title: Volume targeted versus pressure support non-invasive ventilation in patients with super obesity and chronic respiratory failure: a randomised controlled trial.
abstract: BACKGROUND
  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.
  
  
  METHODS
  The primary outcome was change in daytime arterial PCO(2) (PaCO(2)) 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 0.6 kPa, 95% CI 0.2 to 1.1, p<0.01 vs 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 vs 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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Lane Fox Respiratory Unit, St Thomas' Hospital, Westminster Bridge Road, London, UK. patrick.b.murphy@kcl.ac.uk
authors.forename: Patrick Brian
authors.initials: PB
authors.lastname: Murphy
authors.forename: Craig
authors.initials: C
authors.lastname: Davidson
authors.forename: Matthew David
authors.initials: MD
authors.lastname: Hind
authors.forename: Anita
authors.initials: A
authors.lastname: Simonds
authors.forename: Adrian J
authors.initials: AJ
authors.lastname: Williams
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Hopkinson
authors.forename: John
authors.initials: J
authors.lastname: Moxham
authors.forename: Michael
authors.initials: M
authors.lastname: Polkey
authors.forename: Nicholas
authors.initials: N
authors.lastname: Hart
mesh_terms: D000328:Adult; D000368:Aged; D000886:Anthropometry / Q000379:methods; D002245:Carbon Dioxide / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology; D010845:Obesity Hypoventilation Syndrome / Q000097:blood / Q000503:physiopathology / Q000628:therapy*; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D011175:Positive-Pressure Respiration / Q000379:methods*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D011788:Quality of Life; D016037:Single-Blind Method; D016896:Treatment Outcome; D015431:Weight Loss / Q000502:physiology
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen