Effects of Suboptimal CPAP Therapy on Symptoms of Obstructive Sleep Apnoea

Obstructive sleep apnoea (OSA) is a highly prevalent sleep-related breathing disorder. The most effective treatment for OSA is continuous positive airway pressure (CPAP). CPAP therapy has been shown to significantly reduce subjective sleepiness and blood pressure in patients with symptomatic OSA. Its effectiveness tends to depend on its nightly usage and a commonly held view is that CPAP should be used for at least 4h/night. However, previous studies have estimated that a considerable proportion of CPAP users fail to achieve this. In addition, there is inadequate evidence to support this apparent threshold effect and so it is unclear whether such patients actually benefit from treatment or whether they could be withdrawn from CPAP, thus substantially reducing health care costs, or encouraged to increase their nightly usage of CPAP. The aim of the proposed project is to study the effect of CPAP withdrawal on subjective sleepiness in OSA patients using CPAP for less than 4h/night on average. We hypothesize that two-week CPAP withdrawal in patients with 3-4h/night use will lead to a return of OSA-related symptoms. This trial will better establish the minimum level of CPAP adherence which could generally be regarded as effective in reducing OSA-related symptoms.

Sham-CPAP is achieved by setting the CPAP machine to the lowest pressure, insertion of a flow-restricting connector at the machine outlet, and insertion of six extra holes in the collar of the main tubing at the end of the mask to allow air escape and to prevent rebreathing of CO2.

Standard, well-established Epworth questionnaire. Score values between 0 and 24 represent severity of daytime sleepiness.

AHI acquired non-invasively by respiratory polygraphy at baseline and after 2 weeks. Measured in events per hour it represents severity of sleep apnoea.

ODI acquired non-invasively by respiratory polygraphy at baseline and after 2 weeks. Measured in events per hour it represents severity of sleep apnoea.

Acquired automatically by the CPAP/sham-CPAP devices over the course of 2 weeks. Measured in hours per night it represents treatment adherence.

Resting heart rate acquired non-invasively during wakefulness following respiratory polygraphies at baseline and after 2 weeks. Measured in beats per minute (bpm).

Mean resting blood pressure acquired non-invasively during wakefulness following respiratory polygraphies at baseline and after 2 weeks. Measured in mmHg.

Standard, well-established FSS questionnaire. Score values between 7 and 63 represent severity of daytime fatigue.

FOSQ-10 is a standard, well-established 10-item patient-reported survey of impact of disorders of excessive sleepiness on activities of daily living.

OSLER is a standard test consisting of one to three 40-min sessions assessing the patients ability of performing a repetitive task. The OSLER error index measured in events per hour correlates statistically with sleep latency.

MURT is a standard test consisting of two 10-min sessions assessing the patient's alertness. The MURT time measured in milliseconds represents the patients reaction time and correlates with sleep latency.

Inclusion Criteria: Objectively confirmed OSA (at the time of original diagnosis) with an oxygen desaturation index (ODI, ≥4% dips) of ≥15/h and an ESS of >10. Currently ≥15/h oxygen desaturations (≥4% dips) during an ambulatory nocturnal pulse oximetry performed at the end of a 4-night period without CPAP. Eligible patients must have been treated with CPAP for more than 12 months with a mean compliance between 3 and 4h/night. Apnoea-hypopnoea index (AHI) must be less than 10 with treatment (according to CPAP machine download data). Exclusion Criteria: Previous ventilatory failure (awake PaO2<9.0kPa or arterial PaCO2>6kPa). Unstable, untreated coronary or peripheral artery disease, severe arterial hypertension (>180/110mmHg). Previously diagnosed with Cheyne-Stokes breathing. Current professional driver. Age < 20 or > 75 years at trial entry.

Gaisl T, Rejmer P, Thiel S, Haile SR, Osswald M, Roos M, Bloch KE, Stradling JR, Kohler M. Effects of suboptimal adherence of CPAP therapy on symptoms of obstructive sleep apnoea: a randomised, double-blind, controlled trial. Eur Respir J. 2020 Mar 20;55(3):1901526. doi: 10.1183/13993003.01526-2019. Print 2020 Mar.