Relationship of Pulse Arrival Time patterns and Obstructive Sleep Apnea in wake to sleep transitions

Obstructive sleep apnea (OSA) is a disease with known autonomic pathophysiological characteristics: frequent respiratory events during sleep induce intermittent hypoxia, arousals and awakenings, and sympathetic over-activation. Over time, they can alter haemodynamic regulation and lead to pathological conditions, such as disrupting the natural physiological nocturnal blood pressure (BP) dip and increasing cardiovascular inflammation. However, BP measurements during the night are not part of polysomnography (PSG) clinical routine. Alternatively, pulse arrival time (PAT) is a useful marker of autonomic BP control and respiratory effort, but of different interpretation over long time periods. Therefore, we focused on the transient physiological effects happening between wake and sleep. We estimated PAT changes after repeated wake-sleep transitions during PSG in 547 people (age: $50 \pm 11$ years, 252 females) with suspected sleep disorders. Preliminary results shown that the PAT total change over 5 minutes has a U -shape relationship with some OSA, sleep, and oxygen saturation metrics.