Blood pressure measurement: current practice and future trends

The Reliability of Noninvasive Blood Pressure Measurement Through Layers of Autumn/Winter Clothing: A Prospective Study

INTRODUCTION

In recent years a number of publications have appeared describing noninvasive blood pressure (NIBP) measurement with 1 layer of light cloth between the patient's skin and the NIBP cuff. In this study we investigated the reliability of NIBP measurements performed through 2 and 3 layers of autumn/winter clothing in 2 research groups: healthy volunteers and patients.

METHODS

Oscillometric NIBP measurements were made in a random order: 1) on the exposed arm; 2) on the arm covered by a standardized cotton and polar fabric test sleeve; and 3) with the arm covered by a cotton-polar fabric and down jacket test sleeve. The time taken for measurement was also recorded.

RESULTS

We performed measurement in 101 volunteers and 50 patients and found no clinically or statistically significant differences in NIBP. Mean±SD values in the volunteer group were 1) 130/80±14/8 mm Hg; 2) 130/81±15/8 mm Hg; and 3) 128/81±14/8 mm Hg. In the patient group the values were 1) 140/82±34/15 mm Hg; 2) 140/84±33/15 mm Hg; and 3) 137/84±32/15 mm Hg. Measuring over a sleeved arm extended the time of measurement by an average of 3.5 s in comparison with bare arm measurement.

CONCLUSIONS

Our findings confirm that it is possible to perform reliable NIBP measurements over 2 and 3 layers of autumn/winter clothing. Measuring NIBP with a clothed arm does not show clinical or statistically significant differences in comparison with measurements performed on the bare arm.

A critical look at nursing observations

Our experience has suggested that not only do nurses on hospital wards waste time making too many unnecessary clinical observations, but that it is very difficult to persuade them to modify the pattern of their practice. We therefore conducted a survey by questionnaire among trained nurses in one health district of their everyday ward practice and attitudes to clinical observations. This showed that whilst a majority of nurses questioned believe in the importance of routine observations for patient care, there is a lack of consistency in the criteria and communication procedures used that must seriously limit the value of the information obtained by the individual nurse. We believe that uncritical faith in routine observations is a barrier to rationalizing procedures to optimize efficient use of the professional skills of ward nurses in this regard. There is need for more thought to be given to the problem and in particular it is important that doctors play a more active role in decision making.

Assessing the prevalence of hypertension in populations: are we doing it right?

BACKGROUND

Although it is well recognized that the diagnosis of hypertension should be based on blood pressure (BP) measurements taken on several occasions, notably to account for a transient elevation of BP on the first readings, the prevalence of hypertension in populations has often relied on measurements at a single visit.

OBJECTIVE

To identify an efficient strategy for assessing reliably the prevalence of hypertension in the population with regards to the number of BP readings required.

DESIGN

Population-based survey of BP and follow-up information.

SETTING AND PARTICIPANTS

All residents aged 25-64 years in an area of Dar es Salaam (Tanzania).

MAIN OUTCOME MEASURES

Three BP readings at four successive visits in all participants with high BP (n = 653) and in 662 participants without high BP, measured with an automated BP device.RESULTS BP decreased substantially from the first to third readings at each of the four visits. BP decreased substantially between the first two visits but only a little between the next visits. Consequently, the prevalence of high BP based on the third reading--or the average of the second and third readings--at the second visit was not largely different compared to estimates based on readings at the fourth visit. BP decreased similarly when the first three visits were separated by 3-day or 14-day intervals.

CONCLUSIONS

Taking triplicate readings on two visits, possibly separated by just a few days, could be a minimal strategy for assessing adequately the mean BP and the prevalence of hypertension at the population level. A sound strategy is important for assessing reliably the burden of hypertension in populations.

Early observations of the effect of extracorporeal shockwave lithotripsy on blood pressure: a prospective randomized control clinical trial

OBJECTIVE

To determine, in a randomized controlled clinical trial, the effect of extracorporeal shock wave lithotripsy (ESWL) on blood pressure.

PATIENTS AND METHODS

The trial included 228 patients with small (< 15 mm) asymptomatic calyceal stones who were randomised to undergo ESWL (113 patients) or to an untreated (observed) control group (115 patients). Blood pressure was recorded at randomization using a standardized protocol. Patients undergoing ESWL received a mean (SD) of 5281 (3462) shocks over a mean of 1.75 sessions on one of two lithotripters. Patients were then followed annually, assessing blood pressure and changes in medication. Data were analysed on an intention-to-treat basis.

RESULTS

At randomization, 43% of patients in the control group and 53% in the ESWL group were hypertensive. Of the 228 randomized, 200 patients completed at least one annual follow-up, of whom 192 (93 in the control and 99 in the ESWL group) had their blood pressure recorded. The mean follow-up was 2.2 years; 35 (37%) patients in the control and 46 (46%) in the ESWL group were hypertensive (P = 0.19). Seven (7%) patients in the control group and 11 (11%) in the ESWL group were newly diagnosed to be hypertensive (P = 0.35).

CONCLUSIONS

In this randomized controlled clinical trial there was no evidence that ESWL causes changes in blood pressure.

Blood pressure screening, management and control in England: results from the health survey for England 1994

OBJECTIVE

To assess the current levels of awareness, treatment and control of hypertension in England and to determine the number and type of drugs prescribed.

DESIGN

A cross-sectional household-based survey of English adults.

SUBJECTS

A random sample from the adult English population of 12,116 adults who participated in the 1994 Health Survey for England.

MAIN OUTCOME MEASURES

Prevalences of treatment hypertension, awareness and control.

RESULTS

Using a definition of hypertension as a systolic blood pressure > or = 160 mmHg or a diastolic blood pressure > or = 95 mmHg, or a patient's being administered antihypertensive treatment, the prevalence of awareness of hypertension was 63%. Among hypertensives, 50% were receiving treatment and 30% had their hypertension controlled (< 160 mmHg/95 mmHg). Awareness, treatment and control rates are considerably lower than the most recently reported rates from the USA. Diuretics and beta-blockers remain the most common antihypertensive agents used in England.

CONCLUSION

There is considerable scope for improving the treatment and control of hypertension in the English adult population.

Comparative accuracy of three automated techniques in the noninvasive estimation of central blood pressure in men

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

Clinical evaluation of the Philips 5306B electronic blood pressure monitor

A patient-recorded home blood pressure series using an electronic manometer is used increasingly to provide a representative sample of blood pressure (BP) and to avoid frequent office visits and office rises in BP. Few of the many available electronic manometers have undergone rigorous testing and validation against a standard mercury manometer. We have evaluated fully the commonly used Philips 5306B electronic manometer against a Hawksley random zero mercury manometer employing a randomized, single-blind, crossover design and statistical analyses that have been validated previously. Although correlation coefficients greater than 0.9 were achieved for both systolic and diastolic pressure, the electronic manometer gave systolic and diastolic readings that differed from the mercury manometer by greater than or equal to +/- 5 mmHg in some 33% of patients and by greater than or equal to +/- 1- mmHg in some 18% of patients. Thus, in common with most electronic manometers, the Philips 5306B needs to be improved to correlate more closely with the standard mercury manometer to enhance its clinical usefulness.

Correlates of blood pressure in 15 year olds in the west of Scotland

STUDY OBJECTIVE

The aim was to examine social and physical correlates of blood pressure in 15 year olds.

DESIGN

This was the first, baseline, sweep of a longitudinal survey of 15 year olds based on a two stage stratified clustered random sample.

SETTING

The Central Clydeside Conurbation, in the West of Scotland. In 1981 this had a population of 1.7 million and a standardised mortality ratio (relative to Scotland as a whole) of 109.

SUBJECTS

A random sample of households containing 15 year olds were approached by Strathclyde Regional Council; 70% agreed to have their names passed on to the MRC (15% refused, 10% could not be contacted, and 5% had moved). Of these 1177, 11% refused to participate, 3% were not contactable/had moved, and 4% did not provide full data. Complete blood pressure data are available for 959 15 year olds (464 males and 495 females).

MEASUREMENTS AND MAIN RESULTS

Blood pressure, pulse rate, height, weight, and room temperature were measured by nurses in the subjects' homes. Smoking, drinking, and frequency of vigorous exercise were self reported. Maternal height, birthweight, occupation of head of household, and housing tenure were reported by parents. After controlling for the other variables, systolic blood pressure was significantly associated with weight, pulse rate, and room temperature in males and with weight, pulse rate, housing tenure, smoking, and exercise in females. Diastolic blood pressure was associated with room temperature in males and with mother's height, pulse rate, and housing tenure in females. Controlling for current weight, birthweight was inversely related to systolic blood pressure in males and positively associated in females, though in neither case were these associations statistically significant.

CONCLUSIONS

In males, blood pressure was mainly related to anthropometric factors whereas in females it was additionally related to socioeconomic and behavioural variables. Although not reaching significance, the weight standardised relationship between birthweight and systolic blood pressure was consistent for males, but not females, with those reported by recent British studies of children and adults. The longitudinal design of this study will allow us to examine correlates of blood pressure in the same individuals as they reach social and physical maturity.

Ambulatory blood pressure monitoring in the evaluation of drug efficacy

Conventional clinic measurement of blood pressure is influenced by many factors that make the technique unsuitable for the assessment of antihypertensive drug efficacy. The major drawback of conventional measurement is that it cannot indicate the duration of drug effect or the influence of antihypertensive drugs on nocturnal blood pressure. Noninvasive 24-hour ambulatory blood pressure measurement has a number of advantages over conventional measurement: it provides a profile of blood pressure over the 24-hour period; it detects white coat responders; it is free of regression to the mean and the placebo response, thereby making it possible to consider efficacy studies which need not have a placebo phase; it enables considerably more observations than is possible with clinic measurement by increasing the power of studies, which may reduce significantly the numbers of patients needed for antihypertensive drug studies. Twenty-four-hour ambulatory blood pressure measurement offers the opportunity to study antihypertensive drugs in fewer patients with greater accuracy than is possible with conventional clinic measurement and should be a mandatory requirement for such studies.

Clinical evaluation of a novel ambulatory automatic blood pressure monitoring system

Reliability and reproducibility of a new automatic ambulatory blood pressure recorder were tested on 31 subjects (18 normotensives and 13 hypertensives). Of 3688 recordings, 1424 measurements were cross-checked with a sphygmomanometer in standing or sitting position at the beginning and at the end of a twenty-four hour monitoring period. In the normotensive subjects cross-checkings were performed also during a treadmill exercise stress test. Analysis of variance did not indicate statistical differences between the two types of measurement (p greater than 0.09 for systolic and p greater than 0.62 for diastolic), and a significant linear correlation was found at rest (r = 0.99, p less than 0.001 for systolic and r = 0.98, p less than 0.001 for diastolic pressure). During the effort test the device was unable to correctly measure blood pressure values after the first step. During the twenty-four hour monitoring period only 1.1% of the preprogrammed measurements were lost for each subject. The recorder seems to be a suitable and reliable tool for automatic blood pressure monitoring.

Measuring blood pressure in the elderly: does atrial fibrillation increase observer variability?

OBJECTIVE

To compare the interobserver and intraobserver variability of blood pressure measurements in geriatric patients in atrial fibrillation and in sinus rhythm.

DESIGN

Prospective assessment of blood pressure measurements carried out in random order in two groups of elderly patients by five doctors unaware of the aims of the study.

SETTING

Acute assessment wards for geriatric medicine, Cardiff Royal Infirmary.

PATIENTS

50 Elderly patients in sinus rhythm and 50 in atrial fibrillation.

MAIN OUTCOME MEASURES

Interobserver and intraobserver variability of blood pressure measurements in the two groups expressed as the coefficient of variability and compared by the Mann-Whitney U test.

RESULTS

Interobserver variability was significantly greater in the patients with atrial fibrillation for both systolic and diastolic pressures. Intraobserver variability was significantly greater in the atrial fibrillation group for diastolic pressures but the difference was not significant for systolic pressures. These differences were not related to pulse rate, age, or level of blood pressure.

CONCLUSIONS

The findings suggest that in the presence of atrial fibrillation physicians' interpretations of Korotkoff sounds are less uniform, which may have important clinical implications. Possibly a standardised methodology may overcome this problem.

Does extracorporeal shockwave lithotripsy cause hypertension?

Several series have suggested that the incidence of hypertension following extracorporeal shockwave lithotripsy (ESWL) may be as high as 8%. In this study, changes in blood pressure and the incidence of hypertension have been observed in 733 patients 12 to 44 months after renal ESWL on the Dornier HM3. The incidence of hypertension following ESWL was 8.1%. In patients with a pre-ESWL diastolic pressure less than 90 mmHg, the incidence of those with a diastolic greater than or equal to 100 mm Hg post-operatively was significantly greater than that predicted by historical data. There was no overall change in the mean blood pressure of the group. The hypertensive risk of ESWL remains unclear. However, blood pressure surveillance should be performed following ESWL and a prospective study is required.

Age differences in cardiovascular and cognitive performance under noise conditions

Ambient white noise (80 dB), compared with quiet (52-dB) testing conditions, improved the performance of elderly and younger subjects on simple addition. Reliable age-related interactions were found on health measures of systolic and diastolic blood pressure, as well as heart rate. Heightened sensory conditions reduced the physiological measures of arousal in the younger group, whereas significant cardiovascular reactivity was found among the older group. The results are suggestive of the potential for increased cardiovascular risk as a function of sensory stimulation in the elderly despite improvements on cognitive tasks. Additional research is needed to evaluate the multidimensional effects of extended sensory stimulation on the elderly.

Effect of timing and number of baseline blood pressure determinations on postural blood pressure response

We hypothesized that the blood pressure response to standing may depend on the method of establishing baseline blood pressure. Three hundred elderly subjects previously completed a postural blood pressure protocol with three supine baseline blood pressure readings obtained two minutes apart prior to standing. Comparison of the readings showed a significant drop between the first and the second (P less than .001) but not between the second and third supine systolic blood pressures. The difference between the first supine systolic blood pressure and the one minute standing blood pressure was significantly greater than that between the third supine systolic blood pressure and the one minute standing blood pressure (P less than .001). A second group was prospectively studied to determine whether the change in blood pressure after standing was greater if only a single baseline reading was taken rather than multiple readings, and whether the decline in blood pressure over three readings was related to duration supine or to the number of blood pressures taken. This group also demonstrated a decline in systolic blood pressure with three serial readings. We conclude that supine blood pressure declines significantly between the first and second readings taken two minutes apart and is secondary to the repetition of readings and not the duration supine. However, this change in supine blood pressure does not significantly alter the blood pressure response to standing. Thus, it appears that a single baseline supine blood pressure measurement is adequate for determining the postural blood pressure response, and that pooling of multiple baseline readings may not be appropriate.

New insights and new approaches for the treatment of essential hypertension: selection of therapy based on coronary heart disease risk factor analysis, hemodynamic profiles, quality of life, and subsets of hypertension

The pharmacologic therapy of mild primary hypertension (diastolic blood pressure less than 105 mm Hg) has effectively reduced hypertensive arteriolar end organ disease such as cerebrovascular accidents, congestive heart failure, and nephropathy, but there has been no convincing evidence that coronary heart disease (CHD) or its complications, acute myocardial infarction or angina, have been reduced. The risks of therapy with certain antihypertensive drugs may outweigh their treatment benefits as it relates to CHD. The optimal treatment strategy should be to reduce all CHD risk factors, reverse the hemodynamic abnormalities present by lowering the systemic vascular resistance (SVR), preserving cardiac output (CO) and perfusion, and to select the best antihypertensive drug for concomitant medical diseases or problems while maintaining a good quality of life. Antihypertensive drugs that have favorable or neutral effects on CHD risk factors include alpha blockers, calcium channel blockers, central alpha agonists, and angiotensin-converting enzyme inhibitors. On the other hand, diuretics and beta blockers without intrinsic sympathomimetic activity have unfavorable effects on many CHD risk factors. Baseline and serial evaluation of the effects of these drugs on serum lipids, lipid subfractions, glucose, uric acid, electrolytes, exercise tolerance, left ventricular hypertrophy, blood pressure, SVR, CO, perfusion, concomitant diseases, and side effects is necessary to evaluate overall cardiovascular risk.

Monitoring in emergency medicine

Clinical observation is the most valuable monitoring technique we have. Complexity and invasiveness of monitoring increases from prehospital care to Emergency Department, to Anaesthesia and Intensive Care. Many methods of monitoring have specific applications. Non-invasive blood pressure monitoring has no advantages over conventional cuff methods, other than freeing the hands of the operator. Non-invasive cardiac output measurement, transcutaneous oxygen and carbon dioxide measurement are unlikely to play a major role in the foreseeable future in the emergency setting. The most exciting development in recent years has been the widespread availability of pulse oximetry, which allows beat by beat analysis of haemoglobin oxygen saturation.

Comparison of a new portable electronic sphygmomanometer (Copal UA251) with the Hawksley random zero machine

The performance of the Copal Digital Sphygmomanometer UA251, a new semi-automatic blood pressure recorder, was evaluated by comparing the results obtained simultaneously and on the same arm using the standard zero-muddler sphygmomanometer. The study was performed on 67 hypertensive patients displaying a wide range of blood pressure and arm circumference. The agreement was acceptable with a mean difference, using the first set of readings of -0.45 (S.D. 2.9, range 8 to -5) and -0.95 (S.D. 2.6, range 6 to -4) mmHg for the systolic and diastolic pressures respectively. The repeatability of the Copal machine was also good; the mean difference between first and second measurements was -0.21 (S.D. 3.4, range 11 to -11) and -0.69 (S.D. 1.9, range 5 to -8) mmHg for systolic and diastolic readings respectively. Since this electronic machine has an acceptable accuracy, is readily portable, simple to use and relatively inexpensive, it seems suitable for use both in clinics and for more frequent monitoring of blood pressure throughout the day.

Ambulatory and exercise-induced blood pressure responses in type I diabetic patients and normal subjects

We evaluated the ambulatory blood pressure (BP) readings during daily activities and compared the values with the casual office BPs in 12 type I diabetic patients and 12 age-matched, non-diabetic normal controls. The BP responses to 750 kpm/min exercise work load on bicycle ergometer were also evaluated in all the subjects. The mean ambulatory BPs were significantly higher in the diabetic patients compared with non-diabetic subjects. However, the ambulatory and casual office BPs were remarkably similar in each group. Mean peak exercise BPs were higher in the diabetics, but significantly so for diastolic BP (P less than 0.05) and mean arterial pressure (MAP) (P less than 0.01). The mean ambulatory MAP significantly correlated with the casual office MAP in both the diabetics (r = 0.75, P less than 0.005) and non-diabetics (r = 0.58, P less than 0.02). A significantly positive relationship (r = 0.87, P less than 0.001) existed between the ambulatory and peak exercise MAP in the diabetics, but not in the non-diabetic subjects. The mean peak exercise BP responses were significantly (P less than 0.01) higher in the diabetic patients with proliferative retinopathy vs. those with non-proliferative retinopathy. We conclude that casual office BPs reflect the ambulatory values in both diabetics and non-diabetics. Exaggerated BP responses to exercise are found in diabetic patients, especially in the presence of proliferative retinopathy. These findings are suggestive of possible defects in the cardiovascular, autonomic and autoregulatory mechanisms that maintain a normal MAP during daily stresses and exercise in the diabetic patients.

Detection of hypertension in accident and emergency departments

Routine blood pressure measurements are performed on all non-ambulatory patients attending the Accident and Emergency Department, Leicester Royal Infirmary, England. However, the patient's general practitioner is not always informed of the reading, even if it is found to be raised. One of the chief reasons for this omission is the fact that single, elevated blood pressure readings taken in an accident and emergency department are considered to be of doubtful significance. Sixty patients with a single, elevated blood pressure measurement were studied. Fifteen of these patients were found to continue to have an elevated blood pressure measurement when reviewed in a quiet, relaxed environment. Fourteen of these 15 patients are currently being treated for hypertension after independent assessment by their family practitioners. It was concluded that single, elevated blood pressure readings are useful indicators of hypertension in non-ambulatory patients attending accident and emergency departments. It is, therefore, important to inform general practitioners of incidentally raised blood pressure readings.

Blood pressures higher in the home than in the clinic in rural Kenya

The conditions under which blood pressures (BPs) are recorded are critical, and it has been demonstrated several times that BPs measured in the home are lower than those measured in the clinic. However, these comparisons are based on home BPs measured by the patients or their friends and relatives and clinic BPs measured by doctors and nurses. To our knowledge, no comparison of home and clinic BPs measured by the same observer has been reported, and we present the results of such a study which is the first to demonstrate higher BPs in the home environment, perhaps reflecting the unacculturated nature of the study population.