Volume targeted versus pressure support non-invasive ventilation in patients with super obesity and chronic respiratory failure: A randomised controlled trial

Abstract

Introduction: Automatic titration modes of non-invasive ventilation, including average volume assured pressure support (AVAPS), are hybrid technologies that target a set volume by automated adjustment of pressure support (PS). These automated modes could offer potential advantages over fixed level PS, in particular, in patients who are super obese. Methods: Consecutive patients with obesity hypoventilation syndrome were enrolled in a two-centre prospective single-blind randomised controlled trial of AVAPS versus fixed-level PS using a strict protocolised setup. Measurements: The primary outcome was change in daytime arterial PCO2 (PaCO2) at 3 months. Body composition, physical activity (7-day actigraphy) and health-related quality of life (severe respiratory insufficiency questionnaire, SRI) were secondary outcome measures. Results: 50 patients (body mass index 50±7 kg/m 2; 55±11 years; 53% men) were enrolled with a mean PaCO 2 of 6.9±0.8 kPa and SRI of 53±17. 46 patients (23 AVAPS and 23 PS) completed the trial. At 3 months, improvements in PaCO 2 were observed in both groups (AVAPS Δ0.6 kPa, 95% CI 0.2 to 1.1, p<0.01 vs PS Δ0.6 kPa, 95% CI 0.1 to 1.1, p=0.02) but no between-group difference (Δ-0.1 kPa, 95% CI -0.7 to 0.6, p=0.87). SRI also improved in both groups (AVAPS Δ11, 95% CI 6 to 17, p<0.001 vs PS Δ7, 95% CI 1 to 12, p=0.02; between groups Δ5, 95% CI -3 to 12, p=0.21). Secondary analysis of both groups combined showed improvements in daytime physical activity that correlated with reduction in fat mass (r=0.48; p=0.01). Conclusion: The study demonstrated no differences between automated AVAPS mode and fixed-level PS mode using a strict protocolised setup in patients who were super obese. The data suggest that the management of sleep-disordered breathing may enhance daytime activity and promote weight loss in super-obese patients. Trial registration details available at http:// www.controlled-trials. com/ISRCTN63940700.