New York Times
U.S.
Earl H. Wood Is Dead at 97; Helped Invent G-Suit
By JEREMY PEARCE
Published: March 26, 2009
Dr. Earl H. Wood, a physiologist and an essential member of the team that invented a revolutionary pressurized garment, the G-suit, that helps pilots avoid blacking out while in flight, died on March 18 in Rochester, Minn. He was 97.
Mayo Clinic
Dr. Earl H. Wood, in the 1940s, in a human centrifuge his team used to create G-forces and a design to counteract them.
Dr. Wood’s death was confirmed by his family.
In 1942, Dr. Wood joined a pioneering team at the Mayo Clinic that was charged with helping military air crews survive increased physical stress brought to bear by more powerful aircraft.
Turning and diving in faster planes leads to a sharp increase in forces created by acceleration, also known as g forces (so-named because they could be several times the force of gravity). The acceleration temporarily impedes the heart’s pumping power and cuts blood supply to the brain. A tight turn might cause the pilot to lose consciousness briefly, leading to a crash.
The Mayo team set out to study the forces’ physiological effects and how it might be possible to counteract them. Other researchers had already devised a water-filled suit to stabilize a pilot’s blood pressure, but the device, the Franks flying suit, was found to be too cumbersome and too heavy for use in tropical climates.
Dr. Wood and the team, which included Edward Baldes, Charles Code, Edward Lambert and others, built a centrifuge and attached a basket to carry a human rider.
When the centrifuge whirled, G-forces acted on the rider, whose blood pressures at the head and heart levels were measured with special instruments. The rider sometimes blacked out.
Dr. Wood himself was a regular volunteer for the centrifuge. He later noted with mild surprise that in the course of hundreds of rides he had lost consciousness for a total of 15 minutes, without any lasting ill effects.
To counter a precipitous drop in blood pressure, the team designed a suit that placed air bladders at a pilot’s calves, thighs and abdomen; a valve inflated the bladders as G-forces increased. Constriction of the bladders on the arteries raised blood pressure and helped keep blood flowing to the brain. The suit’s prototype was tested successfully by Dr. Wood and others in a dive bomber on flights that involved steep descents.
At the same time, the Mayo team developed an exercise, called the M1 maneuver, in which a pilot would shout or grunt under G-force conditions. The grunting compressed arteries and tensed muscles and was at least as important as the revolutionary suit for resisting G-forces.
The team’s suit and recommendations were initially resisted by some pilots, who found flying under fire distracting enough. But figures comparing numbers of enemy planes shot down by fighter pilots strongly suggested that pilots who wore G-suits were more successful than those who did not.
The suit was issued to combat pilots in 1944. By the late 1940s, with the introduction of jet aircraft, G-suits based on the Mayo pattern came into general use and remain standard today.
In the 1950s and ’60s, Dr. Wood went on to study and refine techniques for measuring blood flow within and to the heart, in work that helped pave the way for cardiac catheterization. That research was rooted in the Mayo team’s blood pressure experiments on the centrifuge, said Dr. Jan Stepanek, an assistant professor of medicine at Mayo and a senior aviation medical examiner for the Federal Aviation Administration.
In 1955, Dr. Wood received a patent for an oximeter, a diagnostic tool used to measure oxygen levels in the bloodstream. His device could be clamped to a patient’s ear to show the level optically, without having to draw blood. He also helped develop a light-absorbing green dye, indocyanine, used in tracing the circulatory system and diagnosing heart defects.
Earl Howard Wood was born in Mankato, Minn., to a family of academics and public servants. Dr. Wood’s sister, Louise A. Wood, was executive director of the Girl Scouts of America from 1961 to 1972. A brother, Dr. Harland Wood, was chairman of the biochemistry department at Case Western.
Earl Wood received his medical degree and a doctorate in physiology from the University of Minnesota in 1941.
He taught briefly at the University of Pennsylvania and Harvard before joining Mayo, which named him a professor of physiology and medicine in 1951. From 1962 to 1967, Dr. Wood was also a career investigator for the American Heart Association. He retired from Mayo in 1982.
He was a former president of the American Physiology Society.
Dr. Wood, who lived in Rochester, is survived by a daughter, Phoebe Busch of Denver; three sons, E. Andrew, of Rochester, Guy, of Corvallis, Ore., and Mark, of Fresno, Calif.; and four grandchildren.
