[Nocturnal hypoxia index: a new pulse oxymetry index of nocturnal hypoventilation in neuromuscular disorders].

: Respiratory insufficiency due to progressive muscle wasting is a major cause of death in various neuromuscular disorders. Morning headache and anorexia leading to slowly progressive body weight loss are frequently observed as initial symptoms of insufficient ventilation. From our experience nocturnal pulse oxymetry is a valuable study to detect early respiratory insufficiency and helpful to evaluate the effectiveness of ventilatory assistance, since ventilation is more impaired during sleep in early stage of respiratory insufficiency. Percent desaturation time (total desaturation time (SaO2 or = SaO2 > 90%) + (% time of 90% > or = SaO2 > 85%) x 2 + (% time of 85% > or = SaO2 > 80%) x 3 + (% time of 80% > or = SaO2 > 75%) x 4 + (% time of 75% > or = SaO2 > 70%) x 5.... This index is good for any stage of respiratory failure, and applicable to nocturnal hypoxia of other causes. The criteria for initiating mechanical ventilation in DMD can be substituted by "NHI is above 130.