Mark O'Brien, 49, a poet whose determination to live a life independent of his iron lung breathing machine inspired an Oscar-winning documentary, died July 4 at his Berkeley, Calif., home from complications of bronchitis.

Months of failing health had left him tethered to the iron lung for all but a few hours a week, associates said.

His story was the subject of the documentary "Breathing Lessons: The Life and Work of Mark O'Brien," which won an Academy Award in 1997.

Born in Boston and raised in California, Mr. O'Brien contracted polio at age 6, leaving him paralyzed and able to breathe only through an iron lung.

He eventually grew strong enough to breathe on his own during the day, using the machine only at night. He earned a bachelor's degree from the University of California-Berkeley and was halfway through graduate school when, severely weakened by post-polio syndrome, he was forced back on the iron lung full-time.

Mr. O'Brien launched a career as a writer, publishing an essay on independent living that led to a job at the San Francisco-based Pacific News Service, where he wrote about sports, religion and the politics of being disabled.

"At first, he wrote stories by dictating," Pacific News Service Executive Editor Sandy Close told the San Francisco Examiner. "Then he wrote by manipulating a stick with his mouth to press the keys . . . as he laid in the iron lung with his neck stuck outside."

Close produced the 1997 documentary on Mr. O'Brien with money from a MacArthur Foundation "genius" grant. Later Mr. O'Brien co-founded the Lemonade Factory, a small press in Berkeley that specializes in publishing poetry written by people with disabilities.

Mr. O'Brien, who said his strong Roman Catholic faith helped him cope with his disability, was known for two overriding passions: baseball and Shakespeare.

But it was his eloquent descriptions of a life built around the simple mechanics of breath that spoke most clearly. In the title poem from the 1990 collection "Breathing," O'Brien wrote of his constant struggle with the iron lung for air:

All I get is a thin stream of it

A finger's width of the rope that ties me to life

As I labor like a stevedore to keep the connection.

CAPTION: Mark O'Brien was determined to be free of his iron lung breathing machine.