Pulmonary exchange as related to altered pulmonary mechanics in anesthetized dogs

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Abstract
Pulmonary mechanics and gas exchange were studied in supine anesthetized dogs, with and without periodic hyperinflations of the lungs, and after a single forced deflation. After a period without hyperinflations the lung compliance decreased to 66% of control values and patchy atelectasis was observed, but no changes were observed in diffusing capacity (Dl) or per cent venous admixture (Qva/ Qt). Following a single forced deflation the compliance was 40% of control. Dl was 40% and Qva/Qt 180% of control values, respectively. These data could be accounted for if there was an accompanying shift of blood flow from atelectatic to nonatelectatic areas, the compensation being very nearly complete for moderate, but less than complete for marked reductions in compliance. Alternative explanations of the apparent compensation are: 1) preferential initial atelectasis of regions with high ventilation-perfusion ratios (as proposed by Farhi) and 2) substantial reductions in compliance without closure of air space, as might result from changes in surface forces with time. aerotonometer; atelectasis; venous admixture; mechanics of breathing; compliance of dog lungs; diffusion capacity of dog lungs; ventilation perfusion; relationships of dog lungs Submitted on October 28, 1963