PURPOSE:Passive leg raising (PLR) centralizes blood volume and increases preload. The effects of PLR on wave reflection are unknown.
METHODS:We studied 29 healthy subjects (40±12 yrs) using applanation tonometry. Systolic BP (SBP), diastolic BP (DBP) and pulse pressure (PP) were recorded. Central BPs (C-BPs), augmented pressure (AP), augmentation index (AIx), ejection duration (ED) and reflected wave travel time (Tr) were measured before and after 1 min of 45° PLR.
RESULTS:At 1 min there was a decrease in peripheral (P) BPs (SBP: 120±11 to 112±9mmHg, p<0.001; DBP: 74±7 to 70±6mmHg, p<0.001; PP: 46±9 to 42±7mmHg, p=0.016) and C-BPs (SBP: 107±9 to 99±11mmHg, p<0.001; DBP: 75±7 to 70±10mmHg, p=0.002; PP: 31±6 to 29±5mmHg, p=0.014). HR was unchanged (65±11 to 64±10bpm, p=0.39). There were increase in ED (432±14 to 442±13 ms, p<0.001) and in Tr (148±11 to 157±20 ms, p=0.003). There were no changes in AP or AIx. On multivariate analysis, changes in C-PP accounted for 70% of the variance in changes in P-PP. To characterize the age related changes subjects were divided into older (age > 40 yrs; n=14) and younger groups (age < 40; n= 15). Baseline AIx was higher in older subjects (20.4±7.3 vs. 8.7±10.7%, p=0.002). Although changes in C-BPs were similar, older group trended towards greater change in P-SBP (11±13 vs. 6±7mmHg, p=0.18) and change in P-PP (7±6 vs. 1±4mmHg, p=0.10).
CONCLUSION:P-BPs and C-BPs decrease whereas, ED and Tr increase with PLR. Change in P-PP is chiefly driven by change in C-PP. Changes in BPs with PLR may be age dependent.
CLINICAL IMPLICATIONS:The effects on wave reflection with PLR may be a measure of baroreflex activation.
DISCLOSURE:Haroon Kamran, No Financial Disclosure Information; No Product/Research Disclosure Information