Pulse Transit Time Measurement Research Articles

The use of pulse transit time in diagnostics of sleep-disordered breathing in children

<b><br>Introduction:</b> Sleep is the physiological state of the body where proper morphology and duration are indispensable for human functions throughout both, physical and mental spheres. Disordered breathing during sleep impairs its morphology and results in major disorders in any age group. Adverse effects of Obstructive Sleep Apnea Syndrome in children and poor availability of centers offering children’s polysomnography call for a reliable and easily accessible screening method.</br> <b><br>Aim:</b> The aim of the study were to evaluate the usefulness of pulse transit time in the diagnostics of disordered sleep breathing in children and to attempt to employ the parameter in screening tests. Pulse transit time is a physiological parameter determining the time needed for the pulse wave to travel between two measurement points.</br> <b><br>Material and methods:</b> Enrolled in the retrospective study were 153 patients (100 boys and 53 girls) suspected of obstructive sleep apnea syndrome who underwent polysomnography at I. Mościcki ENT Hospital in Chorzów.</br> <b><br>Results:</b> Statistically significant relations between apnea/hypopnea index and pulse transit time were observed in both, individual age groups and all of the patients. Pulse transit time results proved a negative correlation with apnea/hypopnea index values commonly accepted as a parameter concluding the polysomnography procedures.</br> <b><br>Conclusions:</b> The results of the study indicate that pulse transit time measurements may find application in screening tests of sleep-disordered breathing in children.</br>

Doppler-derived pulmonary pulse transit time measurements in chronic obstructive pulmonary disease: Reproducibility and cardiopulmonary function.

Doppler-derived pulmonary pulse transit time (pPTT) is an auspicious hemodynamic marker in chronic pulmonary diseases. The aim is to compare four distinct pPTT measurements and its relation to right cardiac and pulmonary function. Prospectively, 25 chronic obstructive pulmonary disease (COPD) patients (four patients excluded) and 32 healthy subjects underwent repeated distinct pPTT measurements, standard echocardiography, and pulmonary function testing on the same day. pPTT was defined as the interval from the R or Q-wave in the electrocardiogram to the corresponding pulse wave Doppler peak late systolic (S) 2 or diastolic (D) pulmonary vein flow velocity (pPTT R-S, Q-S, R-D, Q-D). Reproducibility was assessed using Bland-Altman analysis, coefficient of variation (COV), intraclass correlation coefficient (ICC), and power calculations. Associations with right ventricular RV tissue and pulse wave Doppler velocities (RV E', RV S', RV A', RV E, RV A, RV E/E', RV E/A), TAPSE, right ventricular fractional area change, left ventricular systolic and diastolic function (LV ejection fraction, E, A, E/A, E/E', septal E', lateral E'), LA diameters, as well as forced expiratory volume in 1 s, forced vital capacity (FVC) predicted (%), and in liters were analyzed. There was no significant difference and no bias between pPTT measures (p range:.1-.9). COV was in COPD 1.2%-2.3%, in healthy subjects 1.0%-3.1%. ICC ranged from.92 (COPD) to.96 (healthy subjects). In COPD significant correlations were found for pPTT R-S, Q-S and R-D with RV E`, (all>ρ:.49,<p=.0364), pPTT R-S, Q-S with RV E/E` (both>ρ:.49,<p=.0291), pPTT Q-S with RV S´ (ρ:.58, p=.0134), RV A (ρ:.59, p=.0339) and heart rate>ρ: -.39,<p=.0297). pPTT R-S, R-D showed significant correlations with FVC predicted (%) (ρ:.48 p=.0224) and FVC (l) (ρ:.47 p=.0347). All pPTT measures exhibited high reproducibility. In COPD patients pPTT measures correlate with diastolic right ventricular function. Defining Q as starting point seems clinically advantageous considering electromechanical desynchrony in patients with conduction disorders.

Generalized channel separation algorithms for accurate camera-based multi-wavelength PTT and BP estimation

Single-site multi-wavelength (MW) pulse transit time (PTT) measurement was recently proposed using contact sensors with sequential illumination. It leverages different penetration depths of light to measure the traversal of a cardiac pulse between skin layers. This enabled continuous single-site MW blood pressure (BP) monitoring, but faces challenges like subtle skin compression, which importantly influences the PPG morphology and subsequent PTT. We extended this idea to contact-free camera-based sensing and identified the major challenge of color channel overlap, which causes the signals obtained from a consumer RGB camera to be a mixture of responses in different wavelengths, thus not allowing for meaningful PTT measurement. To address this, we propose novel camera-independent data-driven channel separation algorithms based on constrained genetic algorithms. We systematically validated the algorithms on camera recordings of palms and corresponding ground-truth BP measurements of 13 subjects in two different scenarios, rest and activity. We compared the proposed algorithms against established blind source separation methods and against previous camera-specific physics-based method, showing good performance in both PTT reconstruction and BP estimation using a Random Forest regressor. The best-performing algorithm achieved mean absolute errors (MAEs) of 3.48 and 2.61 mmHg for systolic and diastolic BP in a leave-one-subject-out experiment with personalization, solidifying the proposed algorithms as enablers of novel contact-free MW PTT and BP estimation.

A Physical Model-Based Approach to One-Point Calibration of Pulse Transit Time to Blood Pressure.

To develop a novel physical model-based approach to enable 1-point calibration of pulse transit time (PTT) to blood pressure (BP). The proposed PTT-BP calibration model is derived by combining the Bramwell-Hill equation and a phenomenological model of the arterial compliance (AC) curve. By imposing a physiologically plausible constraint on the skewness of AC at positive and negative transmural pressures, the number of tunable parameters in the PTT-BP calibration model reduces to 1. Hence, as opposed to most existing PTT-BP calibration models requiring multiple (≥2) PTT-BP measurements to personalize, the PTT-BP calibration model can be personalized to an individual subject using a single PTT-BP measurement pair. Equipped with the physically relevant PTT-AC and AC-BP relationships, the proposed approach may serve as a universal means to calibrate PTT to BP over a wide BP range. The validity and proof-of-concept of the proposed approach were evaluated using PTT and BP measurements collected from 22 healthy young volunteers undergoing large BP changes. The proposed approach modestly yet significantly outperformed an empiric linear PTT-BP calibration with a group-average slope and subject-specific intercept in terms of bias (5.5 mmHg vs 6.4 mmHg), precision (8.4 mmHg vs 9.4 mmHg), mean absolute error (7.8 mmHg vs 8.8 mmHg), and root-mean-squared error (8.7 mmHg vs 10.3 mmHg, all in the case of diastolic BP). We demonstrated the preliminary proof-of-concept of an innovative physical model-based approach to one-point PTT-BP calibration. The proposed physical model-based approach has the potential to enable more accurate and convenient calibration of PTT to BP.

A Dual-Mode Wearable Sensor with Electrophysiology and Pressure Sensing for Cuffless Blood Pressure Monitoring

Wearable cuffless blood pressure sensing is essential for the monitoring of hypertension and its related cardiovascular diseases in an on-demand, timely, and comfortable manner. Measurement of pulse transit time (PTT)...

The influence of the digital pulse wave reference point on the pulse transit time measurement and variability

By measuring pulse wave velocity (PWV) via an arterial route, one can determine the stiffness of the artery. The duration between the ECG R-wave climax and a reference point on the digital pulse wave (DPW) in the same cardiac cycle must be determined in order to determine the pulse transit time (PTT). The time it takes for a pulse wave to travel from the heart to a peripheral artery location is known as the PTT. To find out the best reference point on the DPW that is associated with the least beat-beat coefficient of variation (CV) of PWV. The study was carried out on 10 healthy young males aged 19 years. A two-minute recording of the left middle fingertip DPW signals (through piezoelectric Finger Pulse Transducer) and lead II ECG (through three surface electrodes) were carried out. PTT was calculated as follows: from the climax of the electrocardiogram R wave to the onset (foot) of the DPW (PTT1); from the apex to the onset points of the DPW at 10% of its amplitude (PTT2); and from the apex to the onset points of the DPW at 50% of its amplitude (PTT3). PTT1, PTT, and PTT3 were measured on each volunteer and on the same cardiac cycles.

A NEW ALGORITHM FOR MEASURING PULSE TRANSIT TIME FROM ECG AND PPG SIGNALS

Pulse transit Time (PTT) is a physiological parameter that is based on characteristics of the pulse waveform, a direct indicator of Cardiovascular Diseases (CVD). The (PTT) is defined as the time taken for the arterial pulse to travel from the heart to a peripheral site. It is commonly derived from Electrocardiogram (ECG) and Photoplethysmogram (PPG) signal calculations and is calculated as the interval between the peak of the electrocardiogram (ECG) R-wave and a time point on the photoplethysmogram (PPG). In this study, we propose a new and lowcomplexity algorithm for the Pulse transit time (PTT) measurement, using these two signals and detecting (PTT- foot) and (PTT- peak). We built a 37 subjects dataset containing a simultaneous recording of the (ECG) and (PPG). The calculation of (PTT) consists of detecting the peak and foot points of a (PPG) and the R-peak of the (ECG) signal. Intermediate operations such as normalization and thresholding to detect the local maxima and minima, are processed on noisy signals, this algorithm is improved by a windowing temporal analysis. The obtained results are promising for the first step. The average sensitivity (SEN) and accuracy (ACC) obtained were (97.5%, and 96.82%) respectively for R-peaks detection and respectively (97.77%, and 97.64%) for (PPG-peak) detection. The sensitivity (SEN) and accuracy (ACC) of (PPG- foot) detection were (98.33%, and 94.14%).

A New Algorithm for Measuring Pulse Transit Time from ECG and PPG Signals

A New Algorithm for Measuring Pulse Transit Time from ECG and PPG Signals

Single measurement estimation of central blood pressure using an arterial transfer function

Background: Central blood pressure (BP) better reflects the loading conditions on the major organs and is more closely correlated with future cardiovascular events. The increased invasiveness and risk of infection prevents the routine measurement of central BP. Arterial transfer functions can provide central BP estimates from clinically available peripheral measurements. However, current methods are either generalized, potentially lacking the ability to adapt to inter and intra subject variability, or individualized based on additional, clinically unavailable, pulse transit time measurements. This work proposes a novel, self-contained method for individualizing an arterial transfer function from a single peripheral pressure measurement, capable of accurately estimating central BP in a range of hemodynamic conditions. Methods: Pulse wave analysis of femoral BP waves was employed to formulate initial approximations of central BP and arterial inlet flow waveforms, to serve as objective functions for the identification of all model parameters. Root mean squared error (RMSE), and systolic and pulse pressure errors were assessed with respect to invasive aortic BP measurements in a seven (7) porcine endotoxin experiments. Systolic and pulse pressure errors were analysed using Bland-Altman analysis. Method accuracy is also compared with an idealized transfer function, derived using the measured aortic-femoral pulse transit time and minimizing the RMSE of model output pressure with respect to reference aortic pressure, a generalized transfer function model, and invasive femoral pressure measurements. Results: Mean bias and limits of agreement (95% CI) for the proposed method were 1.0(-4.6, 6.7)mmHg and -1.0(-6.6, 4.6)mmHg for systolic and pulse pressure, respectively, compared to 3.6(-0.9, 8.2)mmHg and 2.7(-1.8, 7.3)mmHg for the generalized transfer function model. Mean bias and limits of agreement for femoral pressure measurements were -6.4(-15.0, 2.3)mmHg and -9.4(-18.1, -0.8)mmHg, for systolic and pulse pressure, respectively. The pooled mean and standard deviation of the RMSE produced by the single measurement method, relative to reference aortic pressure, was 4.3(1.1)mmHg, consistent with estimates produced by the idealized transfer function, 3.9(1.2)mmHg, and improving of the generalized transfer function, 4.6(1.4)mmHg. Conclusions: The proposed single measurement method provides accurate central BP estimates from routinely available peripheral pressure measurements, and nothing else. The method allows for the individualization of transfer functions on a per patient basis to better capture changes in patient condition during the progression of disease and subsequent treatment, at no additional clinical cost.

Wearable Technology and Pulse Transit Time (PTT) Used to Assess Workplace Violence Incidents in Nursing

Nurses are exposed to incidents of workplace violence involving patients and their family members, and also coworkers. Studies of occupational stressors generally rely on subjective self-reports, questionnaires, or biometric and biochemical markers in long-cycle time intervals, but such assessments offer little guidance to HF/E intervention efforts. This study examined the viability of using wearable sensors to detect workplace violence incidents, and included measurement of pulse transit time (PTT) as a biomarker of continuous blood pressure. Six nurses were monitored over seven days. The electrocardiogram, PTT, and activity level were measured using a custom-designed armband. Participants used a wristwatch (Empatica E4) to log incidents, and a smartphone survey app to rate incident severity. Results show PTT was a more reliable indicator of workplace incidents than low- to high-frequency (LF/LH) ratio heart rate variability, offering a more robust way to continuously monitor critical events noninvasively over long periods in demanding work environments.

Noninvasive Continuous Blood Pressure Estimation From Pulse Transit Time: A Review of the Calibration Models.

Noninvasive continuous blood pressure estimation is a promising alternative to minimally invasive blood pressure measurement using cuff and invasive catheter measurement, because it opens the way to both long-term and continuous blood pressure monitoring in ecological situation. The most current estimation algorithm is based on pulse transit time measurement where at least two measured signals need to be acquired. From the pulse transit time values, it is possible to estimate the continuous blood pressure for each cardiac cycle. This measurement highly depends on arterial properties which are not easily accessible with common measurement techniques; but these properties are needed as input for the estimation algorithm. With every change of input arterial properties, the error in the blood pressure estimation rises, thus a periodic calibration procedure is needed for error minimization. Recent research is focused on simplified constant arterial properties which are not constant over time and uses only linear model based on initial measurement. The elaboration of continuous calibration procedures, independent of recalibration measurement, is the key to improving the accuracy and robustness of noninvasive continuous blood pressure estimation. However, most models in literature are based on linear approximation and we discuss here the need for more complete calibration models.

Assessing hemodynamics from the photoplethysmogram to gain insights into vascular age: a review from VascAgeNet.

The photoplethysmogram (PPG) signal is widely measured by clinical and consumer devices, and it is emerging as a potential tool for assessing vascular age. The shape and timing of the PPG pulse wave are both influenced by normal vascular aging, changes in arterial stiffness and blood pressure, and atherosclerosis. This review summarizes research into assessing vascular age from the PPG. Three categories of approaches are described: 1) those which use a single PPG signal (based on pulse wave analysis), 2) those which use multiple PPG signals (such as pulse transit time measurement), and 3) those which use PPG and other signals (such as pulse arrival time measurement). Evidence is then presented on the performance, repeatability and reproducibility, and clinical utility of PPG-derived parameters of vascular age. Finally, the review outlines key directions for future research to realize the full potential of photoplethysmography for assessing vascular age.

Evaluation of a dual-PPG system for pulse transit time monitoring.

This work presents a new dual-photoplethysmographic (PPG) system for pulse transit time (PTT) monitoring. An experiment has been set up in order to compare the PTT measurement between carotid and radial arteries from two systems: our physiological multimodal platform (PMP) and the Complior® tonometer. This work explores the comparison between such optical and mechanical modalities. The results show that the PPG device tends to overestimate the PTT (RMSE = 16 ms). Furthermore, both mechanical and optical signals have been superposed and demonstrated that pulse morphologies are quite similar.Clinical Relevance-Carotid-radial pulse wave velocity (PWV) is compared on a small cohort of subjects and significant differences are observed between optical and mechanical-based systems.

Blood pressure wave propagation—a multisensor setup for cerebral autoregulation studies

Objective. Cerebral autoregulation is critically important to maintain proper brain perfusion and supply the brain with oxygenated blood. Non-invasive measures of blood pressure (BP) are critical in assessing cerebral autoregulation. Wave propagation velocity may be a useful technique to estimate BP but the effect of the location of the sensors on the readings has not been thoroughly examined. In this paper, we were interested in studying whether the propagation velocity of a pressure wave in the direction from the heart to the brain may differ compared with propagation from the heart to the periphery, as well as across different physiological tasks and/or health conditions. Using non-invasive sensors simultaneously placed at different locations of the human body allows for the study of how the propagation velocity of the pressure wave, based on pulse transit time (PTT), varies across different directions. Approach. We present a multi-sensor BP wave propagation measurement setup intended for cerebral autoregulation studies. The presented sensor setup consists of three sensors, one placed on each of the neck, chest and finger, allowing simultaneous measurement of changes in BP propagation velocity towards the brain and to the periphery. We show how commonly tested physiological tasks affect the relative changes of PTT and correlations with BP. Main results. We observed that during maximal blow, valsalva and breath hold breathing tasks, the relative changes of PTT were higher when PTT was measured in the direction from the heart to the brain than from the heart to the peripherals. In contrast, during a deep breathing task, the relative change in PTT from the heart to the brain was lower. In addition, we present a short literature review of the PTT methods used in brain research. Significance. These preliminary data suggest that the physiological task and direction of PTT measurement may affect relative PTT changes. The presented three-sensor setup provides an easy and neuroimaging compatible method for cerebral autoregulation studies by allowing measurement of BP wave propagation velocity towards the brain versus towards the periphery.

Enabling Wearable Pulse Transit Time-Based Blood Pressure Estimation for Medically Underserved Areas and Health Equity: Comprehensive Evaluation Study.

BackgroundNoninvasive and cuffless approaches to monitor blood pressure (BP), in light of their convenience and accuracy, have paved the way toward remote screening and management of hypertension. However, existing noninvasive methodologies, which operate on mechanical, electrical, and optical sensing modalities, have not been thoroughly evaluated in demographically and racially diverse populations. Thus, the potential accuracy of these technologies in populations where they could have the greatest impact has not been sufficiently addressed. This presents challenges in clinical translation due to concerns about perpetuating existing health disparities.ObjectiveIn this paper, we aim to present findings on the feasibility of a cuffless, wrist-worn, pulse transit time (PTT)–based device for monitoring BP in a diverse population.MethodsWe recruited a diverse population through a collaborative effort with a nonprofit organization working with medically underserved areas in Georgia. We used our custom, multimodal, wrist-worn device to measure the PTT through seismocardiography, as the proximal timing reference, and photoplethysmography, as the distal timing reference. In addition, we created a novel data-driven beat-selection algorithm to reduce noise and improve the robustness of the method. We compared the wearable PTT measurements with those from a finger-cuff continuous BP device over the course of several perturbations used to modulate BP.ResultsOur PTT-based wrist-worn device accurately monitored diastolic blood pressure (DBP) and mean arterial pressure (MAP) in a diverse population (N=44 participants) with a mean absolute difference of 2.90 mm Hg and 3.39 mm Hg for DBP and MAP, respectively, after calibration. Meanwhile, the mean absolute difference of our systolic BP estimation was 5.36 mm Hg, a grade B classification based on the Institute for Electronics and Electrical Engineers standard. We have further demonstrated the ability of our device to capture the commonly observed demographic differences in underlying arterial stiffness.ConclusionsAccurate DBP and MAP estimation, along with grade B systolic BP estimation, using a convenient wearable device can empower users and facilitate remote BP monitoring in medically underserved areas, thus providing widespread hypertension screening and management for health equity.

The use of multi-site photoplethysmography (PPG) as a screening tool for coronary arterial disease and atherosclerosis

Objective. We present the design and validation of a non-invasive smart-phone based screening tool for atherosclerosis and coronary arterial disease (CAD), which is the leading cause of mortality worldwide. Approach. We designed a three-channel photoplethysmography (PPG) device that connects to a smart phone application for measuring pulse transit time (PTT) and pulse wave velocity (PWV) using PPG probes that are simultaneously clipped onto to the ear, index finger, and big toe, respectively. Validation was performed through a clinical study with 100 participants (age 20 to 77) at a research hospital in Nagpur, India. Study subjects were stratified by age and divided into three groups corresponding to the disease severity: CAD, hypertensive (‘Pre-CAD’), and Healthy. Main results. PWV measurements derived from the Ear-Toe probe measurements yielded the best performance, with median PWV values increasing monotonically as a function of disease severity and age, as follows: 14.2 m s−1 for the older-patient CAD group, 12.2 m s−1 for the younger-patient CAD group, 11.6 m s−1 for the older-patient Pre-CAD group, 10.2 m s−1 for the younger-patient Pre-CAD group, 9.7 m s−1 for the older healthy controls, and 8.4 m s−1 for the younger healthy controls. Using just two simple features, the PTT and patient height, we demonstrate a machine learning prediction model for CAD with a median accuracy of 0.83 (AUC). Significance. This work demonstrates the ability to predict atherosclerosis and CAD using a single simple physiological measurement with a multi-site PPG tool that is electrically powered by a mobile phone and does not require any electrocardiogram reference. Furthermore, this method only requires a single anthropometric measurement, which is the patient’s height.

Wearable Cuff-Less Blood Pressure Estimation at Home via Pulse Transit Time.

We developed a wearable watch-based device to provide noninvasive, cuff-less blood pressure (BP) estimation in an at-home setting. The watch measures single-lead electrocardiogram (ECG), tri-axial seismocardiogram (SCG), and multi-wavelength photoplethysmogram (PPG) signals to compute the pulse transit time (PTT), allowing for BP estimation. We sent our custom watch device and an oscillometric BP cuff home with 21 healthy subjects, and captured the natural variability in BP over the course of a 24-hour period. After calibration, our Pearson correlation coefficient (PCC) of 0.69 and root-mean-square-error (RMSE) of 2.72mmHg suggest that noninvasive PTT measurements correlate with around-the-clock BP. Using a novel two-point calibration method, we achieved a RMSE of 3.86mmHg. We further demonstrated the potential of a semi-globalized adaptive model to reduce calibration requirements. This is, to the best of our knowledge, the first time that BP has been comprehensively estimated noninvasively using PTT in an at-home setting. We showed a more convenient method for obtaining ambulatory BP than through the use of the standard oscillometric cuff. We presented new calibration methods for BP estimation using fewer calibration points that are more practical for a real-world scenario. A custom watch (SeismoWatch) capable of taking multiple BP measurements enables reliable remote monitoring of daily BP and paves the way towards convenient hypertension screening and management, which can potentially reduce hospitalizations and improve quality of life.

Estimating Central Blood Pressure From a Single Peripheral Pressure Measurement

Abstract This paper presents a set of criteria used to identify the parameters describing a tube-load model of the arterial system to estimate central blood pressure (BP). The criteria are generalizable to accommodate for inter- and intra-subject variability encountered in the ICU. The proposed single measurement transfer function (SMTF) requires only a single peripheral pressure measurement, commonly available in the ICU, for central pressure estimation, removing the need for an additional measurement of pulse transit time, common to other central BP estimation models. The method was tested using data from six (6) porcine experiments where septic shock was induced and subsequent treatment was performed. Systolic pressure (SP), pulse pressure (PP) and root-mean-squared (RMSE) errors relative to invasive measurements of aortic pressure were used to assess accuracy. The SMTF method produced mean errors ≤5mmHg across all metrics with 84.4, 88.7 and 63.2% of SP, PP, and RMSE, respectively, within this bound of measured central pressure. Peripheral BP accuracy was also assessed as it is commonly used as a surrogate for central BP in clinical settings. Finally, two alternate methods utilizing the same model equations with additional inputs, one using the measured pulse transit time and the other minimizing the RMSE with measured aortic pressure, were implemented to compare the SMTF accuracy to best case outputs given the model equations.

Comparision of photo pulse plethysmography module with Mobil-O-graph for measurement of pulse wave velocity

IntroductionPulse wave velocity (PWV) is an indicator of arterial stiffness and one of the prognostic tools in clinical practice. We compared the finger photo pulse plethysmography (PPG) module with the Mobil-O-Graph for assessment of PWV. Material and methods80 healthy subjects and patients have participated in this study, among them, 42 were males, and 38 were females. Recording for the subjects was executed between 9, and 11 a.m., after a light breakfast. Lead – II ECG along with PPG were recorded in dual channel AD converter and Mobil-O-Graph simultaneously. The analogue signals of both the devices of the AD converter were digitized by using the sound card of the computer for the measurement of Pulse Transit Time [PTT]. ResultsThe mean age of the participants was 41.5 ± 5.48 and BMI-26.42 ± 5.80. PWV values measured by the devices were similar (P > 0.05). There is a significant positive correlation of PWV between PPG and Mobil O graph, r-0.92 (p = 0.001). Bland-Altman analysis indicated that a mean difference for PWV is .0.3 m/s, which is limits of agreement (1.4–2.4) between PPG and Mobil-O-Graph. Intra-class correlation (ICC) for PWV was 0.89, and the coefficient of variation (CV) was 9.2%. ConclusionBased on the findings of the present study, we suggest that the measurement of PWV obtained from the PPG is probably a reliable one. It offers the advantages of lower cost and greater practicality about application and usage.

Wearable Millimeter-Wave Device for Contactless Measurement of Arterial Pulses.

Wearable monitors for measuring vital signs such as blood pressure will greatly impact the medical field. This work presents a millimeter-wave, radar-based system for performing accurate measurements of arterial pulse waveforms without contacting the region that is pulsing. Electromagnetic and radar-system simulation models are utilized to demonstrate the viability and safety of this approach. This is followed by hardware/software implementation and a study on 12 human subjects. Measured radial arterial waveforms exhibit signal strengths that are well above the noise floor of the system and a morphology that would be expected in an arterial pulse. Finally, comparison of the radar-based signals with a reference tonometer indicates a strong correlation between waveforms, as well as similar spectral signatures. The results observed suggest a millimeter-wave based approach for arterial pulse detection is very promising for future applications in pulse wave analysis and pulse transit time measurement for blood pressure tracking.