Night-time pulse oximetry with nasal flow measurement was performed using the validated ApneaLink (ResMed, San Diego, California, USA) device24 (link)
25 (link) to obtain information on night-time oxygen saturation, apnoeas and hypopnoeas. Sleep study analyses were based on automatic scoring analysis. The sleep study was performed at the patient's home. Individuals were instructed by a trained study nurse on how to put on the nasal cannula and the oximetry probe. An apnoea was defined as a reduction of nasal airflow of ≥80% compared with baseline for ≥10 s. Hypopnoea was defined as a reduction of nasal airflow of ≥30% compared with baseline followed by a simultaneous decrease in oxygen saturation ≥4%. The apnoea index was defined as the number of apnoeas per hour. The REI was defined as the number of apnoeas and hypopnoeas per hour of sleep according to the 2015 updated version of the American Academy of Sleep Medicine (AASM) criteria.26–28 (link) Subclinical sleep apnoea was defined to be present when the REI was 5, but <15 per hour. The ODI was defined as the number of oxygen desaturations ≥4% per hour of sleep.29 (link) An ODI of ≥5 per hour was considered to be abnormal. In addition to REI and ODI, mean night-time SpO2 and the per cent of total sleep time with SpO2<90% were calculated.
25 (link) to obtain information on night-time oxygen saturation, apnoeas and hypopnoeas. Sleep study analyses were based on automatic scoring analysis. The sleep study was performed at the patient's home. Individuals were instructed by a trained study nurse on how to put on the nasal cannula and the oximetry probe. An apnoea was defined as a reduction of nasal airflow of ≥80% compared with baseline for ≥10 s. Hypopnoea was defined as a reduction of nasal airflow of ≥30% compared with baseline followed by a simultaneous decrease in oxygen saturation ≥4%. The apnoea index was defined as the number of apnoeas per hour. The REI was defined as the number of apnoeas and hypopnoeas per hour of sleep according to the 2015 updated version of the American Academy of Sleep Medicine (AASM) criteria.26–28 (link) Subclinical sleep apnoea was defined to be present when the REI was 5, but <15 per hour. The ODI was defined as the number of oxygen desaturations ≥4% per hour of sleep.29 (link) An ODI of ≥5 per hour was considered to be abnormal. In addition to REI and ODI, mean night-time SpO2 and the per cent of total sleep time with SpO2<90% were calculated.
