O052 Hypoxemia and arousals modulate nocturnal respiratory event-related cardiac function variations in obstructive sleep apnea patients

Abstract Introduction Obstructive sleep apnea (OSA) and its related consequences (i.e. desaturations or arousals) are known to immediately impact cardiac function. However, the dynamics of variations in heart function due to individual obstructive events and their consequences are not fully explored. We hypothesized that the respiratory events without immediate physiological consequences cause no post-event variations in cardiac function. Methods Variations in RR and rate-corrected QT (QTc) intervals were studied separately before, during, and after 4310 respiratory events from 134 OSA patients with no comorbidities (except diagnosed hypertension) or medications affecting heart function. Mixed-effect models were used to assess the impact of desaturation and arousal on cardiac function variations, independent of age, body mass index, sex, and diagnosed hypertension. Results In general, mean QTc intervals significantly (p<0.05) decreased during and increased after respiratory events compared to before events. Detailed analysis revealed that arousal (RR estimate= -23.6 millisecond, p<0.05; QTc estimate= 5.7 millisecond, p<0.05) or both desaturation and arousal (RR estimate= -33.0, p<0.05; QTc estimate= 8.4, p<0.05) modulated mean post-events RR and QTc intervals independently of confounding factors and between-subject variations, while desaturation alone affected only the RR interval (estimate= -9.4, p<0.05). In respiratory events without desaturation and arousal, mean post-event RR and QTc intervals showed no significant variation compared to before events. Discussion Respiratory events cause distinct cardiac responses if severe enough to cause desaturations and arousal. This indicates that the impact of respiratory events on cardiac function varies based on their immediate physiological consequences; without them, post-event cardiac variations are non-significant.