Lung function in sickle cell hemoglobinopathy patients compared with healthy subjects.

Previous studies of lung function tests performed on patients with sickle cell disease have shown a restrictive ventilatory defect, usually a diffusion defect, and mild hypoxia at rest. The present study was undertaken to explain the pathophysiology of these changes and to extend these studies to include functional measurements not reported previously.Lung function studies were performed at rest and during treadmill walking on 66 patients with sickle cell anemia and on 16 healthy control subjects. Patients had restrictive ventilatory defects, decreased lung compliance, and uneven ventilation-perfusion ratios. These abnormalities caused an increased alveolar-arterial oxygen tension difference that caused hypoxemia. The diffusion defects were because of the sickle cell disease.Carboxyhemoglobin levels were increased in patients with sickle cell disease. This increase may be caused by a combination of factors, including increased cigarette smoking, hemolysis, and preferential survival of red blood cells that contain carbon monoxide and which do not sickle. During treadmill walking, the patients with sickle cell disease showed a decreased work tolerance caused by impaired oxygen delivery. The anaerobic threshold is reached sooner in patients with sickle cell disease and may also account for the limitations in work capacity of these patients.