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.     

Correlation study of arterial blood pressure level to the amplitude of the pressure pulse waveform

Automated blood pressure measurements are usually characterized by poor operational reliability and a considerable degree of complexity in performing the measurement. This paper introduces a new technique for the indirect measurement of the systolic and diastolic blood pressure of an individual. The technique is based upon a statistically consistent relationship between the amplitude of the pulsative pressure waveform at the systolic and diastolic points, and the amplitude of pulse signals detected when the artery is fully occluded. Clinical testing and statistical analysis techniques are used to derive appropriate numerical values for these relationships. The proposed procedure thus incorporates an adaptive measurement philosophy achieving minimum observer involvement and consequently high instrument accuracy. Overall measurement errors are maintained well within proposed standards for automated sphygmomanometers.     

Defects in sphygmomanometers: an important source of error in blood pressure recording.

Almost half the sphygmomanometers in a teaching hospital group had defects in the control valve which interfered with accurate blood-pressure reading. Ward staff should be taught to check sphygmomanometers regularly and replace control valves; time consumption and cost are low. The cuffs in general use in these hospitals, and of the standard size sold in Britain, had rubber bags which did not encircle the arm of more than half the patients on whom they were used. This deficiency causes over-reading of blood pressure in obese people. The size of error is uncertain but it should be avoided by adopting a cuff with a longer bag.     

Measured blood pressure and hypertension among young adults: a comparison between two nationally representative samples

Measurement and distribution of systolic and diastolic blood pressure and related health risk factors in the National Longitudinal Study of Adolescent Health (Add Health) were compared with data from the National Health and Nutrition Examination Survey (NHANES) 2007-2008. Sociodemographic patterns of blood pressure, prevalence of hypertension, and measurement characteristics in Add Health were also examined. Prevalence of hypertension (20.88%) in Add Health was significantly higher than that in NHANES (4.60%). This difference was only partially explained by body mass index and waist circumference and could reflect different measurement techniques, sample composition differences, or masked hypertension.     

Measured Blood Pressure and Hypertension among Young Adults: A Comparison between Two Nationally Representative Samples

Measurement and distribution of systolic and diastolic blood pressure and related health risk factors in the National Longitudinal Study of Adolescent Health (Add Health) were compared with data from the National Health and Nutrition Examination Survey (NHANES) 2007–2008. Sociodemographic patterns of blood pressure, prevalence of hypertension, and measurement characteristics in Add Health were also examined. Prevalence of hypertension (20.88%) in Add Health was significantly higher than that in NHANES (4.60%). This difference was only partially explained by body mass index and waist circumference and could reflect different measurement techniques, sample composition differences, or masked hypertension.     

A comparison of blood pressure measurement over a sleeved arm versus a bare arm

Background

The measurement of blood pressure is a common clinical exam with important health consequences. We sought to determine whether the measurement of blood pressure over a sleeved arm varies from that taken on a bare arm.

Methods

We recruited 376 patients between 18 and 85 years of age from a family medicine clinic between September 2004 and November 2006. They all had their blood pressure recorded using the same automatic oscillometric device, with the cuff placed over their bare arms for the first reading. Each patient was then randomly assigned to either the bare-arm group, for which the second blood pressure reading was also taken on a bare arm, or the sleeved-arm group, for which the second reading was taken with the cuff placed over the patient''s sleeve.

Results

The mean age of the 376 participants was 61.6 years (standard deviation 15.0), 61% of the participants were male, 41% had hypertension and 11.7% had diabetes. We found no clinically important differences between the bare-arm group (n = 180) and the sleeved-arm group (n = 196) in age, sex or body mass index. The mean differences between the first and second readings for patients in the bare-arm group were 4.1 mm Hg (95% confidence interval [CI] 2.8 to 5.5) for systolic blood pressure and 0.1 mm Hg (95% CI –0.7 to 0.9) for diastolic blood pressure. The mean differences between the first and second readings for patients in the sleeved-arm group were 3.4 mm Hg (95% CI 2.1 to 4.7) for systolic blood pressure and 0.4 mm Hg (95% CI –0.4 to 1.3) for diastolic blood pressure. The between-group differences in these values was 0.76 mm Hg (95% CI –1.13 to 2.65) for systolic and –0.31 mm Hg (95% CI –1.48 to 0.86) for diastolic blood pressure; neither of these differences was clinically important or statistically significant.

Interpretation

We found that there was no significant difference in blood pressure recorded over a sleeve or on a bare arm. For practical purposes, the decision to measure blood pressure on a bare arm or over a sleeved arm should be left to the judgment of the health care professional taking the blood pressure.The measurement of blood pressure is one of the most common examinations undertaken in family practice and has important health and management consequences for the patient. Accurate assessment of blood pressure, therefore, is very important. Current guidelines outline standards for obtaining accurate and reproducible blood pressure measurements.¹ These standards include guidelines for the sizes of blood pressure cuffs and the position of the patient''s arm, as well as a recommendation that the patient be seated for 5 minutes before his or her blood pressure is taken. In addition, it has been recommended that blood pressure be measured over the patient''s bare arm.¹ However, the current recommended method to determine blood pressure² has several limitations (e.g., high variability of blood pressure at different times of day or if measured only once, loss of proper technique post-training).Three previous studies have assessed whether blood pressure varies significantly when taken over a sleeved arm compared with a bare arm. Details of the literature review are described in Appendix 1, available online at www.cmaj.ca/cgi/content/full/178/5/585/DC2. In one study, involving 36 patients, Holleman et al³ found no significant differences in systolic or diastolic blood pressure readings taken over the sleeved or bare arm of each patient. However, this study was limited because of its small sample and because blood pressure measurements were taken on both arms simultaneously. A study by Kahan et al,⁴ involving 201 patients, compared blood pressure measurements taken over a sleeved arm, a bare arm and below a rolled-up sleeve. They found that the degree of clothing under the sphygmomanometer cuff did not have a clinically important effect on the reading. Although they found no significant difference in the effect of clothing on blood pressure readings, the study was limited by their design of measuring blood pressure below a rolled-up sleeve. The third study, conducted by Liebl et al,⁵ was published while our study was in progress. Their study, which involved 201 patients, compared blood pressure measurements taken over a sleeved arm and a bare arm with both sphygmomanometric and oscillometric devices. They concluded no significant difference in readings between the sleeved and bare-arm groups. In contrast to previous studies, we sought to determine whether the measurement of blood pressure over a sleeved arm varies from that taken over a bare arm through the use of a control group in which patients'' blood pressure was taken only over a bare arm.     

Sphygmomanometers in hospital and family practice: problems and recommendations.

The accuracy and working condition of 210 sphygmomanometers were tested: 100 (50 and mercury and 50 aneroid) models were used in family practices and 100 mercury models in hospitals. Faults in the inflation-deflation system were common and caused mainly by dirt or wear in the control valves. Leakage occurred in 48% of the hospital and 33% of the family practice sphygmomanometers. In the mercury models the mercury or air vents were often in an unsatisfactory condition or the calibrated glass tube dirty. The accuracy of the gauges was examined at 90 and 150 mm Hg: fewer than 2% of the mercury sphygmomanometers but 30% of the aneroid models had errors greater than +/- 4 mm Hg at either pressure. Over half of the cuffs examined had bladders widths less than the recommended size, and 94% had bladders shorter than the length recommended for use on normal adults. Mercury sphygmomanometers should be bought in preference to aneroid models as they are more accurate, less expensive in the long term, and can be maintained by the owner; they should be checked every six to 12 months depending on usage. Replacement parts should be kept readily available.     

Ambulatory blood pressure monitoring: assessing the diurnal variation of blood pressure

The purposes of this paper are to examine the effects of activity, situation of measurement, mood, and occupation on the daily variation of blood pressure and to discuss the potential utility of ambulatory blood pressure monitoring in physical anthropological studies. The subjects of the blood pressure variability study are 125 men who were referred to the Hypertension Center at New York Hospital--Cornell Medical Center for evaluation of hypertension. There were 1,386 blood pressure measurements from these subjects available for study, which were taken using noninvasive ambulatory blood pressure monitoring techniques. Pressures were transformed to z scores using the subject's daily mean pressure and standard deviation to assess the relative elevation during the experience of the various factors. The results show that activity and mood are the most significant sources of blood pressure variation (P less than .005) and are additive. Occupation, which may be an indicator of social class in this population, also modified the mood effects. Because ambulatory blood pressure monitors obtain many readings over a day under a variety of circumstances, their use can improve epidemiological and human biological studies of the inheritance and variability of blood pressure. Ambulatory blood pressure monitoring is an important new tool in the study of human biological variation.     

Blood pressure in first 10 years of life: the Brompton study.

OBJECTIVES--To determine the normal range of blood pressure and its pattern of change in the first 10 years of life. To estimate at what age (if any) children consistently appear in one part of the blood pressure distribution and at what age familial correlations in blood pressure become significant. DESIGN--Longitudinal cohort study. SETTING--South east England. SUBJECTS--2088 children of both sexes born consecutively in Farnborough Hospital, Kent, and their parents. MAIN OUTCOME MEASURE--Blood pressure measured by Doppler ultrasonography and sphygmomanometry. RESULTS--Systolic blood pressure rose from a mean of 88.5 mm Hg at age 6 months to 96.2 mm Hg at 8 years measured with a 8 cm cuff and from 89.1 mm Hg at age 5 years to 94.3 mm Hg at age 10 years measured with a 12 cm cuff. The larger cuff gave blood pressure readings about 6 mm Hg lower. This effect was independent of body weight and arm circumference. Diastolic blood pressure rose from 57.8 mm Hg at 5 years to 61.8 mm Hg at 10 years (12 cm cuff). There was only about 1 mm Hg difference between sexes. Blood pressure was correlated with weight, weight adjusted for height, height, and arm circumference at all ages studied. The correlation coefficient of repeated yearly measurements increased steadily with age from 0.28 at 2 years to 0.59 at 10 years. The correlation coefficients between child''s blood pressure and mother''s average blood pressure increased from 0.1 at age 1 year to 0.23 at age 10. CONCLUSIONS--Blood pressure changes relatively little between the ages of 6 months and 10 years. Yet because of the increasing strength of between occasion and family correlations, children are more consistently occupying a specific part of the blood pressure distribution as they grow older. Studies in children should help determine why some adults have hypertension and others do not.     

Estimation of blood pressure-related parameters by electrical impedance measurement.

In 13 healthy volunteers a computerized experimental set-up was used to measure the electrical impedance of the upper arm at changing cuff pressure, together with the finger arterial blood pressure in the contralateral arm. On the basis of a model for the admittance response, the arterial blood volume per centimeter length (1.4 +/- 0.3 ml/cm), the venous blood volume as a percentage of the total blood compartment (49.2 +/- 12.6%), and the total arterial compliance as a function of mean arterial transmural pressure were estimated. The effective physiological arterial compliance amounted to 2.0 +/- 1.3 microliters.mmHg-1.cm-1 and the maximum compliance to 33.4 +/- 12.0 microliters.mmHg-1.cm-1. Additionally, the extravascular fluid volume expelled by the occluding cuff (0.3 +/- 0.3 ml/cm) was estimated. These quantities are closely related to patient-dependent sources of an unreliable blood pressure measurement and vary with changes in cardiovascular function, such as those found in hypertension. Traditionally, a combination of several methods is needed to estimate them. Such methods, however, usually neglect the contribution of extravascular factors.     

Blood flow in a brachial artery compressed externally by a pneumatic cuff.

Blood flow in human brachial arteries, compressed by a pneumatic cuff for blood pressure measurement, is examined using several different noninvasive techniques. From the experimental results it is shown that, when arterial pressure distal to the cuff is always lower than cuff pressure, flow in the artery under the cuff becomes supercritical near the cuff downstream margin and no reflection occurs there and the reflected wave from the peripheral vascular system of the arm does not propagate beyond the cuff downstream margin. Therefore an unsteady transition from supercritical to subcritical flow occurs near the cuff downstream margin. When the peak value of distal arterial pressure exceeds cuff pressure, a reflection occurs near the cuff downstream margin. The reflection becomes stronger corresponding to decrement of the cuff pressure and the whole artery segment under the cuff inflates fully at systole. At diastole, however, the artery segment under the cuff does not collapse completely and, hence, the phenomenon becomes that of pressure wave propagation in a partially collapsed artery segment.     

Shift work is not associated with high blood pressure or prevalence of hypertension

Background

Working mostly at night has been suggested to be associated with upset of chronobiological rhythms and high blood pressure, but the evidence from epidemiological studies is weak.

Methods

In a cross-sectional survey, we evaluated the association between shift work and blood pressure, pre-hypertension and hypertension. In total, 493 nurses, nurse technicians and assistants, were selected at random in a large general hospital setting. Hypertension was diagnosed by the mean of four automatic blood pressure readings ≥140/90 mmHg or use of blood pressure lowering agents, and pre-hypertension by systolic blood pressure ≥120–139 or diastolic blood pressure ≥80–89 mmHg. Risk factors for hypertension were evaluated by a standardized questionnaire and anthropometric measurements. The association between the shift of work and blood pressure, pre-hypertension and hypertension was explored using univariate and multivariate analyses that controlled for risk factors for hypertension by covariance analysis and modified Poisson regression.

Results

The mean age of the participants was 34.3±9.4 years and 88.2% were women. Night shift workers were older, more frequently married or divorced, and less educated. The prevalence of hypertension in the whole sample was 16%, and 28% had pre-hypertension. Blood pressure (after adjustment for confounding) was not different in day and night shift workers. The prevalence of hypertension and pre-hypertension by shift work was not different in the univariate analysis and after adjustment for confounding (all risk ratios  = 1.0).

Conclusion

Night shift work did not increase blood pressure and was not associated with hypertension or pre-hypertension in nursing personnel working in a large general hospital.     

Indirect systolic and mean blood pressure determination by a new tail cuff method in spontaneously hypertensive rats

A new tail cuff method for determining systolic and mean blood pressure in rats was developed based on photoelectric detection of tail arterial blood flow and pulsatile volume oscillation. Indirect systolic and mean blood pressure measured by this method correlated well with direct systolic and mean blood pressures recorded by a transducer and polygraph after carotid artery cannulation in stroke-resistant spontaneously hypertensive rats (SHR), stroke-prone SHR and normotensive Wistar Kyoto rats. Blood pressures were sharply, and transiently raised for about 1 min when rats were picked up by an investigator to be placed in a hot box or immobilized in a restrainer for measuring blood pressure. Therefore, blood pressures should be measured at least 1 min after the rats are put in a restrainer. This new tail cuff method for measuring blood pressure provides reliable mean blood pressure readings in conscious rats.     

Genetics of hypertension: From experimental animals to humans

Essential hypertension affects 20 to 30% of the population worldwide and contributes significantly to cardiovascular mortality and morbidity. Heridability of blood pressure is around 15 to 40% but there are also substantial environmental factors affecting blood pressure variability. It is assumed that blood pressure is under the control of a large number of genes each of which has only relatively mild effects. It has therefore been difficult to discover the genes that contribute to blood pressure variation using traditional approaches including candidate gene studies and linkage studies. Animal models of hypertension, particularly in the rat, have led to the discovery of quantitative trait loci harbouring one or several hypertension related genes, but translation of these findings into human essential hypertension remains challenging. Recent development of genotyping technology made large scale genome-wide association studies possible. This approach and the study of monogenic forms of hypertension has led to the discovery of novel and robust candidate genes for human essential hypertension, many of which require functional analysis in experimental models.     

Molecular aspects of blood pressure regulation.

After 100 years of measurement, reasons for interindividual and populational variation in blood pressure have proven difficult to identify. Use of 24-hr blood pressure monitoring has revealed additional intra-individual variation. Variability in kidney function, extracellular sodium and potassium (Na:K) balance, and factors affecting water, sodium, and potassium resorption obviously affect blood pressure. Alterations in these and additional factors predict development of hypertension. In recent decades the molecular revolution has increased scrutiny of genetic factors contributing to interindividual and populational differences in blood pressure and hypertension. Most investigations across populations and environments have focused on components of the renin-angiotensin-aldosterone system. DNA polymorphisms within this system clearly are associated with blood pressure and hypertension; however, these associations tend to vary across race and ethnicity, ecological settings, and sex. There is clear evidence that polymorphisms at the renin, angiotensinogen, and angiotensin-converting enzyme loci influence both blood pressure and hypertension. In addition, evidence suggests gene-gene and gene-environment interactions along with sex-specific actions of these loci on blood pressure.     

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.     

Endotracheal cuff pressure and tracheal mucosal blood flow: endoscopic study of effects of four large volume cuffs.

Large volume, low pressure endotracheal tube cuffs are claimed to have less deleterious effect on tracheal mucosa than high pressure, low volume cuffs. Low pressure cuffs, however, may easily be overinflated to yield pressures that will exceed capillary perfusion pressure. Various large volume cuffed endotracheal tubes were studied, including Portex Profile, Searle Sensiv, Mallinkrodt Hi-Lo, and Lanz. Tracheal mucosal blood flow in 40 patients undergoing surgery was assessed using an endoscopic photographic technique while varying the cuff inflation pressure. It was found that these cuffs when overpressurised impaired mucosal blood flow. This impairment of tracheal mucosal blood flow is an important factor in tracheal morbidity associated with intubation. Hence it is recommended that a cuff inflation pressure of 30 cm H2O (22 mm Hg) should not be exceeded.     

Non-invasive blood pressure measurement in Yucatan miniature swine using tail cuff sphygmomanometry

A relatively new non-invasive method using a photo-electric flow sensor in non-heated animals, was evaluated for its accuracy in measuring systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) in 40-90 Kg normotensive and hypertensive Yucatan miniature swine. Directly measured SBP, DBP and electronically averaged MAP were recorded from chronic arterial catheters simultaneously with indirect pressures, cuff pressure and tail blood flow under various conditions. In all of the tests tail cuff SBP estimation averaged within 5% of directly measured SBP. The correlation of the two methods was significant (r = .95, P less than 0.01). Over a 60 to 202 mmHg range of blood pressure induced pharmacologically or due to DOCA hypertension, the tail cuff SBP was within 4-10% of directly measured SBP. The tail cuff method was also used to determine DBP and MAP. DBP determined from the tail cuff record was found consistently to underestimate the direct measured DBP by approximately 17%. The two methods were correlated (r = .87 P less than 0.01). The measured tail cuff MAP generally underestimated the direct MAP by approximately 5%. The correlation of directly measured MAP and tail cuff methods was significant (r = .72, P less than 0.01). These results indicated that this system may be used to accurately assess blood pressure in miniature swine.     

Dopamine-Beta-Hydroxylase: An Index of Adrenergic Function in Hypertensive Patients

Previous attempts to assess sympathetic nervous system activity in patients with hypertension have used a variety of physiologic, pharmacologic and biochemical techniques. Results have been conflicting and confusing. Recently, the activity in plasma of the catecholamine synthesizing enzyme, dopamine-beta-hydroxylase (DBH), has been proposed as an index of sympathetic nervous system activity. Studies of apparently healthy subjects show that high values (greater than 60 units per liter) for plasma DBH activity correlate with pronounced daily lability of blood pressure and frequent readings greater than 130/85 mm of mercury. Studies of patients referred for evaluation of established hypertension show significantly higher values for plasma DBH activity in patients with primary hypertension than in those with commonly recognized forms of secondary hypertension—that is, renovascular, renal parenchymal and adrenocortical. Therefore, the measurement of plasma DBH activity may be helpful in the study and differential diagnosis of hypertensive diseases. Measurement of DBH in plasma is inexpensive, reproducible and relatively easy to do.     

Venous cuff pressures from 30 mmHg to diastolic pressure are recommended to measure arterial inflow by plethysmography.

Venous occlusion strain gauge plethysmography (VOP) is based on the assumption that the veins are occluded and arterial inflow is undisturbed by the venous cuff pressure. Literature is not clear concerning the pressure that should be used. The purpose of this study was to determine the optimal venous occlusion pressure at which the highest arterial inflow is achieved in the forearm, calf, and leg by using VOP. We hypothesized that, for each limb segment, an optimal (range of) venous cuff pressure can be determined. Arterial inflow in each limb segment was measured in nine healthy individuals by VOP by using pressures ranging from 10 mmHg up to diastolic blood pressure. Arterial inflows were similar at cuff pressures between 30 and 60 mmHg for the forearm, leg, and calf. Arterial inflow in the forearm was significantly lower at 10 mmHg compared with the other cuff pressures. In addition, arterial inflows at 20 mmHg tended to be lower in each limb segment than flow at higher cuff pressures. In conclusion, no single optimum venous cuff pressure, at which a highest arterial inflow is achieved, exists, but rather a range of optimum cuff pressures leading to a similar arterial inflow. Venous cuff pressures ranging from 30 mmHg up to diastolic blood pressure are recommended to measure arterial inflow by VOP.