Can nocturnal respiratory failure predict adherence to PAP therapy in patients with OSAS?

<bold>Introduction:</bold> A considerable number of patients with OSAS shows nocturnal respiratory failure (NRF), defined by a nighttime oxygen saturation <90% in more than 30% of the total sleep time (TST90). While NRF could substantially impact sleep quality and OSAS-related symptoms, there are few data on the relationship between NRF and PAP adherence. <bold>Aims and Objectives:</bold> To investigate the different adherence to PAP therapy according to the presence of NRF. <bold>Methods:</bold> In this prospective observational study, we enrolled 129 patients with moderate-severe OSAS, 74 of whom also had NRF. <bold>Results:</bold> Patients with OSAS and NRF were more frequently male (p = 0.02), had a higher BMI (p < 0.001) and a higher AHI (p < 0.0001). Patients with NRF were more frequently treated with CPAP (p = 0.04) or BPAP (p = 0.005), while autoCPAP was more frequently preferred in patients with OSAS only (p < 0.0001). CPAP titration pressures were lower in the OSAS group (p < 0.0001). At time-to-event analysis, NRF was significantly associated to higher registered adherence to device use (p = 0.02), as also confirmed by Cox univariate regression analysis (p = 0.01). After correcting the model for age, gender, AHI and time elapsed from the start of treatment to the first follow-up did, NRF remained the only significant predictor for PAP adherence (OR = 3.04, p = 0.02). <bold>Conclusions:</bold> This study underlines the importance of nocturnal hypoxia in patients' compliance to PAP therapy. Further investigations on nocturnal respiratory failure in OSAS patients are needed to better explain the impact of NRF on PAP adherence.