Abstract
Arterial oxygen tension has been continuously measured in the carotid artery of 3 newborn lambs and 3 adult cats using a small, rapid response oxygen electrode which samples the arterial stream directly. When the animals breathed air, small fluctuations of Pao 2, ±1–4 mm Hg, having the same period as respiration were observed. These fluctuations varied directly with the mean Pao 2; they varied inversely with the rate of respiration and were enhanced with an increase in mean expiratory pressure. The results suggest that these fluctuations are caused by corresponding oscillations of alveolar Po 2 within the respiratory cycle 2.5–3 sec previously and that they are subject to damping from venous admixture. The effects of mixing within the left side of the heart were found to be small. The possible physiological significance of these fluctuations is discussed.
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