Bilevel PAP data was downloaded from the device at 3 and 12 months. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI) where a score of ≥5 indicates impaired sleep quality and the minimal clinically important difference (MCID) has been defined as ranging from 1.5 to 3 (22 (link),23 (link)). Subjective daytime sleepiness was assessed using the Epworth Sleepiness Scale (ESS), where a score of >10 indicates excessive daytime sleepiness and the MCID ranges from 2 to 3 (24 (link)). Fatigue was assessed using the Pichot Fatigue Scale, where a score >22 indicates excessive fatigue. Questionnaires were administered and scale scores were determined at baseline prior to initiation of bilevel PAP when patients were still being treated with CPAP/APAP, and then at sleep center visits after 3 and 12 months. The presence or absence of therapy-related side effects was determined by patient interview at each follow-up visit. The presence/severity of side effects was rated on a visual analogue scale from 0 (not at all) to 10 (very important). Patient satisfaction with bilevel PAP was determined based on direct questioning, and asking the question “Do you want to continue treatment?”.