Airview

Actigraphy and polygraphy were used to measure SDB. Participants were assigned an Actiwatch (Philips Respironics) to wear at sea level for 1–3 days and throughout the duration of their 3‐day stay at White Mountain Research Center (Barcroft Station, 3800 m). Participants were also instrumented with respiratory polygraphy (Apnealink Air, ResMed) for 1 night at sea level and each night while at altitude. The Apnealink Air was chosen because it is designed to allow participants to activate the device on their own after training for simple at‐home testing at sea level. These methods were used to quantify SDB via apnea–hypopnea index (AHI), oxygen desaturation index (ODI), minutes of wakefulness after sleep onset (WASO), sleep efficiency, and nocturnal pulse oximetry. In the morning, SSS and PROMIS questionnaires assessing their subjective sleep and health were obtained as described above. The actigraphy and polygraphy data were scored blindly by a registered polysomnographic technologist using American Academy of Sleep Medicine criteria for scoring and Chicago criteria for events via Philips Actiware 6 software and Airview, respectively. Due to equipment limitations and subject adherence, complete sleep studies were obtained from ten individuals at sea level, nine on night 1 at high altitude, eight on night 2, and six on night 3.

At recruitment, demographic information (age, sex) and SRI questionnaire were obtained from the patient. Daytime arterial blood gas (ABG) analysis was obtained according to standard recommendations in sitting patients without ventilation, with the current oxygen flow provided [20 (link)]. Clinical data [body mass index (BMI), disease, time with HMV, ventilation interface, humidifier] were collected from the electronic hospital records. Pulmonary function test data was obtained from the electronic clinical records if obtained at least 12 months previous to the beginning of the study. Ventilation parameters and daily usage were recorded by the readout of the ventilator’s built-in software (ResMed AirView® and Philips EncoreAnywhere® platforms), obtained during a scheduled medical visit. At 5 years, patients completed the SRI again during scheduled medical visits. Time to complete the questionnaire was recorded at both times.
If patient died in the study period, date of death was obtained from the electronic hospital records or national patient information registry (if death was outside the hospital).