Alterations in the pulmonary capillary bed during early O2 toxicity in man.

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Abstract
The effect of O2 toxicity on the pulmonary capillary bed of humans was evaluated in 6 normal subjects who breathed 99.8% O2 at 1,500 mm Hg for 6-11 hr. in a pressure chamber. The pulmonary diffusing capacity (DlCO), pulmonary capillary blood volume (Vc), diffusing capacity of the alveolar membrane (Dm), capillary blood flow (Qc), and pulmonary parenchymal tissue volume (Vt) were measured with single-breath techniques before and after O2 exposure. Following O2 at high pressure (OHP) measurements were made 0.5-4 hr. after return to sea level (post-O2 measurements) and again 12-20 hr. after the termination of OHP (follow-up measurements). Of the above findings, only changes in DLCO and Vc were statistically significant either at post-02 or follow-up measurements. The lack of significant changes in Vt associated with a modest decrease in Vc suggests that marked alterations in pulmonary structure, such as seen in animals during severe O2 poisoning, was not present in these subjects. Most likely, the fall in Vc and Dlco was secondary to a toxic effect of O2 on the pulmonary capillaries.