Respiratory Changes in Thromboembolic Disease

Abstract

The respiratory functions were examined in 13 patients with thrombo-embolic disease in a period of latency, in the majority of whom signs of pulmonary arterial hypertension were found at catheterization. A slight hyperventilation in these patients is caused by an increase in the alveolar dead space (mean value 79 ml). Mean Pa-ACO2 [arterial-alveolar CO2 gradient] was increased to 3. 2 mm Hg, the percentage of nonperfused alveoli with preserved ventilation was 9.05% according to Severinghaus, 12.04% according to Robin. These are higher values than those found in normal subjects, but lower than in patients with pulmonary emphysemia. The percentage of non-perfused alveoli with preserved ventilation correlates significantly with the total pulmonary resistance. This value obviously depends on the extent of the obstruction in the pulmonary arterial bed, and can not be taken as direct indicator of the extent of the damage but as indicator of the ability to adapt gas distribution in the lungs to the changes in perfusion. Constant findings in patients with thromboembolic disease were increased PA-aO2 (on an average 24 mm Hg) as well as decreased diffusing capacity of the lungs (30-66" of the predicted values) with prevalently affected blood components.