Blood-gas transfer, hemolysis, and diffusing capacity in a bubble tonometer

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Abstract
The performance of a test-tube tonometer is described. The 95% equilibration times in 10 ml blood are 2.9 and 14 min, respectively, with small and large bubbles at a bubble flow rate of 1 ml/sec. Small bubbles have the disadvantage that surface tension significantly raises gas pressure above atmospheric. With large bubbles surface tension effects are negligible and hydrostatic pressure is only about 0.5% of an atmosphere. Hence, large bubbles are preferred for calibrating an oxygen electrode for use with blood of a high Po2. Hemolysis produces less than 150 mg/100 ml plasma hemoglobin in the time needed for equilibration. The diffusing capacity for oxygen of the bubble interface in 10 ml blood in the tonometers is about 0.001 and 0.008 ml mm-1 sec-1 with large and small bubbles, respectively, when blood Po2 is about 20 mm Hg, and is one-tenth as much when blood Po2 is over 500 mm Hg. This type of tonometer appears to be a useful adjunct to the oxygen electrode. oxygen; equilibration Submitted on July 1, 1963