P065 NOCUTRNAL BLOOD PRESSURE AND ITS CLINICAL CLASSIFICATION ARE GREATLY AFFECTED BY HYDROSTATIC PRESSURE AND POSTURAL CHANGES BETWEEN MEASUREMENTS

Background and Objective: The assessment of nocturnal blood pressure (BP) is central in evaluating and monitoring cardiovascular health. However, the determination of dipping patterns has shown poor reproducibility. This is possibly caused by influences such as changes in body position during sleep and the resulting variations in hydrostatic pressure. This study aims to investigate the impact of hydrostatic pressure on nocturnal BP and to assess its clinical relevance. Methods: 26 subjects aged 18 to 30 years, as well as 25 participants aged 50 years and older underwent nocturnal oscillometric BP measurements with concomitant assessment of the hydrostatic pressure difference between the cuff and heart level. Results: We observed that the cuff was frequently above the heart level while asleep, leading to negative pressure differences between the cuff and the heart level. With a mean of -9.61 mmHg, the right-sided posture revealed the largest hydrostatic pressure difference during sleep. Correcting for hydrostatic pressure led to reclassification of nocturnal hypertension in 14 subjects (27.5%). Dipping patterns changed in 19 participants (37.3%). In total, 25 subjects (49.0%) changed either their nocturnal hypertension and/or their dipping classification. Conclusion: Our findings underscore the importance of accounting for hydrostatic pressure in ambulatory BP monitoring. Hydrostatic pressure differences provide a plausible reason for the variability seen in nocturnal dipping patterns. Further research should focus on incorporating hydrostatic pressure compensation mechanisms in 24-hour BP measurement. Limiting the noticeable effect of hydrostatic pressure differences could greatly improve hypertension diagnosis, classification, and treatment monitoring.