EFFECT OF UNDERCUFFING ON AUSCULTATORY AND OSCILLOMETRIC BLOOD PRESSURE MEASUREMENT

Abstract

Abstract Objective: The objective of the present investigation was to identify the effect of using a blood pressure (BP) cuff size smaller than that appropriate for patient's arm circumference (undercuffing) on auscultatory and oscillometric measurements. Design and method: It was a single-centre equivalence trial that recruited 47 adult subjects with upper arm circumferences between 35 and 44 cm. After ten minutes rest, six sequential BP measurements were performed 30 and, at most, 60 seconds apart while seated. First, third and fifth measurements were performed using blinded, simultaneous, two-observer auscultation using a calibrated anaeroid sphygmomanometer and requiring a between-observer agreement equal to or less than 4 mmHg. Second, fourth and sixth were performed with the Omron HBP-1100 oscillometric monitor. The first two measurements (one auscultatory and one oscillometric) were performed using a large adult cuff (16 x 36 cm), which represented appropriate cuffing for the study subjects. Third, fourth, fifth and sixth measurements were performed with a standard adult cuff size (16 × 30 cm). BP differences were calculated using device – observer measurement. A paired t-test was used to identify statistically significant differences between BP readings in each method. Results: 282 complete measurements were available. Mean upper arm circumference size was 38.38 (±2.85) cm. Mean SBP and DBP when the appropriate cuff was used was 115.08 ± 18.32/70.25 ± 12.3 mmHg using the auscultatory method vs. 120.91 ± 17.15/72.57 ± 11.74 mmHg using the oscillometric method (p-value < 0.005). When smaller cuff size was used, mean SBP and DBP was 119.97 ± 15.88/76.78 ± 12.03 mmHg in the auscultatory method vs. 126.95 ± 16.17/74.56 ± 10.97 mmHg in the oscillometric method (p-value < 0.005). The mean device-observer disagreement for SBP (Fig 1) was 5.82 (±9.12) when appropriate cuff size was used and 6.98 (±8.06) with a smaller cuff size (p-value = 0.79). For DBP (Fig 2), the disagreement was 2.31 (±6.28) vs. -2.22 (±5.88) (p-value < 0.005). Conclusions: Using a smaller cuff size overestimates SBP and DBP, in both auscultatory and oscillometric methods and also results in a greater systolic disagreement between these two measurement methods.