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.     

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.     

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.     

Voluntary Blood Pressure Reductions Measured With Pulse Transit Time: Training Conditions and Reactions to Mental Work

Blood pressure reductions aided by exteroceptive feedback were compared with those produced with simple instructions in two groups of 10 subjects. The degree of environmental stimulation during sessions was equated in the two conditions. Additionally, the effect of feedback on blood pressure reactions to an auditory choice reaction time task was studied. Pressure changes were monitored with the pulse wave velocity method. Feedback training led to greater modifications than instructions during pressure control trials. Associated adjustments in interbeat interval and respiration rate were also observed, but were of similar magnitude in the two groups. Some carryover of training effects to the reaction time task was found, but this comparison was confounded by larger initial reactions in the feedback group.     

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 Wave Velocity as a Measure of Blood Pressure Change

The use of arterial pulse wave velocity (PWV) as a continuous measure of blood pressure changes is outlined. Theoretical considerations indicate that changes in PWV reflect changes in blood pressure, and an experiment was carried out to assess this relationship. PWV along an arm artery was monitored in 26 subjects at a time when the arterial distending pressure of the limb was altered over a wide range by means of externally applied positive and negative pressures. The results show that changes in PWV reliably follow changes in blood pressure. This method can be considered suitable for studies requiring changes rather than absolute values of blood pressure.     

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 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.     

The Covariation of Blood Pressure and Pulse Transit Time in Hypertensive Patients

To examine the relationship between blood pressure (BP) and pulse transit time (PTT) as measured by the time between the ECG R-wave and an associated peripheral pulse, BP was recorded via a radial artery catheter in 3 hvpertensive subjects who underwent a variety of conditions to alter BP. Overall. 70% of the data was usable. Absolute levels of systolic blood pressure (SBP) but not diastolic blood pressure (DBP) were found to correlate appreciably with PTT. There were significant associations between PTT and both SBP and mean BP but not DBP for direction of BP change. With large SBP changes (> 4 mmHg) an increase in the strength of association occurred in 14 of the 21 conditions across subjects. Overall, PTT did not accurately predict actual BP. PTT and SBP covaried more appreciably in these hypertensives than has been reported for normotensives.     

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.     

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。     

The Relationship between Arterial Blood Pressure and Pulse Transit Time During Dynamic and Static Exercise

The relationships between arterial systolic and diastolic blood pressure (SBP and DBP), interbeat interval (IBI), and various pulse transit times were investigated in 5 young, healthy males during physical exercise and at rest. Transit times monitored were radial, brachial and dorsalis pedis RPIs (ECG R-wave to pulse intervals), and brachial-radial and radial-dorsalis pedis PPIs (pulse to pulse intervals). Experimental sessions consisted of three periods: two involving mild dynamic exercise plus rests, and one involving static exercise (handgrips) plus rests. Correlation and regression analyses within period and subject were performed on individual beat data. Radial RPI was highly correlated with SBP (during dynamic periods, range ?.57 to ?.89, median r?.81; during static periods, range ?.80 to ?.88, median r=?.87) and moderately correlated with DBP (during dynamic periods, range ?.10 to ?.63, median r?.52; during static periods, range ?.17 to ?.77, median r?.66). Median correlations of radial RPI with SBP and DBP during exercise and rest separately were ?.75 and ?.40 (dynamic), ?.79 and ?.57 (static), and ?.74 and ?.26 (rest). The IBI X radial RPI product was very highly correlated with the rate-pressure product (heart rate X SBP), an index of myocardial oxygen consumption (median r=?.96). The only PPI which reliably indexed SBP or DBP change was brachial-radial PPI during the static exercise period (median r=?.86 and ?.83).     

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。     

Effects of Feedback and Stimulus Control on Pulse Transit Time Discrimination

The present study was designed to determine the effects of feedback on discrimination of pulse transit time (TT). Eighteen normotensive subjects were randomly assigned to one of three groups: (I) Random Feedback Control, (II) Contingent Feedback, and (III) Feedback plus Exteroceptive Cues. For each subject an ABBA within-session design was used in which subjects compared TT to a predetermined mean approximately every 20 sec across four phases: a 10-min baseline, followed by two 10-min experimental phases, and a final 10-min baseline phase. Results for discrimination accuracy indicated superior discrimination for subjects presented exteroceptive cues and/or feedback (Groups II and III). A decrement in performance was found for both Groups II and III during the final baseline phase, with slightly better maintenance for the feedback plus exteroceptive cues subjects. Measures of EMG, respiration, HR and vasomotor activity were obtained during training and were correlated with discrimination accuracy. Results showed that none of the physiological responses were reliably correlated with discriminative performance, and probably did not function as discriminative stimuli for TT discrimination.     

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.     

利用脉搏波传播时间计算动脉血压的研究

本研究的目的是研究动脉血压和脉搏波传播时间的关系,探讨通过脉搏波传播时间计算动脉血压的可靠性。采用麻省理工学院MIMIC数据库,通过心电和光电容积脉搏波计算得到脉搏波传播时间,通过有创动脉血压获得平均动脉压,使用线性回归方法分段求得脉搏波传播时间和平均动脉压之间的线性方程,应用该方程结合脉搏波传播时间计算动脉血压,并与实际血压比较评价算法的效果。结果表明,脉搏波传播时间和动脉血压存在负相关关系,在一定时间范围内,可通过脉搏波传播时间计算平均动脉压,均方根误差小于5 mmHg。对临床采集数据的分析同样说明,通过脉搏波传播时间计算动脉血压是可行的。     

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.     

基于舒张期时间的个体化血压建模方法研究

本研究提出了一种基于脉搏波舒张期时间(diastolic time,DT)的无袖带式血压估计方法,能够有效提升可穿戴式设备的血压测量精度。该方案首先从脉搏波(photoplethysmography,PPG)中提取DT,再利用线性回归方法建立个体化血压估计模型。本研究对采集的30个样本的实验数据,进行血压建模并加以验证,实验结果显示收缩压的平均误差为1.859 mmHg,标准差为5.640 mmHg;舒张压的平均误差为1.049mmHg,标准差为6.107 mmHg,证明了该方案的可行性。通过将该方案的估计结果与基于脉搏波传导时间(pulse transit time,PTT)的血压模型的估算结果进行对比研究,结果表明交感神经活动较强时,基于DT的血压模型能够有效提升血压估计精度。     

抢救危重病人的心血管循环反馈治疗仪及动物实验

目的 国内外医疗仪器的发展正朝着自动化、智能化、模块化方向发展，但主要集中于诊断方面，用于治疗仪器极少，设计原理及工作程序 心血管循环反馈治疗仅是综合临床上的丰富成功经验设计研制的，其程序结合实验中的数学模型汇编而成，通过在线闭环自动检测，直接、快速、连续、高密度地采集血压，肺毛细血管契压（PCW）、心率等重要生理参数，经压力传感器、A/D转换卡实时连续地输入计算机，通过用户界面人机对话，由医生选择药物，经数学模型及程序的运算，D/A转换器输出指令经输液器来控制给药量，而药物在机体的反应又及时、迅速地经在线闭环自动检测系统反馈回计算机，计算机不断更新计算结果，以此调节给药的速率及剂量，此外该系统还具有监控、报警、故障白诊断、智能化运行等特点。实验结果 通过八只犬的实验表明，计算机取样及时、准确、快速，可以避免一些人为的误差以及取样间隔时间过长的不足，实验中给药结果证明能按照预期设计要求达到治疗目的，因此实用性强，高科技含量高，可以预测将来应用于临床抢救危重病人，可靠性、精确性将大大高于传统方法。讨论 传统的临床治疗方法从收集病人数据到决定准确的给药量反馈过程太长，还有不少人为及计算的干扰和误差，因此抢救成功率极低，动物试验中发现该系统从获取血压变化到多次反馈调整给药整个周期短（2-5min）、计算准确，疗效可靠。当某药无效则可以及时提示医生换药，为临床争取了时间，是一个很有发展前景的抢救危重病人的系统与仪器，目前该系统及仪器仍待进入临床评价。