In obese patients scheduled for BS, a gender-specific difference was observed in the performance of the evaluated OSA screening questionnaires. This needs to be considered when these questionnaires are used. Our results underline the need for better gender-specific OSA screening algorithms in morbidly obese patients.

Transcutaneous PCO2 monitoring shows a good concordance with PaCO2 and is a reliable, feasible, patient-friendly and safe alternative to repeated blood gas analysis for patients with severe hypoxaemic and/or hypercapnic respiratory failure receiving emergency NIV in the emergency department. An initial blood gas analysis to evaluate the respiratory and metabolic state and to rule out a significant discrepancy compared with the transcutaneous measurement is recommended.

AIMS OF THE STUDY: Noninvasive ventilation (NIV) is a well-established treatment option for hypercapnic respiratory failure; however, the best mode of ventilation remains unknown. The aim of this retrospective study was to compare patients' adherence to NIV using either pressure support ventilation (PSV) or intelligent volume-assured pressure support (iVAPS). PATIENTS AND METHODS:In this retrospective cohort study, we assessed in-and outpatients suffering from hypercapnic respiratory failure of various aetiologies (chronic obstructive pulmonary disease [COPD], obese COPD [body mass index >30 kg/m 2 ], obesity hypoventilation syndrome and other diseases such as amyotrophic lateral sclerosis or interstitial lung disease) after NIV initiation with PSV or iVAPS. Adherence to treatment was compared between these modes using the Wilcoxon test. Within-group differences were tested using linear regression models. Mortality and emergency hospital readmission rates were modelled using Kaplan-Meier estimates and Cox proportional hazards models. RESULTS: Adherence to treatment was similar in both groups throughout the observation period -after 6 weeks: PSV 363 min/night (interquartile range [IQR] 200-448), iVAPS 369 min/night (IQR 310-468) (p = 0.619); after 1 year: PSV 423 (323-500), iVAPS 429 (298-475) (p = 0.901); at the last follow up: PSV 481 (395-586), iVAPS 426 (391-565) (p = 0.284). NIV reduced PaCO 2 significantly compared with baseline at all follow-ups: PSV −1.29/−1.49/−1.49 kPa, iVAPS −1.47/−1.23/−1.24 kPa, p <0.001 each, PSV vs iVAPS: p = 0.250, 0.756 and 0.352, respectively. Median survival time (PSV 5.06 years, iVAPS median not reached; p = 0.800) and time to first readmission (PSV 3.6 years, iVAPS 7.33 years, p = 0.200) did not differ between groups. Obese COPD patients had a longer time to hospital readmission than lean COPD patients (3.8 vs 1.5 years, hazard ratio (HR) 0.39, 95% confidence interval [CI] 0.16-0. 74; p = 0.007). Good adherence (>4 h/ night and >80% nightly usage) was associated with a lower mortality rate (HR 0.34, 95% CI 0.15-0.77; p = 0.010).CONCLUSION: In a real-world setting of a mixed population with hypercapnic respiratory failure, iVAPS and PSV seem to be similarly effective in improving gas exchange and demonstrate excellent adherence to treatment. A longer survival was noted in NIV-adherent patients. Randomised controlled studies are necessary to identify patients who might benefit more from hybrid ventilation modes.