Randomised trial of compliance with flexible (C-Flex) and standard continuous positive airway pressure for severe obstructive sleep apnea

Nathaniel S. Marshall*, Alister M. Neill, Angela J. Campbell

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

39 Citations (Scopus)


Introduction: Obstructive sleep apnea (OSA) is often treated with continuous positive airway pressure (CPAP) but the effectiveness of treatment is probably limited by poor compliance. CPAP manufacturers are thus attempting to devise more comfortable PAP devices in an effort to improve compliance. An example of such a novel device is Flexible expiratory-modulated PAP (C-Flex mode Respironics REMstar Pro, Murraysville, PA, USA). Materials and methods: We aimed to compare compliance between C-Flex and standard CPAP in patients with severe OSA in a randomised controlled trial. Nineteen patients with severe OSA (mean±SD Apnea Hypopnea Index=78±33/h, Epworth 14±4, PAP 8-17 cm H2O, BMI=39±10 kg/m2) and aged 20-63 years were randomly assigned to 4 weeks of either C-Flex (setting II, n=9) or CPAP (n=10). Results: Patients treated with C-Flex exhibited a trend toward higher compliance with their PAP devices compared to patients treated with standard CPAP (4.7±2.9 vs. 3.0±2.1 h/night, p=0.15, effect size=0.68). Paradoxically, improvements in subjective sleepiness (Epworth Sleepiness Scale) were greater in those who received CPAP than C-Flex (8.1 + 4.9 vs. 2.1 + 4.0 points, p=0.014, effect size=1.46). Improvements in objective wakefulness (Modified Maintenance of Wakefulness Test) and simple reaction times (Psychomotor Vigilance Task) were not significantly different between treatments. This randomised trial provides some evidence that C-Flex might increase initial treatment compliance, compared to CPAP, in patients with severe OSA. However, this trend toward greater compliance was not associated with better short-term treatment outcomes for patients. These findings need to be confirmed in a larger, longer-term trial.

Original languageEnglish
Pages (from-to)393-396
Number of pages4
JournalSleep and Breathing
Issue number4
Publication statusPublished - 2008
Externally publishedYes


  • C-Flex
  • Continuous positive airway pressure
  • Obstructive sleep apnoea syndromes
  • Randomised controlled trial
  • Treatment adherence
  • Treatment compliance


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