EFFECTS OF BREATHING GASES CONTAINING OXYGEN AND CARBON DIOXIDE AT 1 AND 3 ATMOSPHERES PRESSURE ON BLOOD FLOW AND OXYGENATION OF TUMORS

Abstract
Mice with established, immunologically compatible tumors were allowed to breathe air, O2, or 5% CO2 and 95% O2 at 1 and 3 atmospheres pressure. Tumor blood flow was determined by using the thermal circulation index, and oxygenation was measured polarographically. Pure oxygen at 1 atmosphere had no significant effect on blood flow within the tumor and in normal skin, but inhalation at 3 atmospheres decreased flow within both tissues. The addition of 5% CO2 to the oxygen increased flow at both pressures. Oxygenation was often improved in anoxic areas within the tumor on breathing 100% O2 at 1 atmosphere and in almost all animals at 3 atmospheres; the addition of 5% CO2 at either pressure usually further improved the oxygenation, but sometimes had the opposite effect at 3 atmospheres. The application of these results to the use of hyperbaric O2 in radiotherapy is discussed.

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