Non-invasive assessment of central, aortic systolic blood pressure variability and baroreceptor sensitivity: comparison to measures using a peripheral pulse

Background: The difference between aortic and peripheral (e.g., brachial) systolic blood pressure (SBP) is heart rate dependent. Traditionally, SBP variability and baroreceptor sensitivity (BRS) is calculated from a peripheral pulse, yet the organs of impact and the baroreceptors are located centrally. Aims: To ascertain whether there is a difference between SBP variability and BRS estimated using a peripheral pulse or a derived, central aortic pulse. Methods: Continuous finger blood pressure (Nexfin, Edwards Life Sciences) and electrocardiogram were measured in 33 subjects (age 20–66 years; 17 female) over a 10-minute interval in the supine position. A generalized transfer function was used to calculate central aortic pressure from the finger blood pressure waveform. BRS was estimated using both the sequence technique and spectral analysis and SBP variability was calculated, all using both the finger and the calculated aortic blood pressure. Results: Aortic SBP variability was highly correlated with peripheral SBP variability (R2 =0.96, P<0.001). Peripheral SBP variability was, however, greater than aortic SBP variability at higher levels of variability (slope=0.94). The same trend was seen in BRS calculated by the sequence technique, with BRS calculated using the peripheral pulse being correlated with calculation by the aortic pulse (R2 =0.92, P<0.001) but higher at higher values of BRS (slope –0.82). Spectral techniques of BRS estimation showed the same trend but the overestimation was greater in the low frequency range (0.05–0.15 Hz, slope=0.67, R2 =0.93, P<0.001) than in the high frequency range (0.15–0.4 Hz, slope=0.86, R2 =0.86, P<0.001). Conclusion: Given the heart rate-dependent amplification of the arterial pulse between the aorta and peripheral sites, both SBP and BRS calculated using the peripheral pulse differ from that calculated using the aortic pulse, with the magnitude of the difference being greater at higher values of SBP and BRS.