Clinical Comparison of Automatic, Noninvasive Measurements of Blood Pressure in the Forearm and Upper Arm With the Patient Supine or With the Head of the Bed Raised 45°: A Follow-Up Study

A Pilot Study: Comparison of Arm Versus Ankle Noninvasive Blood Pressure Measurement at 2 Different Levels of Backrest Elevation

BACKGROUND

Standard practice for obtaining noninvasive blood pressure includes arm blood pressure (BP) cuff placement at the level of the heart; however, some critical care patients cannot have BPs taken in their arm because of various conditions, and ankle BPs are frequently used as substitutes.

OBJECTIVE

The aim of this study was to determine if there was a significant variation between upper arm and ankle BP measurements at different backrest elevations with consideration of peripheral edema factors.

METHODOLOGY

After institutional review board approval was obtained, a pilot study was implemented to evaluate noninvasive BP measurements of the arm and ankle with backrest elevation at 0° and 30° in a population of medical intensive care unit patients. Participants served as their own controls and were randomly assigned to left- versus right-side BP readings. Data were also collected on presence of arm versus ankle edema.

RESULTS

A total of 30 participants enrolled in the study and provided 120 BP measurements. Blood pressure readings were analyzed in terms of diastolic and systolic findings as well as backrest elevations and edema presence. Thirteen participants presented with either arm or ankle edema. There was a statistical difference between the systolic arm and ankle BP measurements in the 0° (P = .008) and 30° (P < .001) backrest elevation positions. The correlation between arm and ankle diastolic BP is greater for participants without ankle edema (P = .038, r = 0.54) than for participants with ankle edema (P = .650, r = 0.14), but it is not statistically significant (P = .47).

DISCUSSION

Even though ankle BPs are often substituted for arm BPs when the arm is unable to be used, ankle BPs and arm BPs are not interchangeable. Adjustments in backrest elevation and considerations of edema do not normalize the differences. Blood pressures obtained from the ankle are significantly greater than those obtained from the arm. This information needs to be considered when arms are not available and legs are used as surrogates for the upper arm.

Level of Agreement Between Forearm and Upper Arm Blood Pressure Measurements in Patients With Large Arm Circumference

PURPOSE

The purpose of the study was to determine if forearm blood pressures (BPs) measured in three different locations agree with the recommended upper arm location for noninvasive BP measurement.

DESIGN

A method-comparison design was used.

METHODS

In a convenience sample of postanesthesia care unit patients with large upper arm circumference, BP's were obtained in three different forearm locations (lower forearm, middle forearm, and upper forearm) and compared to upper arm BP using an automated BP measuring device. The level of agreement (bias ± precision) between each forearm location and the upper arm BP was calculated using standard formulas. Acceptable levels of agreement based on expert opinion were set a priori at bias and precision values of less than ±5 mm Hg (bias) and ±8 mm Hg (precision).

FINDINGS

Forty-eight postanesthesia patients participated in the study. Bias and precision values were found to exceed the acceptable level of agreement for all but one of the systolic and diastolic BP comparisons in the three forearm BP locations. Fifty-six percent of all patients studied had one or more BP difference of at least 10 mm Hg in each of the three forearm locations, with 10% having one or more differences of at least 20 mm Hg.

CONCLUSIONS

The differences in forearm BP measurements observed in this study indicate that the clinical practice of using a forearm BP with a regular-sized BP cuff in place of a larger sized BP cuff placed on the upper arm in postanesthesia care unit patients with large arm circumferences is inappropriate. The BPs obtained at the forearm location are not equivalent to the BPs obtained at the upper arm location.

Blood pressure and the obese

With the prevalence of obesity escalating globally, an increasing number of patients who are obese are seeking elective or requiring emergency surgery. Certified registered nurse anesthetists are challenged to provide vigilant, safe care. The ability to provide supportive therapy and make anesthetic adjustments is often hindered with obesity. Although technological advancements may enhance patient care delivery, health care providers must question why and how specific tasks are performed. Health care providers should challenge themselves to acquire and evaluate current evidence that enables communication with colleagues, dissemination of findings to health care providers worldwide, and implementation of evidence-based practice.

Blood pressure assessment in severe obesity: validation of a forearm approach

OBJECTIVE

Obesity is frequently associated with systemic hypertension. Blood pressure measure is inaccurate in severely obese patients because of poor cuff size fitting. The aim of the study is to assess the degree of agreement between the intra-arterial method as the gold standard vs. noninvasive methods, i.e., forearm blood pressure and upper-arm blood pressure measures.

DESIGN AND METHODS

A total of 1285 measures of intra-arterial and forearm blood pressure were taken in 51 severely obese patients in a supine position in the operating and the recovery room. A subset of 352 upper-arm measures were taken in the recovery room and compared to the intra-arterial and the forearm methods.

RESULTS

Correlation between the intra-arterial and the forearm measures was 0.90 (P < 0.001) for the 2570 data (systolic and diastolic). Compared to intra-arterial, the forearm method overestimated systolic (6 ± 16 mm Hg, P < 0.001) and underestimated diastolic blood pressure (2 ± 11 mm Hg, P = 0.03). Compared to intra-arterial, upper-arm underestimated systolic (8 ± 16 mm Hg, P < 0.01) and overestimated diastolic blood pressure (9 ± 7 mm Hg, P < 0.001).

CONCLUSION

The magnitude of differences between the intra-arterial and forearm method was less than differences between the intra-arterial and upper-arm method. Our results suggest that forearm method may be a more accurate alternative to upper-arm measurement to assess blood pressure in severely obese patients.

Postanesthesia patients with large upper arm circumference: is use of an "extra-long" adult cuff or forearm cuff placement accurate?

The purpose of this study was to determine if blood pressure (BP) measured in the forearm or with an extra-long BP cuff in the upper arm accurately reflects BP measured in the upper arm with an appropriately sized BP cuff in patients with large upper arm circumference. A method-comparison design was used with a convenience sample of 49 PACU patients. Noninvasive blood pressures were obtained in two different locations (forearm; upper arm) and in the upper arm with an extra-long adult and recommended large adult cuff sizes. Data were analyzed by calculating bias and precision for the BP cuff size and location and Student's t-tests, with P < .0125 considered significant. Significantly higher forearm systolic (P < .0001) and diastolic (P < .0002) BP measurements were found compared to BP obtained in the upper arm with the reference standard BP cuff. Significantly higher systolic (t(48df) = 5.38, P < .0001), but not diastolic (t(48df) = 4.11, P < .019), BP differences were found for BP measured with the extra-long cuff at the upper arm site compared to the upper arm, reference standard BP. Findings suggest that the clinical practice of using the forearm or an extra-long cuff in the upper arm for BP measurement in post anesthesia patients with large upper arm circumferences may result in inaccurate BP values.

Forearm and Upper-Arm Oscillometric Blood Pressure Comparison in Acutely III Adults

When patients’ upper arms are not accessible and/or when cuffs do not fit large upper arms, the forearm site is often used for blood pressure (BP) measurement. The purpose of this study is to compare forearm and upper-arm BPs in 70 acutely ill adults, admitted to a community hospital’s 14-bed ICU. Using Philips© oscillometric monitors, three repeated measures of forearm and upper-arm BPs are obtained with head of bed flat and with head of bed elevated at 30°. Arms are resting on the bed. Paired t tests show statistically significant differences in systolic BPs, diastolic BPs, and mean arterial pressures in the supine and head-elevated positions. Bland—Altman analyses indicate that forearm and upper-arm oscillometric BPs are not interchangeable in acutely ill adults.

The effects of anatomical structures on adult forearm and upper arm noninvasive blood pressures

OBJECTIVE

The purpose of this study was to determine the effects of anatomical structures, specifically limb subcutaneous tissue and vessels on differences between forearm and upper arm oscillometric noninvasive blood pressure measurements.

METHODS

Nineteen volunteers with a mean age of 21.7+/-3.7 years and without peripheral vascular disease or coronary artery disease participated. Circumference and skinfolds were measured for the upper arm and forearm. Body mass indices were calculated. Ultrasound measured vessel depth and diameter in the upper arm and forearm. Dual energy X-ray absorptiometry determined percentage of subcutaneous tissue in the arm. With participants seated, American Heart Association guidelines were used to measure blood pressures, first by auscultatory method (upper arm only) and then by oscillometric method (upper arm and forearm) with a Dinamap 100 oscillometric blood pressure monitor.

RESULTS

Statistically significant differences were seen between upper arm auscultatory and oscillometric systolic blood pressures (t=-4.88; P=0.000) and mean arterial pressures (t=-3.07; P=0.007). Differences between oscillometric forearm and upper arm blood pressure readings were statistically significant for mean arterial pressures (t=-2.39; P=0.028). A regression model suggested that forearm and upper arm vessel depth, forearm vessel diameter, and upper arm circumference explained a statistically significant portion of the difference between forearm and upper arm blood pressures.

CONCLUSIONS

Differences between forearm and upper arm oscillometric blood pressures can be partially explained by vessel size, depth and upper arm circumference.