Event-level nocturnal blood pressure dynamics in obstructive sleep apnea assessed by cuffless monitoring

STUDY OBJECTIVES: Obstructive sleep apnea (OSA) contributes to abnormal blood pressure (BP) variability (BPV). While OSA has been linked to increased BPV using intermittent or cuff-based measurements, the hemodynamic responses to individual respiratory events remain poorly understood. We aimed to delineate event-level BP dynamics of OSA using a cuffless continuous monitoring device. METHODS: We prospectively enrolled adults who underwent overnight polysomnography for suspected OSA. Continuous systolic and diastolic BPs were recorded using a validated cuffless photoplethysmography-based ring device. Time-stamped respiratory events (apnea and hypopnea) were annotated and synchronized with cardiovascular signals. We analyzed the BP, heart rate (HR), and oxygen saturation (SpO₂) trajectories relative to each respiratory event, and applied linear mixed-effects models to evaluate factors influencing BP changes. Participant-level BPV indices, including the standard deviation and average real variability, were calculated throughout the night. RESULTS: A total of 12,724 respiratory events from 62 patients were analyzed. Events were followed by a consistent pattern: a BP dip during the event, followed by a rebound surge that peaked at 11.4 s post-event. This peak occurred after the HR peak (8.2 s) but before the SpO₂ nadir (14.7 s). In mixed-effects analyses, longer event duration, apnea (vs. hypopnea), and REM sleep were associated with larger BP fluctuations. At the participant-level, the mean upward duration of event-related BP surges correlated with the SpO₂ nadir. CONCLUSION: OSA induces BP fluctuations at the level of individual respiratory events. These findings demonstrate that OSA influences cardiovascular dynamics at event-level, beyond traditional measures of nocturnal BPV.