Reliability of a noninvasive device to measure systemic hemodynamics in hemodialysis patients

OBJECTIVE: To evaluate the reliability of a noninvasive hemodynamic monitor in hemodialysis patients. METHODS: We enrolled 15 male patients (mean age 63+/-12 years) on stable chronic hemodialysis. Blood pressure and hemodynamic readings were obtained with the Dynapulse 500 Guardian device (Pulsemetric Inc., San Diego, California, USA), which measures systemic hemodynamics on the basis of oscillometric waveforms obtained through a cuff placed over the brachial artery. Measurements were taken sequentially, in duplicate, before, during and after hemodialysis, in the supine, seated and standing positions on four separate midweek dialysis sessions over a 2-week period. RESULTS: The repeatability of the method was tested using 200 pairs of valid measurements. The average values (+/-SD) were 137+/-22 mmHg for systolic blood pressure, 80+/-13 mmHg for diastolic blood pressure, 76+/-15 bpm for heart rate, 1320+/-268 mmHg/s for dP/dtmax, 2.8+/-0.5 l/min/m for cardiac index, and 1455+/-359 dyn/s/cm for systemic vascular resistance. The mean differences (+/-SD of the difference) between readings were 0.1+/-10.4 mmHg for systolic blood pressure, 0.3+/-6.0 mmHg for diastolic blood pressure, -0.2+/-8.0 bpm for heart rate, 0.2+/-234 mmHg/s for dP/dtmax, 0.03+/-0.26 l/min/m for cardiac index and -10+/-177 for systemic vascular resistance, yielding limits of agreement (95%) of -20 to 20 mmHg for systolic blood pressure, -11 to 12 mmHg for diastolic blood pressure, -16 to 17 bpm for heart rate, -458 to 458 mmHg/s for dP/dtmax, -0.5 to 0.5 l/min/m for cardiac index and -338 to 357 dyn/s/cm for systemic vascular resistance. Other hemodynamic parameters fared similarly, and coefficients of variation were all between 7 and 18%. CONCLUSION: We conclude that the Dynapulse 500 Guardian has adequate reliability indices in hemodialysis patients.     

Accuracy of automated auscultatory blood pressure measurement during supine exercise and treadmill stress electrocardiogram-testing

OBJECTIVES: Monitoring of brachial blood pressure during exercise-electrocardiogram (ECG) testing is mandatory and changes in blood pressure (BP) can provide critical management evidence. Patient movement, mechanical vibration, artifactual sounds and observer variability make standard manual techniques problematic. This was an investigator-initiated study to assess an automated auscultatory technique of BP assessment [Tango exercise blood pressure monitor (SunTech Medical Instruments, NC, USA)] to adequately measure BP during stress-ECG testing. METHODS: Initially five fit young male volunteers underwent invasive right brachial artery BP recording using a low-compliance fluid-filled catheter with simultaneous manual and automated assessment. Secondarily, during exercise-ECG testing, the system was assessed against beat-to-beat brachial blood pressures obtained from a catheter-tip solid-state pressure manometer positioned in the ipsilateral brachial artery. RESULTS: In the supine study overall mean difference (+/-SEM) between invasive and manual blood pressures was 3.26 (1.53) and 3.89 (1.90) mmHg for diastolic BP (DBP) and systolic BP (SBP) respectively. Corresponding differences between invasive and automated results, and manual and automated were 3.68 (0.84) and -7.31 (1.83) mmHg, and -0.64 (+/-1.43) and -11.42 (+/-1.59) mmHg. During treadmill exercise-ECG testing the combined mean difference (+/-SEM) between invasive and automated SBP and DBP was 4.79 (+/-0.14) and 6.33 (+/-0.10) mmHg, respectively. CONCLUSION: Automated BP assessment during exercise-ECG testing is feasible with the use of appropriate automatic devices likely to be at least as accurate as manual BP registration. The Tango device is tolerant to exercise and provides reliable automatic BP assessment with absolute differences within an acceptable clinical range.     

Pulse pressure in sustained essential hypertension: a haemodynamic study

Central and forearm haemodynamics were studied in 73 middle-aged male subjects: 14 normotensive controls and 59 patients with sustained essential systolic/diastolic hypertension. Hypertensives were divided into two groups: pulse pressure within the normal range (40-60 mmHg; group I) or above 60 mmHg (group II) for the same level of mean arterial pressure (MAP). Indices of systemic and forearm arterial compliance and distensibility for the same age and MAP were reduced to the same extent in group I and II. In contrast, the peak systolic blood flow velocity of the brachial artery, cardiac output (CO) and stroke volume (SV) were significantly greater in group II than in group I. Systemic and forearm vascular resistances were significantly increased in group I but remained within the normal range in group II. The study provided evidence that, in middle age, there is a group of hypertensive patients characterized by a disproportionate increase in pulse pressure for the level of MAP. The elevation of the pulsed component of blood pressure (BP) reflects a relative hyperkinesia with an increase in CO and arteriolar vasodilatation. The subsequent increase in systolic pressure is produced by a combination of reduced arterial distensibility and increased SV.     

Measurement of arterial pressure using 3 measurement methods in medial arterial calcification

Medial calcification of the arteries, because of non-distensibility of the blood vessel walls, may overestimate the real intra-arterial pressure when blood pressure (BP) is measured by indirect sphygmomanometry cuff. In order to assess the best method for measuring BP, we compared direct intra-arterial measurements with indirect cuff sphygmomanometry as well as automatic oscillometric measurements in 15 hypertensive patients. Mean age +/- standard deviation (SD) was 62 +/- 9 years; all patients had medial calcifications of forearm and/or brachial arteries, and Osler's maneuver was negative in all. Ten sets of direct and indirect BP measurements were obtained for each patient. Results are expressed as mean +/- SD: (table; see text) There was no significant difference between cuff pressure and systolic intra-arterial pressure. The automatic oscillometric method underestimated systolic intra-arterial BP. Great individual variability was observed and could not be predicted clinically. Indirect diastolic BP values were greater than intra-arterial BP in all patients with the sphygmomanometer cuff and in 10 patients with the oscillometric recorder. There existed a direct relation between intra-arterial BP and differences between indirect BP measurements and intra-arterial BP as follows: intra-arterial BP was overestimated by indirect methods for values under 150 mmHg, and underestimated above 150 mmHg. In conclusion, invasive intra-arterial BP measurement seem to be necessary to distinguish between hypertensive and pseudo-hypertensive patients, in case of radiologic evidence of arterial calcification.     

The prevalence of central hypertension defined by a central blood pressure type I device and its association with target organ damage in the community-dwelling elderly Chinese: The Northern Shanghai Study

We aimed to investigate the prevalence of central hypertension and its association with target organ damage (TOD). 1983 community-dwelling elderly Chinese people were recruited for this analysis. Brachial and central blood pressure (BP) were measured by an oscillometric device and SphygmoCor (type I device), respectively. Brachial hypertension was defined by brachial systolic BP/diastolic BP ≥140/90 mmHg or using antihypertensive medications. Central hypertension was defined by central systolic BP/diastolic BP ≥130/90 mmHg or using antihypertensive medications. TOD included left ventricular hypertrophy and diastolic dysfunction, carotid-femoral pulse wave velocity, and urinary albumin-creatinine ratio. In this cohort, there were 563 (28.4%) brachial and central consistent normotension, 46 (2.3%) isolated brachial hypertension, 27 (1.4%) isolated central hypertension, and 1347 (67.9%) brachial and central combined hypertension (BCCH). In analysis of variance, BCCH showed significantly higher levels in all TOD than brachial and central consistent normotension. In multiple logistic regression, all TOD were significantly associated with BCCH (left ventricular hypertrophy: adjusted odds ratios [95% confidence interval] = 2.03 [1.55, 2.68]; left ventricular diastolic dysfunction: 2.29 [1.53, 3.43]; carotid-femoral pulse wave velocity >10 m/s: 3.41 [2.55, 4.58]; urinary albumin-creatinine ratio >30 mg/g: 1.97 [1.58, 2.44]), rather than isolated brachial hypertension or isolated central hypertension. In conclusion, central hypertension was prevalent (69.3%) in this elderly cohort. BCCH was independently and significantly associated with cardiac, arterial, and renal damage. This finding implies that both brachial and central BPs need to be considered for managing hypertension.     

Hemodynamic characterization of hypertensive patients with an exaggerated orthostatic blood pressure variation

Exaggerated orthostatic blood pressure variation (EOV) is a poorly understood phenomenon related to high cardiovascular risk. We aimed to determine whether hypertensive patients with EOV have a distinct hemodynamic pattern, assessed through impedance cardiography. Methods: In treated hypertensive patients, we measured the cardiac index (CI), systemic vascular resistance index (SVRI), blood pressure (BP), and heart rate (HR) in the supine and standing (after 3 minutes) positions, defining three groups according to BP variation: 1) Normal orthostatic BP variation (NOV): standing systolic BP (stSBP)-supine systolic BP (suSBP) between ?20 and 20 mmHg and standing diastolic BP (stDBP)-supine diastolic BP (suDBP) between ?10 and 10 mmHg; 2) orthostatic hypotension (OHypo): stSBP-suSBP≤-20 or stDBP-suDBP≤-10 mmHg; 3) orthostatic hypertension (OHyper): stSBP-suSBP≥20 or stDBP-suDBP≥10 mmHg. We performed multivariable analyses to determine the association of hemodynamic variables with EOV. Results: We included 186 patients. Those with OHyper had lower suDBP and higher orthostatic SVRI variation compared to NOV. In multivariable analyses, orthostatic HR variation (OR = 1.06 (95%CI 1.01–1.13), p = 0.03) and orthostatic SVRI variation (OR = 1.16 (95%CI 1.06–1.28), p = 0.002) were independently related to OHyper. No variables were independently associated with OHypo. Conclusion: Patients with OHyper have a distinct hemodynamic pattern, with an exaggerated increase in SVRI and HR when standing.     

Blood pressure and Turner syndrome

INTRODUCTION: Elevated blood pressure (BP) is an important predictor of morbidity and mortality from cardiovascular disease. Patients with Turner syndrome (TS) have a higher morbidity and mortality in middle age than the normal population. As BP in childhood or early adulthood is predictive of BP later in adult life, we assessed manual and 24 h ambulatory BP in patients with TS to determine whether the BP pattern is altered at an early stage in these patients who are known to be at risk of cardiovascular disease. PATIENTS AND METHODS: We studied manual and 24 h ambulatory BP profiles in 75 girls with Turner syndrome, age range 5.4-22.4 years. A monitor with an oscillometric device (SpaceLabs model 90207) and an appropriate sized cuff was used. BP was measured during the day-time (0800-2000 h) and the night-time periods (2200-0800 h). The BP measured were compared with population standards. The effect of different growth promoting agents on BP was also evaluated. RESULTS: Mean manual and 24 h ambulatory BP measurements were 118/77 mmHg (range 95/60-140/102) and 115/70 mmHg (range 93/57-154/99), respectively. There was minimal difference between the two methods with a positive bias of 2.4 mmHg for diastolic BP and a negative bias of 2.1 mmHg for systolic BP. The mean standard deviation scores (SDS) corresponding to the mean BP recordings were 24 h systolic + 0. 81 (range - 1.26 to + 4.45), 24 h diastolic + 0.43 (range - 0.85 to + 3.42), day-time systolic + 1.08 (range - 0.95 to + 4.72), day-time diastolic + 0.70 (range - 0.94 to + 3.71), night-time systolic + 0. 22 (range -2.2 to + 3.64) and night-time diastolic - 0.18 (range -2. 0 to + 2.43). The SDS for both the mean 24 h and day-time systolic and diastolic BP were shifted to the right of the normal distribution. 57% of the girls had less than the normal 10% reduction in nocturnal systolic blood pressure. 17% had diastolic and 21% had systolic blood pressure above the 95th percentile for age and sex. There was no significant difference in the BP SDS between girls on no treatment and those receiving treatment. CONCLUSION: Over 50% of girls with Turner syndrome have an abnormal BP circadian rhythm, which is similar to adult patients with secondary hypertension. Patients with Turner syndrome have higher blood pressure measurements compared to published population standards, as evidenced by the shift to the right of both the systolic and diastolic BP SDS. These findings suggest that girls with Turner syndrome should be carefully monitored in childhood and adulthood for blood pressure and other cardiovascular risk factors.     

Automated device that complies with current guidelines for office blood pressure measurement: design and pilot application study of the Microlife WatchBP Office device

OBJECTIVE: Current guidelines for office blood pressure (BP) measurement recommend mercury devices, both arms measurement in the initial assessment and at least duplicate measurements at follow-up visits. This study presents the design and a pilot application study of an automated device that fulfils American, European, and International guidelines for office BP measurement. DESIGN AND FUNCTIONS: The Microlife WatchBP Office is a professional electronic mercury-free device with three function modes designed for: (a) initial assessment: triplicate automated simultaneous oscillometric both arms measurement at 60-s intervals and when there is a consistent interarm difference more than 20 mmHg systolic and/or more than 10 mmHg diastolic, the arm with the higher BP is indicated. (b) Follow-up assessment: triplicate automated oscillometric single arm measurements at 60-s intervals and their average is displayed. (c) Auscultatory measurement: by an observer using a stethoscope and a digital countdown BP display for patients with arrhythmias and other individuals in whom the oscillometric measurement is not accurate. PILOT APPLICATION STUDY: The 'initial assessment' mode was applied by three physicians in 63 patients (189 readings). Average interarm systolic BP difference was 0.04+/-5.1 mmHg and diastolic 0.4+/-3.2 mmHg. A value more than 10 mmHg interarm difference in nine systolic BP readings (5%) and three (2%) diastolic. No patient had a consistent interarm difference more than 10 mmHg in all three or two of the three readings. CONCLUSION: The Microlife WatchBP Office professional device fulfils current international requirements for office BP measurement and seems to overcome several limitations of this method when applied in clinical practice.     

Accuracy evaluation of the 'Cardiette BP one' ambulatory blood pressure monitor

OBJECTIVE: Blood pressure (BP) 'Cardiette BP one' system (BP one) is an oscillometric ambulatory BP monitor manufactured in Italy in conformity to current regulations for medical devices. We decided to determine the accuracy of measures made with BP one, using the protocol of the British Hypertension Society published in 1990, and revised in 1993, for evaluating the accuracy of BP measurement devices. METHODS: The evaluation included before-use calibration, in-use assessment, after-use calibration, and static device validation that involved 85 participants. RESULTS: The mean difference between manual readings with sphygmomanometer and automatic ones with the device were -0.36+/-5.74 (mean+/-SD) for systolic values and 2.52+/-4.87 for diastolic values. On the basis of the percentages of measurements differing from the mercury sphygmomanometer standard by 相似文献   

Automatic blood pressure measurement: the oscillometric waveform shape is a potential contributor to differences between oscillometric and auscultatory pressure measurements

OBJECTIVE: To explore the differences between oscillometric and auscultatory measurements. METHOD: From a simulator evaluation of a non-invasive blood pressure (NIBP) device regenerating 242 oscillometric blood pressure waveforms from 124 subjects, 10 waveforms were selected based on the differences between the NIBP (oscillometric) and auscultatory pressure measurements. Two waveforms were selected for each of five criteria: systolic over and underestimation; diastolic over and underestimation; and close agreement for both systolic and diastolic pressures. The 10 waveforms were presented to seven different devices and the oscillometric-auscultatory pressure differences were compared between devices and with the oscillometric waveform shapes. RESULTS: Consistent patterns of waveform-dependent over and underestimation of systolic and diastolic pressures were shown for all seven devices. The mean and standard deviation, for all devices, of oscillometric-auscultatory pressure differences were: for the systolic overestimated waveforms, 36 +/- 28/-6 +/- 3 and 23 +/- 2/-1 +/- 3 mmHg (systolic/diastolic differences); for systolic underestimated waveforms, -21 +/- 5/-4 +/- 3 and -11 +/- 4/-3 +/- 3 mmHg; for diastolic overestimated waveforms, 3 +/- 4/12 +/- 5 and 17 +/- 6/10 +/- 2 mmHg; for diastolic underestimated waveforms, 1 +/- 4/-22 +/- 4 and -9 +/- 6/-29 +/- 4 mmHg; and for the two waveforms with good agreement, 0 +/- 6/0 +/- 3 and -2 +/- 4/-4 +/- 3 mmHg. Waveforms for which devices showed good oscillometric and auscultatory agreement had smooth envelopes with clearly defined peaks, compared with the broader plateau and complex shapes of those waveforms for which devices over or underestimated pressures. CONCLUSION: By increasing the understanding of the characteristics and limitations of the oscillometric method and the effects of waveform shape on pressure measurements, simulator evaluation should lead to improvements in NIBP devices.     

Arterial stiffness, cardiovagal baroreflex sensitivity and postural blood pressure changes in older adults: the Rotterdam Study

OBJECTIVE: Arterial stiffness may be involved in the impairment of the arterial baroreflex. In the present study the associations between arterial stiffness and cardiovagal baroreflex sensitivity (BRS) and between BRS and postural blood pressure (BP) changes were investigated within the framework of the Rotterdam Study. METHODS: Arterial stiffness was determined by aortic pulse wave velocity and the carotid distensibility coefficient. Continuous recording of the R-R interval and finger BP was performed with the subject resting supine, and BRS was estimated from the spontaneous changes in systolic BP and corresponding interbeat intervals. Measures of aortic stiffness or carotid distensibility and BRS were available in 2490 and 2083 subjects, respectively. The association between arterial stiffness and ln BRS was investigated by multivariate linear regression analysis and then by analysis of covariance, comparing BRS by quartiles of arterial stiffness. RESULTS: The mean age of the subjects was 71.7 +/- 6.6 (41.7% men). Aortic stiffness was negatively associated [beta = -0.029; 95% confidence interval (CI): -0.040, -0.019] and the carotid distensibility coefficient positively associated with BRS (beta = 0.017; 95% CI: 0.010, 0.024). An orthostatic decrease in systolic BP was absent in 1609 subjects, between 1 and 10 mmHg in 502 and >10 mmHg in 269 subjects, with corresponding mean values (95% CI) of ln BRS of 1.47 (1.44-1.51), 1.43 (1.37-1.49) and 1.36 (1.28-1.44) ms/mmHg (test for trend P < 0.019). An orthostatic decrease in diastolic BP was absent in 1123 subjects, 1-10 mmHg in 1057 and >10 mmHg in 209 subjects, with corresponding mean values of ln BRS of 1.49 (1.45-1.53), 1.41 (1.37-1.45) and 1.45 (1.36-1.54) ms/mmHg (P < 0.04). CONCLUSION: In a large population of older subjects, arterial stiffness appears to be an independent determinant of impaired BRS. Within the same population, impaired BRS was associated with orthostatic BP changes.     

Arm position and blood pressure: a risk factor for hypertension?

The objective of this study was to re-evaluate the effect of arm position on blood pressure (BP) measurement with auscultatory and oscillometric methods including ambulatory blood pressure monitoring (ABPM). The setting was the hospital outpatient department and the subjects chosen were normotensive and hypertensive. The effect of lowering the arm from heart level on indirect systolic BP (SBP) and diastolic BP (DBP) measurement as well as the importance of supporting the horizontal arm were measured. In the sitting position, lowering the supported horizontal arm to the dependent position increased BP measured by a mercury device from 103+/-10/60+/-7 to 111+/-14/67+/-10 mmHg in normotensive subjects, a mean increase of 8/7 mmHg (P<0.01). In hypertensive subjects, a similar manoeuvre increased BP from 143+/-21/78+/-17 to 166+/-29/88+/-20 mmHg, an increase of 23/10 mmHg (P<0.01). Combined results from normotensive and hypertensive subjects demonstrate a direct and proportional association between BP (SBP and DBP) and the increase produced by arm dependency. Similar changes and associations were noted with oscillometric devices in the clinic situation. However, supporting the horizontal arm did not alter BP. Of particular interest, analysis of 13 hypertensive subjects who underwent ABPM on two occasions, once with the arm in the 'usual' position and once with the arm held horizontally for BP measurement during waking hours, demonstrated changes comparable to the other devices. The mean 12-hour BP was 154+/-19/82+/-10 mmHg during the former period and significantly decreased to 141+/-18/74+/-9 mmHg during the latter period (P<0.01). Regression analysis of the change in SBP and DBP with arm position change again demonstrated a close correlation (r(2)=0.8113 and 0.7273; P<0.001) with the artefact being larger with higher systolic and diastolic pressures. In conclusion, arm movements lead to significant artefacts in BP measurement, which are greater, the higher the systolic or diastolic pressure. These systematic errors occur when using both auscultatory and oscillometric (clinic and ABPM) devices and might lead to an erroneous diagnosis of hypertension and unnecessary medication, particularly in individuals with high normal BP levels. Since clinical interpretations of heart level vary, the horizontal arm position should be the unambiguous standard for all sitting and standing BP auscultatory and oscillometric measurements.     

Reconstruction of brachial pressure from finger arterial pressure during orthostasis

INTRODUCTION: In patients with recurrent syncope, monitoring of intra-arterial pressure during orthostatic stress testing is recommended because of the potentially sudden and rapid development of hypotension. Replacing brachial arterial pressure (BAP) by the non-invasively obtained finger arterial pressure (FinAP) has advantages because catheterization in itself may provoke a syncope. OBJECTIVE: To investigate whether reconstruction of the brachial pressure curve (ReBAP) from FinAP can account for systolic and diastolic offset in the recorded pressure on the transition from a supine to an upright position and during maintained postural stress. METHODS: In nine healthy young subjects BAP and FinAP were recorded in the supine position, during 8 min of standing and during 20 min of 70degrees passive head-up tilt (HUT70) whereafter three of the subjects fainted within 20 min of HUT. The FinAP signal was modeled off-line into a reconstructed brachial pressure curve. RESULTS: For FinAP but not for ReBAP, systolic (P < 0.05) and diastolic (P < 0.001) bias increased in the transition from the supine to the HUT position. Bias for the systolic pressure in the supine position and after 7.5 and 20 min of HUT were 2, 7 and 11 mmHg for FinAP but only 0, -2 and 1 mmHg for ReBAP (P < 0.05 for HUT). For the diastolic pressure these values were -2, 5 and 8 mmHg for FinAP and 4, 5 and 6 for ReBAP (P < 0.01 for supine). CONCLUSIONS: Brachial pressure reconstruction from the finger arterial pressure waveform accounts for the bias from the supine to the upright position, eliminates the bias for the systolic but not for diastolic finger pressure and reduces the trend in diastolic bias with increased tilt duration.     

What is hypertension in diabetes? Ambulatory blood pressure in 137 normotensive and normoalbuminuric Type 1 diabetic patients

AIMS: To establish reference data for ambulatory blood pressure (AMBP) in normotensive, normoalbuminuric Type 1 diabetic patients and characterize the relation to clinic blood pressure (BP). To evaluate the statement of the third working party of the British Hypertension Society (BHS) that a target clinic BP in diabetes < 140/80 corresponds to a target day-time AMBP < 130/75 mmHg. PATIENTS AND METHODS: AMBP were performed in 172 normoalbuminuric, adult Type 1 diabetic patients, who had never received anti-hypertensive drugs. Clinic BP was determined as the mean of at least three auscultatory (Hawskley random zero manometer) and as the mean of at least three oscillometric (Spacelabs) BP values obtained just prior to ambulatory monitoring. Five patients with more than three missing hours/24 h were excluded. RESULTS: For 30 patients auscultatory clinic BP exceeded 140 mmHg systolic and/or 90 mmHg diastolic. For the remaining 137 normotensive patients day-time AMBP was 125.7/77.2 mmHg and oscillometric clinic BP was 125.3/76.5 mmHg (mean difference 0.3/0.7 mmHg; 95% confidence interval (CI) -0.9 to 1.5/-0.3 to 1.7 mmHg, P = 0.6/P = 0.2). Sixty-five percent of the patients had a diastolic day-time AMBP > 75 mmHg. CONCLUSIONS: Clinic BP and day-time AMBP measured by the same method were indistinguishable. The target for day-time diastolic AMBP (< 75 mmHg) proposed by the BHS is too low and is based on the misconception that in normotensive subjects day-time AMBP is lower than clinic BP. If the BHS guidelines are strictly adhered to, the consequence may be overtreatment in patients with normoalbuminuria and no end organ damage.     

Faster oscillometric manometry does not sacrifice the accuracy of blood pressure determination

Faster oscillometry enables one to track rapid pressure changes. We therefore examined whether it was possible to shorten the measurement time without sacrificing accuracy. We accelerated and linearized cuff deflation and determined systolic and diastolic pressure values by the appearance and disappearance of oscillometric waves based on the interpolated cuff pressure-oscillometric wave amplitude relationship. The accuracy of faster oscillometry was examined by comparing correlations between invasive radial and oscillometric brachial pressure with either the conventional or the faster oscillometry in 23 patients (32+/-16 measurement pairs). Faster oscillometry shortened the measurement time from 27.7+/-3.5 s to 17.1+/-2.6 s. Neither pressure levels nor heart rate altered the time required for measurement. Bland-Altman analysis indicated that mean and standard deviation of difference between oscillometric and invasive systolic pressure was comparable (conventional, 2.1+/-7.5 mmHg; faster, 1.4+/-7.3 mmHg) without correlations between difference and average of systolic pressure. Similar differences (conventional, 5.0+/-6.8 mmHg; faster, 4.9+/-5.8 mmHg) and lack of correlations were also found for diastolic pressure. In conclusion, we succeeded in shortening the oscillometric measurement time to approximately 60% of the original time without sacrificing accuracy. This was achieved by acceleration and linearization of cuff deflation and by interpolation of the relationship between cuff pressure and oscillometric wave amplitude.     

Advanced glycation endproduct crosslink breaker (alagebrium) improves endothelial function in patients with isolated systolic hypertension

OBJECTIVES: Arterial stiffening and endothelial dysfunction are hallmarks of aging, and advanced glycation endproducts (AGE) may contribute to these changes. We tested the hypothesis that AGE crosslink breakers enhance endothelial flow-mediated dilation (FMD) in humans and examined the potential mechanisms for this effect. METHODS: Thirteen adults (nine men, aged 65 +/- 2 years) with isolated systolic hypertension (systolic blood pressure > 140 mmHg, diastolic blood pressure < 90 mmHg or pulse pressure > 60 mmHg) on stable antihypertensive therapy were studied. Subjects received placebo (2 weeks) then oral alagebrium (ALT-711; 210 mg twice a day for 8 weeks). Subjects and data analyses were blinded to treatment. Arterial stiffness was assessed by carotid augmentation index (AI) and brachial artery distensibility (ArtD) using applanation tonometry and Doppler echo, and endothelial function by brachial FMD. Serum markers of collagen metabolism and vascular inflammation were assessed. RESULTS: Alagebrium reduced carotid AI by 37% (P = 0.007) and augmented pressure (16.4 +/- 10 to 9.6 +/- 9 mmHg; P < 0.001). Heart rate, arterial pressures, and ArtD, were unchanged. FMD increased from 4.6 +/- 1.1 to 7.1 +/- 1.1% with alagebrium (P < 0.05), and was unrelated to altered shear stress or regional arterial distensibility. However, FMD change was inversely related to markers of collagen synthesis, p-selectin and intracellular cell adhesion molecule (all P < 0.05). Alagebrium-associated changes in plasma nitrite plus nitrate was inversely correlated with plasma matrix metalloproteinase 9 and type I collagen (P = 0.007). CONCLUSIONS: Alagebrium enhances peripheral artery endothelial function and improves overall impedance matching. Improved endothelial function correlates better with reduced vascular fibrosis and inflammation markers than with vessel distensibility. AGE-crosslink breakers may reduce cardiovascular risk in older adults by reduced central arterial stiffness and vascular remodeling.     

Determination of accuracies of 10 models of home blood pressure monitors using an oscillometric simulator.

BACKGROUND: Patients and doctors often use home blood pressure monitoring (HBPM) to assess the control of hypertension. Despite its popularity there has always been some uncertainty with regard to its accuracy, reliability, reproducibility, and comparability. Although there are pre-market HBPM standards of accuracy, there are no standards to assure accuracy of individual HBPM units after they have been brought home. OBJECTIVE: Determination of reliability, reproducibility, and comparability of 10 models of home blood pressure monitors. METHODS: We used a Biotek BP Pump as an oscillometric simulator of systolic and diastolic blood pressures to determine reliability, reproducibility, and comparability of 10 devices. RESULTS: All of the units tested, except the Pollonex BP1000, produced reproducible readings with the pooled SD of four blood pressure settings less than 3.10 mmHg both for systolic and for diastolic measurements. The oscillometric blood pressure pump method was found to be very reproducible, with pooled differences of less than 2 mmHg and SD of less than 0.5 mmHg for a repeated series of measurements using the same monitor. Different machines of the same model were also very comparable, with pooled differences of less than 3.6 mmHg and pooled SD less than 0.7 mmHg both for systolic and for diastolic readings. There were 11-14 mmHg differences between models for all of the simulated blood pressure readings except that a 27 mmHg difference was measured at the 200 mmHg systolic blood pressure level. These differences will not necessarily be the same for measurements with humans instead of oscillometric signal generation. A system for grading the accuracy of the tested HBPM that defines accuracy of HBPM as within +/-2 SD of the average of 85 measurements is described. CONCLUSION: All models of home blood pressure monitors tested, with the exceptions of the Pollonex BP1000, produced reproducible readings and different machines of the same model were comparable.     

Evaluation of the Schiller BR-102 ambulatory blood pressure system according to the protocols of the British Hypertension Society and the Association for the Advancement of Medical Instrumentation.

OBJECTIVE: To evaluate the Schiller BR-102 monitor for ambulatory blood pressure measurement according to the protocols of the British Hypertension Society (BHS) and the Association for the Advancement of Medical Instrumentation (AAMI). DESIGN: The BHS protocol is divided into two parts. Part I, which is the part applicable to this study, comprises the main validation procedure and has five phases: before-use device calibration; in-use (field) phase; after-use device calibration; static device validation; and report of evaluation. METHOD: Three Schiller BR-102 recorders passed the before-use device calibration test, after which they entered the in-use (field) assessment phase during which the three recorders were each worn by 10 subjects for 24 h, after which calibration was again assessed. Because there was no difference in results of calibration testing among the three devices, one was selected randomly and the main validation test was carried out on 85 subjects with a wide range of blood pressures both for the auscultatory mode and for the oscillometric mode using the Sphygmocorder. The results were analysed according to the BHS grading system from A to D. The data were also analysed according to the standard of the Association for the Advancement of Medical Instrumentation (AAMI), which stipulates that the mean difference between the test device and the standard shall be 160/100 mmHg) the Schiller BR-102 was less accurate in the high pressure range for diastolic blood pressure but more accurate for systolic blood pressure, achieving A/C grading, while satisfying the AAMI criteria both for systolic and for diastolic blood pressure in the auscultatory mode. In the oscillometric mode the device performed less accurately in the high-pressure range, achieving grade D/C, while failing to satisfy the AAMI criteria both for systolic and for diastolic blood pressure. The means+/-SD of the first mercury sphygmomanometer measurements were 143+/-32 mmHg for systolic blood pressure and 88+/-21 mmHg for diastolic blood pressure. Acceptability to subjects was good and the manufacturer's manual was satisfactory. CONCLUSION: On the basis of these results, the Schiller BR-102 can be recommended for ambulatory blood pressure measurement in clinical practice using the auscultatory mode, but the oscillometric mode, which operates only if the device fails in the auscultatory mode, does not provide accurate measurements.     

A new double cuff sphygmotonometer for accurate blood pressure measurement.

Accurate measurement of blood pressure (BP) is essential in the diagnosis and treatment of hypertension, but neither auscultatory nor oscillometric methods measure intra-arterial BP accurately in all circumstances. Algorithms for automatic BP-measuring devices differ from manufacturer to manufacturer, and no clear authorized algorithm criteria have yet been established. We have devised a double-cuff sphygmotonometer to measure BP on the basis of clear algorithms, and investigated the accuracy of this new method by comparing it with the photo-oscillometric method, which is the most accurate method for non-invasive measurement of intra-arterial BP. In the new method, a small cuff (3x6 cm) replaces the photo-sensor in the brachial cuff (13x24 cm) of the photo-oscillometric device, and BP is determined by means of the oscillation within the small cuff. The comparison based on procedures of AAMI-protocol was performed in 136 hypertensive patients and 54 normotensive subjects. The difference in systolic BP between the photooscillometric and double-cuff methods was -2.26+/-2.31 mmHg (89% under 5 mmHg), and the corresponding difference in diastolic BP was 1.9+/-2.50 mmHg (94% under 5 mmHg). In conclusion, we have devised a new double-cuff method which improves on the photo-oscillometric method, and although it seems to be less accurate than the photo-oscillometric method, the clarity of its algorithm makes it superior to the conventional oscillometric and auscultatory methods employing only one cuff.     

Effect of the shapes of the oscillometric pulse amplitude envelopes and their characteristic ratios on the differences between auscultatory and oscillometric blood pressure measurements

INTRODUCTION: Oscillometric noninvasive blood pressure (NIBP) devices determine pressure by analysing the oscillometric waveform using empirical algorithms. Many algorithms analyse the waveform by calculating the systolic and diastolic characteristic ratios, which are the amplitudes of the oscillometric pulses in the cuff at, respectively, the systolic and diastolic pressures, divided by the peak pulse amplitude. A database of oscillometric waveforms was used to study the influences of the characteristic ratios on the differences between auscultatory and oscillometric measurements. METHODS: Two hundred and forty-three oscillometric waveforms and simultaneous auscultatory blood pressures were recorded from 124 patients at cuff deflation rates of 2-3 mmHg/s. A simulator regenerated the waveforms, which were presented to two NIBP devices, the Omron HEM-907 [OMRON Europe B.V. (OMCE), Hoofddorp, The Netherlands] and the GE ProCare 400 (GE Healthcare, Tampa, Florida, USA). For each waveform, the paired systolic and paired diastolic pressure differences between device measurements and auscultatory reference pressures were calculated. The systolic and diastolic characteristic ratios, corresponding to the reference auscultatory pressures of each oscillometric waveform stored in the simulator, were calculated. The paired differences between NIBP measured and auscultatory reference pressures were compared with the characteristic ratios. RESULTS: The mean and standard deviations of the systolic and diastolic characteristic ratios were 0.49 (0.11) and 0.72 (0.12), respectively. The systolic pressures recorded by both devices were lower (negative paired pressure difference) than the corresponding auscultatory pressures at low systolic characteristic ratios, but higher than the corresponding auscultatory pressures at high systolic pressures. Conversely, the differences between the paired diastolic pressure differences were higher at low diastolic characteristic ratios, compared with those at high diastolic characteristic ratios. The paired systolic pressure differences were within +/-5 mmHg for those waveforms with systolic characteristic ratios between 0.4 and 0.7 for the Omron and between 0.3 and 0.5 for the ProCare. The paired diastolic pressure differences were within +/-5 mmHg for those waveforms with diastolic characteristic ratios between 0.4 and 0.6 for the Omron and between 0.5 and 0.8 for the ProCare. DISCUSSION AND CONCLUSION: The systolic and diastolic paired oscillometric-auscultatory pressure differences varied with their corresponding characteristic ratios. Good agreement (within 5 mmHg) between the oscillometric and auscultatory pressures occurred for oscillometric pulse amplitude envelopes with specific ranges of characteristic ratios, but the ranges were different for the two devices. Further work is required to classify the different envelope shapes, comparing them with patient conditions, to determine if a clearer understanding of the different waveform shapes would improve the accuracy of oscillometric measurements.