Sleep position, respiratory event rates, and nocturnal oxygenation in a clinical monitoring cohort: a positional phenotyping analysis

Background Sleep position may affect respiratory events and nocturnal oxygenation, but positional event rates and their contributions relative to monitoring duration remain incompletely characterised. Methods We retrospectively analysed 320 Level III portable respiratory monitoring records from a single-centre clinical cohort. Overall REI was ≥5 events/h in 249 participants. Supine and non-supine rates were compared in 317 participants with recordings in both positions. POSA classification was assessed in 219 participants with REI ≥5 events/h and at least 30 min of monitoring in each position; central apnoeas were excluded. POSA was defined by a supine event rate at least twice the non-supine rate. Results Supine versus non-supine median respiratory event rates were 22.73 versus 5.05 events/h, and desaturation rates were 7.12 versus 1.86 events/h (both p < 0.001). POSA was identified in 142/219 participants (64.8%). Compared with non-POSA participants, those with POSA had higher minimum SpO₂ (83.5% versus 78.0%, p = 0.004), fewer desaturation events (48.5 versus 85.0, p = 0.035), and lower REI (27.35 versus 42.14 events/h, p = 0.001). REI correlated with minimum SpO₂ (ρ = −0.465) and cumulative desaturation duration (ρ = 0.644). Among 304 participants, supine positioning represented 57.0% of monitoring duration but 73.7% of respiratory and 74.3% of desaturation events. Conclusion Supine positioning was associated with higher event rates and a disproportionate event contribution in this clinical monitoring cohort. POSA findings apply only to eligible participants. Position-specific measures may complement conventional indices but do not establish treatment effects.