Lung volumes and mean apnea duration in obstructive sleep apnea.

Former studies suggested that lung volumes might play a role in pathomechanisms of obstructive sleep apnea (OSA). Mean apnea duration (MAD) is a rarely investigated parameter in OSA but is possibly a surrogate of arousal threshold. The aim of this study was to evaluate the influence of lung volumes to MAD in OSA. In 69 patients with obstructive sleep apnea (51 male und 18 female, BMI 34.2+/-6.0 kg/m(2), age 53.6+/-9.7 years, AHI 43.1+/-21.1/h) we performed a polysomnography and pulmonary function testing in daytime. There was a significant correlation between MAD and residual volume (RV) (r=0.51; p<0.001), which was the highest correlation we found. In linear regression analysis RV remained the only independent variable with significant influence on MAD (p<0.001). We could show that RV seems to play a role in the mechanisms of apnea termination in terms of MAD. MAD reflects the time until a specific negative intrathoracic pressure is reached to induce an arousal. In this process dependency on RV could explain our results. Despite some limitations these results provide some new aspects in understanding pathophysiology of OSA.