Mol Arjen, Maier Andrea B, van Wezel Richard J A, Meskers Carel G M
Department of Human Movement Sciences @AgeAmsterdam, Amsterdam Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, Netherlands.
Department of Biophysics, Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, Netherlands.
Front Physiol. 2020 Mar 3;11:168. doi: 10.3389/fphys.2020.00168. eCollection 2020.
In the poorly understood relationship between orthostatic hypotension and falls, next to blood pressure (BP), baroreflex sensitivity (BRS) and cerebral autoregulation (CAR) may be key measures. The posture- and movement dependency of orthostatic hypotension requires continuous and unobtrusive monitoring. This may be possible using simultaneous photoplethysmography (PPG), electrocardiography (ECG), and near-infrared spectroscopy (NIRS) signal recordings, from which pulse wave velocity (PWV; potentially useful for BP estimation), BRS and CAR can be derived. The PPG, NIRS and PWV signal correlation with BP and BRS/CAR reliability and validity need to be addressed.
In 34 healthy adults (mean age 25 years, inter quartile range 22-45; 10 female), wrist and finger PPG, ECG, bifrontal NIRS (oxygenated and deoxygenated hemoglobin) and continuous BP were recorded during sit to stand and supine to stand movements. Sixteen participants performed slow and rapid supine to stand movements; eighteen other participants performed a 1-min squat movement. Pulse wave velocity (PWV) was defined as the inverse of the ECG R-peak to PPG pulse delay; PPG, NIRS and PWV signal correlation with BP as their Pearson correlations with mean arterial pressure (MAP) within 30 s after the postural changes; BRS as inter beat interval drop divided by systolic BP (SBP) drop during the postural changes; CAR as oxygenated hemoglobin drop divided by MAP drop. BRS and CAR were separately computed using measured and estimated (linear regression) BP. BRS/CAR reliability was defined by the intra class correlation between repeats of the same postural change; validity as the Pearson correlation between BRS/CAR values based on measured and estimated BP.
The highest correlation with MAP was found for finger PPG and oxygenated hemoglobin, ranging from 0.75-0.79 (sit to stand), 0.66-0.88 (supine to stand), and 0.82-0.94 (1-min squat). BRS and CAR reliability was highest during the different supine to stand movements, ranging from 0.17 - 0.49 (BRS) and 0.42-0.75 (CAR); validity was highest during rapid supine to stand movements, 0.54 and 0.79 respectively.
PPG-ECG-NIRS recordings showed high correlation with BP and enabled computation of reliable and valid BRS and CAR estimates, suggesting their potential for continuous unobtrusive monitoring of orthostatic hypotension key measures.
在体位性低血压与跌倒之间尚未完全明晰的关系中，除血压（BP）外，压力反射敏感性（BRS）和脑自动调节（CAR）可能是关键指标。体位性低血压对姿势和运动的依赖性要求进行连续且不引人注意的监测。利用同步光电容积脉搏波描记法（PPG）、心电图（ECG）和近红外光谱（NIRS）信号记录或许可以实现这一点，从中可以得出脉搏波速度（PWV；可能对血压估计有用）、BRS和CAR。需要探讨PPG、NIRS和PWV信号与血压的相关性以及BRS/CAR的可靠性和有效性。
对34名健康成年人（平均年龄25岁，四分位间距22 - 45岁；10名女性）进行研究，在其从坐姿到站立以及从仰卧位到站立的过程中，记录手腕和手指的PPG、ECG、双侧额部NIRS（氧合血红蛋白和脱氧血红蛋白）以及连续血压。16名参与者进行了缓慢和快速的仰卧位到站立动作；另外18名参与者进行了1分钟的深蹲动作。脉搏波速度（PWV）定义为心电图R波峰到PPG脉搏延迟的倒数；PPG、NIRS和PWV信号与血压的相关性定义为它们与姿势改变后30秒内平均动脉压（MAP）的Pearson相关性；BRS定义为姿势改变期间心跳间期下降除以收缩压（SBP）下降；CAR定义为氧合血红蛋白下降除以MAP下降。BRS和CAR分别使用测量的和估计的（线性回归）血压进行计算。BRS/CAR的可靠性通过相同姿势改变重复测量之间的组内相关性来定义；有效性通过基于测量血压和估计血压的BRS/CAR值之间的Pearson相关性来定义。
发现手指PPG和氧合血红蛋白与MAP的相关性最高，在从坐姿到站立过程中为0.75 - 0.79，从仰卧位到站立过程中为0.66 - 0.88，在1分钟深蹲过程中为0.82 - 0.94。在不同的仰卧位到站立动作中，BRS和CAR的可靠性最高，范围分别为0.17 - 0.49（BRS）和0.42 - 0.75（CAR）；有效性在快速仰卧位到站立动作中最高，分别为0.54和0.79。
PPG - ECG - NIRS记录显示与血压高度相关，并且能够计算出可靠且有效的BRS和CAR估计值，表明它们在连续、不引人注意地监测体位性低血压关键指标方面具有潜力。
