The neurophysiological changes associated with pulmonary function in patients with obstructive sleep apnea syndrome

Objective To observe neurophysiological changes and pulmonary function in obstructive sleep apnea syndrome (OSAS) and analyze their inter-relationship. Methods Sixty OSAS patients were studied. Their lung function and phrenic motor nerve conduction (PNC) were examined. Thirty cases without respiratory disorder served as controls. The lung function tests included percentage of the predicted value of vital capacity ( VC% ), percentage of the predicted value of maximal voluntary ventilation ( MVV% ), percentage of the predicted value of forced expiratory volume in one second ( FEV1% ), inspiratory capacity ( IC), and expiratory reserve volume (ERV). The phrenic nerve was stimulated electrically, and the latent period and the diaphragmatic compound muscle action potential (dCMAP) were recorded. Results The VC%, MVV%, FEV1% , IC and ERV of the patients with OSAS were significantly lower than those of the controls. There was no significant difference between the patients and the controls with regard to their PNC latency. In the OSAS patients the amplitude ratio of their dCMAPs was positively correlated with VC% , MVV% , FEV1% , IC and ERV, and negatively with an apnea hypopnea index (AHI).Conclusions PNC examination can provide valuable information for evaluating diaphragmatic dysfunction in those with abnormal lung function. Decreased dCMAP might be associated with abnormal lung function. Key words: Obstructive sleep apnea syndrome;  Lung function;  Phrenic motor nerve conduction