Regulation of respiration in Friedreich's ataxia.

Friedreich's Ataxia (F.A.) is a degenerative disease which commonly leads to premature death of cardiorespiratory origin. To explain the early death of these patients, previous investigations have established the existence of 1) a cardiomyopathy in nearly 100% of cases, 2) a restrictive pulmonary syndrome of scoliotic origin and 3) a mild hypoxemia associated with slight respiratory alkalosis and a normal oxyhemoglobin dissociation curve. To further assess the cause of early death in patients with such neuromyopathy, we evaluated, in eleven F.A. patients, the sensitivity of the respiratory centers to hypercapnia, hypoxia, and hyperoxia. Ventilatory (VE, VT, F, VT/Ti) and occlusion pressure (P0.1) responses were taken as indices of the respiratory centers output during progressive hypercapnia (Read's method) and isocarbic hypoxia (Weil's method). We studied 11 Friedreich's Ataxia patients and 11 age, sex, and armspan matched controls. The responses of patients to hypercapnia were significantly greater than controls but their responses to hypoxia were similar to controls. Our study establishes that the respiratory centers are functioning adequately in early Friedreich's Ataxia and do not contribute to cardio-respiratory insufficiency in such neuromyopathy.