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Volume 14 No. 09
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Accepted Papers

Scientific Investigations

The Association Between Adherence to Positive Airway Pressure Therapy and Long-Term Outcomes in Patients With Obesity Hypoventilation Syndrome: A Prospective Observational Study

Izolde Bouloukaki, MD, PhD; Charalampos Mermigkis, MD, PhD; Stylianos Michelakis, MD; Violeta Moniaki, RN; Eleni Mauroudi, RN; Nikolaos Tzanakis, MD, PhD; Sophia E. Schiza, MD, PhD
Sleep Disorders Center, Department of Thoracic Medicine, University of Crete, Heraklion, Greece

Study Objectives:

To assess the role of different levels of adherence and long-term effects of positive airway pressure (PAP) therapy on gas exchange, sleepiness, quality of life, depressive symptoms, and all-cause mortality in patients with obesity hypoventilation syndrome (OHS).


A total of 252 patients with newly diagnosed OHS were followed up for a minimum of 2 years after PAP initiation. PAP adherence (h/night) was monitored. Arterial blood gas samples were taken with patients being alert for more than 4 hours after morning awakening. Subjective daytime sleepiness (Epworth Sleepiness Scale [ESS]), quality of life (Short Form 36 [SF-36]) and patient's depressive symptoms (Beck Depression Inventory [BDI]) were assessed before and at the end of the follow-up period, along with all-cause mortality.


At the end of the follow-up period (median duration [25th–75th percentile], 30 [24–52] months), PaO2 increased from baseline (72.7 ± 10.3 versus 63.2 ± 10.6, P < .001) and both PaCO2 and HCO3 decreased (43.0 [39.2–45.0] versus 50.0 [46.7–55.4] and 27.5 ± 3.2 versus 31.4 ± 4.2, respectively, P < .001). In addition, PAP therapy significantly improved ESS (7 [4–9] versus 14 [11–16], P < .001), BDI (8.8 ± 4.9 versus 15.5 ± 7.3, P < .001) and SF-36 (82 [78–87] versus 74 [67–79], P < .001) scores. Over the follow-up period 11 patients died. Patients who used PAP for > 6 h/night had significant improvements (P < .05) in blood gases and SF-36 scores than less adherent patients.


Increased hours of use and long-term therapy with PAP are effective in the treatment of patients with OHS. Clinicians should encourage adherence to PAP therapy in order to provide a significant improvement in clinical status and gas exchange in these patients.


A commenary on this article appears in this issue on page 1455.

Clinical Trial Registration:

Title: PAP Therapy in Patients With Obesity Hypoventilation Syndrome, Registry:, Identifier: NCT03449641, URL:


Bouloukaki I, Mermigkis C, Michelakis S, Moniaki V, Mauroudi E, Tzanakis N, Schiza SE. The association between adherence to positive airway pressure therapy and long-term outcomes in patients with obesity hypoventilation syndrome: a prospective observational study. J Clin Sleep Med. 2018;14(9):1539–1550.

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