Oscillometric Pulse Research Articles

Oscillometric pulse wave analysis in newly diagnosed never treated Gujarati hypertensives

INTRODUCTION: Hypertension is on a high with preponderance of undiagnosed and untreated at-risk individuals. Pulse wave analysis (PWA) provides noninvasive assessment of arterial stiffness and central hemodynamic parameters. It provides more discrete and direct inference about cardiovascular aging that is expected to be exaggerated with systemic hypertension. MATERIALS AND METHODS: A case–control study was conducted in 116 newly diagnosed, never treated, apparently healthy hypertensives and 116 matched nonhypertensive controls. Oscillometric PWA was accomplished by Mobil-o-Graph (IEM, Germany) to derive cardiovascular parameters that were further analyzed. P RESULTS: Cases showed significantly higher brachial arterial parameters (blood pressure [BP], heart rate, and rate pressure product); arterial stiffness (augmentation pressure, augmentation index, pulse wave velocity, total arterial stiffness, and pulse pressure amplification); and central hemodynamics (central BP, cardiac output, and stroke work) than age-, gender-, and height-matched controls. Major study parameters correlated with BP, heart rate, and age, but in multiple regressions, they were independent of most of these parameters. CONCLUSIONS: Oscillometric PWA is feasible in our population. It revealed beyond brachial BP abnormal profile suggestive of early cardiovascular aging in new and never treated hypertensives. It also suggests further work to consolidate and explore these results.

Assessing Arterial Stiffness using the Oscillometric Method in Patients with Diabetes and/or Hypertension

Introduction: The parameters of pulse wave analysis, an emerging modality, are strong predictors of cardiovascular events and all-cause mortality. Systemic arterial hypertension and type 2 diabetes mellitus promote arterial stiffness, thereby modifying the characteristics of the pulse wave. This study analyzed and compared the pulse wave parameters of patients with diabetes and/or hypertension, using the oscillometric method. Methods: In this cross-sectional study, the 110 study subjects were divided into three groups: Hypertensive– diabetic, hypertensive, and diabetic. An oscillometric pulse wave test was performed using Mobil-O-Graph® PWA equipment. The following variables were assessed: Age, body mass index, augmentation index, pulse wave velocity, peripheral arterial pressure, and central arterial pressure. Results: The mean age of the study population was 61.3 years (standard deviation: 1.2). The mean body mass index was 29.3 kg/m2 (standard deviation: 2.9). The hypertensive–diabetic group had the highest mean pulse wave velocity and peripheral and central arterial pressure values. Moreover, the systolic peripheral and central arterial pressures of the hypertensive–diabetic group were significantly higher than those of the other two groups (p<0.05). All analyzed parameters were strongly correlated between the diabetic group and the hypertensive group (p<0.0001). Conclusion: Patients with overlapping cardiovascular risk factors of diabetes and hypertension had the highest PWV and peripheral and central arterial pressure values. Hypertension and diabetes, as isolated conditions, were equivalent in their alterations of pulse wave analysis parameters.

Method Comparison and Validation of the Determination of Ejection Duration from Oscillometric Measurements

The ejection duration (ED) is an important indicator of ventricular function as well as ventriculo-arterial coupling, especially for heart failure with reduced ejection fraction. Thus, the non-invasive oscillometric determination of ED from arterial pressure waves could enhance methods of pulse wave analysis. The aim of this work was to compare different approaches to calculate the ED from oscillometric measurements and to test and to validate the determination of ED with results from measurements using radial tonometry. Oscillometric and tonometric pulse wave measurements were obtained in direct succession from each patient with the Mobil-O-Graph and with the Sphygmocor device in a comparative study. Also, the results from the internal algorithm of SphygmoCor were obtained. Several methods for the determination of ED were implemented and applied to the given measurements. The results of Mobil-O-Graph were compared with the ejection durations from the internal algorithm of SphygmoCor. Several algorithms had a mean error lower than the step size of the recordings. The algorithm using numerical central differences to find the maximum curvature of the curve was chosen for the determination of ED due to its lowest standard deviation compared with others, its low mean error and its stability. The mean difference between Mobil-O-Graph and SphygmoCor was 7 ms (35 SD). An algorithm for determination of ED was selected and tested successfully on radial and brachial recordings. As the differences between locations as well as between algorithms are sufficiently small, the determination of ejection duration from brachial oscillometric pulse waves seems feasible.

Aortic pulse wave velocity and augmentation index@75 measured by oscillometric pulse wave analysis in Gujarati nonhypertensives

BACKGROUND: Augmentation indexes (AIxs) and pulse wave velocity (PWV) are arterial stiffness parameters. They can be studied by pulse wave analysis (PWA) noninvasively. Before use, AIx and PWV need normative baseline study to find the predictors. MATERIALS AND METHODS: We conducted a cross-sectional study in 801 nonhypertensives, aged 15–65 (divided into five subgroups) years. PWA was accomplished by Mobil-o-Graph (IEM, Germany) based on oscillometric principle and cardiovascular parameters reported were further analyzed. Value of P RESULTS: There were five age-based subgroups from 15 to 65 years, showing an increase in AIx@75 and PWV with age. Females had significantly higher AIx in male in age groups (31.4 vs. 25.8, 34.95 vs. 27.21, 32.62 vs. 27.61, 34.32 vs. 26.36, 37.09 vs. 29.63; P CONCLUSIONS: Oscillometric measurement of PWV and AIx@75 is feasible in our population. They are dependent on each other and age, totally not dependent on blood pressure and have difference in predictors. This baseline data can be used as a reference for future studies.

Algoritma Interpolasi Nearest-Neighbor untuk Pendeteksian Sampul Pulsa Oscilometri Menggunakan Mikrokontroler Berbiaya Rendah

Non-invasive blood pressure measurement devices are widely available in the marketplace. Most of these devices use the oscillometric principle that store and analyze oscillometric waveforms during cuff deflation to obtain mean arterial pressure, systolic blood pressure and diastolic blood pressure. Those pressure values are determined from the oscillometric waveform envelope. Several methods to detect the envelope of oscillometric pulses utilize a complex algorithm that requires a large capacity memory and certainly difficult to process by a low memory capacity embedded system. A simple nearest-neighbor interpolation method is applied for oscillometric pulse envelope detection in non-invasive blood pressure measurement using microcontroller such ATmega328. The experiment yields 59 seconds average time to process the computation with 3.6% average percent error in blood pressure measurement.

Reliability of oscillometric central blood pressure and central systolic loading in individuals over 50 years: Effects of posture and fasting

Background and aimsThe between-day reliability of oscillometric pulse wave analysis has been demonstrated in a young, healthy population but not in an older sample. This study examined the between-day reliability of the SphygmoCor XCEL in individuals over 50 years. As blood pressure is measured in a range of postures and fasting states (supine/seated, fasted/non-fasted), this study also investigated the effect of these variables on central blood pressure and central systolic loading. MethodsFifty-one adults (m = 21; age 57 ± 6.4 y) were tested on three mornings in supine and seated conditions and in fasted and non-fasted states. Data was analysed as a whole and for normotensive (n = 25) and hypertensive participants (n = 26). ResultsSphygmoCor XCEL demonstrated strong reliability in the whole sample for central systolic and diastolic blood pressures, augmentation index (AIx) and AIx75 (ICC = 0.77–0.95). Significant interaction effects were observed in central diastolic blood pressure, central pulse pressure, augmentation index (AIx) and AIx75 (p < 0.05; ηp2 = 0.10–0.23). Fasting state had a greater influence on central pressures in a seated than supine posture, but a greater effect on central systolic loading measures in a supine posture. ConclusionsThe SphygmoCor XCEL is a reliable tool to assess central haemodynamic variables in an older population. It would be pertinent for clinicians and researchers to record central measures in a supine posture to minimise the effects of food consumption. Conversely, the assessment of central systolic loading should occur in a seated condition to minimise the influence of varying fasting states.

Reliability of oscillometric central blood pressure responses to lower limb resistance exercise

Background and aimsAlthough it is well known that resistance training (RT) is beneficial for patients suffering from a variety of cardiovascular diseases, it remains underutilized as a rehabilitation tool as there is no reliable way to monitor the additional stress placed on the central organs. The current study aimed to determine between-day reliability of central haemodynamic indices using oscillometric pulse wave analysis (PWA) during progressive sub-maximal RT. MethodsNineteen healthy young males were tested on 3 different mornings in a fasted state. Central hemodynamic variables including augmentation index (AIx), AIx normalized to a heart rate of 75 beats per minute (AIx@75), central systolic blood pressure (cSBP), forwards (Pf) and backwards (Pb) wave reflection were determined at rest, as well as during leg extension RT at 10, 15 and 20% of maximal volitional contraction (MVC), and following 1 min and 5 min passive recovery. ResultsDuring RT at 10, 15 and 20% MVC, the intraclass correlation coefficient (ICC) values for AIx@75 (0.76–0.9), cSBP (0.74–0.78), Pf (0.75–0.82) and Pb (0.75–0.83) exceeded the criteria (0.75) for excellent reliability. During the 5 min recovery, the ICC values for AIx@75 (0.87–0.87), cSBP (0.69–0.7), Pf (0.63–0.67) and Pb (0.63–0.66) indicated good to excellent reliability. ConclusionsClinically meaningful changes in central hemodynamic indices can be obtained during resistance training using oscillometric PWA devices. This technology holds potential for advancing resistance training prescription guidelines for patients with overt cardiovascular diseases.

Variation of the Korotkoff Stethoscope Sounds During Blood Pressure Measurement: Analysis Using a Convolutional Neural Network.

Korotkoff sounds are known to change their characteristics during blood pressure (BP) measurement, resulting in some uncertainties for systolic and diastolic pressure (SBP and DBP) determinations. The aim of this study was to assess the variation of Korotkoff sounds during BP measurement by examining all stethoscope sounds associated with each heartbeat from above systole to below diastole during linear cuff deflation. Three repeat BP measurements were taken from 140 healthy subjects (age 21 to 73 years; 62 female and 78 male) by a trained observer, giving 420 measurements. During the BP measurements, the cuff pressure and stethoscope signals were simultaneously recorded digitally to a computer for subsequent analysis. Heartbeats were identified from the oscillometric cuff pressure pulses. The presence of each beat was used to create a time window (1 s, 2000 samples) centered on the oscillometric pulse peak for extracting beat-by-beat stethoscope sounds. A time-frequency two-dimensional matrix was obtained for the stethoscope sounds associated with each beat, and all beats between the manually determined SBPs and DBPs were labeled as "Korotkoff." A convolutional neural network was then used to analyze consistency in sound patterns that were associated with Korotkoff sounds. A 10-fold cross-validation strategy was applied to the stethoscope sounds from all 140 subjects, with the data from ten groups of 14 subjects being analyzed separately, allowing consistency to be evaluated between groups. Next, within-subject variation of the Korotkoff sounds analyzed from the three repeats was quantified, separately for each stethoscope sound beat. There was consistency between folds with no significant differences between groups of 14 subjects (P = 0.09 to P = 0.62). Our results showed that 80.7% beats at SBP and 69.5% at DBP were analyzed as Korotkoff sounds, with significant differences between adjacent beats at systole (13.1%, P = 0.001) and diastole (17.4%, P < 0.001). Results reached stability for SBP (97.8%, at sixth beat below SBP) and DBP (98.1%, at sixth beat above DBP) with no significant differences between adjacent beats (SBP P = 0.74; DBP P = 0.88). There were no significant differences at high-cuff pressures, but at low pressures close to diastole there was a small difference (3.3%, P = 0.02). In addition, greater within subject variability was observed at SBP (21.4%) and DBP (28.9%), with a significant difference between both (P < 0.02). In conclusion, this study has demonstrated that Korotkoff sounds can be consistently identified during the period below SBP and above DBP, but that at systole and diastole there can be substantial variations that are associated with high variation in the three repeat measurements in each subject.

P5454Comparison of non-invasive central blood pressure measurements using applanation tonometry and automated oscillometric radial pulse wave analysis

P5454Comparison of non-invasive central blood pressure measurements using applanation tonometry and automated oscillometric radial pulse wave analysis

Reliability of Pulse Waveform Separation Analysis Responses to an Orthostatic Challenge

PURPOSE: Cardiovascular autonomic nervous system function can be assessed by recording arterial wave reflection responses to an orthostatic challenge. Using pulse wave analysis, arterial wave reflection can be estimated using pulse wave separation analysis, whereby a triangular or a physiologic flow waveform is assumed and the aortic wave is separated into its forward and timing-independent reflected (Pb) components. This study sought to determine the measurement precision (between-day reliability) of Pb responses to an modified tilt-table test. METHODS: Twenty healthy adults (26.4 y (SD 5.2), 55% F, 24.7 kg/m2 (SD 3.8)) were tested on three different mornings in the fasted state, separated by a maximum of seven days. Oscillometric pressure waveforms were recorded on the left upper arm, and aortic waveforms were generated using a generalized transfer function. The criterion for acceptable reliability was an intra-class correlation coefficient (ICC) of 0.75. To express the percentage change that must occur at a group and individual level, the standard error of measurement (%SEM) and smallest detectable change (%SDC) were calculated. RESULTS: The criterion ICC (0.75) was exceeded at baseline (0.79), following 5 min tilt (0.75), and following 5 min recovery from tilt (0.75). The %SEM and %SDC for the 5 min tilt response were 7% and 19%, respectively. CONCLUSION: Arterial wave reflection responses to an orthostatic challenge can be assessed with acceptable between-day reliability using oscillometric pulse wave analysis.

Metrological Characterization of a Method for Blood Pressure Estimation Based on Arterial Lumen Area Model

Accuracy of blood pressure (BP) measurement is a challenging issue in oscillometry. Most of the automated noninvasive BP monitors estimate BP from envelope of the measured oscillometric pulses. The peak and the trough of the oscillometric pulses are very sensitive to noise caused by breathing, heart-rate variability, motion artifacts, muscle contraction, and environmental noise. Therefore, accuracy of the estimated BP based on the oscillometric waveform envelopes is not reliable in some cases. Recently, employing a modeling approach to estimate BP, we obtained the accurate results for a set of healthy subjects. The method is based on the lumen area oscillations model and estimates BP by comparing the actual and corresponding simulated waveforms. The method’s accuracy worsened when we tested it on a broader range of healthy subjects, while a significant drop was observed when the method was used for patients with chronic cardiovascular diseases. The work presented in this paper represents an improved version of our previous approach. We tested the proposed method on both healthy subjects and patients with chronic cardiovascular diseases, and compared the results to two popular BP estimation algorithms: maximum amplitude algorithm and maximum/minimum slope algorithm. We observed up to 56.7% and 57.3% improvements in mean absolute error, 98.9% and 64.4% improvements in mean error, 50% and 59% improvements in standard deviation of errors, and up to 57.6% and 55.8% in measurement uncertainty for the estimated systolic and diastolic pressures, respectively.

Reliability of pulse waveform separation analysis: effects of posture and fasting.

Oscillometric pulse wave analysis devices enable, with relative simplicity and objectivity, the measurement of central hemodynamic parameters. The important parameters are central blood pressures and indices of arterial wave reflection, including wave separation analysis (backward pressure component Pb and reflection magnitude). This study sought to determine whether the measurement precision (between-day reliability) of Pb and reflection magnitude: exceeds the criterion for acceptable reliability; and is affected by posture (supine, seated) and fasting state. Twenty healthy adults (50% female, 27.9 years, 24.2 kg/m) were tested on six different mornings: 3 days fasted, 3 days nonfasted condition. On each occasion, participants were tested in supine and seated postures. Oscillometric pressure waveforms were recorded on the left upper arm. The criterion intra-class correlation coefficient value of 0.75 was exceeded for Pb (0.76) and reflection magnitude (0.77) when participants were assessed under the combined supine-fasted condition. The intra-class correlation coefficient was lowest for Pb in seated-nonfasted condition (0.57), and lowest for reflection magnitude in the seated-fasted condition (0.56). For Pb, the smallest detectible change that must be exceeded in order for a significant change to occur in an individual was 2.5 mmHg, and for reflection magnitude, the smallest detectable change was 8.5%. Assessments of Pb and reflection magnitude are as follows: exceed the criterion for acceptable reliability; and are most reliable when participants are fasted in a supine position. The demonstrated reliability suggests sufficient precision to detect clinically meaningful changes in reflection magnitude and Pb.

Significantly Reduced Blood Pressure Measurement Variability for Both Normotensive and Hypertensive Subjects: Effect of Polynomial Curve Fitting of Oscillometric Pulses.

This study aimed to compare within-subject blood pressure (BP) variabilities from different measurement techniques. Cuff pressures from three repeated BP measurements were obtained from 30 normotensive and 30 hypertensive subjects. Automatic BPs were determined from the pulses with normalised peak amplitude larger than a threshold (0.5 for SBP, 0.7 for DBP, and 1.0 for MAP). They were also determined from cuff pressures associated with the above thresholds on a fitted curve polynomial curve of the oscillometric pulse peaks. Finally, the standard deviation (SD) of three repeats and its coefficient of variability (CV) were compared between the two automatic techniques. For the normotensive group, polynomial curve fitting significantly reduced SD of repeats from 3.6 to 2.5 mmHg for SBP and from 3.7 to 2.1 mmHg for MAP and reduced CV from 3.0% to 2.2% for SBP and from 4.3% to 2.4% for MAP (all P < 0.01). For the hypertensive group, SD of repeats decreased from 6.5 to 5.5 mmHg for SBP and from 6.7 to 4.2 mmHg for MAP, and CV decreased from 4.2% to 3.6% for SBP and from 5.8% to 3.8% for MAP (all P < 0.05). In conclusion, polynomial curve fitting of oscillometric pulses had the ability to reduce automatic BP measurement variability.

Accuracy of pulse interval timing in ambulatory blood pressure measurement.

Blood pressure (BP) monitors rely on pulse detection. Some blood pressure monitors use pulse timings to analyse pulse interval variability for arrhythmia screening, but this assumes that the pulse interval timings detected from BP cuffs are accurate compared with RR intervals derived from ECG. In this study we compared the accuracy of pulse intervals detected using an ambulatory blood pressure monitor (ABPM) with single lead ECG. Twenty participants wore an ABPM for three hours and a data logger which synchronously measured cuff pressure and ECG. RR intervals were compared with corresponding intervals derived from the cuff pressure tracings using three different pulse landmarks. Linear mixed effects models were used to assess differences between ECG and cuff pressure timings and to investigate the effect of potential covariates. In addition, the maximum number of successive oscillometric beats detectable in a measurement was assessed. From 243 BP measurements, the landmark at the foot of the oscillometric pulse was found to be associated with fewest covariates and had a random error of 9.5 ms. 99% of the cuff pressure recordings had more than 10 successive detectable oscillometric beats. RR intervals can be accurately estimated using an ABPM.

Reliability of oscillometric central blood pressure responses to submaximal exercise.

Central blood pressure responses to exercise may provide clinicians with a superior diagnostic and prognostic tool. However, to be of value in a clinical setting these assessments must be simple to conduct and reliable. Using oscillometric pulse wave analysis (PWA), determine the upper limit for between-day reliability of central SBP (cSBP) and central pressure augmentation (AIx) responses to three progressive stages of submaximal exercise in a cohort of young, healthy participants. Fifteen healthy males [25.8 years (SD 5.7), 23.9 kg/m (SD 2.5)] were tested on three different mornings in a fasted state, separated by a maximum of 14 days. Central hemodynamic variables were assessed on the left upper arm. Participants underwent three progressive stages of submaximal cycling at 50 W (low), 100 W (moderate) and 150 W (moderate-hard). During low and moderate-intensity exercise the intra-class correlation coefficient (ICC) values for cSBP (0.79-0.80) and AIx (0.81-0.85) indicated excellent reliability (ICC > 0.75). For the moderate-hard intensity AIx could not be computed, and the ICC for cSBP was adequate (0.72). Findings from this study suggest that, at least in a young, healthy cohort, oscillometric PWA can be used to reliably assess central blood pressure measurements during exercise, up to a moderate intensity. Although further work is required to verify these findings in clinical cohorts, these measurements may potentially provide clinicians with a practical option for obtaining important hemodynamic information beyond that provided by resting peripheral blood pressure.

Respiratory modulation of oscillometric cuff pressure pulses and Korotkoff sounds during clinical blood pressure measurement in healthy adults.

BackgroundAccurate blood pressure (BP) measurement depends on the reliability of oscillometric cuff pressure pulses (OscP) and Korotkoff sounds (KorS) for automated oscillometric and manual techniques. It has been widely accepted that respiration is one of the main factors affecting BP measurement. However, little is known about how respiration affects the signals from which BP measurement is obtained. The aim was to quantify the modulation effect of respiration on oscillometric pulses and KorS during clinical BP measurement.MethodsSystolic and diastolic BPs were measured manually from 40 healthy subjects (from 23 to 65 years old) under normal and regular deep breathing. The following signals were digitally recorded during linear cuff deflation: chest motion from a magnetometer to obtain reference respiration, cuff pressure from an electronic pressure sensor to derive OscP, and KorS from a digital stethoscope. The effects of respiration on both OscP and KorS were determined from changes in their amplitude associated with respiration between systole and diastole. These changes were normalized to the mean signal amplitude of OscP and KorS to derive the respiratory modulation depth. Reference respiration frequency, and the frequencies derived from the amplitude modulation of OscP and KorS were also calculated and compared.ResultsRespiratory modulation depth was 14 and 40 % for OscP and KorS respectively under normal breathing condition, with significant increases (both p < 0.05) to 16 and 49 % with deeper breathing. There was no statistically significant difference between the reference respiration frequency and those derived from the oscillometric and Korotkoff signals (both p > 0.05) during deep breathing, and for the oscillometric signal during normal breathing (p > 0.05).ConclusionsOur study confirmed and quantified the respiratory modulation effect on the oscillometric pulses and KorS during clinical BP measurement, with increased modulation depth under regular deeper breathing.

Model-Based Mean Arterial Pressure Estimation Using Simultaneous Electrocardiogram and Oscillometric Blood Pressure Measurements

An accurate noninvasive estimation of mean arterial pressure (MAP) is of great importance in the evaluation of circulatory function and prognosis of some cardiovascular diseases. This paper proposes a novel oscillometric MAP estimation method based on the dependence of pulse transit time (PTT) on cuff pressure (CP). The PTT computed as the time interval between the electrocardiogram (ECG) R-peaks and the maximum slope points on the oscillometric pulses is mathematically modeled by considering the cuff-arm-artery system and the blood flow dynamics. It is then analytically shown that MAP can be approximated as the CP at which the PTT is maximum. Based on our theoretical findings, a new method of MAP estimation from simultaneous ECG and oscillometric blood pressure measurements is proposed. Our proposed method is validated with a pilot study in which 150 recordings from 10 subjects are analyzed. The reference MAP is computed from the systolic and diastolic pressures measured by the Food and Drug Administration-approved Omron HEM-790IT monitor using three different formulas given in the literature. The performance of our proposed method is compared with the maximum amplitude and zero-crossing methods in terms of mean error (ME), mean absolute error, and standard deviation of error (SDE). It is found that our proposed method achieves improvements of more than 20% in SDE compared with the maximum amplitude method and more than 50% in ME compared with the zero-crossing method.

Reliability of oscillometric central blood pressure and wave reflection readings

Oscillometric pulse wave analysis devices have recently emerged, presenting suitable options for investigating central hemodynamic properties in clinical practice. This study sought to examine whether the between-day reliability of central SBP (cSBP) and systemic arterial wave reflection (augmentation index, AIx) readings exceed the criterion for acceptable reliability or are affected by posture (supine and seated) and fasting state. Twenty healthy adults (50% female, 27.9 years, 24.2 kg/m) were tested on six different mornings: 3 days fasted and 3 days nonfasted. On each occasion, participants were tested in supine and seated postures. Oscillometric pressure waveforms were recorded on left upper arm. For cSBP, there was nonsignificant main effect for fasting state (P = 0.819) but there was a main effect for posture (P = 0.002). Conversely, for AIx, there was nonsignificant main effect for posture (P = 0.537) but there was a large main effect for fasting state (P = < 0.001). The criterion intraclass correlation coefficient value of 0.75 was exceeded for both variables when participants were assessed under the combined supine-fasted condition. For cSBP, the reliability coefficient was lowest (best) when supine fasted (6.8 mmHg) and greatest (worst) when seated nonfasted (8.6 mmHg). For AIx, the reliability coefficient was lower for the supine (11.4-11.7%) compared with the seated (14.0-15.2%) posture. Findings from this study suggest that oscillometric assessments of central hemodynamic variables exceed the criterion for acceptable reliability and are most reliable when participants are evaluated while supine and fasted.

Reliability of oscillometric central hemodynamic responses to an orthostatic challenge.

Monitoring central hemodynamic responses to an orthostatic challenge may provide important insight into autonomic nervous system function. Oscillometric pulse wave analysis devices have recently emerged, presenting clinically viable options for investigating central hemodynamic properties. The purpose of the current study was to determine whether oscillometric pulse wave analysis can be used to reliably (between-day) assess central blood pressure and central pressure augmentation (augmentation index) responses to a 5min orthostatic challenge (modified tilt-table). Twenty healthy adults (26.4y (SD 5.2), 55% F, 24.7kg/m(2) (SD 3.8)) were tested on 3 different mornings in the fasted state, separated by a maximum of 7 days. Central hemodynamic variables were assessed on the left arm using an oscillometric device. Repeated measures analysis of variance indicated a significant main effect of the modified tilt-table for all central hemodynamic variables (P<0.001). In response to the tilt, central diastolic pressure increased by 4.5mmHg (CI: 2.6, 6.4), central systolic blood pressure increased by 2.3 (CI: 4.4, 0.16) mmHg, and augmentation index decreased by an absolute - 5.3%, (CI:-2.7,-7.9%). The intra-class correlation coefficient values for central diastolic pressure (0.83-0.86), central systolic blood pressure (0.80-0.87) and AIx (0.79-0.82) were above the 0.75 criterion in both the supine and tilted positions, indicating excellent between-day reliability. Central hemodynamic responses to an orthostatic challenge can be assessed with acceptable between-day reliability using oscillometric pulse wave analysis.

Improved Measurement of Blood Pressure by Extraction of Characteristic Features from the Cuff Oscillometric Waveform.

We present a novel approach to improve the estimation of systolic (SBP) and diastolic blood pressure (DBP) from oscillometric waveform data using variable characteristic ratios between SBP and DBP with mean arterial pressure (MAP). This was verified in 25 healthy subjects, aged 28 ± 5 years. The multiple linear regression (MLR) and support vector regression (SVR) models were used to examine the relationship between the SBP and the DBP ratio with ten features extracted from the oscillometric waveform envelope (OWE). An automatic algorithm based on relative changes in the cuff pressure and neighbouring oscillometric pulses was proposed to remove outlier points caused by movement artifacts. Substantial reduction in the mean and standard deviation of the blood pressure estimation errors were obtained upon artifact removal. Using the sequential forward floating selection (SFFS) approach, we were able to achieve a significant reduction in the mean and standard deviation of differences between the estimated SBP values and the reference scoring (MLR: mean ± SD = −0.3 ± 5.8 mmHg; SVR and −0.6 ± 5.4 mmHg) with only two features, i.e., Ratio2 and Area3, as compared to the conventional maximum amplitude algorithm (MAA) method (mean ± SD = −1.6 ± 8.6 mmHg). Comparing the performance of both MLR and SVR models, our results showed that the MLR model was able to achieve comparable performance to that of the SVR model despite its simplicity.