Comparison of performance of various sphygmomanometers with intra-arterial blood-pressure readings.

Seven types of sphygmomanometer were used in random order on each of nine hypertensive patients and the readings compared with simultaneous intra-arterial blood-pressure recordings. All the devices gave significantly different values for systolic pressure, and only two measured diastolic pressure without significant error. Systolic pressure was consistently underestimated (range 31-7 mm Hg), and all but one instrument overestimated diastolic pressure (range 10-2 mm Hg). The variability of readings was least with the standard mercury sphygmomanometer and the random-zero machine, while with some of the more automated devices single readings were in error up to -68/33 mm Hg. The strong correlations found between intra-arterial and cuff systolic pressures with all devices tested and significant correlations for diastolic pressure with all but one device indicate that, with one possible exception, the sphygmomanometers would give accurate results where a change in blood pressure was the main concern.     

Evaluation of the characteristics and performance of an automatic sphygmomanometer (Omega 1400)

24 hour pressure monitoring is a newly developing technique potentially yielding important informations in hypertensive patients. Numerous automated devices are available whose performance characteristics are poorly documented. To evaluate an automated sphygmomanometer commonly used in our Division (Omega 1400, Invivo Research Laboratories), we performed a series of measurements, simultaneously recording blood pressure in the opposite arm with a common sphygmomanometer. Each measure was then repeated reversing the position of the two devices (manual and automated), thus abolishing possible differences between the two arms. We observed a mean underestimation of 1.90 mmHg of systolic pressure and of 4.82 mmHg of diastolic blood pressure by the automated device. We conclude that the device by us evaluated is not advisable in the basal blood pressure evaluation, but useful in monitoring inpatients.     

Comparative accuracy of two new electronic devices for the noninvasive determination of blood pressure

Recent developments in behavioral approaches to cardiovascular disease have called for physiological monitoring devices that reduce experimenter bias, are easy to operate, can be used ambulatorily, and/or provide ongoing, automated monitoring of pertinent cardiovascular functions--i.e., blood pressure and heart rate. Neither the invasive monitoring (via catheterization) nor the standard auscultatory method of blood pressure determination, however, has these characteristics. In the present study, two new methods/devices--(1) a low-weight, low-cost, battery-operated sphygmomanometer (SM), and (2) a more expensive automated electronic SM with electrical pump-are compared with each other and with the more common auscultatory method and a standard mercury SM. Both new devices were also compared with a standard pulse count. Data were derived from 10 readings of 10 healthy subjects each across the three possible comparisons, thus totaling N = 30. Correlation coefficients and average differences were computed and indicated high intercorrelations (between r = .89 and r = .99) between each pairing of the new electronic devices and the mercury SM. Intercorrelations of blood pressure determination with the two new electronic devices, however, were only moderate. Potential reasons for the variability are discussed, and guidelines for the optimal use of the new, easy-to-operate electronic devices are presented.     

Evaluation of a community-based automated blood pressure measuring device

Background

Automated devices are widely available in the community for people to measure their blood pressure. We assessed the accuracy and reproducibility of a brand of community-based automated device against the standard mercury sphygmomanometer.

Methods

Same-arm pairs of blood pressure readings were obtained with the Vita-Stat 90550 automated device, a sphygmomanometer and the Omron HEM-705CP automated device in random order on volunteers in 3 community pharmacies using a modified protocol for evaluating blood pressure devices. Comparison of readings between the Omron device and the sphygmomanometer served as a positive control of how well a laboratory-validated automated device could perform in the community. Both the Association for the Advancement of Medical Instrumentation (AAMI) and British Hypertension Society (BHS) criteria were used to assess the accuracy and reproducibility of readings.

Results

The mean blood pressure reading and standard error (SE) of the mean for the 108 volunteers (66 women and 42 men) was 133/77 (SE 2/1) mm Hg with the Vita-Stat device, 131/77 (SE 2/1) mm Hg with the Omron device and 129/76 (SE 2/1) mm Hg with the sphygmomanometer. The mean difference in readings was 4.4/1.0 (standard deviation [SD] 9.4/6.2) mm Hg between the Vita-Stat device and the sphygmomanometer and 1.6/0.6 (SD 9.3/6.4) mm Hg between the Omron device and the sphygmomanometer. Neither automated device met the AAMI accuracy criteria for the systolic readings. The BHS grades were C/A (systolic unacceptable/diastolic acceptable) for each automated device. According to the BHS analytical criterion, all devices achieved acceptable reproducibility grades.

Interpretation

Neither automated device met the AAMI or BHS criteria for accuracy while in use in the community, and neither performed as well in the community as in the laboratory.Measurement of blood pressure outside the office setting, using ambulatory monitors, home recorders or community-based devices has become popular among both physicians and patients. These devices may help to improve patients'' involvement in their care¹ and they may allay physicians'' concerns about a possible “white-coat syndrome.” However, incorrect readings could lead to a false sense of security or incorrect clinical decisions.The British Hypertension Society (BHS)² and the Association for the Advancement of Medical Instrumentation (AAMI)³ have developed laboratory protocols to evaluate automated blood pressure measuring devices. Many devices have failed to meet minimum standards for accuracy and reproducibility.⁴One community-based device, the Vita-Stat, has been available in various models since 1976, although none has performed uniformly well in community evaluations.^5,6,7,8,9 The newest model, the Vita-Stat 90550, available in about 3000 Canadian communities since 1990, provides 40 million readings yearly (Fred Sarkis, Spacelabs Medical: personal communication, 2000). Hence, we decided to evaluate the Vita-Stat 90550 against the mercury sphygmomanometer for accuracy and reproducibility in the community. To assess how well a laboratory-validated device could perform in the community, we compared the Omron HEM-705CP, which has met both the BHS and the AAMI criteria,¹⁰ against the mercury sphygmomanometer.     

Comparative accuracy of two new electronic devices for the noninvasive determination of blood pressure

Recent developments in behavioral approaches to cardiovascular disease have called for physiological monitoring devices that reduce experimenter bias, are easy to operate, can be used ambulatorily, and/or provide ongoing, automated monitoring of pertinent cardiovascular functions—i.e., blood pressure and heart rate. Neither the invasive monitoring (via catheterization) nor the standard auscultatory method of blood pressure determination, however, has these characteristics. In the present study, two new methods/devices — (1) a low-weight, low-cost, battery-operated sphygmomanometer (SM), and (2) a more expensive automated electronic SM with electrical pump — are compared with each other and with the more common auscultatory method and a standard mercury SM. Both new devices were also compared with a standard pulse count. Data were derived from 10 readings of 10 healthy subjects each across the three possible comparisons, thus totalingN=30. Correlation coefficients and average differences were computed and indicated high intercorrelations (betweenr=.89 andr=.99) between each pairing of the new electronic devices and the mercury SM. Intercorrelations of blood pressure determination with the two new electronic devices, however, were only moderate. Potential reasons for the variability are discussed, and guidelines for the optimal use of the new, easy-to-operate electronic devices are presented.     

Age, gender and circadian or circasemidian blood pressure and heart rate variation of children.

Systolic (S) and diastolic (D) blood pressure (BP) and heart rate (HR) of clinically healthy children (24 boys and 15 girls) 3 to 7 years of age were measured with a standard mercury sphygmomanometer at 3-hour intervals for 24 hours in April 1991. The children slept and/or rested from 2100 to 0700 and napped from 1230 to 1530; they had meals at 0730, 1200 and 1800. A statistically significant circadian and about 12-hour (circasemidian) component of variation is documented for SBP and DBP of boys and girls and for HR of boys. No gender difference was found for the circadian and circasemidian components. A positive correlation with age is found for the MESOR and circadian amplitude of SBP and DBP (p < 0.05); a negative correlation with age is found for the MESOR of HR (p < 0.001).     

Transducer for monitoring respiration during imaging procedures

A transducer system for monitoring respiration is described; it uses a ‘liquid column’ sensor with a remote integrated circuit pressure module. It was designed primarily for non-invasive monitoring and control of respiration during diagnostic imaging procedures, but has also found applications in other areas, e.g. physiotherapy and pulse monitoring. The device is a new version of a system developed several years ago and takes advantage of relatively low cost commercial ‘building blocks’. The output is an analogue voltage (from a low impedance source) capable of driving a wide range of recorders, amplifiers and computer interfaces. Reference is also made in the text to a bio-feedback signal processing and display unit (described elsewhere) which, when used with this transducer, provides a versatile respiratory control system.     

A simple method for obtaining blood pressure in rhesus monkeys (Macaca mulatta).

A relatively simple procedure was devised to obtain blood pressures in rhesus monkeys. This procedure utilized a polygraph, pulse transducer, pressure transducer, blood pressure mixer unit, and pediatric sphygmomanometer cuff. Previous attempts to auscultate the Korotkoff sounds by use of a sphygmomanometer cuff and stethoscope were unsuccessful. Blood pressure can be obtained by cannulation of the femoral artery, but repeated puncture may cause serious trauma to the arterial wall. This procedure was developed and used in our laboratory to obtain repeated blood pressures over a 90-da period. Results from using the cuff and polygraph have been shown to correlate favorably with cannulation of the femoral artery.     

Central Pressure Appraisal: Clinical Validation of a Subject-Specific Mathematical Model

IntroductionCurrent evidence suggests that aortic blood pressure has a superior prognostic value with respect to brachial pressure for cardiovascular events, but direct measurement is not feasible in daily clinical practice.AimThe aim of the present study is the clinical validation of a multiscale mathematical model for non-invasive appraisal of central blood pressure from subject-specific characteristics.MethodsA total of 51 young male were selected for the present study. Aortic systolic and diastolic pressure were estimated with a mathematical model and were compared to the most-used non-invasive validated technique (SphygmoCor device, AtCor Medical, Australia). SphygmoCor was calibrated through diastolic and systolic brachial pressure obtained with a sphygmomanometer, while model inputs consist of brachial pressure, height, weight, age, left-ventricular end-systolic and end-diastolic volumes, and data from a pulse wave velocity study.ResultsModel-estimated systolic and diastolic central blood pressures resulted to be significantly related to SphygmoCor-assessed central systolic (r = 0.65 p <0.0001) and diastolic (r = 0.84 p<0.0001) blood pressures. The model showed a significant overestimation of systolic pressure (+7.8 (-2.2;14) mmHg, p = 0.0003) and a significant underestimation of diastolic values (-3.2(-7.5;1.6), p = 0.004), which imply a significant overestimation of central pulse pressure. Interestingly, model prediction errors mirror the mean errors reported in large meta-analysis characterizing the use of the SphygmoCor when non-invasive calibration is performed.ConclusionIn conclusion, multi-scale mathematical model predictions result to be significantly related to SphygmoCor ones. Model-predicted systolic and diastolic aortic pressure resulted in difference of less than 10 mmHg in the 51% and 84% of the subjects, respectively, when compared with SphygmoCor-obtained pressures.     

Long-acting nifedipine versus metoprolol as monotherapy for essential hypertension. A randomized,controlled crossover study.

We assessed the efficacy of long-acting nifedipine as monotherapy in 52 patients with mild to moderate essential hypertension in a randomized, controlled crossover study. Good blood pressure control was achieved in 34 of 40 patients (85%) receiving nifedipine (mean daily dose, 52 mg in 2 divided doses) compared with 23 of 40 patients (58%) receiving metoprolol (mean daily dose, 155 mg in 2 divided doses). After treatment for 4 weeks, the mean blood pressures with nifedipine (149.7 +/- 16.6/88.7 +/- 11.1 mm of mercury) and metoprolol administration (163.9 +/- 23.3/94.2 +/- 10.2 mm of mercury) were significantly lower than with placebo (176.7 +/- 17.3/100.9 +/- 7.1 mm of mercury) (P less than .05). The mean systolic pressure during nifedipine treatment was 14.2 mm of mercury lower (95% confidence interval [CI], 3.9 to 24.5 mm of mercury) and mean diastolic pressure 5.5 mm of mercury (95% CI, 0.3 to 10.7 mm of mercury) lower than with metoprolol therapy. Both drugs were reasonably well tolerated, and intolerance requiring withdrawal was encountered in 3 of 45 (7%) patients receiving nifedipine, compared with 1 of 45 (2%) of those taking metoprolol and placebo, respectively. Adverse effects of nifedipine, most of which were transient, included palpitations, headache, facial flushing, and ankle edema. Long-acting nifedipine is a promising agent when given alone for mild to moderate hypertension and can be safely administered in clinical practice.     

Comparison of hair, nails and urine for biological monitoring of low level inorganic mercury exposure in dental workers.

Creatinine-corrected urine mercury measurements in spot urine samples are routinely used in monitoring workers exposed to inorganic mercury. However, mercury measurement in other non-invasive biological material has been used in some epidemiological studies. Dentists and dental nurses remain a group of workers with potential exposure to inorganic mercury through their handling of mercury-containing amalgam, although changes in work practices have reduced the current, likely exposure to mercury. Therefore, dental workers remain an occupational cohort in whom the value of using different biological media to identify exposure to low level inorganic mercury can be investigated. Samples of head hair, pubic hair, fingernails, toenails and urine were analysed for mercury content from a cohort of UK dentists (n=167) and a socioeconomically similar reference population (n=68) in whom any mercury exposure was primarily through diet. The mercury content in all biological material was significantly higher in the dental workers than in the control population (p<0.0001). The geometric mean and 90th percentile mercury concentrations in the urine samples from dentists were 1.7 and 7.3 micromol mol(-1) creatinine, respectively, with only one sample having a value at around the UK's Health and Safety Executive biological monitoring health guidance level of 20 micromol mol(-1) creatinine. Receiver operator characteristic analyses suggested that the ability of the biological material to discriminate between dentists and referents were fingernails>urine approximately equal to toenails>pubic hair approximately equal to head hair. Further investigation is warranted as to why fingernails appear to be such a good discriminator, possibly reflecting some contribution of direct finger contact with amalgam or contaminated surfaces rather than systemic incorporation of mercury into growing nails. Good correlation between head hair and pubic hair mercury levels in all subjects was obtained (r=0.832), which was significantly improved when hair samples weighing <10 mg were excluded (r=0.868). Therefore, under these exposure conditions and using the described pre-analytical washing steps, there is little influence from atmospheric contamination on the level of mercury content of head hair. The choice of non-invasive biological materials for mercury analysis depends on a number of considerations. These include the toxicokinetics of urinary mercury excretion, the growth rates of hair and nail, the nature and time-frame of exposure, and the fact that urine mercury may not reflect the body burden level from dietary methyl mercury. However, the data from this study suggests that urine mercury remains the most practical and sensitive means of monitoring low level occupational exposure to inorganic mercury.     

A new testing device for measuring gliding resistance and work of flexion in a digit

In order to move the finger the tendon force must overcome the gliding resistance of the tendon as well as the forces to move the joints, finger inertias, and external load. These sources, combined, make up the work of flexion (WOF) which has been experimentally used to evaluate the finger function. In this study, we have designed a new device, which can measure the forces at the proximal and distal end of the tendon during finger flexion, so that gliding resistance can be isolated from the WOF. Two index fingers from a pair of human cadaver hands were used for testing this device. Preliminary data showed that internal resistance occupied about 10% of WOF with an intact tendon. However, after tendon repair, the gliding resistance increased 31% of WOF for a modified Kessler repair and 50% of WOF for a Becker repair compared to intact tendon. We simulated joint stiffness by injection of saline solution into the proximal interphalangeal joint. This increased the overall WOF but not the gliding resistance. We believe that this testing device provides a useful tool to evaluate finger function after tendon repair in an experimental model.     

Considerations on the flow configuration of membrane chromatography devices for the purification of human basic fibroblast growth factor from crude lysates

Membrane chromatography possesses numerous advantages such as operation at high flow rates, low back pressure, ease of handling and scale up, which make the membrane adsorber process a viable alternative to conventional packed column chromatography. A purification process for the isolation of human recombinant basic fibroblast growth factor (FGF‐2) based on membrane chromatography was investigated using devices with different flow configurations. In the first process, the FGF‐2 capture step was performed with an axial flow device, while the alternative method achieved direct capture of FGF‐2 from unclarified cell lysate with a tangential flow device. In both processes, FGF‐2 purities exceeded 82% and the purified cytokine displayed high biological activity. Binding capacity (BC) from fermentation broth of the axial flow device was 28 mg/mL. This was 50% higher than the BC obtained with the tangential flow device under particle‐free supernatant conditions (18 mg/mL) and 150% higher compared to the BC achieved with unclarified cell lysate (11 mg/mL). While membrane chromatography in tangential flow mode omits clarification and thus reduces the number of stages in the downstream process, it displays lower peak resolution and leads to a lower overall process yield.     

Noninvasive, automatic 24-h ambulatory blood pressure monitoring in normotensive subjects

The reliability of noninvasive, automatic blood pressure monitoring is not yet clearly established. A 24-h ambulatory blood pressure profile was obtained in 9 healthy, normotensive subjects with an automatic, noninvasive device. The blood pressure profile showed the typical circadian pattern with lower systolic and diastolic values during sleep, although pulse pressure was fairly constant (about 40 mm Hg). The systolic blood pressure rose steeply in the early morning hours--before waking up. The results were compared with simultaneous hourly readings using the auscultatory method. There were no statistically significant differences between the automatic and auscultatory readings, 13 of the 18 mean values at different time points being within 2 mm Hg of each other. All the auscultatory means fell within the 95% confidence limits of those measured hourly by the automatic method. Although the automatic method seemed to be reliable compared with the auscultatory method, its sensitivity to motion artifacts is a disadvantage in a truly ambulatory setting.     

Biological monitoring,by in vivo XRF measurements,of occupational exposure to lead,cadmium, and mercury

In vivo X-ray fluorescence (XRF) techniques were used for biological monitoring of lead, cadmium, and mercury. Lead accumulates in bone, the level of which may thus be used for monitoring of exposure. However, there was no close association between lead levels in bone and exposure time, partly because of differences in exposure patterns and partly, probably, because of variations in the toxicokinetics of lead. There are at least two separate bone lead compartments. The average over-all half-time is probably 5–10 yr. The finger bone level may be an index of the lead status of the total skeleton. In lead workers, the mobilization of bone lead causes an “internal” lead exposure and affects the blood lead level considerably. In cadmium workers, in vivo XRF is a sensitive and risk-free method for assessment of accumulation in kidney cortex, the critical tissue as to toxic effects; workers displayed increased levels. However, there was no clear association with duration and intensity of exposure, cadmium levels in urine, or microglobulinuria. Determinations of kidney cadmium may add important information on the state of accumulation and, thus, risk of kidney damage. Workers exposed to elemental mercury vapor, as well as fishermen exposed to methyl mercury, had mercury levels in bone below the detection limit of the XRF method.     

Evaluation of screening for hypertension in general practice with an automatic machine.

An automatic device for measuring blood pressure was used to screen all patients aged 30 to 65 years registered at a health centre. Of those who were eligible, 55% attended. Patients with previously recognised hypertension were more common among the attenders than among the non-attenders. High readings obtained on the automatic device possibly deterred some patients from reattending for follow up measurements of blood pressure. Although the device is quick and easy to use, the logistic challenge of formal blood pressure screening is considerable. Hypertension was discovered in 52 patients (mean diastolic pressure greater than 100 mm Hg). Retrospective analysis of their medical records showed that a third had had an abnormal blood pressure reading noted during the past 10 years and no further action had been taken, and almost three quarters had attended their practitioner during the previous year without having a blood pressure measurement recorded. One year after the screening procedure two fifths of the newly discovered hypertensive patients had defaulted from follow up and treatment. Automatic devices are not a short cut to the discovery of occult hypertension. Case finding by routine measurement of blood pressure at surgery visits is more efficient.     

Functional characteristics of the cardiovascular system in adolescents with high normal blood pressure

Sanogenetic monitoring of schoolchildren’s health has demonstrated that, among high school students, the proportion of adolescents with elevated blood pressure (hypertension + hypernormotension) has risen from 15–20% in 8th-year students to 30–50% in 9th- to 11th-year students, while the proportion of adolescents with hypertension was 3.7% in all age groups. The level of blood pressure (BP) was compared with parameters of the autonomic control of the cardiovascular system. A high normal BP in adolescents 13–14 and 17–18 years of age was correlated with the higher proportion of low frequencies in the spectrum of heart rate variability (HRV) and with the lower sensitivity of the arterial baroreflex. At the age of 15–16 years, a high normal BP was accompanied by a reduced heart rate and a higher sensitivity of the arterial baroreflex; BP correlated also with a decrease in power of the high-frequency region of the HRV spectrum. Unlike normotensive age-matched subjects, hypernormotensive adolescents 15–16 years of age have a lower finger blood pressure and reduced relative power of the low-frequency range in the HRV spectrum during the functional test (an increase in the dead space). This may be a result of a functional inadaptability of sympathetic autonomic regulation.     

TAT蛋白质转导结构域与SV40启动子特异的三锌指结构融合蛋白的表达与纯化

利用蛋白质转导结构域(PTDs)可以将与之融合表达的蛋白质直接送入细胞中。将通过筛选噬菌体展示锌指库得到的特异作用于SV40启动子上9bp序列的三锌指结构的序列插入含有TAT蛋白的蛋白质转导结构域的表达载体pET—TAT-NLS中,构建融合蛋白的表达载体pET-TAT-NLS—clone3。融合蛋白在E．coli BL21(DE3)中得到了可溶性表达,含量约占总蛋白的18％;并通过镍亲和凝胶层析柱得到了较好的纯化融合蛋白。     

Influence of arm position on measurement of blood pressure.

A series of measurements of blood pressure in normotensive and hypertensive subjects showed that measurements made with a sphygmomanometer with the arm dependent by the side were consistently higher than those made with the arm horizontal at heart level. The mean difference in a group of 90 hypertensive outpatients was 11/12 mm Hg. Failure to appreciate the importance of arm position may lead to erroneous measurements of blood pressure. This has important implications for clinical practice and research.     

Controlled evaluation of thermal biofeedback in treatment of elevated blood pressure in unmedicated mild hypertension

In the first of two studies, 42 unmedicated mild hypertensives completed either 16 sessions of thermal biofeedback (TBF) training for hand (7 sessions) and foot (9 sessions) warming or 8 weeks of monitoring BPs at home. There was a trend (p<.10) for more of those treated (57.1%) to have DBPs lower than 90 mm Hg than for those only monitoring BPs at home (33%). Analyses of clinic BP values from random zero sphygmomanometer measurements, from 24-hour ambulatory BP monitoring, and from home BP measurements made by the patient showed no advantage for treatment versus BP monitoring. Sixteen of the 21 patients in BP monitoring were later treated. Analyses of treatment effects across all treated subjects by gender revealed a significant (p=.02) decrease in DBP for treated female subjects (n=13) but not for males (n=24). In the second study the 22 initial treatment successes, that is, those whose DBP was below 90 mm Hg at posttreatment (59.4% of those who completed treatment), were randomized to an intensive follow-up (monthly visits for 6 months, then visits every two months) emphasizing regular home practice with an electronic TBF device or regular follow-up (visits every 3 months). Twelve of the 22 were still normotensive at 12 months. There were no differences at any point during the follow-up between the two conditions in success rate or BPs despite a numerical advantage in reported frequency of home practice by those in the intensive follow-up condition.This research was supported by a grant from NHLBI, HL-31189.