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Effects of CPAP therapy withdrawal on exhaled breath pattern in obstructive sleep apnoea
  1. Esther I Schwarz1,
  2. Pablo Martinez-Lozano Sinues2,
  3. Lukas Bregy2,
  4. Thomas Gaisl1,
  5. Diego Garcia Gomez2,
  6. Martin T Gaugg2,
  7. Yannick Suter2,
  8. Nina Stebler1,
  9. Yvonne Nussbaumer-Ochsner1,
  10. Konrad E Bloch1,3,4,
  11. John R Stradling5,
  12. Renato Zenobi2,
  13. Malcolm Kohler1,3,4
  1. 1Department of Pulmonology and Sleep Disorders Centre, University Hospital of Zurich, Zurich, Switzerland
  2. 2Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology, Zurich, Switzerland
  3. 3Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
  4. 4Zurich Centre for Interdisciplinary Sleep Research, University of Zurich, Zurich, Switzerland
  5. 5Oxford Centre for Respiratory Medicine and NIHR Oxford Biomedical Research Centre, Churchill Hospital, Oxford, UK
  1. Correspondence to Professor Malcolm Kohler, Chair Respiratory Medicine, Clinical Director, Department of Pulmonology and Sleep Disorders Centre, University Hospital of Zurich, Raemistrasse 100, Zurich CH-8091, Switzerland; malcolm.kohler{at}


Background Obstructive sleep apnoea (OSA) is highly prevalent and associated with cardiovascular and metabolic changes. OSA is usually diagnosed by polysomnography which is time-consuming and provides little information on the patient's phenotype thus limiting a personalised treatment approach. Exhaled breath contains information on metabolism which can be analysed by mass spectrometry within minutes. The objective of this study was to identify a breath profile in OSA recurrence by use of secondary-electrospray-ionization-mass spectrometry (SESI-MS).

Methods Patients with OSA effectively treated with CPAP were randomised to either withdraw treatment (subtherapeutic CPAP) or continue therapeutic CPAP for 2 weeks. Exhaled breath analysis by untargeted SESI-MS was performed at baseline and 2 weeks after randomisation. The primary outcome was the change in exhaled molecular breath pattern.

Results 30 patients with OSA were randomised and 26 completed the trial according to the protocol. CPAP withdrawal led to a recurrence of OSA (mean difference in change of oxygen desaturation index between groups +30.3/h; 95% CI 19.8/h,40.7/h, p<0.001) which was accompanied by a significant change in 62 exhaled features (16 metabolites identified). The panel of discriminating mass-spectral features allowed differentiation between treated and untreated OSA with a sensitivity of 92.9% and a specificity of 84.6%.

Conclusion Exhaled breath analysis by SESI-MS allows rapid and accurate detection of OSA recurrence. The technique has the potential to characterise an individual's metabolic response to OSA and thus makes a comprehensible phenotyping of OSA possible.

Trial registration number NCT02050425 (registered at

  • Sleep apnoea
  • Exhaled Airway Markers

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