Improved accuracy of indirect blood pressure measurement in patients with obese arms

Which cuff should I use? Indirect blood pressure measurement for the diagnosis of hypertension in patients with obesity: a diagnostic accuracy review

OBJECTIVE

To determine the diagnostic accuracy of different methods of blood pressure (BP) measurement compared with reference standards for the diagnosis of hypertension in patients with obesity with a large arm circumference.

DESIGN

Systematic review with meta-analysis with hierarchical summary receiver operating characteristic models. Bland-Altman analyses where individual patient data were available. Methodological quality appraised using Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS2) criteria.

DATA SOURCES

MEDLINE, EMBASE, Cochrane, DARE, Medion and Trip databases were searched.

ELIGIBILITY CRITERIA

Cross-sectional, randomised and cohort studies of diagnostic test accuracy that compared any non-invasive BP tests (upper arm, forearm, wrist, finger) with an appropriate reference standard (invasive BP, correctly fitting upper arm cuff, ambulatory BP monitoring) in primary care were included.

RESULTS

4037 potentially relevant papers were identified. 20 studies involving 26 different comparisons met the inclusion criteria. Individual patient data were available from 4 studies. No studies satisfied all QUADAS2 criteria. Compared with the reference test of invasive BP, a correctly fitting upper arm BP cuff had a sensitivity of 0.87 (0.79 to 0.93) and a specificity of 0.85 (0.64 to 0.95); insufficient evidence was available for other comparisons to invasive BP. Compared with the reference test of a correctly fitting upper arm cuff, BP measurement at the wrist had a sensitivity of 0.92 (0.64 to 0.99) and a specificity of 0.92 (0.85 to 0.87). Measurement with an incorrectly fitting standard cuff had a sensitivity of 0.73 (0.67 to 0.78) and a specificity of 0.76 (0.69 to 0.82). Measurement at the forearm had a sensitivity of 0.84 (0.71 to 0.92) and a specificity 0.75 of (0.66 to 0.83). Bland-Altman analysis of individual patient data from 3 studies comparing wrist and upper arm BP showed a mean difference of 0.46 mm Hg for systolic BP measurement and 2.2 mm Hg for diastolic BP measurement.

CONCLUSIONS

BP measurement with a correctly fitting upper arm cuff is sufficiently sensitive and specific to diagnose hypertension in patients with obesity with a large upper arm circumference. If a correctly fitting upper arm cuff cannot be applied, an incorrectly fitting standard size cuff should not be used and BP measurement at the wrist should be considered.

Comparison of Oscillometric and Intraarterial Systolic and Diastolic Blood Pressures in Lean, Overweight, and Obese Patients

To assess the effect of obesity on blood pressure measurement the authors obtained simultaneous oscillometric and intraarterial systolic and diastolic blood pressures on 188 lean, overweight, class I/II obese, and class III obese subjects. Oscillometric arm cuff/bladder size was selected in accordance with standard guidelines. Oscillometry significantly underestimated systolic and significantly overestimated diastolic blood pressures in each of the 4 weight groups studied. The differences between oscillometric and intraarterial systolic and diastolic pressures were not significantly different among lean, overweight, class I/II obese, and class III obese subjects. Thus, obesity per se does not influence the accuracy of blood pressure measurement. However, oscillometric blood pressure measurement is associated with significant error when compared to intraarterial blood pressure.

Arterial blood pressure monitoring in overweight critically ill patients: invasive or noninvasive?

Introduction

Blood pressure measurements frequently guide management in critical care. Direct readings, commonly from a major artery, are considered to be the gold standard. Because arterial cannulation is associated with risks, alternative noninvasive blood pressure (NIBP) measurements are routinely used. However, the accuracy of NIBP determinations in overweight patients in the outpatient setting is variable, and little is known about critically ill patients. This prospective, observational study was performed to compare direct intra-arterial blood pressure (IABP) with NIBP measurements obtained using auscultatory and oscillometric methods in overweight patients admitted to our medical intensive care unit.

Method

Adult critically ill patients with a body mass index (BMI) of 25 kg/m² or greater and a functional arterial line (assessed using the rapid flush test) were enrolled in the study. IABP measurements were compared with those obtained noninvasively. A calibrated aneroid manometer (auscultatory technique) with arm cuffs compatible with arm sizes and a NIBP monitor (oscillometric technique) were used for NIBP measurements. Agreement between methods was assessed using Bland-Altman analysis.

Results

Fifty-four patients (23 males) with a mean (± standard error) age of 57 ± 3 years were studied. The mean BMI was 34.0 ± 1.4 kg/m². Mean arm circumference was 32 ± 0.6 cm. IABP readings were obtained from the radial artery in all patients. Only eight patients were receiving vasoactive medications. Mean overall biases for the auscultatory and oscillometric techniques were 4.1 ± 1.9 and -8.0 ± 1.7 mmHg, respectively (P < 0.0001), with wide limits of agreement. The overestimation of blood pressure using the auscultatory technique was more important in patients with a BMI of 30 kg/m² or greater. In hypertensive patients both NIBP methods underestimated blood pressure as determined using direct IABP measurement.

Conclusion

Oscillometric blood pressure measurements underestimated IABP readings regardless of patient BMI. Auscultatory measurements were also inaccurate, tending to underestimate systolic blood pressure and overestimate mean arterial and diastolic blood pressure. NIBP can be inaccurate among overweight critically ill patients and lead to erroneous interpretations of blood pressure.

Heritability of ambulatory and office blood pressure phenotypes in Swedish families

OBJECTIVE

The aim of this study was to estimate the heritability of 24-h ambulatory blood pressure and office blood pressure phenotypes in Swedish families.

METHODS

We measured ambulatory and office blood pressure in 260 siblings without antihypertensive treatment from 118 families. Blood pressure heritability was estimated using standard quantitative genetic variance component analysis implemented in the 'SOLAR' software package after adjustment for significant covariates.

RESULTS

Heritability values were significant for night-time systolic (37%), diastolic (32%) and mean (32%) ambulatory blood pressure (P < 0.05 for all). During daytime, systolic ambulatory blood pressure was significantly heritable (33%, P < 0.05). Twenty-four-hour systolic (30%) and diastolic (29%) ambulatory blood pressure also had significant values of heritability (P < 0.05). Pulse pressure ambulatory blood pressure was significantly heritable over 24 h (63%, P < 0.01), during daytime (53%, P < 0.01) and at night (34%, P < 0.05). None of the office blood pressure phenotypes had a significant heritability.

CONCLUSIONS

We conclude that ambulatory blood pressure, in particular at night, seems better than office blood pressure to capture the heritable part of blood pressure, suggesting that ambulatory blood pressure may be a more exact estimate of an individual's true blood pressure. Genetic studies using ambulatory blood pressure as the phenotype are likely to be more powerful than those using office blood pressure. The high heritability of pulse pressure ambulatory blood pressure indicates that variation in arterial stiffness in subjects free from antihypertensive medication is strongly affected by genetic factors.

Effect of standard cuff on blood pressure readings in patients with obese arms. How frequent are arms of a 'large circumference'?

OBJECTIVE

To measure the effect on blood pressure readings when a standard cuff is used on patients with arms of a large circumference, and to determine the frequency of arms of a large circumference.

SUBJECTS

Blood pressures were taken in 120 subjects with an arm circumference greater than 33 cm. Also, the arm circumference was determined in 244 patients from a family health unit, and in 216 patients from a hypertension clinic.

METHOD

A mercury sphygmomanometer and two different cuff sizes were used in a random sequence; therefore, 60 patients' blood pressure were first measured with a large cuff, followed by a standard cuff; the opposite sequence was then applied for another 60 patients. With the obtained values and using a regression analysis, the difference in blood pressure overestimation was calculated. Arm circumference measurement percentages were used to determine the frequency of arms of a large circumference.

RESULTS

Both systolic and diastolic blood pressures were significantly greater when the standard cuff was used. For every 5 cm increase in arm circumference, starting at 35 cm, a 2-5 mmHg increase in systolic blood pressure, and a 1-3 mmHg increase in diastolic blood pressure was observed. The prevalence of arms with a large circumference in the family medicine unit and hypertension clinic was 42% and 41.8%, respectively.

CONCLUSIONS

There is an overestimation of blood pressure when a standard cuff is used in obese subjects. The high prevalence of these individuals in our environment, both in the hypertensive and normotensive population, makes it necessary to have on hand different sizes of cuffs for taking blood pressure in order to avoid incorrect decisions.

Association between serum leptin levels and 24-hour blood pressure in obese women

OBJECTIVE

To assess the relationship between serum leptin and 24-hour blood pressure (BP) in obese women, according to body fat distribution.

RESEARCH METHODS AND PROCEDURES

A cross-sectional study was carried out in a population of 70 nondiabetic, normotensive, obese women (40 with android and 30 with gynoid type of obesity) and 20 nonobese healthy women as a control group. All subjects underwent 24-hour ambulatory BP monitoring. Blood samples were collected for serum leptin and plasma insulin measurements. Total cholesterol and high-density lipoprotein cholesterol were also measured.

RESULTS

Serum leptin levels were significantly higher in obese subjects than in controls, and they were more elevated in android obese women than in gynoid ones. Leptin levels were positively related to body mass index (BMI), insulin, and waist and hip circumferences in the android group. Among gynoid subjects, leptin levels showed positive associations with BMI and insulin. In women with android obesity, strong positive correlations (p < 0.001) were found between leptin levels and 24-hour systolic BP (SBP), daytime SBP, nighttime SBP, 24-hour diastolic BP (DBP), and daytime DBP. Multiple regression analyses, including age, insulin and leptin concentrations, BMI, and waist and hip circumferences on 24-hour and daytime SBP and DBP, showed that only leptin levels contributed to the variability of BP.

CONCLUSIONS

Our study shows that serum leptin levels are directly related to 24-hour BP levels in normotensive women with android fat distribution, independently of BMI.

Large waist circumference and risk of hypertension

OBJECTIVE

To examine the relationship between 24 h ambulatory blood pressure monitoring and three commonest anthropometric measurements for obesity--body mass index (BMI), waist-to-hip ratio (WHR) and waist circumference (W).

DESIGN

Cross-sectional survey among outpatients at the Obesity Research Center.

SUBJECTS AND METHODS

Four-hundred and sixty-one overweight or obese subjects, non-diabetic, otherwise healthy, aged 20-70 y, of either sex, were consecutively recruited. All subjects underwent 24 h ambulatory blood pressure monitoring. The population study was separated in normotensive and hypertensive males and females and the possible risk factors for hypertension (W, WHR, BMI and age) were subdivided into different classes of values.

RESULTS

Logistic regression shows that W is the most important anthropometric factor associated with the hypertensive risk. Among males with W> or =102 cm the odds ratio (OR) for hypertension is three times that of males with W<94 cm using casual BP measure (OR 3.04), nearly four times higher using 24 h BP mean (OR 3.97), and even five times higher using day-time BP mean (OR 5.19). Females with W> or =88 cm have a risk for hypertension twice that of females with W<80 cm, whatever BP measurement was take (casual, 24 h or day-time). Males with WHR> or =0.96 and females with WHR> or =0.86 show significant OR for hypertension only by 24 h BP measurement and by day-time BP measurement. BMI seems to have no significant relationship to hypertensive risk. Age shows a significant relationship to hypertensive risk only considering males aged > or =55 y and females aged > or =50 y.

CONCLUSION

The waist circumference seems to have a strong association with the risk of hypertension, principally by the ambulatory BP monitoring, when compared with casual BP measurement.

Tissue-specific regulation of type 1 angiotensin II receptor mRNA levels in the rat

Most of the biological effects of the renin-angiotensin system are mediated by the binding of angiotensin II (Ang II) to the type 1 Ang II (AT1) receptor, the predominant receptor subtype present after fetal life. To study tissue-specific regulation of the expression of the AT1 receptor in the rat, we altered activity of the renin-angiotensin system by feeding rats a low (0.07% NaCl), normal (0.3% NaCl), or high (7.5% NaCl) salt chow for 14 days; infusing Ang II (200 ng/kg per minute IP) or vehicle for 7 days; and administering an angiotensin-converting enzyme inhibitor (captopril, 100 mg/dL in the drinking water) or vehicle for 7 days. Renin, angiotensinogen, and total AT1 receptor mRNA levels were measured by slot-blot hybridization with cRNA probes, and AT1 receptor subtypes (A and B) were measured by reverse transcription-polymerase chain reaction in the presence of a cRNA internal standard. Plasma renin concentration and renal renin, renal and hepatic angiotensinogen, and hepatic AT1 receptor mRNA levels were all inversely related to salt intake; in contrast, renal AT1 receptor mRNA levels were significantly lower in rats fed low salt, a difference that was exclusively due to a decrease in the AT1A subtype. This difference did not appear to be mediated by a change in the circulating levels of Ang II, because Ang II infusion reduced plasma renin concentration and renal renin mRNA with no effect on either angiotensinogen or AT1 receptor mRNA levels in kidney or liver, renal Ang II receptor density (determined by in situ autoradiography) decreased, presumably via a posttranscriptional mechanism. Similarly, inhibition of Ang II generation with captopril increased plasma renin concentration and renal renin mRNA levels without altering renal or hepatic angiotensinogen mRNA or renal AT1 receptor mRNA levels. Thus, AT1 receptor gene expression is regulated in a tissue-specific manner that is distinct from other components of systemic and local renin-angiotensin systems and that appears to be mediated by a mechanism other than through changes in the circulating levels of Ang II.

Systematic difference between blood pressure readings caused by cuff type

In this study we determine whether blood pressure readings using a cuff of fixed size systematically differed from readings made with a triple-bladder cuff (Tricuff) that automatically adjusts bladder width to arm circumference and assessed subsequent clinical and epidemiological effects. Blood pressure was measured with a standard cuff or a Tricuff in 454 patients visiting an outpatient clinic in the Seychelles (Indian Ocean). Overall means of within-individual standard cuff-Tricuff differences in systolic and diastolic blood pressures were examined in relation to arm circumference and sex. The standard cuff-Tricuff difference in systolic and diastolic blood pressures increased monotonically with circumference (from 4.7 +/- 0.8/3.2 +/- 0.7 mm Hg for arm circumference of 30 to 31 cm to 10.0 +/- 1.1/8.0 +/- 0.9 mm Hg for arm circumference > or = 36 cm) and was larger in women than men. Multivariate linear regression indicated independent effects of arm circumference and sex. Forty percent of subjects with a diastolic blood pressure of > or = 95 mm Hg measured with a standard cuff had values less than 95 mm Hg measured with a Tricuff. Extrapolation to the entire population of the Seychelles decreased the prevalence of blood pressure greater than or equal to 160/95 mm Hg by 11.5% and 24.0% in men and women, respectively, aged 35 to 64 years. The age-adjusted effect of body mass index on systolic and diastolic blood pressures decreased twofold using blood pressure readings made with a Tricuff instead of a standard cuff.(ABSTRACT TRUNCATED AT 250 WORDS)