The effect of treatment on diaphragm contractility in obstructive sleep apnea syndrome.

In untreated obstructive sleep apnea syndrome (OSAS) inspiratory efforts are made against an occluded airway and diaphragm fatigue might therefore complicate OSAS. To test this hypothesis we measured twitch transdiaphragmatic pressure (Tw Pdi) in response to bilateral cervical magnetic stimulation of the phrenic nerve roots in nine patients with OSAS before and one month after successful therapy with nasal continuous positive airways pressure (nCPAP). The mean Tw Pdi before therapy was 23.2cm H2O and after therapy was 22.8cm H2O (P = 0.59); the mean change after initiation of nCPAP was 0.4cm H2O with 95% confidence intervals of -1.3cm H2O and +2.1 cm H2O. We conclude that low frequency diaphragm fatigue does not complicate untreated OSAS.