Respiratory capacity course in patients with infantile spinal muscular atrophy. 
To describe the clinical and respiratory course in infantile spinal muscular atrophy (SMA) type I, type II, and type III, and to evaluate the respiratory needs for these patients, using noninvasive or tracheostomy ventilation.  Retrospective cohort study.  We report 33 patients with SMA true type I (onset before age 3 months), 35 patients with SMA intermediate type I (onset between 3 months and 6 months), 100 patients with SMA type II (onset between 6 months and 18 months), 12 patients with SMA type III (onset after age 18 months).  We report the clinical symptoms, respiratory course, and respiratory management: respiratory physiotherapy, periodic hyperinsufflation, nasal nocturnal ventilation (NNV), and tracheostomy.  Also, we measured the FVC over several years during childhood and adolescence.  In patients with SMA true type I, 82% of patients died, one third of whom underwent tracheostomy.  In patients with SMA intermediate type I, 43% needed NNV, 57% underwent tracheostomy, and 26% died.  In patients with SMA type II, 38% needed NNV, 15% underwent tracheostomy, and 4% died.  In patients with SMA type III, respiratory impairment was moderate and began during the second decade of life.  This data shows the progressively worsening course of restrictive respiratory insufficiency in patients with SMA, and the importance of early respiratory management to limit pulmonary complications and improve the quality of life for these patients.