Apnea and hypopnea events were not distinguished as separate event types during scoring. Both were classified as a respiratory event that required a 50% reduction in Nasal Flow signal for at least 10 seconds.Estimated sleep duration, providing an approximation of total sleep duration (i.e. total sleep time) inferred from analysis of non-EEG channels
Zhao et al., 2017 (PMID:27707441) Any continuous periods of >=20 min with loss of respiratory channel was marked as wake and not included in the estimates.