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Article Reviews and Commentary


Discrepancies Between Direct and Indirect Blood Pressure Measurements Using Various Recommendations for Arm Cuff Selections
Clark JA, Lieh0Lai MW, Sarnaik A et al. Pediatrics 2002;110:920-923

The National Heart, Lung and Blood Institute Task Force on Blood Pressure Control in Children defined normal BPO in children and the proper methods for its measurement. In 1996 the Task Force changed its recommendation for the proper size of a blood pressure cuff, stating that the arm cuff should have a width equal to 40% of the upper arm circumference (UAC). Formerly the recommendation was that the width of cuff be 2/3 to 3/4 of the upper arm length (UAL) measured from the olecrenon to the acromium.

The authors compared direct blood pressure measurements with indirect measurements made using each of the three above-mentioned criteria for BP cuff size. Subjects for the study were recruited from admissions to the PICU. Exclusion criteria included: morbid obesity, ECMO, hemodialysis. The natural frequency and damping coefficient of the direct pressure monitoring system were evaluated using standard published procedures. Indirect pressure measurement was made with a mercury sphygmomanometer. Three cuffs whose widths approximated 2/3, 3/4 of the UAL and 40% of the circumference of the upper arm were used on each subject. These cuffs were selected from standard BP cuffs. Systolic BP was the 1st Korotkoff sound, and diastolic BP was taken as the 4th Korotkoff sound. There were 172 measurement made in 65 patients.

The authors noted that use of the 2/3 or 3/4 UAL criteria lead to the use of larger cuffs than the use of the 40% arm circumference criteria. Because of the unavailability of larger cuffs, measurement using the 2/3 or 3/4 UAL criteria was often done with a smaller than ideal cuff. When the cuff size was determined using the 40% UAC criteria, there were available adequately sized cuffs.

In comparison to direct measurements, 40% UAC cuffs systolic BP did not differ significantly but diastolic pressure did differ significantly. Mean blood pressure measurements in mmHg with the cuff were 114+/-14 over 69+/-16 compared to the direct measurement of 115+/- over 62+/-12. With both of the UAC criteria, the cuff blood systolic and diastolic pressure measurements both differed significantly when compared to direct measurements, with cuff measurements lower than direct measurements.

The authors conclude that commercially available cuffs are inadequate with use of the 2/3 or 3/4 of the upper arm length as criteria for cuff width. Generally smaller cuffs are required with use of 40% of arm circumference as the criteria for cuff width. With use of the new UAC criteria, the measured systolic BP agrees with direct measurement but diastolic BP is 7 mmHg above direct measurement.

Commentary Thomas J. Mancuso, MD, FAAP

Since we measure blood pressure every 5 minutes, this paper, which carefully evaluates direct and indirect measurement of this important vital sign, is important for us. The references, which describe the evaluation of direct blood pressure measurement, are also worth review. Anesthesiology 1981;54:227-236, Anesthesiology 1992:77:1215-1220 and J Clin Monitoring 1993;9:45-53

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