Vascular Dynamics During Respiratory Arousal From Sleep Assessed by Oximeter-Based Vascular Stiffness Measures

Cortical arousals significantly impact obstructive sleep apnoea (OSA) pathophysiology and cardiovascular consequences, often mediated by sympathetic activation. While pulse oximetry (PPG) provides an accessible reflection of autonomic responses such as changes in pulse rate (PR) and pulse wave amplitude (PWA), the dynamic influence on other vascular indices remains less explored. We investigated dynamic changes in PPG-derived pulse propagation time (PPT), a metric reflecting modulation in vascular stiffness. It is hypothesised that PPT beat-to-beat responses to arousals are specific and independent from other pulse wave parameters. Polysomnography data from 87 patients were analysed (mean age 54 ± 12 years, 26% female, mean BMI 27.7 ± 3.6 kg/m², mean Apnea-Hypopnea Index 33 ± 23 events/h; total 18,275 respiratory events). The mean percentage change (shortening, vascular stiffening) of the PPT following respiratory events was significantly greater when accompanied by an EEG arousal in both apnoeas (-21.1% vs. -17.9%, p < 0.001) and hypopneas (-19.4% vs. -17.0%, p < 0.001). In a multivariate logistic mixed-effect model, ∆PPT emerged as an independent predictor of EEG arousal presence (p < 0.001, scaled odds ratio: 1.14; 95% CI: 1.09-1.20), accounting for event type, anthropometrics and changes in PWA, PR, SpO₂. Dynamic, short-term changes in PPG-derived PPT are significantly associated with cortical arousals following respiratory events in OSA patients. This parameter provides independent predictive information beyond established PPG metrics, likely reflecting rapid, arousal-induced alterations in vascular tone. These findings highlight a novel PPG-based marker that could quantify the vascular stress in OSA.