Effect of Cuff Design on Auscultatory and Oscillometric Blood Pressure Measurements.

BACKGROUND: Two-piece blood pressure (BP) cuffs are the historical cuff standard. Use of 1-piece cuffs is increasing. Substituting 1-piece for 2-piece cuffs has an unknown effect on measurement accuracy. We compared these cuff types in a 2-phase study using auscultatory and oscillometric techniques. METHODS: Consenting subjects (aged ≥18 years) with BP levels between 80 and 220mm Hg/50 and 120mm Hg and arm circumferences between 25 and 43cm were studied using the International Standards Organization (ISO) 2013 protocol (modified). A Baum 2-piece cuff was used as the reference standard. A 1-piece Welch Allyn cuff was the comparator. In phase 1 (2-observer auscultation with a mercury sphygmomanometer), 88 subjects were required to obtain 255 paired BP determinations. In phase 2 (oscillometric measurement with a Spacelabs 90207 device), 85 subjects were studied. Each phase was analyzed separately using paired t-tests. RESULTS: Phase 1 mean age was 54.2±20.5 years, mean arm circumference was 29.9±3.7cm, 60% were female, and 32% had hypertension. One-piece cuff mean BPs were lower than the 2-piece cuff means (115.5±15.5/66.4±9.3 vs. 117.8±15.2/67.9±9.2; difference of -2.4±3.6/-1.5±2.4; P values <0.0001 for systolic and diastolic comparisons). Phase 2 mean age was 52.8±20.8 years, mean arm circumference was 29.4±3.9cm, 67% were female, and 38% had hypertension. Mean BPs were lower for the 1-piece compared to the 2-piece cuff (116.5±12.8/67.1±8.1 vs. 120.8±13.5/70.4±8.5; difference of -4.4±3.6/-3.3±2.7; P values <0.0001 for both). CONCLUSIONS: Mean BP is lower with 1-piece cuffs vs. 2-piece cuffs. Differences are greater with oscillometry. When performing validation studies and measurements for clinical purposes, cuff type should be taken into account.

Effect of overcuffing on the accuracy of oscillometric blood pressure measurements.

Overcuffing (using too large a blood pressure [BP] cuff), is known to artificially lower auscultatory BP measurements; however, its effect on oscillometric readings is unclear. The possibility that overcuffing biases oscillometric readings is currently widely disregarded. We sought to confirm that overcuffing lowers auscultatory readings and to assess its effect on oscillometric measurements. Community-dwelling adults (aged ≥18 years) with arm circumferences within the standard range of 25-32 cm were recruited. Using primarily the International Standards Organization 2009 protocol, we compared the standard Baum adult (25-35 cm) to the large adult (33-47 cm) cuff. The standard cuff was considered the "reference standard." In Phase I, auscultatory measurements were performed by two trained observers. In Phase II, oscillometric measurements were performed. Each phase was analyzed independently using paired t-tests and by generating Bland-Altman plots. Of 108 participants, 87 contributed data for Phase I, 85 for Phase II, and 69 were common to both phases. Phase I mean age was 38.0 ± 18.5 years, mean arm circumference was 28.0 ± 1.9 cm, and 21% had a past hypertension. The Phase I results confirmed that overcuffing reduced auscultatory BP measurements by 3.6 ± 5.1/2.8 ± 4.0 mm Hg (P-values <.0001 for both). For Phase II, mean age was 39.3 ± 18.3 years, mean arm circumference was 28.0 ± 1.9 cm, and 22% had past hypertension. Mean BPs were 112.2 ± 13.1/67.8 ± 7.3 mm Hg for the large cuff and 117.8 ± 13.3/71.2 ± 7.1 mm Hg for the standard cuff (5.5 ± 5.9/3.4 ± 5.2 mm Hg lower with the large cuff; P-values <.0001).Overcuffing leads to a clinically important downward bias in oscillometric measurements. An upper size limits for oscillometric cuffs should be specified.