O58 CONTINUOUS MEASUREMENT OF BLOOD PRESSURE DURING NIGHT - INSIGHTS INTO THE GENESIS OF THE NOCTURNAL BLOOD PRESSURE FLUCTUATIONS

Background and Objective: Nighttime blood pressure (BP) is a strongly predictive marker for overall cardiovascular risk. Traditional cuff-based BP measurements methods provide only discrete BP data. Short-term BP fluctuations are not detectable with such methods. Therefore, we applied two independent and continuously measuring methods with the aim to characterize systolic nocturnal blood pressure fluctuations (NBPF) related to sleep apnoea or periodic leg movements (PLM). Methods: BP fluctuations were analysed in patients with suspected sleep disturbances. The Portapres™ device (Penaz method) and a system based on the measurement of the pulse transit time (SOMNOscreen®) were used to measure the BP in addition to a polysomnography performed under the conditions of a clinical sleep laboratory. The calculation of the BP by the SOMNOscreen® was performed using a BP-pulse wave velocity (PWV) transfer function. Results: We saw BP fluctuations which occurred in connection with obstructive apnoeic events as well as in connection with PLM. Both methods recorded the same apnoea related NBPF. The amplitudes of these NBPF accounted for 24.7 mmHg and 22.8 mmHg (Portapres™ and SOMNOscreen®, respectively, 11 patients, number of events: n=695). PLM related PB fluctuations (in 5 of 11 patients, n=317) amounted to 18.4 mmHg (Portapres™ and 16.9 mmHg (SOMNOscreen®). Most of the patients did not show BP dipping when comparing awake with sleep time periods and they had a moderate to severe apnoea/hypopnoea index. Conclusions: The study demonstrates a strong relation between apnoeic events/PLM and NPBF. The NBPF were similarly detected by two different BP measuring methods suggesting that the more indirect method of BP determination using the PWV provides a reliable measurement of NBPF. The results suggest that OSA and PLM related NBPF strongly contribute to non- or reverse dipping of patients with these sleep disorders.