Influence of head flexion and rotation on obstructive sleep apnea severity during supine sleep.

Head posture influences the collapsibility of the passive upper airway during anaesthesia. However, little is known about the impact of head posture during sleep. The objective of this study was to develop and validate an instrument to measure head posture during supine sleep and to apply this instrument to investigate the influence of head posture on obstructive sleep apnea (OSA) severity. A customized instrument to quantify head flexion and rotation during supine sleep was developed and validated in a benchtop experiment. Twenty-eight participants with suspected OSA were successfully studied using diagnostic polysomnography with the addition of the customized instrument. Head posture in supine sleep was discretized into four categories by two variables: head flexed or not (flexion >15°); and head rotated or not (rotation >45°). Sleep time in each posture and the posture-specific apnea-hypopnea index (AHI) were quantified. Linear mixed-effect modelling was applied to determine the influence of flexion and rotation on supine OSA severity. Twenty-four participants had ≥15 min of supine sleep in at least one head-posture category. Only one participant had ≥15 min of supine sleep time with the head extended. Head flexion was associated with a 12.9 events/h increase in the AHI (95% CI: 3.7-22.1, p = .007). Head rotation was associated with an 11.0 events/h decrease in the AHI (95% CI: 0.3-21.6, p = .04). Despite substantial interparticipant variability, head flexion worsened OSA severity, and head rotation improved OSA severity. Interventions to promote rotation and restrict flexion may have therapeutic benefit in selected patients.