Negative expiratory pressure (NEP) parameters can predict obstructive sleep apnea syndrome in snoring patients

The objective of this study was to assess whether parameters of the negative expiratory pressure (NEP) technique are able to detect obstructive sleep apnea syndrome (OSAS) in snoring patients. A cross-sectional study included 42 OSAS patients diagnosed by polysomnography (PSG), 34 simple snorers, and 32 healthy subjects. Lung function was measured by using a plethysmograph and the NEP technique was performed with the patient in the seated and supine positions in a random order. The depression was fixed to 5 cmH(2)O. All patients had normal forced expiratory flow/volume loops. Apneic patients had lower Dflow in both positions with a number of oscillations on the expiratory curve obtained with NEP and an expiratory flow limitation (EFL) in the supine position higher than that of other groups (p < 0.05). Changing from the sitting to the supine position raised the EFL of the three groups, with a significant decrease in Dflow and an increase in the number of oscillations in snoring and OSAS patients (p < 0.05). The analysis of variance showed that only the number of oscillations was significantly different between apneic and snoring patients. NEP constitutes a simple and useful tool for the screening OSAS by EFL, especially the number of oscillations obtained with NEP.