Studies of ventilatory control, improved methods of sleep monitoring, and evidence of familial clustering have led to speculation that abnormal ventilatory control contributes to the pathogenesis of a number of clinical entities. Primary alveolar hypoventilation ("Ondine's curse"), the obesity-hypoventilation syndrome (Pickwickian syndrome), sleep apnea syndromes, hypercapnic chronic obstructive pulmonary disease (COPD) with patients characterized as "blue bloaters," and the sudden infant death syndrome are examples of such entities.
PRIMARY ALVEOLAR HYPOVENTILATION
This appears to result from a defect in the central chemoreceptor's responsiveness to carbon dioxide (CO2). Chronic arterial hypercapnia and hypoxemia occur in the presence of normal lungs and chest bellows. Early symptoms are related to cerebral vasodilation with headache, somnolence, confusion, and irritability. Chronic hypercapnia may eventuate in cor pulmonale. Dyspnea is not a feature of this syndrome despite the presence of grossly abnormal arterial blood gas levels. The central nature of the defect is demonstrated by