O57 NOCTURNAL BLOOD PRESSURE FLUCTUATION AND DIPPING PATTERNS IN PATIENTS WITH SEVERE OBSTRUCTIVE SLEEP APNOEA

Background and Objective: Nighttime blood pressure (BP) is important for diagnosis of hypertension and for cardiovascular risk stratification. Remarkably, a reverse dipping pattern is a strong and independent predictor of overall mortality and major adverse cardiovascular events. Therefore, the further clarification of the underlying mechanisms of non- and reverse dipping is crucial to improve the treatment of patients with nighttime hypertension. Methods: We investigated 97 patients with suspected obstructive sleep apnoea (OSA, AHI >30) using standard polysomnography and continuous BP measurement based on the pulse-transit-time method (SOMNOscreen Plus®, SOMNOmedics). Frequency and amplitude of fluctuations in systolic BP following sleep disturbances (OSA) were investigated. Results: Apnoeic events went along with transient increases of BP. In some cases, systolic BP did not reach the value before the apnoea but increased over time. We defined elevations of the systolic BP baseline by >10 mmHg with a duration of >10 min as BP superpositions. The superposition periods were also characterized by increased BP amplitudes with peak values of BP up to 220 mmHg. Superposition occurred in 48 patients. Further, 65% of the OSA patients were identified as non-dippers. However, nearly all the patients with superposition (98%) were identified to have non-dipper or reverse dipper patterns. Conclusions: Our study strongly suggests that non-dipping and reverse dipping in patients with severe OSA are causally linked to OSA related BP fluctuations. Further, continuous elevations in SBP baseline (superpositions) result in extreme BP values. This behaviour with high BP peaks may be contributing to the increased mortality in patients with reverse dipping. Therefore, identification and adequate treatment of patients with reverse dipping reduces the cardiovascular risk and may prolong their life.