The expiratory positive pressure is essential in ventilation of Obstructive Sleep Apnea (OSA)

Purpose: The specific role of inspiratory and expiratory positive pressure in the ventilatory treatment of OSA remain not completely understood. In our study we verified the role of expiratory component (EPAP) of continuous positive airway pressure (CPAP) in maintaining the upper airway patency in OSA patients. Methods: We studied 10 patients (9 males, 1 females, with mean age 43 years, mean Body Mass Index 35,6 kg/m2, mean PaO2 85,3 mmHg, mean PaCO2 39 mmHg, mean Apnea/hypopnea Index, AHI, 66/hour, Mean Nocturnal Minimal oxyemoglobin saturation, Nadir, 61,7%) affected by moderate-severe normocapnic OSA, who required therapeutic pressure level of CPAP at least 9 cmH2O (mean 11,3 cmH2O). These patients were placed on spontaneous pressure ventilation (PSV) by BiPAP, with EPAP=O and IPAP value equal to the therapeutic CPAP pressure, previously determined, evaluating snoring, AHI, Nadir. Subsequently, unchanged IPAP pressure, we adjusted EPAP pressure progressively increasing the value (BiLEVEL) until therapeutic effect was reached. Results: In all patients BiLEVEL was effective at lower levels of EPAP, compared with previously determined CPAP (mean IPAP 11,3 cmH2O, mean EPAP 7,7 cmH2O, mean difference between IPAP and EPAP 3,7 cmH2O). PSV, with EPAP = 0 was not tolerated in 2 patients and was not effective in other patients. Conclusions: Our results confirm that expiratory component of CPAP is a determinant factor in the ventilatory treatment of OSA and IPAP without EPAP is not effective in these patients.