Proceedings of The Physiological Society

Physiology 2016 (Dublin, Ireland) (2016) Proc Physiol Soc 37, PCB008

Poster Communications

The Allies planned for a 40,000 foot air war in World War II (WWII): development and testing of the demand type pressure breathing O2 equipment used by the U. S. Army Air Force (USAAF), 1942-45

J. B. Dean1

1. Molecular Pharmacology & Physiology, Hyperbaric Biomedical Research Laboratory, University of South Florida, Tampa, Florida, United States.

  • Evolution of the USAAF's pressure breathing O2 mask, 1942-44. a) Wright Field, Aug. 1942. Using 10.5-11.5 in. H2O, USAAF volunteers reached 49,300-50,00 ft in the Aero Med Lab's altitude chamber; arterial %O2 sat.= 71-83%. b) Wright Field, Nov. 1942. Using 2-12 in. H2O, USAAF volunteers reached 41-48,000 ft in the altitude chamber. Later, Col. Randy Lovelace, Aero Med Lab, flew with members of the Boeing Flight Test Unit to 40-42,900 for 1.5 hr in a B-17E flying fortress research laboratory. Later, on 30 April 1943, Col. Lovelace flew "piggy-back" with Jim Towle (Lockheed Aircraft Corp.) to 44,980 ft in a P-38 to set the American altitude record for the war. c) The final product, the A-13 mask used in all theatres of operations, 1944-45. (a-c, from declassified Aero Med Lab reports (2-4).

In the early days of WWII, Sir Frederick Grant Banting, 1923 Nobel Laureate (co-discovery of insulin), pioneering aviation physiologist, and Major in the Royal Canadian Air Force stated "…whichever power gets up to 40,000 feet first and stays there longest with the heaviest guns will win the war (1)." At 40,000 ft, however, air is only 1/5 as dense as it is at sea level, inspired pO2 has decreased to ~1/5 its sea level value, and ambient temperature drops to -60° to -100°F! One way to survive in the stratosphere for 1.5-8 hr during flight operations without suffering "oxygen want" or "anoxia" was to fly in a pressurized aircraft; however, pressurized flight was rare in WWII until America deployed the B-29 Superfortress bomber in April 1944 in the Pacific war. The alternative, which was pursued by the USAAF aero physiologists beginning in January 1942 (2), was an accelerated research and testing program to develop the demand type pressure breathing (PB) O2 mask and regulator (3). The PB mask works like a small hyperbaric chamber strapped to the aviator's face, increasing ambient pressure by 2-12 inches of water pressure (in H2O) so that airman's "ceiling" on pure O2 was extended from 33,000 ft to as high as 39-50,000 ft for short periods of time in unpressurized aircraft (3). For example, arterial O2 saturation (%O2 sat.) started decreasing above 33-41,000 ft using the continuous flow O2 mask (A-8 & A-9) and conventional demand type O2 mask (A-14). Using the demand type PB O2 mask (A-13 & A-15) and A-14 regulator, however, arterial %O2 sat. remained in the near normal to normal range (high 70s-low 90s) depending on the altitude (2-5). PB equipment underwent a rapid metamorphosis during 1942-43 (Fig. 1a-c), finally being deployed operationally in Feb. 1944 in photographic reconnassiance squadrons and later, fighter and bomber groups (Fig. 1c). Using PB equipment, the altitude record for an unpressurized B-17G flying fortress research laboratory was set at 43,299 ft by members of Boeing's Flight Test Unit, July 1945. In the end, Sir Frederick G. Banting had overestimated the altitude at which the Allies would have to fly and fight to win air superiority. The air war of 1939-1945 was waged mostly at 25,000 to 35,000 ft with limited numbers of missions penetrating higher, but when they did, PB was available and used. Despite the mostly substratospheric air war, Major Banting's goal of 40,000 ft had shaped the goals of the aero medical research and altitude indocrination programs in America for the duration of the war. Consequently, the availability of PB equipment made for an easy transition to the jet age with it's higher operational altitudes in the post-war period.

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