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Volume targeted versus pressure support non-invasive ventilation in patients with super obesity and chronic respiratory failure: a randomised controlled trial [with consumer summary]
Murphy PB, Davidson C, Hind MD, Simonds A, Williams AJ, Hopkinson NS, Moxham J, Polkey M, Hart N
Thorax 2012 Aug;67(8):727-734
clinical trial
6/10 [Eligibility criteria: Yes; Random allocation: Yes; Concealed allocation: No; Baseline comparability: Yes; Blind subjects: Yes; Blind therapists: No; Blind assessors: No; Adequate follow-up: Yes; Intention-to-treat analysis: No; Between-group comparisons: Yes; Point estimates and variability: Yes. Note: Eligibility criteria item does not contribute to total score] *This score has been confirmed*

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/m2; 55 +/- 11 years; 53% men) were enrolled with a mean PaCO2 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 PaCO2 were observed in both groups (AVAPS 0.6 kPa, 95% CI 0.2 to 1.1, p < 0.01 versus PS 0.6 kPa, 95% CI 0.1 to 1.1, p = 0.02) but no between-group difference (-0.1 kPa, 95% CI -0.7 to 0.6, p = 0.87). SRI also improved in both groups (AVAPS 11, 95% CI 6 to 17, p < 0.001 versus PS 7, 95% CI 1 to 12, p = 0.02; between groups 5, 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.
Reproduced with permission from the BMJ Publishing Group.

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