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Original Article
Autoadjusted versus fixed CPAP for obstructive sleep apnoea: a multicentre, randomised equivalence trial
  1. Konrad E Bloch1,2,
  2. Fabienne Huber1,
  3. Michael Furian1,
  4. Tsogyal D Latshang1,
  5. Christian M Lo Cascio1,
  6. Yvonne Nussbaumer-Ochsner1,
  7. Oliver Senn3,
  8. Erich W Russi1,2,
  9. Malcolm Kohler1,2,
  10. Otto D Schoch4,
  11. Alexander Turk5,
  12. Edelbert Imhof6,
  13. Irène Laube6,
  14. Felix Matthews1,
  15. Robert Thurnheer7
  1. 1Sleep Disorders Center and Pulmonary Division, University Hospital Zurich, Zurich, Switzerland
  2. 2Zurich Center for Interdisciplinary Sleep Research, University of Zurich, Zurich, Switzerland
  3. 3Institute of Primary Care, University Hospital Zurich, University of Zurich, Zurich, Switzerland
  4. 4Sleep Disorders Center and Pulmonary Division, Cantonal Hospital St. Gallen, St. Gallen, Switzerland
  5. 5Sleep Disorders Center and Pulmonary Division, Zurich Rehabilitation Clinic, Wald, Switzerland
  6. 6Sleep Disorders Center and Pulmonary Division, City Hospital Triemli, Zurich, Switzerland
  7. 7Sleep Disorders Center and Pulmonary Division, Cantonal Hospital Munsterlingen, Munsterlingen, Switzerland
  1. Correspondence to Professor Konrad E Bloch, Pulmonary Division and Sleep Disorders Center, University Hospital Zurich, Rämistrasse 100, Zurich CH-8091, Switzerland; konrad.bloch{at}


Background The obstructive sleep apnoea syndrome (OSAS) is conventionally treated by continuous positive airway pressure set at a fixed level (fCPAP). Automatic mask pressure adjustment (autoCPAP) is increasingly used during home therapy. We investigated whether autoCPAP is equivalent to fCPAP in improving sleepiness in patients with OSAS in the long-term.

Methods In this multicentre equivalence trial, 208 patients with OSAS, with median Epworth sleepiness score (ESS) 13, apnoea/hypopnoea index 48.4/hour, were randomised to treatment with autoCPAP (5–15 mbar) or fCPAP (pressure set at the 90th percentile applied by autoCPAP during 2–4 weeks adaptation). Coprimary outcomes were changes in subjective and objective sleepiness from baseline to 2 years after treatment. Equivalence ranges were ±2 points in ESS and ±3 min sleep resistance time evaluated by recording responses to light signals.

Results At 2 years, in the intention to treat analysis, the reduction in sleepiness versus pretreatment baseline was similar in patients using autoCPAP (n=113, mean ESS-change −6.3, 95% CI −7.1 to −5.5; sleep resistance time +8.3 min, +6.9 to +9.7) and fCPAP (n=95, mean ESS-change −6.2, 95% CI −7.0 to −5.3; sleep resistance time +6.3 min, +4.7 to +7.8). The 95% CI of difference in ESS-reduction between autoCPAP and fCPAP was −0.9 to +1.4 and the 95% CI of difference in increase in sleep resistance time was −2.6 to +1.0 min. Blood pressure reduction and OSAS-related costs were similar between groups.

Conclusions AutoCPAP and fCPAP are equivalent within prespecified ranges in improving subjective and objective sleepiness in patients with OSAS over the course of 2 years. Costs of these treatments are similar.

Trial registration number NCT00280800.

  • sleep apnoea
  • non invasive ventilation
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  • Contributors KEB contributed to conception and design of the study, acquisition, analysis, interpretation of data and drafting the article. FH contributed to the data analysis and drafted the article with input from KEB. MF contributed to data analysis and interpretation and to the manuscript revision. RT and EWR contributed to conception and design of the study, acquisition and interpretation of data. TDL, CMLC, YN-O, OS, MK, ODS, AT, EI, IL contributed to acquisition, analysis and interpretation of data. FM contributed to study design, data acquisition and analysis. All authors reviewed and commented on the manuscript.

  • Funding The study was supported by the Swiss National Science Foundation, the Lung Leagues of Zurich, St. Gallen and Thurgau and by unconditional grants from the Respironics Foundation and ResMed Switzerland.

  • Disclaimer This was an investigator initiated trial, and the commercial companies were not involved in study design, data acquisition and analysis or writing the manuscript.

  • Competing interests KEB reports grants to his institution from Swiss National Science Foundation, Zurich Lung League, Respironics Foundation, ResMed Switzerland, during the conduct of the study. The other authors report no competing interests.

  • Patient consent Obtained.

  • Ethics approval Kantonale Ethikkommission Zurich.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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