The role of rib infarcts in the acute chest syndrome of sickle cell diseases.

The acute chest syndrome is a generic term for pulmonary complications of sickle cell diseases with heterogeneous etiologies that include pneumonia, vaso-occlusion of pulmonary arterioles, rib infarction, and fat embolism syndrome. My review summarizes these etiologies, the evidence, and pathophysiology supporting the hypothesis that infarction of segments of ribs by the same vaso-occlusive process responsible for the acute episodes of pain (characteristic of the sickle cell diseases) is often involved in the acute chest structure. Inflammation associated with the infarct then causes splinting, hypoventilation, and hypoxia and further vaso-occlusion. The relationship with adult respiratory distress syndrome and fat embolism is also discussed. Use of the incentive spirometer combined with effective analgesia when chest pain is present is advocated for prevention of the pulmonary infiltrates. Newer understanding of the role of nitric oxide in regulating oxygen transport and its relationship to blood transfusions used in therapy of the acute chest syndrome are discussed.