A New Skin-Protective Sphygmomanometer Cuff

Repeated blood pressure measurement with a sphygmomanometer often produces skin redness and subcutaneous hemorrhage. Although the skin may be protected by using a sheet of lint placed under the blood pressure cuff, this may cause a discrepancy in blood pressure value and result in a 2.3% higher mean pressure than without the lint [1]. Pilot studies with volunteers have shown that skin damage is worse when a loose-fitting cuff is used [2], which suggests that an arm-fitted, fan-shaped cuff would be better than those now used. Therefore, we created a new disposable fan-shaped sphygmomanometer cuff with an additional, thin, double inner layer (Figure 1) and compared it with a standard blood pressure cuff.Figure 1: The new skin-protective sphygmomanometer cuff. There are two cuff sizes, one for adults (130 x 260 mm) and one for small adults (100 x 220 mm). The outer layer was made of cushioned nylon pile (tricot); the middle layer was made of a breathable nonwoven fabric sheet; and the inner layer was made of a flexible plastic cuff (polyvinyl chloride).Methods After approval by the hospital ethics committee, we studied 50 adult volunteers (40 female and 10 male) with an average age of 29 +/- 6 yr (mean +/- SD). After randomly fitting standard (based on American Heart Association recommendation) and new cuffs, blood pressure measurements (180 mm Hg, default driving pressure of the machine) were repeated three times after restarting using an automatic sphygmomanometer. The appearance of skin redness and subcutaneous bleeding were checked by a blinded observer 3 min after the cuff was removed in three parts (proximal, middle, and distal) of the compressed upper arm. Thirty volunteers in whom the difference of mean blood pressure between the arms was <5 mm Hg were selected from the study group. Blood pressure was measured simultaneously in both arms with the same instruments. Measurements were repeated three times. To minimize radiograph radiation, after confirmation of the same measurements for male and female subjects and old and young subjects in the preliminary arm computed tomography (CT) scans, the arms of an average-weight male volunteer were scanned in detail by a helical CT scanner, and two- and three-dimensional images were constructed from various viewpoints. All numerical data were analyzed by using the chi squared method and Mann-Whitney U-test. P < 0.05 was considered statistically significant. Results Skin redness and subcutaneous hemorrhages were significantly decreased with the new cuff (Figure 2). Blood pressure value differences (new cuff - standard cuff) were 0.74 +/- 5.43 mm Hg for systolic pressure, -0.79 +/- 4.43 mm Hg for diastolic pressure, and -0.97 +/- 4.21 mm Hg for mean pressure (Figure 3).Figure 2: Frequency of skin damage in each part. Skin redness and subcutaneous hemorrhages were significantly decreased with the new cuff. *Significantly different from standard cuff, P < 0.05.Figure 3: Percent difference of new cuff pressure from standard cuff pressure.A standard manometer cuff is loose in the distal parts, but the new fan-shaped cuff fits tightly in all parts (Figure 4). After inflation, the skin was compressed between large cuff folds in the standard cuff, whereas there were many small, even cuff folds with the new cuff (Figure 5).Figure 4: Cuffs fit to skin before air inflation. The standard cuff is loose in the distal part. By contrast, the new fan-shaped cuff fits all parts well.Figure 5: Arm deformity after cuff inflation. Small and even cuff folds can be seen in the new cuff.A general view of upper arm deformity was taken by three-dimensional imaging (Figure 6). Skin compression between big cuff folds was prominent in the standard cuff.Figure 6: Three-dimensional images of upper arm deformity with sphygmomanometry. When using the standard cuff at left, small beads were attached on the surface of the skin to help with the analysis.Discussion There are very many factors that can be used to evaluate skin changes, such as length, width, depth, and continuity. However, for the sake of simplicity and clarity, we evaluated skin redness and subcutaneous hemorrhage by number to analyze the extent of skin damage. Our clinical observation was that the extent of skin damage was very slight and superficial in the new cuff group. As shown in Figure 4, the new cuff distributed skin tension evenly but had many small cuff folds. In a previous study [2], we found that a loose cuff results in large cuff folds that severely compress the skin. Therefore, we made a fan-shaped cuff. Although this cuff shape is not officially accepted internationally, it has good reliability. Additionally, our new cuff is very thin (0.4 mm) compared with the standard rubber cuff (1.2 mm), which may mean that the new cuff is more sensitive for signals, including artifact detection. This was supported by our preliminary instrumental data, which showed a good relationship between pulsatile movements and cuff pressure (unpublished observations). We previously used thick skin-protecting materials, such as a lint sheet, and expensive skin-dressing materials. These materials are effective in protecting the skin [8], but measured pressure values are higher than those obtained using the standard method. Finally, we achieved good results by putting two thin layers-a nylon pile and an unwoven sheet-under the cuff. To ensure the comfort of the patient during blood pressure measurements, both machine-related factors-including the measurement algorithm-and cuff factors must be considered. In conclusion, we created a new disposable sphygmomanometer cuff that offers both measurement reliability and skin protection. We thank Ryoichi Hirohata (Nippon Colin Co.) for his manufacturing support and the Division of Operating Facility at Sapporo Medical University Hospital, especially Tada-aki Kawae, Ikuko Ishikawa, and Hideko Yokoyama, for their support of this study.