Pulmonary and Cardiac Function in Sickle Cell Lung Disease: Preliminary Report

(1)Pulmonary thrombosis in sickle subjects appears to be a consequence of mechanical obstruction of small pulmonary vessels by sickled cells. Such cells may gain entrance into the pulmonary vascular bed in high concentration because of abnormally low oxygen concentrations in the venous blood. This desaturation is the end-result of several independent factors. Fever and an acid pH of venous blood also may potentiate sickling. Vessels in hypoventilated areas of the lung may constrict under the influence of abnormal alveolar oxygen and carbon dioxide tensions, rendering them especially susceptible to thrombotic occlusion by the sickled cells.(2)If thrombotic events involve a large area of the pulmonary vascular bed, cardiopulmonary abnormalities may develop. These include fixation of pulmonary vascular resistance, pulmonary hypertension, increased right ventricular work and diffusion insufficiency for oxygen. The high cardiac output imposed by anemia in these patients tends to exaggerate these abnormalities. However, the extent of vascular loss may become apparent only when the pulmonary blood flow is raised, as by exercise.(3)The variability in extent of pulmonary thrombotic involvement among patients with S-S hemoglobin remains unexplained, though a number of possibilities exist.(4)Effective prophylaxis and therapy in these patients awaits the discovery of satisfactory methods for preventing or reversing the sickling phenomenon in vivo.