The role of the expiratory phase in obstructive sleep apnoea

The role of the expiratory phase in obstructive sleep apnoea (OSA) is not w ell known, The aim of our study tvas to verify the contribution of expirato ry narrowing to apnoea in a group of OSA patients by evaluating the effects of short-term treatment with continuous positive airway pressure (CPAP). i ntermittent positive pressure ventilation (IPPV) and bi-level positive airw ay pressure (BIPAP). We studied a selected group of 10 OSA patients whose therapeutic pressure l evel of CPAP was at least 10 cm H2O During CPAP therapy the mean apnoea/hyp opnoea index (AHI) and oxyhaemoglobin desaturation index (ODI) decreased fr om 64.8 to 6.3(P<0.001) and from 58.5 to 6.1 (P<0.001), respectively and me an nadir SAO(2) increased from 62.0 to 91.6 (P<0.001). None of the patients reached optimal setting (elimination of snoring, reduc tion of apnoeas and non-apnoeic desaturation events at least to 15 or less per hour of sleep and maintenance of oxygen saturation approximately 90%) d uring IPPV and two patients did not tolerate final IPAP pressure levels. Wh en a critical level of EPAP (BIPAP) was applied in the same night to these patients, optimal setting was reached in all subjects. During BIPAP, mean A HI decreased from 64.8 to 7.4(P<0.001): ODI decreased from 58.5 to 7.6(P<0. 001) and nadir SAO(2) increased from 62.0 to 91.6 (P<0.001). Our study confirms the essential role of a critical level of EPAP in succes sful ventilatory treatment in OSA, thereby indicating, in agreement with fe w previous studies, the critical role of end of expiratory occlusion in OSA pathogenesis.