P006 Effect of CPAP on Heart Rate and Heart Rate Variability in Patients with Obstructive Sleep Apnoea

Abstract Introduction Heart Rate (HR) and Heart Rate Variability (HRV) are both indicators of the autonomic nervous system. Both low HR and high HRV indicate greater vagal/sympathetic ratio consistent with better sleep quality. However, high HRV may also reflect untreated OSA due to the large negative intra-thoracic pressure swings. Thus, effects of CPAP treatment of OSA on HR and HRV are poorly described. Aim To assess HRV and HR in patients with OSA before and after CPAP controlled for sleep stage (SS) and body position. Methods 15 Patients (age 33-75, (8M/7F), average BMI 33.7kg/m2) with a confirmed diagnosis of sleep-disordered breathing, mean AHI of 42.9 (range: 23.8-118.0), underwent a diagnostic and CPAP in-laboratory polysomnography. HR and HRV were measured using 5-10min blocks in each SS (wake, N2, N3, REM) in lateral, prone and supine positions using ProfusionTM PSG4 (Compumedics, Abbotsford). LabChart® (ADInstruments, Dunedin) was used for HRV analysis. HRV was measured using the non-linear metrics of SD1 and SD2, derived from Poincaré plots. HRV and HR were then compared off and on CPAP. Results Preliminary results in 5 patients (age 33-72, 4M/1F, average BMI 30.5kg/m2) show HR decreased 9.6±2.4% and R-R interval increased 12.2±2.3% with CPAP. Preliminary analysis does not show that HRV decreased with CPAP (Diagnostic vs CPAP, SD1: 33.3 + 10.5ms vs 34.5 + 12.9ms and SD2: 76.3 + 18.6ms vs 73.6 + 22.1ms, respectively). Conclusion CPAP treatment of OSA is associated with a fall in HR representing a rise in vagal/sympathetic ratio. Further analysis may be needed to determine whether there is a rise in HRV.