Measurement of central aortic pulse pressure: noninvasive brachial cuff-based estimation by a transfer function vs. a novel pulse wave analysis method

Mathematical Modeling of Oscillometric Blood Pressure Measurement: A Complete, Reduced Oscillogram Model

OBJECTIVE

Oscillogram modeling is a powerful tool for understanding and advancing popular oscillometric blood pressure (BP) measurement. A reduced oscillogram model relating cuff pressure oscillation amplitude ( ∆O) to external cuff pressure of the artery ( Pe) is: [Formula: see text], where g(P) is the arterial compliance versus transmural pressure ( P) curve, Ps and Pd are systolic and diastolic BP, and k is the reciprocal of the cuff compliance. The objective was to determine an optimal functional form for the arterial compliance curve.

METHODS

Eight prospective, three-parameter functions of the brachial artery compliance curve were compared. The study data included oscillometric arm cuff pressure waveforms and invasive brachial BP from 122 patients covering a 20-120 mmHg pulse pressure range. The oscillogram measurements were constructed from the cuff pressure waveforms. Reduced oscillogram models, inputted with measured systolic and diastolic BP and each parametric brachial artery compliance curve function, were optimally fitted to the oscillogram measurements in the least squares sense.

RESULTS

An exponential-linear function yielded as good or better model fits compared to the other functions, with errors of 7.9±0.3 and 5.1±0.2% for tail-trimmed and lower half-trimmed oscillogram measurements. Importantly, this function was also the most tractable mathematically.

CONCLUSION

A three-parameter exponential-linear function is an optimal form for the arterial compliance curve in the reduced oscillogram model and may thus serve as the standard function for this model henceforth.

SIGNIFICANCE

The complete, reduced oscillogram model determined herein can potentially improve oscillometric BP measurement accuracy while advancing foundational knowledge.

New Method to Estimate Central Systolic Blood Pressure From Peripheral Pressure: A Proof of Concept and Validation Study

Objective: The non-invasive estimation of central systolic blood pressure (cSBP) is increasingly performed using new devices based on various pulse acquisition techniques and mathematical analyses. These devices are most often calibrated assuming that mean (MBP) and diastolic (DBP) BP are essentially unchanged when pressure wave travels from aorta to peripheral artery, an assumption which is evidence-based. We tested a new empirical formula for the direct central blood pressure estimation of cSBP using MBP and DBP only (DCBP = MBP²/DBP).

Methods and Results: First, we performed a post-hoc analysis of our prospective invasive high-fidelity aortic pressure database (n = 139, age 49 ± 12 years, 78% men). The cSBP was 146.0 ± 31.1 mmHg. The error between aortic DCBP and cSBP was −0.9 ± 7.4 mmHg, and there was no bias across the cSBP range (82.5–204.0 mmHg). Second, we analyzed 64 patients from two studies of the literature in whom invasive high-fidelity pressures were simultaneously obtained in the aorta and brachial artery. The weighed mean error between brachial DCBP and cSBP was 1.1 mmHg. Finally, 30 intensive care unit patients equipped with fluid-filled catheter in the radial artery were prospectively studied. The cSBP (115.7 ± 18.2 mmHg) was estimated by carotid tonometry. The error between radial DCBP and cSBP was −0.4 ± 5.8 mmHg, and there was no bias across the range.

Conclusion: Our study shows that cSBP could be reliably estimated from MBP and DBP only, provided BP measurement errors are minimized. DCBP may have implications for assessing cardiovascular risk associated with cSBP on large BP databases, a point that deserves further studies.

Association of central arterial blood pressure and left ventricular hypertrophy in patients with chronic kidney disease

AIMS

In the general population, central arterial blood pressure has proved to be more closely related to left ventricular hypertrophy (LVH) than brachial arterial blood pressure. We aimed to investigate whether this relationship was true in patients with chronic kidney disease (CKD).

METHODS

In this retrospective study, we reviewed the medical records of 289 adult patients with CKD from the Zhejiang Provincial People's Hospital in Zhejiang, China. Demographic, echocardiographic and brachial and central blood pressure parameters were retrieved from medical records. Central blood pressure was measured using the SphygmoCor® CvMS (AtCor, Australia) device and its corresponding software. Multivariate logistic regression analyses were performed to identify independent predictors of LVH. Receiver operating characteristic curves were used to determine the ability of central and brachial blood pressure to predict LVH.

RESULTS

The left ventricular mass index was positively associated with both central and brachial blood pressures. However, multiple logistic regression analysis demonstrated that a central pulse pressure (CPP) ≥ 58 mm Hg was an independent risk factor for LVH (OR = 5.597, 95%CI 2.363-13.259, p < .001). Brachial pulse pressure is not superior to CPP in predicting LVH (area under the curve [AUC] = 0.695, 95%CI 0.634-0.756, p < .001 vs. AUC = 0.687, 95%CI: 0.626-0.748, p < .001, respectively; p = .4824).

CONCLUSION

Our results suggested that, similarly to the general population, CPP is a better parameter for predicting the occurrence of LVH in patients with CKD.

A systematic review of invasive, high-fidelity pressure studies documenting the amplification of blood pressure from the aorta to the brachial and radial arteries

It is commonly accepted that systolic blood pressure (SBP) is significantly higher in the brachial/radial artery than in the aorta while mean (MBP) and diastolic (DBP) pressures remain unchanged. This may have implications for outcome studies and for non-invasive devices calibration. We performed a systematic review of invasive high-fidelity pressure studies documenting BP in the aorta and brachial/radial artery. We selected articles published prior to July 2015. Pressure amplification (Amp = peripheral minus central pressure) was calculated (weighted mean). The six studies retained (n = 294, 76.5% male, mean age 63.5 years) mainly involved patients with suspected coronary artery disease (CAD). In two studies at the aortic/brachial level (n = 64), MBP and DBP were unchanged (MPAmp = 0.1 mmHg, DPAmp = -1.3 mmHg), while SBP increased (SPAmp = 4.2 mmHg; relative amplification = 3.1%). In four studies in which MBP was not documented (n = 230), brachial DBP remained unchanged and SBP increased (SPAmp = 6.6 mmHg; 4.9%). One of these four studies also reported radial SBP and DBP, not MBP (n = 12). Few high-fidelity pressure studies were found, and they have been performed mainly in elderly male patients with suspected CAD. Counter to expectations, the mean amplification of SBP from the aorta to brachial artery was < 5%. Further studies on SPAmp phenotypes (positive, null, negative) are advocated. Non-invasive device calibration assumptions were confirmed, namely unchanged MBP and DBP from the aorta to the brachial artery. Data did not allow for firm conclusions on the amount of BP changes from the aorta to the radial artery, and from the aorta to the brachial/radial arteries in other populations.

Observer-Based Deconvolution of Deterministic Input in Coprime Multichannel Systems With Its Application to Noninvasive Central Blood Pressure Monitoring

Estimating central aortic blood pressure (BP) is important for cardiovascular (CV) health and risk prediction purposes. CV system is a multichannel dynamical system that yields multiple BPs at various body sites in response to central aortic BP. This paper concerns the development and analysis of an observer-based approach to deconvolution of unknown input in a class of coprime multichannel systems applicable to noninvasive estimation of central aortic BP. A multichannel system yields multiple outputs in response to a common input. Hence, the relationship between any pair of two outputs constitutes a hypothetical input-output system with unknown input embedded as a state. The central idea underlying our approach is to derive the unknown input by designing an observer for the hypothetical input-output system. In this paper, we developed an unknown input observer (UIO) for input deconvolution in coprime multichannel systems. We provided a universal design algorithm as well as meaningful physical insights and inherent performance limitations associated with the algorithm. The validity and potential of our approach were illustrated using a case study of estimating central aortic BP waveform from two noninvasively acquired peripheral arterial pulse waveforms. The UIO could reduce the root-mean-squared error (RMSE) associated with the central aortic BP by up to 27.5% and 28.8% against conventional inverse filtering (IF) and peripheral arterial pulse scaling techniques.

Central blood pressure for the management of hypertension: Is it a practical clinical tool in current practice?

Since noninvasive central blood pressure (BP) measuring devices are readily available, central BP has gained growing attention regarding its clinical application in the management of hypertension. The disagreement between central and peripheral BP has long been recognized. Some previous studies showed that noninvasive central BP may be better than the conventional brachial BP in association with target organ damages and long-term cardiovascular outcomes. Recent studies further suggest that the central BP strategy for confirming a diagnosis of hypertension may be more cost-effective than the conventional strategy, and guidance of hypertension management with central BP may result in less use of medications to achieve BP control. Despite the use of central BP being promising, more randomized controlled studies comparing central BP-guided therapeutic strategies with conventional care for cardiovascular events reduction are required because noninvasive central and brachial BP measures are conveniently available. In this brief review, the rationale supporting the utility of central BP in clinical practice and relating challenges are summarized.

Formulas to Explain Popular Oscillometric Blood Pressure Estimation Algorithms

Oscillometry is the blood pressure (BP) measurement principle of most automatic cuff devices. The oscillogram (which is approximately the blood volume oscillation amplitude-external pressure function) is measured, and BP is then estimated via an empirical algorithm. The objective was to establish formulas to explain three popular empirical algorithms in the literature—the maximum amplitude, derivative, and fixed ratio algorithms. A mathematical model of the oscillogram was developed and analyzed to derive parametric formulas for explaining each algorithm. Exemplary parameter values were obtained by fitting the model to measured oscillograms. The model and formulas were validated by showing that their predictions correspond to measurements. The formula for the maximum amplitude algorithm indicates that it yields a weighted average of systolic and diastolic BP (0.45 and 0.55 weighting) instead of commonly assumed mean BP. The formulas for the derivative algorithm indicate that it can accurately estimate systolic and diastolic BP (<1.5 mmHg error), if oscillogram measurement noise can be obviated. The formulas for the fixed ratio algorithm indicate that it can yield inaccurate BP estimates, because the ratios change substantially (over a 0.5–0.6 range) with arterial compliance and pulse pressure and error in the assumed ratio translates to BP error via large amplification (>40). The established formulas allow for easy and complete interpretation of perhaps the three most popular oscillometric BP estimation algorithms in the literature while providing new insights. The model and formulas may also be of some value toward improving the accuracy of automatic cuff BP measurement devices.

Tapered vs. Uniform Tube-Load Modeling of Blood Pressure Wave Propagation in Human Aorta

In this paper, tapered vs. uniform tube-load models are comparatively investigated as mathematical representation for blood pressure (BP) wave propagation in human aorta. The relationship between the aortic inlet and outlet BP waves was formulated based on the exponentially tapered and uniform tube-load models. Then, the validity of the two tube-load models was comparatively investigated by fitting them to the experimental aortic and femoral BP waveform signals collected from 13 coronary artery bypass graft surgery patients. The two tube-load models showed comparable goodness of fit: (i) the root-mean-squared error (RMSE) was 3.3+/−1.1 mmHg in the tapered tube-load model and 3.4+/−1.1 mmHg in the uniform tube-load model; and (ii) the correlation was r = 0.98+/−0.02 in the tapered tube-load model and r = 0.98+/−0.01 mmHg in the uniform tube-load model. They also exhibited frequency responses comparable to the non-parametric frequency response derived from the aortic and femoral BP waveforms in most patients. Hence, the uniform tube-load model was superior to its tapered counterpart in terms of the Akaike Information Criterion (AIC). In general, the tapered tube-load model yielded the degree of tapering smaller than what is physiologically relevant: the aortic inlet-outlet radius ratio was estimated as 1.5 on the average, which was smaller than the anatomically plausible typical radius ratio of 3.5 between the ascending aorta and femoral artery. When the tapering ratio was restricted to the vicinity of the anatomically plausible typical value, the exponentially tapered tube-load model tended to underperform the uniform tube-load model (RMSE: 3.9+/−1.1 mmHg; r = 0.97+/−0.02). It was concluded that the uniform tube-load model may be more robust and thus preferred as the representation for BP wave propagation in human aorta; compared to the uniform tube-load model, the exponentially tapered tube-load model may not provide valid physiological insight on the aortic tapering, and its efficacy on the goodness of fit may be only marginal.

Estimation of Cardiovascular Risk Predictors from Non-Invasively Measured Diametric Pulse Volume Waveforms via Multiple Measurement Information Fusion

This paper presents a novel multiple measurement information fusion approach to the estimation of cardiovascular risk predictors from non-invasive pulse volume waveforms measured at the body's diametric (arm and ankle) locations. Leveraging the fact that diametric pulse volume waveforms originate from the common central pulse waveform, the approach estimates cardiovascular risk predictors in three steps by: (1) deriving lumped-parameter models of the central-diametric arterial lines from diametric pulse volume waveforms, (2) estimating central blood pressure waveform by analyzing the diametric pulse volume waveforms using the derived arterial line models, and (3) estimating cardiovascular risk predictors (including central systolic and pulse pressures, pulse pressure amplification, and pulse transit time) from the arterial line models and central blood pressure waveform in conjunction with the diametric pulse volume waveforms. Experimental results obtained from 164 human subjects with a wide blood pressure range (systolic 144 mmHg and diastolic 103 mmHg) showed that the approach could estimate cardiovascular risk predictors accurately (r ≥ 0.78). Further analysis showed that the approach outperformed a generalized transfer function regardless of the degree of pulse pressure amplification. The approach may be integrated with already available medical devices to enable convenient out-of-clinic cardiovascular risk prediction.

Systemic arteriosclerosis is associated with left ventricular remodeling but not atherosclerosis: a TASCFORCE study

BACKGROUND

Arteriosclerosis (arterial stiffening) is associated with future cardiovascular events, with this effect postulated to be due to its effect on cardiac afterload, atherosclerosis (plaque formation) progression or both, but with limited evidence examining these early in disease formation. The aim of the current study is to examine the association between arteriosclerosis, atherosclerosis and ventricular remodelling in a population at low-intermediate cardiovascular risk.

METHODS

One thousand six hundred fifty-one subjects free of clinical cardiovascular disease and with a < 20% 10 year cardiovascular risk score underwent a cardiovascular magnetic resonance (CMR) study and whole body CMR angiogram. Arteriosclerosis was measured using total arterial compliance (TAC) - calculated as the indexed stroke volume divided by the pulse pressure. Atherosclerosis was quantified using a standardised atheroma score (SAS) which was calculated by scoring 30 arterial segments within the body based on the degree of stenosis, summating these scores and normalising it to the number of assessable segments. Left ventricular remodelling was measured using left ventricular mass to volume ratio (LVMVR).

RESULTS

One thousand five hundred fifteen (38% male, 53.8 ± 8.2 years old) completed the study. On univariate analysis TAC was associated with SAS but this was lost after accounting for cardiovascular risk factors in both males (B = - 0.001 (- 0.004-0.002),p = 0.62) and females (B = 0.000(95%CI -0.002--0.002),p = 0.78). In contrast compliance correlated with LVMVR after accounting for cardiovascular risk factors (B = - 0.12(95%CI -0.16--0.091),p < 0.001 in males; B = - 0.12(95%CI -0.15--0.086),p < 0.001 in females).

CONCLUSION

Systemic arteriosclerosis is associated with left ventricular remodelling but not atherosclerosis. Future efforts in cardiovascular risk prevention should thus seek to address both arteriosclerosis and atherosclerosis individually.

Central Blood Pressure Monitoring via a Standard Automatic Arm Cuff

Current oscillometric devices for monitoring central blood pressure (BP) maintain the cuff pressure at a constant level to acquire a pulse volume plethysmography (PVP) waveform and calibrate it to brachial BP levels estimated with population average methods. A physiologic method was developed to further advance central BP measurement. A patient-specific method was applied to estimate brachial BP levels from a cuff pressure waveform obtained during conventional deflation via a nonlinear arterial compliance model. A physiologically-inspired method was then employed to extract the PVP waveform from the same waveform via ensemble averaging and calibrate it to the brachial BP levels. A method based on a wave reflection model was thereafter employed to define a variable transfer function, which was applied to the calibrated waveform to derive central BP. This method was evaluated against invasive central BP measurements from patients. The method yielded central systolic, diastolic, and pulse pressure bias and precision errors of -0.6 to 2.6 and 6.8 to 9.0 mmHg. The conventional oscillometric method produced similar bias errors but precision errors of 8.2 to 12.5 mmHg (p ≤ 0.01). The new method can derive central BP more reliably than some current non-invasive devices and in the same way as traditional cuff BP.

Central aortic systolic blood pressure can predict prolonged QTc duration better than brachial artery systolic blood pressure in rural community residents

OBJECTIVES

Previous studies have suggested that prolonged electrocardiogram QTc duration was independent risk factor for both increased cardiovascular and all-cause mortality, but there was no dating about the relationship between central aortic systolic blood pressure (CASP) and QTc duration. The aim of this study was to analyze the relationship between CASP and QTc duration, and assess whether CASP can predict prolonged QTc duration more than BSBP.

METHODS

A total of 500 patients were enrolled in this study, central and brachial aortic blood pressure and electrocardiogram QTc duration were measured. Pearson correlation was assessed for determining the associations of QTc duration with clinical conditions. Multivariate logistic regression analyses were performed to determine the independent predictor of prolonged QTc duration. Receiver operating characteristic (ROC) curve was used to evaluate the utility of blood pressure for prolonged QTc duration.

RESULTS

We found QTc durations were significantly positive with CASP (r = 0.308, p < 0.001), BSBP (r = 0.227, p < 0.001), and age (r = 0.154, p = 0.010), but negatively related to heart rate (r = -440, p < 0.001). A multiple logistic regression analysis demonstrated that the CASP was an independent determinant of prolonged QTc (OR = 1.648; 95%CI: 1.032, 2.101; p < 0.001). CASP had a better predictive value for prolonged QTc duration than (AUC: 0.771 vs. 0.646, p < 0.001) BSBP.

CONCLUSION

Our results suggested that the non-invasive CASP is independently correlated with QTc duration, and CASP can predict prolonged QTc duration more than BSBP.

Patient-Specific Oscillometric Blood Pressure Measurement: Validation for Accuracy and Repeatability

Oscillometric devices are widely used for automatic cuff blood pressure (BP) measurement. These devices estimate BP from the oscillometric cuff pressure waveform using population average methods. Hence, the devices may only be accurate over a limited BP range. The objective was to evaluate a new patient-specific method, which estimates BP by fitting a physiologic model to the same waveform. One-hundred and forty-five cardiac catheterization patients and normal adults were included for study. The oscillometric cuff pressure waveform was obtained with an office device, while reference BP was measured via brachial artery catheterization or auscultation, during baseline and/or nitroglycerin administration. Fifty-seven of the subject records were utilized for refining the patient-specific method, while the remaining 88 subject records were employed for evaluation. The precision errors for all BP levels of the patient-specific method ranged from 6.3 to 7.6 mmHg. These errors were significantly lower than those of the office device (by 29% on average) in subjects with high pulse pressure (>50 mmHg) while being comparable to those of the device in subjects with normal pulse pressure (<50 mmHg). The bias and precision of the differences in repeated estimates for all BP levels of the patient-specific method ranged from 0.1 to 1.1 and 2.1 to 5.9 mmHg, respectively. These precision differences were significantly lower than those of the office device (by 64% on average). The patient-specific method may afford more accurate automatic cuff BP measurement in patients with large artery stiffening while limiting the number of required cuff inflations/deflations per measurement.

Is Noninvasive Brachial Systolic Blood Pressure an Accurate Estimate of Central Aortic Systolic Blood Pressure?

OBJECTIVES

Noninvasive brachial systolic blood pressure (nSBP-B) usually approaches invasive central systolic blood pressure (iSBP-C) with a high correlation. Whether nSBP-B is an accurate estimate of iSBP-C remained to be investigated. Thus, this study aimed to compare the errors of nSBP-B and noninvasive central systolic blood pressure (nSBP-C) with different techniques in estimating iSBP-C.

METHODS

Simultaneous invasive high-fidelity central aortic pressure waveforms and the noninvasive left brachial pulse volume recording (PVR) waveform were recorded in a Generation group ( N = 40) and a Validation group ( N = 100). The accuracy of the noninvasive estimates of iSBP-C obtained from analysis of the calibrated PVR waveform using the generalized transfer function (GTF), pulse waveform analysis (PWA), and N-point moving average (NPMA) methods was examined in the Validation group by calculating the mean absolute error (MAE).

RESULTS

In Generation group, the MAE was 4.6±4.1mm Hg between nSBP-B and invasive brachial SBP, and 6.8±5.5mm Hg between nSBP-B and iSBP-C. In comparison, the MAE of between iSBP-C and nSBP-C with PWA, NPMA, and GTF were 5.5±4.5, 5.8±4.9, and 5.9±5.0mm Hg, respectively. In Validation group, the MAE of nSBP-B (6.9±4.6mm Hg) for estimating iSBP-C was significantly greater than that of PWA (5.0±3.4mm Hg) and NPMA (6.1±4.4mm Hg), and GTF (6.1±4.9mm Hg). The percentage of absolute band error ≤5mm Hg was 62% for nSBP-B, 69% for GTF, 83% for PWA, and 69% for NPMA.

CONCLUSIONS

The accuracy of nSBP-B was inferior to the n SBP-C measures in estimating iSBP-C.

Practical Suitability of a Stand-Alone Oscillometric Central Blood Pressure Monitor: A Review of the Microlife WatchBP Office Central

Accumulating evidence indicates that central blood pressure (CBP) is a better cardiovascular risk predictor than brachial blood pressure (BP). Although more additional benefits of CBP-based treatment above usual hypertension treatment are to be demonstrated, the demand for implementing CBP assessment in general clinical practice is increasing. For this, the measurement procedure must be noninvasive, easy to perform, and cost- and time-efficient. Therefore, oscillometric devices with the possibility to assess CBP seem the best option. Recently, such an oscillometric BP monitor, the Microlife WatchBP Office Central, was developed, which demonstrated its high accuracy in a validation study against invasive BP measurement. Calibration errors of this device are limited because the procedure is automated, standardized, and performed at the same place of and within 30 s from pulse wave assessment. The transformation from the peripheral pulse wave to CBP is done by means of an individual-based pulse wave analysis according to a theory of arterial compliance and wave reflections. In addition, the device has demonstrated to enable a more reliable diagnosis of hypertension by CBP than by peripheral BP, with a lower frequency of over- and underdiagnosis. Altogether, the available clinical evidence suggests that the Microlife WatchBP Office Central fulfills the criteria for general clinical use.

Patient-Specific Oscillometric Blood Pressure Measurement

OBJECTIVE

Most automatic cuff blood pressure (BP) measurement devices are based on oscillometry. These devices estimate BP from the envelopes of the cuff pressure oscillations using fixed ratios. The values of the fixed ratios represent population averages, so the devices may only be accurate in subjects with normal BP levels. The objective was to develop and demonstrate the validity of a patient-specific oscillometric BP measurement method.

METHODS

The idea of the developed method was to represent the cuff pressure oscillation envelopes with a physiologic model, and then estimate the patient-specific parameters of the model, which includes BP levels, by optimally fitting it to the envelopes. The method was investigated against gold standard reference BP measurements from 57 patients with widely varying pulse pressures. A portion of the data was used to optimize the patient-specific method and a fixed-ratio method, while the remaining data were used to test these methods and a current office device.

RESULTS

The patient-specific method yielded BP root-mean-square-errors ranging from 6.0 to 9.3 mmHg. On an average, these errors were nearly 40% lower than the errors of each existing method.

CONCLUSION

The patient-specific method may improve automatic cuff BP measurement accuracy.

SIGNIFICANCE

A patient-specific oscillometric BP measurement method was proposed and shown to be more accurate than the conventional method and a current device.

Reliability assessment for pulse wave measurement using artificial pulse generator

This study aimed to assess intrinsic reliabilities of devices for pulse wave measurement (PWM). An artificial pulse generator system was constructed to create a periodic pulse wave. The stability of the periodic output was tested by the DP103 pressure transducer. The pulse generator system was then used to evaluate the TD01C system. Test-re-test and inter-device reliability assessments were conducted on the TD01C system. First, 11 harmonic components of the pulse wave were calculated using Fourier series analysis. For each harmonic component, coefficient of variation (CV), intra-class correlation coefficient (ICC) and Bland-Altman plot were used to determine the degree of reliability of the TD01C system. In addition, device exclusion criteria were pre-specified to improve consistency of devices. The artificial pulse generator system was stable to evaluate intrinsic reliabilities of devices for PWM (ICCs > 0.95, p < 0.001). TD01C was reliable for repeated measurements (ICCs of test-re-test reliability > 0.95, p < 0.001; CVs all < 3%). Device exclusion criteria successfully excluded the device with defect; therefore, the criteria reduced inter-device CVs of harmonics and improved consistency of the selected devices for all harmonic components. This study confirmed the feasibility of intrinsic reliability assessment of devices for PWM using an artificial pulse generator system. Moreover, potential novel findings on the assessment combined with device exclusion criteria could be a useful method to select the measuring devices and to evaluate the qualities of them in PWM.

Diagnostic performance of a stand-alone central blood pressure monitor: application of central blood pressure in the diagnosis of high blood pressure

BACKGROUND

Oscillometric central blood pressure (CBP) monitors have emerged as a new technology for blood pressure (BP) measurements. With a newly proposed diagnostic threshold for CBP, we investigated the diagnostic performance of a novel CBP monitor.

METHODS

We recruited a consecutive series of 138 subjects (aged 30-93 years) without previous use of antihypertensive agents for simultaneous invasive and noninvasive measurements of BP in a catheterization laboratory. With the cutoff (CBP ≥130/90 mm Hg) for high blood pressure (HBP), the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the novel CBP monitor were calculated with reference to the measured CBP. In comparison, the diagnostic performance of the conventional cuff BP was also evaluated.

RESULTS

The noninvasive CBP for detecting HBP in a sample with a prevalence of 52% showed a sensitivity of 93% (95% confidence interval (CI) = 91-95), specificity of 95% (95% CI = 94-97), PPV of 96% (95% CI = 94-97), and NPV of 93% (95% CI = 90-95). In contrast, with cuff BP and the traditional HBP criterion (cuff BP ≥140/90 mm Hg), the sensitivity, specificity, PPV, and NPV were 49% (95% CI = 44-53), 94% (95% CI = 92-96), 90% (95% CI = 86-93), and 63% (95% CI 59-66), respectively.

CONCLUSIONS

A stand-alone oscillometric CBP monitor may provide CBP values with acceptable diagnostic accuracy. However, with reference to invasively measured CBP, cuff BP had low sensitivity and NPV, which could render possible management inaccessible to a considerable proportion of HBP patients, who may be identifiable through noninvasive CBP measurements from the CBP monitor.

The barriers to clinical application of non-invasively obtained central blood pressure

With the demonstration of superior prognostic value of central blood pressure (CBP) beyond traditionally used brachial BP, there have been increasing interest in the development of novel devices reporting parameters of CBP. The emerging devices for non-invasive estimation of CBP, based on either tonometry-based or cuff-based techniques, were evaluated with various validation studies. Therefore, the research community and clinicians have been faced with challenges regarding the conduction and interpretation of the validation studies for the non-invasively obtained CBP. We summarize here the barriers to the clinical application of the CBP concept, which provide research opportunities to further the subsequent translation.

Measurement accuracy of a stand-alone oscillometric central blood pressure monitor: a validation report for Microlife WatchBP Office Central

BACKGROUND

The superiority of prognostic value of blood pressure (BP) measured at central aorta (CBP) over conventional brachial BP measured by cuff-based BP monitors has reignited the development of new noninvasive techniques for estimating CBP. The present study validated the accuracy of CBP measured by a newly developed stand-alone CBP monitor.

METHODS

The CBP monitor provided readings of brachial systolic BP (SBP), brachial diastolic BP (DBP), central SBP, and central pulse pressure (PP). Brachial PP and central DBP were calculated from the relevant readings. The accuracy of the brachial and central SBP, PP, and DBP was validated against the simultaneously recorded invasively measured central aortic SBP, PP, and DBP, according to the invasive standard requirements for the noninvasive brachial BP monitors from the Association for the Advancement of Medical Instrumentation (AAMI) in 85 subjects (255 measurements; age range, 30-93 years).

RESULTS

The mean differences of cuff BP with reference to the invasively measured central SBP, PP, and DBP were -2.6 ± 9.0, -8.6 ± 11.2, and 6.1 ± 7.0 mm Hg, respectively, with the former two being obviously underestimated at high CBP and overestimated at low CBP. In contrast, the corresponding differences for the central SBP, PP, and DBP measured by the CBP monitor were -0.6 ± 5.5, -0.4 ± 7.0, and -0.2 ± 6.5 mm Hg, respectively, without obvious systematic bias. The distribution of measurement errors for central SBP, PP, and DBP surpassed the AAMI criteria.

CONCLUSION

Central SBP, PP, and DBP can be measured accurately by a stand-alone automatic BP monitor.