Observations on a model of proliferative lung disease. II. Description of pulmonary gas exchange and comparison of Fick and dye cardiac outputs.

Measurements of gas exchange in dogs with granulomatous lung disease resembled those which have been made in similar disorders of man. The minute volume of ventilation was large, the oxygen extracted from each liter of ventilation was low, and the arterial blood oxygen saturation tended to be subnormal despite hyperventilation. When the diseased dogs breathed 21% oxygen and had alveolar oxygen tensions above 100 mm Hg, the pulmonary blood flows calculated from the Fick principle were significantly higher than those estimated by the dye-dilution method. By way of contrast, the two values agreed when the alveolar tensions were lowered. Whether the agreement of the flows is causally related to the alveolar tension remains an open question. A possible explanation may lie in the effect of alveolar tension on the oxygen consumed by the diseased lung.