He identified the cause of a respiratory condition that once killed 10,000 infants annually in the United States and helped design a drug that drastically reduced mortality rates.
Dr. John A. Clements, a towering figure in the field of pulmonary research who in the 1950s solved one of the great mysteries of the human lung, then helped to save thousands of lives by designing a drug to treat lung failure in premature infants, died on Sept. 3 at his home in Tiburon, Calif., north of San Francisco. He was 101.
The death was confirmed by his daughter Carol Clements.
In 1949, Dr. Clements was fresh out of Cornell University Medical College (now Weill Cornell Medical College) and working for the Army as a physiologist when he became intrigued by the miraculous mechanics of human breathing.
How could the millions of tiny air sacs in the lungs deflate when a person breathes out, but not collapse like a balloon? Dr. Clements theorized that there must be some chemical relaxing the surface tension of the air sacs, and he went on to identify the substance as a surfactant, a class of lubricants that work like household detergents.
In a 1956 paper, based on research done with a crude instrument he built himself, Dr. Clements demonstrated the presence of a surfactant in the lungs.
His work led to a breakthrough three years later by two Harvard researchers whom Dr. Clements advised: Pulmonary surfactant, they found, was absent in premature babies with undeveloped lungs who died of respiratory distress syndrome, or R.D.S.