Alveolar-arterial gradients for oxygen at 1, 2, and 3 atmospheres absolute.

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Abstract
The functioning of an unmodified, commercially produced Oo electrode (Radiometer E 5044) at ambient pressures of 2 ana 3 atmospheres absolute (Ata) was assessed; the coefficient of variation of duplicate gas readings at these pressures was similar to that obtained at normal pressure. The response of this microcathode electrode to blood, when using a membrane of 20 [mu]. polypropylene, averaged 93[plus or minus]2% of the gas reading. When 6 [mu]. polyethylene teraphthalate (Melinex or Mylar) was substituted for polypropylene, the blood-gas difference was reduced to negligible proportions. The alveolar-arterial [A-a] gradient for O2 during 100% O2 breathing was measured in 5 subjects at normal barometric pressure, 5 subjects at 2 Ata, and 6 subjects at 3 Ata. The (A-a)DO2 lalveolar -arterial gradient for oxygen] gradient was not increased above the normobaric values during short periods of exposure to hyperbaric O2 and 3 Ata.