Pulse Wave Transmission Time Research Articles

Flexible Sensors Array Based on Frosted Microstructured Ecoflex Film and TPU Nanofibers for Epidermal Pulse Wave Monitoring

Recent advances in flexible pressure sensors have fueled increasing attention as promising technologies with which to realize human epidermal pulse wave monitoring for the early diagnosis and prevention of cardiovascular diseases. However, strict requirements of a single sensor on the arterial position make it difficult to meet the practical application scenarios. Herein, based on three single-electrode sensors with small area, a 3 × 1 flexible pressure sensor array was developed to enable measurement of epidermal pulse waves at different local positions of radial artery. The designed single sensor holds an area of 6 × 6 mm2, which mainly consists of frosted microstructured Ecoflex film and thermoplastic polyurethane (TPU) nanofibers. The Ecoflex film was formed by spinning Ecoflex solution onto a sandpaper surface. Micropatterned TPU nanofibers were prepared on a fluorinated ethylene propylene (FEP) film surface using the electrospinning method. The combination of frosted microstructure and nanofibers provides an increase in the contact separation of the tribopair, which is of great benefit for improving sensor performance. Due to this structure design, the single small-area sensor was characterized by pressure sensitivity of 0.14 V/kPa, a response time of 22 ms, a wide frequency band ranging from 1 to 23 Hz, and stability up to 7000 cycles. Given this output performance, the fabricated sensor can detect subtle physiological signals (e.g., respiration, ballistocardiogram, and heartbeat) and body movement. More importantly, the sensor can be utilized in capturing human epidermal pulse waves with rich details, and the consistency of each cycle in the same measurement is as high as 0.9987. The 3 × 1 flexible sensor array is employed to acquire pulse waves at different local positions of the radial artery. In addition, the time domain parameters including pulse wave transmission time (PTT) and pulse wave velocity (PWV) can be obtained successfully, which holds promising potential in pulse-based cardiovascular system status monitoring.

A Flexible Pressure Sensor with a Mesh Structure Formed by Lost Hair for Human Epidermal Pulse Wave Monitoring

Flexible pressure sensors with the capability of monitoring human vital signs show broad application prospects in personalized healthcare. In this work, a hair-based flexible pressure sensor (HBPS) consisting of lost hair and polymer films was proposed for the continuous monitoring of the human epidermal arterial pulse waveform. A macroscale mesh structure formed by lost hair provides a simplified spacer that endows the triboelectric-based flexible pressure sensor with sufficient contact-separation space. Based on this mesh structure design, the hair-based flexible pressure sensor can respond to the slight pressure change caused by an object with 5 mg weight and hold a stable output voltage under 1-30 Hz external pressure excitation. Additionally, the hair-based flexible pressure sensor showed great sensitivity (0.9 V/kPa) and decent stability after 4500 cycles of operation. Given these compelling features, the HBPS can successfully measure the human epidermal arterial pulses with obvious details at different arteries. The proposed HBPS can also be used to monitor the pulse signals of different subjects. Furthermore, the three different pulse wave transmission time (PTT) values (PTT-foot, PTT-middle, and PTT-peak) can be obtained by simultaneously monitoring human pulse and electrocardiogram signals, which has enormous application potential for assessing cardiovascular system health.

맥파 전달 속도(PWV) 측정을 위한 특징점 검출 알고리즘 개발

The compliance and stiffness of artery are closely related with disease of arteries. Pulse wave velocity(PWV) in the blood vessel is a basic and common parameter in the hemodynamics of blood pressure and blood flow wave traveling in arteries because the PWV is affected directly by the conditions of blood vessels. However, there is no standardized method to measure the PWV and it is difficult to measure. The conventional PWV measurement has being done by manual calculation of the pulse wave transmission time between coronary arterial proximal and distal points on a strip chart on which the pulse wave and ECG signal are recorded. In this study, a pressure sensor consisting of strain gauges is used to measure the blood pressure of arteries in invasive method and regular ECG electrodes are used to record the ECG signal. The R-peak point of ECG is extracted by using a reference level and time windowing technique and the ascending starting point of blood pressure is determined by using differentiation of the blood pressure signal and time windowing technique. The algorithm proposed in this study, which can measure PWV automatically, shows robust and good results in the extraction of feature points and calculation of PWV.

Baroreflex Sensitivity of an Arterial Wall During Rotary Blood Pump Assistance

It is well known that the baroreflex system is one of the most important indicators of the pathophysiology in hypertensive patients. We can check the sensitivity of the baroreflex by observing heart rate (HR) responses; however, there is no simple diagnostic method to measure the arterial behavior in the baroreflex system. Presently, we report the development of a method and associated hardware that enables the diagnosis of baroreflex sensitivity by measuring the responses of both the heart and the artery. In this system, the measurements are obtained by monitoring an electrocardiogram and a pulse wave recorded from the radial artery or fingertip. The arterial responses were measured in terms of the pulse wave velocity (PWV) calculated from the pulse wave transmission time (PTT) from the heart to the artery. In this system, the HR change corresponding to the blood pressure change in time series sequence was observed. Slope of the changes in blood pressure and HR indicated the sensitivity of the baroreflex system of the heart. This system could also measure the sensitivity of the baroreflex system of an artery. Changes in the PWV in response to the blood pressure changes were observed. Significant correlation was observed in the time sequence between blood pressure change and PWV change after calculating the delay time by cross-correlation. The slope of these parameter changes was easily obtained and it demonstrated the sensitivity of the baroreflex system of an artery. We evaluated this method in animal experiments using rotary blood pump (RBP) with undulation pump ventricular assist device, and PTT elongation was observed in response to increased blood pressure with RBP assistance. Furthermore, when tested clinically, decreased sensitivity of the baroreflex system in hypertensive patients was observed. This system may be useful when we consider the ideal treatment and follow-up of patients with hypertension.

Evaluation of adaptation to visually induced motion sickness based on the maximum cross-correlation between pulse transmission time and heart rate

BackgroundComputer graphics and virtual reality techniques are useful to develop automatic and effective rehabilitation systems. However, a kind of virtual environment including unstable visual images presented to wide field screen or a head mounted display tends to induce motion sickness. The motion sickness induced in using a rehabilitation system not only inhibits effective training but also may harm patients' health. There are few studies that have objectively evaluated the effects of the repetitive exposures to these stimuli on humans. The purpose of this study is to investigate the adaptation to visually induced motion sickness by physiological data.MethodsAn experiment was carried out in which the same video image was presented to human subjects three times. We evaluated changes of the intensity of motion sickness they suffered from by a subjective score and the physiological index ρmax, which is defined as the maximum cross-correlation coefficient between heart rate and pulse wave transmission time and is considered to reflect the autonomic nervous activity.ResultsThe results showed adaptation to visually-induced motion sickness by the repetitive presentation of the same image both in the subjective and the objective indices. However, there were some subjects whose intensity of sickness increased. Thus, it was possible to know the part in the video image which related to motion sickness by analyzing changes in ρmax with time.ConclusionThe physiological index, ρmax, will be a good index for assessing the adaptation process to visually induced motion sickness and may be useful in checking the safety of rehabilitation systems with new image technologies.

Quantification of Emotional Reaction Based on Cross-Correlation between Pulse Wave Transmission Time and Heart Rate in the Mayer Wave-Band

Quantification of Emotional Reaction Based on Cross-Correlation between Pulse Wave Transmission Time and Heart Rate in the Mayer Wave-Band

Increased Pulse Wave Velocity and Shortened Pulse Wave Transmission Time in Hypertension and Aging

We measured pulse wave velocity (PWV) and pulse transmission time (PTT) in 29 patients with hypertension, ranging in age from 37 to 73 years, in a series of 36 normal subjects with the same age range, and in an additional series of 44 normal subjects aged 18-35 years. PWV increases linearly with age for both normal subjects and patients with hypertension, with a corresponding significant decrease in PTT. There was a statistically highly significant (p < 0.001) increase in PWV in hypertension at all ages examined. The present simple noninvasive methods may be useful when evaluating risk factors for atherosclerosis and when evaluating response to therapeutic intervention.

Pulse Wave Transmission Times in Central Aorta and Peripheral Arteries in Normal Children

Pulse wave transmission times and pulse wave velocities in central aorta and peripheral arteries were measured in a group of 85 healthy children and adolescents between the ages of 1 and 21 years. A new external plethysmograph is described which gives reliable tracings of external pulsations. A method is given to calculate real pulse wave transmission time from the aortic valves to the groin.

Contour of the toe pulse, reactive hyperemia, and pulse transmission velocity: Group and repeat variability, effect of age, exercise, and disease

1. 1. In 170 normal young men, 270 normal middle-aged men, 57 patients with arterial hypertension, and 36 patients with peripheral vascular disease, the toe pulse was photoelectrically recorded before and for vive minutes after arterial occlusion (reactive hyperemia). The following items were measured: absolute and relative crest time (per cent of cycle length); relative amplitude (per cent of peak amplitude) at one-fourth and one-half of the diastolic phase; amplitude changes during reactive hyperemia (in per cent of amplitude before arterial occlusion). 2. 2. There was an initial drop of the amplitude ten seconds after release of arterial occlusion in the normal groups and in the patients with peripheral vascular disease, but not in the hypertensive patients. 3. 3. The reactive hyperemia was not significantly different in the normal younger and older age groups but was much weaker and delayed in patients with peripheral vascular disease; in the more advanced cases it was entirely absent. The maximum increase of the amplitude during reactive hyperemia was moderately decreased also in the hypertensive patients. 4. 4. There was a statistically highly significant increase of the absolute and relative crest time, and slowing of the decline in the diastolic phase with age. 5. 5. The hypertensive patients showed no significant differences in the crest time, but a significantly slower diastolic decline as compared to normals. 6. 6. The rise as well as the decline of the pulse was significantly slower in patients with peripheral vascular disease. 7. 7. The separation of the patients with peripheral vascular disease from normals, investigated by distribution analysis, was excellent for all items of the contours analysis, particularly for the relative crest time and relative amplitude at one-fourth of the diastolic phase, and superior to the separation by means of reactive hyperemia. 8. 8. In about 10 per cent of hyperentsive patients the crest time and the diastolic decline were significantly delayed, even in the absence of clinical peripheral arteriosclerosis. 9. 9. The deviation of pulse contour and reactive hyperemia in patients with peripheral vascular disease depends on the degree of impairment rather than on the type of disease. 10. 10. The highly significant separation between the groups with all items of contour analysis is contrasted by a relatively poor consistency in repeat experiments in twenty-six normal young men. 11. 11. The pulse transmission velocity was determined in meters per second from the interval first heart sound to footpoint of the pulse, a correction for the isometric phase of contraction, and the distance from heart to toe. The values are in general agreement with earlier observations. The increase of the pulse transmission velocity with age and in hypertension, and the decrease in perpheral vascular disease were statistically highly significant. 12. 12. There was no interindividual correlation between blood pressure and pulse transmission time in the normal groups, but there was a significant correlation between intraindividual variations of blood pressure and pulse wave transmission time. In hypertensive patients, there was a significant inter-individual correlation. 13. 13. The effect of exercise on pulse transmission velocity, contour of the toe pulse, and reactive hyperemia was studied in seven normal young men. 14. 14. The results substantiate the diagnostic value of analysis of the digital pulse for early recognition of vascular degeneration with age or in disease, and normal limits for separation of normal and abnormal are suggested.