Effect of sampling technique on the determination of PaO2, during oxygen breathing.

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Abstract
Studies of the effects of sampling techniques on determination of arterial O2 pressure (PaO2 ) were carried out with arterial blood from subjects breathing O2 and with water equilibrated with 90% 02. An initial loss of 23 mm Hg O2 pressure occurs when samples are drawn into syringes. When allowed to stand at room temperature the Po2 of arterial blood samples decreased further at the rate of 8 mm Hg per minute due to the metabolism of O2 by blood cells. Immediate chilling of blood samples in syringes did not eliminate early losses of oxygen, but did prevent continuing losses once chilled. The mean decrease in Po2 of nonchilled and chilled syringe samples was 43 mm Hg and 74 mm Hg, respectively. Variability of determinations of Pao2 with nonchilled syringe samples was 2.5 times and with chilled syringe samples 1.5 times greater than with direct arterial sampling.