VENOUS ADMIXTURE TO THE PULMONARY CIRCULATION IN HUMAN SUBJECTS BREATHING 100 PER CENT OXYGEN*

Abstract

Pulmonary venous admixture was determined during air breathing and after breathing 100% oxygen in 6 normal subjects, in 15 patients with chronic obstructive pulmonary emphysema, 14 with diffuse pulmonary fibrosis or infiltration, and 12 with marked obesity. All groups of patients demonstrated a mean increase in venous admixture relative to the normal subjects. Deep breathing reduced the shunt on oxygen in obese patients, but not in patients with emphysema or pulmonary fibrosis. The shunt component remaining after nitrogen washout could be explained largely by the continued perfusion of alveoli that were atelectatic or otherwise non-ventilated, or that permitted no oxygen diffusion.