[Diurnal sleep apnea in myotonic dystrophy]

We investigated diurnal sleep apnea in myotonic dystrophy with respiratory inductive plethysmography. Five of eight patients met criteria for sleep apnea syndrome and had central apnea mainly. In a case showing periodic breathing with apnea like Cheyne-Stokes type breathing, the duration of apnea and breath was even and the tidal volume went waxing and waning regularly. In the other four cases, central apneas were observed in sequence, but the duration of apnea and the tidal volume changed variously. Large breaths between apneas elevated arterial oxygen saturation rather than stable breaths without apnea. We suspected that hypoxemia, which exacerbated by involvement of respiratory muscles, supine position and sleep, initiated the hyperventilation between apneas. And then the saturation of oxygen raised by hyperventilation would cause central sleep apnea.