advocate running a fundraiser for Alexander, also confirmed his death in a GoFundMe update posted on Tuesday.

"His story traveled wide and far, positively influencing people around the world. Paul was an incredible role model that will continue to be remembered," said Ulmer.

A prior update on Alexander's official TikTok account said he had been rushed to the emergency room after contracting Covid-19.

A nurse caring for a polio patient in 1960. (CDC Public Health Image Library)

Iron lungs are sealed chambers fitted with pumps. Raising and lowering the pressure inside the chamber expands and contracts the patient's lungs.

Invented in the 1920s, their use fell away after the invention of the polio vaccine by Jonas Salk, which became widely available in 1955 and helped consign the devastating paralytic illness to history.

Alexander held the official Guinness World Record for time spent in a lung.

According to his Guinness page, he was able to leave the device for periods of time after he learned to "frog breathe" with the help of a physical therapist.

This involved "using his throat muscles to force air into his lungs, gulping down air one mouthful at a time." Eventually, he only returned to his iron lung at night to sleep.

As a practicing lawyer, he was able to represent clients in court in a special wheelchair that held his paralyzed body upright.

Seventy-five-year-old Martha Lillard of Shawnee, Oklahoma is reportedly the last surviving person in an iron lung.

© Agence France-Presse