Estimation Of Central Blood Pressure Research Articles

Oscillometric estimation of central blood pressure

Hypertension is a major risk factor for a wide range of cardiovascular diseases and is typically identified by measuring blood pressure (BP) at the brachial artery. Although such a measurement may accurately determine diastolic BP, systolic BP is not reflected accurately. Current noninvasive techniques for assessing central aortic BP require additional recording of an arterial pressure wave using a high-fidelity applanation tonometer. Within one measurement cycle, the Mobil-O-Graph BP device uses brachial oscillometric BP waves for a noninvasive estimation of central BP. We therefore validated the Mobil-O-Graph against the SphygmoCor device, which is widely known as the commonly used approach for a noninvasive estimation of central BP. For each individual, we compared three readings of the central BP values obtained by the Mobil-O-Graph and SphygmoCor device consecutively. One hundred individuals (mean age 56.1 ± 15.4 years) were recruited for measurement.Differences between the central BP values of the test device and the SphygmoCor device were calculated for each measurement. The mean difference (95% confidence interval) for the estimated central systolic BP between both devices was -0.6 ± 3.7 mmHg. Comparison of the central BP values measured by the two devices showed a statistically significant linear correlation (R=0.91, P<0.0001). The mean between-method difference was 0.50 mmHg for central systolic BP estimation. The intrarater reproducibility between both the devices was also comparable. Bland and Altman analyses showed that the mean differences (95% confidence interval) between repeated measurements were 1.89 (0.42-3.36) mmHg and 1.36 (-0.16 to 2.83) mmHg for the SphygmoCor and the Mobil-O-Graph device, respectively. Thus, neither of these differences was statistically significantly different from 0. The limits of agreement were -16.34 to 19.73 and -15.23 to 17.17 mmHg for the SphygmoCor and the Mobil-O-Graph device, respectively. Oscillometric noninvasive estimation of central BP with the Mobil-O-Graph BP device is as effective as using the well-established SphygmoCor applanation tonometry device. In comparison, the Mobil-O-Graph combines the widespread benefits of brachial BP measurement and also provides central BP within one measurement.

Rationale and design of a randomized study to determine the value of central Blood Pressure for GUIDing managEment of hypertension: The BP GUIDE study

Noninvasive estimates of central blood pressure (BP) predict cardiovascular morbidity and mortality independent of brachial BP. However, there are limited data on the usefulness of central BP in clinical practice. This study aims to test the value of central BP as a management tool for physicians treating patients with essential hypertension. Participants with uncomplicated essential hypertension (N = 284) will be randomized to 12 months of treatment decisions guided by usual care (based on office, home, and 24-hour ambulatory brachial BP) or, in addition, by central BP estimated using radial tonometry (based on age- and sex-specific normal central systolic BP values). Recommendations regarding titration of antihypertensive medication (increase, decrease, or maintain dose) will be provided to each participant's general practitioner as well as the participant themselves. Relevant clinical information (eg, comorbidities, left ventricular [LV] mass, blood biochemistry, and BP-related symptoms) will be considered when making titration recommendations in all participants. The primary outcome measures will be (1) change in LV mass (by real-time 3-dimensional echocardiography), (2) amount of medication used, and (3) quality of life. Analysis will be by intention to treat. It is expected that there will be no significant difference in LV mass between groups. However, it is hypothesized that there will be significantly reduced use of medication and improved quality of life in the central BP group because more appropriate titration choices will be made to maintain normal central systolic BP. Results are expected in 2012.

A comparison between central blood pressure values obtained by the Gaon system and the SphygmoCor system

Central pulse pressure is correlated with carotid atherosclerosis and the incidence of cardiovascular events more significantly than brachial pulse pressure. Augmentation index (Aix) has been shown to be an independent predictor of cardiovascular morbidity and mortality. Pulse wave analysis using the Gaon system allows for the estimation of central blood pressure (CBP), corrected augmentation index (Aix@HR75), ejection duration (ED) and subendocardial viability ratio (SEVR), and is widely used in clinical research in Korea. However, the accuracy of this system is controversial. From February 2008 to March 2011, 99 patients were recruited for this study. Measurements were taken both by the Gaon system and the SphygmoCor system on the same day for all study participants. The estimated values of CBP, Aix@HR75, ED and SEVR for the two systems were compared using paired t-tests, simple correlation analyses and Bland-Altman plots. Systolic blood pressure (SBP) estimated by the two systems was significantly (P<0.001) correlated; the coefficient was 0.982. The two s.d. of the difference in SBP between these systems was quite small--<7 mm Hg. Aix@HR75, ED and SEVR as estimated by the two systems were also significantly correlated, although they, especially SEVR, showed much weaker correlations than were observed in SBP: coefficients for Aix@HR75, ED and SEVR were 0.727, 0.648 and 0.230, respectively. We assessed the CBP of Korean patients estimated by the two systems and observed that the correlations of Aix, ED and SEVR were weaker than that of CBP. Such variations may be due to the difference in measuring methods between the devices. As even a slight change in pulse waveforms may result in a large difference in estimations, parameters, including Aix@HR75, ED and SEVR, should be carefully interpreted by experienced clinicians.

Impact of calibration on estimates of central blood pressure

Impact of calibration on estimates of central blood pressure

Validation of the Noninvasive Assessment of Central Blood Pressure by the SphygmoCor and Omron Devices Against the Invasive Catheter Measurement

To investigate the accuracy of the SphygmoCor and Omron HEM9000-AI devices in the estimation of central blood pressure (BP) in comparison with the simultaneous invasive catheter measurement. The radial arterial pulse was sequentially recorded by the use of the Omron and SphygmoCor devices in 33 patients, with the calibration of the brachial oscillometric BP, to derive central BPs, which were also measured simultaneously with a catheter-based fluid-filled manometer system. The procedure was repeated three times to obtain 99 pairs of noninvasive and invasive measurements. The noninvasive central systolic BP estimations were significantly (P < 0.001) associated with the invasive measurement at the ascending aorta, with a correlation coefficient of 0.91 and 0.90 for the SphygmoCor and Omron devices, respectively. However, both devices underestimated central systolic BP with a difference of -15 mm Hg (95% confidence interval (CI), -17 to -13 mm Hg, P < 0.001) for SphygmoCor and -2 mm Hg (95% CI, -4 to 0 mm Hg, P < 0.05) for Omron. In comparison with the invasive catheter measurement at the brachial artery, the oscillometric Omron device underestimated brachial systolic BP by -19 mm Hg (95% CI, -23 to -15 mm Hg, P < 0.001). Both devices underestimated central systolic BP, with a larger deviation by SphygmoCor. Nonetheless, these noninvasive estimations of central BP closely correlate with the invasive measurements, and can still be properly used, on the condition that device specific diagnostic thresholds become available.

Validation of the central blood pressure estimation by the SphygmoCor system in Chinese

Pulse wave analysis using the SphygmoCor system allows the estimation of central blood pressures (BP). However, there is controversy over its accuracy for clinical use. In 45 patients undergoing coronary angiography, we compared the ascending aorta BPs measured by the invasive catheter with the estimations by the SphygmoCor system, using paired t-tests, simple correlation analysis, and Bland-Altman plots. The estimation of central systolic BP by SphygmoCor was lower, although statistically insignificant, than that measured by the catheter (144±29 vs. 148±30 mmHg; P=0.98). The standard deviation of the difference amounted to 17 mmHg. Both the measured and estimated central systolic BPs were significantly (P<0.001) lower than the brachial systolic BP (156±30 mmHg). The diastolic BP measured at the brachial artery (87±15 mmHg) and provided by SphygmoCor (90±15 mmHg) were systematically higher (P<0.001) than that measured by the catheter (74±13 mmHg). The SphygmoCor system underestimated the central pulse pressure by -20±14 mmHg compared with the catheter method. The correlation coefficients for systolic BP, diastolic BP, and pulse pressure between catheter measurements and the SphygmoCor estimations were 0.84, 0.60, and 0.82 (P<0.001), respectively. When the radial waveform was calibrated with the oscillometric brachial pressures, the SphygmoCor system could not provide accurate estimation of central BPs. The inaccurate measurement of cuff pressure was the major limiting factor for the use of the transfer function in the clinical settings.

Noninvasive assessment of central and peripheral arterial pressure (waveforms): implications of calibration methods

Noninvasive estimation of central blood pressure (BP) from radial artery pressure waveforms is increasingly applied. We investigated the impact of radial artery waveform calibration on central BP assessment and calculated pressure amplification, with focus on the one-third rule used to estimate mean arterial BP (MAP). Pressure waveforms were noninvasively measured at the radial and carotid arteries in 1873 individuals (age 45.8+/-6.1 years). Radial and carotid artery waveforms were calibrated using brachial artery DBP and SBP, MAP estimated with the one-third rule and MAP estimated as brachial DBP along with 40% of brachial artery pulse pressure. Central SBP obtained via a transfer function was 123.5 +/- 15.7, 117.8 +/- 14.2 and 126.0 +/- 15.4 mmHg (mean +/- SD) following above-mentioned three calibration schemes, respectively. Using the same calibration schemes, carotid artery SBP was 131.4 +/- 15.2, 118.4 +/- 14.4 and 126.8 +/- 15.7 mmHg, respectively. Central-to-brachial amplification was 13.0 +/- 3.6 mmHg using second method as compared with 4.6 +/- 3.8 mmHg with third method. Brachial-to-radial amplification was actually negative (-6.3 +/- 4.5 mmHg) using second method, whereas 3.4 +/- 5.5 mmHg was found with third method. Both carotid artery SBP and central SBP obtained via a transfer function are highly sensitive to the calibration of the respective carotid artery and radial artery pressure waveforms. Our data suggest that the one-third rule to calculate MAP from brachial cuff BP should be avoided, especially when used to calibrate radial artery pressure waveforms for subsequent application of a pressure transfer function. Until more precise estimation methods become available, it is advisable to use 40% of brachial pulse pressure instead of 33% to assess MAP.

Caution Using Brachial Systolic Pressure to Calibrate Radial Tonometric Pressure Waveforms: Lessons From Invasive Study

To the Editor: We were very interested to read the recent article by Segers et al1 that prompted the correspondence from O’Rourke and Takazawa,2 who were concerned about the reliability of brachial artery tonometry and the lack of relevant invasive data, as well as the subsequent response from Segers et al.3 We have recently conducted an invasive study that may help resolve …

Validation of the central blood pressure estimation by the SphygmoCor system in Chinese

Background Pulse wave analysis using the SphygmoCor system allows the estimation of central blood pressures (BP). However, there is controversy over its accuracy for clinical use. Methods In 45 patients undergoing coronary angiography, we compared the ascending aorta BPs measured by the invasive catheter with the estimations by the SphygmoCor system, using paired t-tests, simple correlation analysis and Bland–Altman plots. Results The estimation of central systolic BP by SphygmoCor was lower, although statistically insignificant, than that measured by the catheter (144 ± 29 vs.

New insights into cardiovascular risk from the exercise central waveform

Numerous studies in healthy individuals with normal office blood pressure (BP) have shown that a hypertensive response to exercise predicts the future onset of hypertension, as well as cardiovascular morbidity and mortality, independent of office BP. The mechanisms underlying the predictive value of exercise BP are incompletely understood. However, it has been proposed that the additional cardiovascular stress imposed by exercise may unmask the presence of concealed hypertension. A new non-invasive method of exercise arterial pressure waveform analysis (and central BP estimation) may provide additional clinical information, as well as insight into mechanisms, beyond the BP obtained by traditional upper arm cuff methods.

A generalized arterial transfer function derived at rest underestimates augmentation of central pressure after exercise

Peripheral exercise blood pressure and resting central blood pressure are considered more relevant to cardiovascular health than resting peripheral blood pressure. Central exercise blood pressure may well be an even more useful measure, but there is no simple non-invasive means of determining it. The aim of the present study was to establish whether the estimation of central blood pressure from peripheral blood pressure using a transfer function derived at rest, would hold after aerobic exercise. Thirty healthy young men were studied before and immediately (< 1 min) and 10 min after 15 min bicycle exercise at 65-70% of maximum heart rate. Simultaneous carotid and radial artery waveforms were recorded, and radial-to-carotid generalized transfer functions (GTF) were calculated using Fourier analysis for rest and immediately postexercise. Central systolic blood pressure (SBP) and augmentation index (AIx) were calculated for measured and derived waves. The resting GTF underestimated central SBP and AIx immediately (-5.8 +/- 2.1 mmHg, P = 0.01; -8.3 +/- 2.9%, P = 0.008) and 10 min after (-2.0 +/- 0.7 mmHg, P = 0.008; -7.0 +/- 2.1%, P = 0.003) exercise. No significant bias was found between measured and derived (using resting GTF) carotid values at rest. The use of an exercise-specific GTF resulted in no specific bias immediately or 10 min after exercise, although it overestimated blood pressure and AIx at rest (2.5 +/- 1.0 mmHg, P = 0.02; 11.3 +/- 3.0%, P = 0.001). A peripheral-to-central arterial GTF derived at rest significantly underestimates key measures of central arterial pressure immediately after exercise, and pressure estimations may be improved by the use of an exercise-specific GTF.

Effect of calibration method on estimation of central pressure at rest and during cold pressor testing

Non-invasive estimates of central blood pressure (CP) using a radial transfer function would be valuable in physiologic studies since central systolic pressure (CSP) better reflects myocardial demand. However, this technique appears to be dependent on the calibration method. The purpose of this study was to determine the effect of different calibration procedures on CP estimates at rest and during cold pressor testing. Fifteen healthy subjects (age 23.5 ± 2 years) underwent blood pressure measurement in the left brachial artery (BP) and simultaneous recording of brachial and radial artery waveforms in the right arm. The right foot was placed in ice water and measurements were repeated 90 seconds later. The radial pressure wave was calibrated using BSP and BDP (Cuff), diastolic and brachial mean arterial pressure (MAP) determined from the brachial wave (BM), or diastolic and MAP calculated as 1/3PP + DP (CM). CP was estimated for each calibration method from the radial wave via a transfer function. Cold pressure testing increased (p<0.05) BSP (109 ± 2 vs. 127 ± 3 mmHg) and BDP (62 ± 2 vs. 77 ± 3 mmHg). Radial SP varied from BSP by + 9 and + 7 mmHg when calibrated using BM and CM respectively. As a result BM-CSP was 6.1 ± 1 and 4.5 ± 1 mmHg greater (p<0.05) than Cuff-CSP and EM-CSP respectively however all 3 methods tracked the cold pressor response similarly. Estimates of CP using a radial transfer function are dependent on the method of calibration. However, the ability to track changes in CP using a transfer function is not dependent on calibration and may provide valuable physiologic information.

Comparative Accuracy of Three Automated Techniques in the Noninvasive Estimation of Central Blood Pressure in Men

Automated devices have regularly replaced manual sphygmomanometry for the determination of blood pressure not only in homes and clinics, but also in emergency and critical care settings. Few studies exist that correctly assess the accuracy of these devices, and even fewer that specifically compare commercially available units that rely on different physiologic events for measurement. Six hundred pressure measurements were obtained from 120 subjects using 1 of 3 randomly selected blood pressure monitors. In addition, central arterial pressure measurements were obtained simultaneously and directly from the ascending aorta of each subject. Overall, these devices tended to overestimate diastolic (+2.5 mm Hg, p <0.0001) and mean (+3.8 mm Hg, p < 0.0001) pressures, but not systolic (+0.7 mm Hg, p = NS) pressure. Compared with the other 2 devices, device I, relying on oscillometric detection, demonstrated a significantly smaller mean absolute error for diastolic pressure (4.9 ± 3.0 vs 7.0 ± 4.8 and 6.2 ± 5.3 mm Hg, p <0.0001) and mean pressure (4.0 ± 3.2 vs 7.8 ± 5.9 and 8.6 ± 7.5 mm Hg, p <0.0001), and a trend toward smaller error with systolic pressure (6.8 ± 6.5 vs 7.3 ± 6.8 and 8.0 ± 5.6 mm Hg, p = 0.19). Clinically significant (±10 mm Hg) errors were common with each device (24.8% overall), but serious (±20 mm Hg) errors were unusual (3.2%) and did not occur at all with device I during diastolic and mean pressure measurement. All of the devices tested could be expected to perform satisfactorily in most clinical settings provided that an average error of 4.0 to 8.6 mm Hg is tolerable. This level of accuracy typically extended throughout the range of pressures anticipated in most noncritical clinical situations. As implemented in the devices tested, noninvasive measurement by oscillometry with stepped deflation is more accurate than automated auscultation.