Pulse Wave Velocity and Blood Pressure Change: Calibration and Applications

An adaptation of the technique for measuring pulse wave velocity is described in which the interval between the R wave of the ECG and the radial pressure pulse is monitored. The resulting transit time (TT) is suitable for use as an indirect measure of blood pressure change. The reliability of the measure was assessed in 5 subjects who volunteered for arterial cannulation on 2 occasions. Simultaneous recordings of intra-arterial pressure and TT were taken during a variety of maneouvres, including mental arithmetic, isometric exercise, and amyl nitrite inhalation. The dependence of changes in TT on arterial pressure was confirmed for all procedures except amyl nitrite inhalation. Linear correlations between TT and mean arterial pressure were high, varying between ?.913 and ?.98. The regression coefficients were reproducible and similar in all individuals. The reasons for the anomalous amyl nitrite response are discussed, together with the limits of application of the measure.     

Aortic-Radial Pulse Transit Time and ECG Q-Wave to Radial Pulse Wave Interval as Indices of Beat-By-Beat Blood Pressure Change

This study examined beat-by-beat relationships between blood pressure, the time interval from the ECG Q-wave to the radial pulse wave (QRPI), and its two components, the cardiac pre-ejection period (PEP) and aortic-radial arterial pulse transit time (AR-PTT). In 8 subjects, intra-arterial systolic (SBP) and diastolic (DBP) blood pressure, QRPI, PEP, and AR-PTT were measured during rest, mental arithmetic, cold pressor, and inhalation of amyl nitrite. Both PEP and AR-PTT varied widely during each experimental condition indicating that QRPI change reflected both PEP and AR-PTT change. AR-PTT varied inversely with SBP and DBP; PEP sometimes varied directly and sometimes inversely with both SBP and DBP. QRPI varied inversely with both SBP and DBP with the magnitude of the correlation in a particular instance depending on the relationships for that instance between blood pressure and both PEP and AR-PTT. Implications of the results for the use of either QRPI or AR-PTT as indices of blood pressure change are discussed.     

Blood Pressure Control: A Comparison of Feedback and Instructions Using Pulse Wave Velocity Measurements

A comparison was made between blood pressure changes with exteroceptive feedback and simple instructions. Twenty subjects were instructed either to raise or lower pressure for four sessions, while a further 20 were allowed to view an analogue visual display of mean arterial pressure. Pressure changes were continuously monitored with the pulse wave velocity method. When changes were analyzed from the initial baseline, both groups showed divergence between Increase and Decrease over trials, but feedback enhanced control in Increase only. On assessment from the running baseline, feedback control was superior in both direction conditions. This difference may In due to interaction between running baseline changes and experimental conditions. Control by feedback groups deteriorated when feedback was withdrawn. Modifications were accompanied by alterations in heart rate, respiratory activity and movement, although the association was of a gross nature only, being more prominent in increase conditions.     

Pulse Transit Time Feedback and Bidirectional Blood Pressure Change

The current study examined the effects of pulse transit time feedback on systolic and diastolic blood pressure. Three subjects were given feedback designed to increase or decrease transit times. Eleven-twelve one-hour training sessions were provided over a two-week period. The results showed that during increase training, significant increases in systolic pressure and heart rate were observed, while pulse transit time showed a significant decrease. Diastolic blood pressure increases were moderate and only inconsistently observed. During decrease training, diastolic pressure and heart rate declined significantly below baseline. Pulse transit time increases were consistent but lower in magnitude than observed for the opposite training condition. Moderate systolic blood pressure decreases were inconsistently observed.     

Pulse Transit Time and Blood Pressure: An Intensive Analysis

Relationships between pulse transit time (PTT) and intra-arterial systolic (SBP), diastolic (DBP), and mean arterial blood pressure (MAP) were examined in 4 subjects under three conditions: rest, paced respiration, and mental arithmetic. PTT was measured from the EKG R-wave to two peripheral pulses (brachial and radial) and from one pulse to the other. Three points on each pulse wave were used (peak, foot, slope) in the measurements, yielding nine different measures of PTT. The nine PTT measures were not consistently intercorrelated. PTTs initiated by the R-wave were moderately correlated with SBP, but not with DBP or MAP. Brachial to radial PTTs were not correlated with any measures of BP. Relationships between PTT and BP also varied from subject to subject. The limited magnitude of the correlations and their inconsistency suggest caution in the simple substitution of PTT for beat-to-beat measures of BP.     

An Arterial to Peripheral Pulse Wave Velocity Measure

Optical pulse transducers (photoplethysmographs) provide convenient measures of pulse wave velocity (PWV). If measured between arterial and arteriolar sites, PWV should be a sensitive index of sympathetic nervous system influences on the vasculature. Evidence of such a sensitivity was found in a study of rats in which vasoactive drug reactions simulated changes in sympathetic activity. Application of arterial to arteriolar PWV in humans further required the definition of optimal points on the two waveforms to be used in velocity calculations. An examination of different PWV indices supported use of a foot-to-foot index. Overall, our results support the promise of optical PWV techniques, but do not yet establish its validity as an index of peripheral sympathetic influences.     

孕妇血压与其脉搏波的相关性研究与应用

通过实验研究发现：孕妇的血压与其脉搏波具有很好的相关性，在临床上，根据这一原理，实现对妊高征孕妇的血压进行连续监测，并同时获得心率、血管紧张素转换酶活性。结果表明：平均动脉压和血管紧张换酶活性的变化与临床上妊高征病情的变化一致。     

The Regulation of Blood Pressure Reactions to Taxing Conditions using Pulse Transit Time Feedback and Relaxation

Two experiments are described in which 40 normotensive subjects were trained to reduce blood pressure (BP) both in undistracting conditions and while performing taxing tasks. Biofeedback was compared with relaxation in each case, and BP was continously monitored by the pulse wave velocity method. In Study 1, feedback and relaxation groups produced similar BP reductions when control was attempted in isolation. However, the relaxation group was significantly disturbed during performance of an auditory choice reaction time (RT) task. In contrast, feedback subjects showed identical BP modifications in the two conditions. In Study 2, the differences during the RT task proved to be short lived. However, the feedback group overcame pressor reactions to a mental arithmetic test more rapidly than could relaxation subjects, and the difference between groups persisted during no-feedback trials. In both studies, modifications were more specific in the feedback condition, since alterations in heart rate, respiration and general activity were less prominent. It is suggested that it may be fruitful to use feedback for training people to overcome BP reactions to taxing conditions, rather than trying to modify tonic level alone.     

脉搏波波速法无创血压测量中多模量血压计算模型研究

针对脉搏波波速法无创血压测量中血压计算模型建模困难和模型计算精度较低的问题,结合T_PTT、ln(T_PTT)及(1/T_PTT)²等模量建立多模量血压计算模型。首先,利用99名随机测试者的实验数据确定多模量模型参数,并基于实验数据计算各模型性能评价指标,其中多模量血压计算模型拟合相关系数最大,为0.891,误差方差最小,仅为6.1,实验表明,多模量血压计算模型具有更好的拟合效果和更低的计算误差。然后,利用医用水银血压计和自主设计的多模量血压测量系统两种方法采集另外36名随机测试者的收缩压和舒张压数据,并计算两种方法采集数据间的相关参数,其中收缩压差值的绝对值d<6 mmHg,差值均值E_d=0.55 mmHg,差值的标准差δ_d=2.98 mmHg;舒张压差值的绝对值d<6 mmHg,差值均值E_d=0.57 mmHg,差值的标准差δ_d=3.42 mmHg,完全符合美国医疗仪器促进协会SP10-199中对电子血压计测量差值＜8 mmHg的要求。最后,采用Bland-Altman差值法,对两种方法测量数据一致性进行检验,发现舒张压与收缩压的95 %一致性界限分别为(-5.3,6.4)和(7.2,-6.2),完全在临床血压测量可接受范围之内,较好地证明多模量血压计算模型用于无创血压测量的有效性。研究结果表明,多模量血压计算模型可以应用于脉搏波波速法无创血压测量。     

脉搏波传导速度测量算法的研究及其进展

动脉弹性功能下降是心血管疾病的早期特征之一,而动脉脉搏波速度能够很好地反映动脉弹性,因此准确测量动脉脉搏波速度对预防和治疗心血管疾病有很大的帮助。测量脉搏波速度的方法主要有两种:基于容积脉搏波的检测方法和基于压力波的检测方法,其检测精度取决于波速参考点的提取。波速参考点的提取方法主要有切线法、最低点法、峰值法以及斜率最大值点法。本文分析了现有测量算法的优点和存在的不足之处,探讨了国内外的研究动向,提出测量算法的改进方案。     

基于脉搏波传导时间的连续血压测量系统

针对现有连续无创血压测量系统采样频率和计算精度较低的问题,我们设计了一套基于STM32F103T4和DSP TMS320C5535芯片的双核血压测量系统。利用STM32和DSP芯片在信号高速采样及高精度运算上的优势,实现了对脉搏波信号的高速采样和计算,改善了连续无创血压测量方法的精度。实验测量30名随机受试者,其医用水银血压计和本系统测量结果的差值均符合美国医疗仪器促进协会(AAMI)标准要求,通过Bland-Altman差值法对两种方法进行一致性检验分析,结果表明两者具有很好的一致性。本研究设计的连续无创血压测量系统可初步在家庭和临床医疗方面进行人体血压的动态跟踪测量。     

基于压力波的人体脉搏波传播速度无创检测研究

脉搏波传播速度的变化往往是血管弹性程度发生变化的最早体征,因此脉搏波速度的检测对动脉硬化等疾病的诊断有较高的参考价值,其检测精度主要取决于波速参考点的提取算法。在分析实际采集的脉搏压力波信号特征的基础上,对波峰、波足等特征点进行了识别,并提出了一种根据脉搏波前沿内斜率最大值点的个数和位置确定惟一波速参考点的新算法。临床实验证明,新方法能够有效地提取脉搏波速度,有助于动脉血管弹性程度的辅助诊断。     

基于脉搏波的新型血压与血管硬度测量仪的研制

目的：根据脉搏波理论研制出一种新型血压与血管硬度测量仪。方法：利用示波法原理在波形特征法和幅度系数法的基础上提出一种系数差分比值法来间接测量血压的新方法，通过采集肱动脉和桡动脉两处波形，获得了脉搏波传播速度（PWv）、动脉顺应性（C1、C2）和动脉硬化指数（ASI）三个反映受试者动脉弹性的参数指标。结果：通过大量病例分析和临床测试证实了算法的有效性和可靠性，而且此算法已经应用LabVIEW开发成软件并在医院进行临床应用。结论：血压与血管硬度检测仪能判断心血管病患者与正常人的差异性，对我国心血管病方面流行病学的调查、疾病预防、疾病早期发现都具有很大的意义。     

脉搏波速度在高血压病早期干预中的临床意义

目的探讨脉搏波传导速度（PWV）与高血压病早期干预的相关性及其相关因素。方法应用脉搏波速度自动测量系统对104例健康人和397例高血压病患者进行肱动脉-踝动脉脉搏波传导速度（baPWV）检测。结果高血压患者的脉搏波传导速度显著高于健康人（P〈0.01）。年龄是影响健康人大动脉弹性功能最主要的因素,年龄、收缩压和脉压与高血压患者的大动脉弹性功能密切相关。结论脉搏波传导速度是敏感反映高血压大动脉弹性的重要指标,年龄、收缩压和脉压是影响baPWV值的主要因素,可作为心血管疾病的一个危险信号,以指导早期预防干预。     

Relationships ol Pulse Transmission Times to Pre-ejection Period and Blood Pressure

This research addressed the question of whether pulse transmission time to the ear (E-PTT) serves as a satisfactory estimate of pre-ejcction period (PEP) and whether the intracardiac or arterial components of pulse transmission times are correlated with hlood pressure. A median correlation of .86 was found for within-suhject correlations between E-PTT and PEP, and a correlation of .97 was found on trial means across subjects. Pulse transmission times to the ear and finger (measured from the Q-wave) were substantially correlated with systolic but not diastolic blood pressure. PEP, the intracardiac component of pulse transmission time, was moderately correlated with systolic blood pressure, but the arterial components were not. It was concluded that E-PIT estimates PEP in within-subject comparisons, and that the association of the pulse transmission times with systolic blood pressure is by virtue of the fact that these intervals encompass PEP rather than the arterial components. It was further concluded that pulse transmission times more directly reflect sympathetic cardiac influences than they do blood pressure.     

R波相关振动法血压测量

为了提高振地血压测量的准确性，提出了一咱基于心电Ｒ波与血压振动波之间相关性，识别振动信号的一种抗干扰方法＝－Ｒ波相关法，结合振动波形特征识别，该方法可有效地提取信号，消除干扰影响，该算法已在１６位８０９８单片机上实现，本文同时给出了程序的详细流程图。     

基于脉搏波传导时间的连续血压监测系统

为了实现无创连续血压测量,提出了一种基于脉搏波传导时间(pulse transit time,PTT)的连续血压测量方案。通过同步采集心电(electrocardiogram,ECG)信号与光电脉搏波(photoplethysmograph,PPG)信号,以ECG的R波峰值点作为PTT的开始点,PPG信号的最大值点作为PTT的结束点,得到PTT,与水银血压计测得舒张压(diastolic blood pressure,DBP)与收缩压(systolic blood pressure,SBP)进行回归分析,得到了DBP和SBP的数学模型。利用该方法对41名身体健康的青年人进行实验,利用本方案得到的SBP与水银血压计的相关系数为0.82,其差值的平均数与标准偏差为0.15±2.05 mm Hg;得到的DBP与水银血压计的相关系数为0.73,其差值的平均数与标准偏差为0.12±2.16 mm Hg。利用Bland-Altman差值法对本系统血压测量方法与水银血压计测血压方法进行一致性检验,结果显示两种血压测量方法具有很好的一致性。     

Pulse Transit Time: Relationship to Blood Pressure and Myocardial Performance

The purpose of this research was to evaluate, in human subjects, the degree to which pulse transit time (PTT) covaries with systolic (SBP) and diastolic (DBP) blood pressure, and the degree to which PTT is sensitive to sympathetic influences on myocardial performance. Six studies were performed involving 118 young adult males. In all subjects, cardiovascular activity was assessed in both the resting state and during three stressors: the cold pressor, a pornographic movie and unsignaled shock avoidance reaction time task. The studies differed with respect to where on the arterial tree the pulse wave was transduced, whether blood pressure was measured invasively or noninvasively, and whether the myocardial sympathetic innervations were intact or not. It was observed that PTT covaried quite consistently with SBP but very inconsistently with DBP. The degree of covariation was influenced by the individual's reactivity and, with DBP, by the type of stress. PTT was appreciably influenced by myocardial sympathetic excitation and to a lesser degree by vascular processes. The use of PTT as an index of blood pressure and myocardial performance is discussed.     

Pulse Transit Time as an Indicator of Arterial Blood Pressure

The relationship between pulse-arrival times and diastolic blood pressure was measured in 10 anesthetized dogs. The pulse-arrival time was measured using the R-wave of the electrocardiogram (ECG) as a time reference. Pulse-transit time was also measured between the carotid and femoral pulses. Blood pressure was raised with epinephrine injected intravenously and lowered with vagal stimulation. In all cases, pulse arrival and transit times decreased with an increase in diastolic pressure for diastolic pressures ranging from 15 to 250 mmHg. The correlation between pulse-arrival time and pressure was poorest when the ECG was used as a timing reference. The best correlation was found with true pulse-transit time and diastolic pressure. When pulse-transit time was used to compute pulse-wave velocity, it was found to increase nearly linearly with blood pressure. From 90–100 mmHg, the pulse-wave velocity increased typically by slightly less than six percent.     

Measurement of pulse-wave velocity using a beat-sampling technique

The relationship between pulse-wave velocity (PWV) and blood pressure was investigated using a new method in which multiple pulse-wave velocities were determined within each blood-pressure pulse. The technique employed measuring pressure at two sites within the aorta and measuring multiple time differences between each pair of pressure waves. Blood pressure was manipulated with drugs. The technique of obtaining multiple PWVs within a beat dramatically reduced the variability of the data in the linear and nonlinear region of PWV versus pressure relationship. Supported by a grant from 3M Co., St. Paul, MN.