The effect of wrist cuff width on oscillometric blood pressure waveforms

Accuracy of blood pressure (BP) measurement with any method is affected by cuff size. Narrow cuff overestimates BP and wide cuff underestimates BP. Wrist cuff oscillometric BP monitors typically use narrow cuffs with bladders about 6 cm wide. The segment of the radial artery compressed by the wrist cuff presents a hydraulic resistance (Rc) to blood flow during BP measurement. Narrow cuff presents smaller Rc than wide cuff. Changes in Rc alter the amplitude envelope of oscillometric waveforms. Narrow cuff allows blood flow under the cuff and into the hand sooner than wide cuff. The objective of this study was to demonstrate that narrow cuff alters the amplitude envelope in a manner that results in increased BP values when characteristic ratio algorithm is used. A specialized experimental system was used to acquire wrist oscillometric BP data from a narrow (6 cm) cuff and from a wide (10 cm) cuff. Data were acquired from 10 volunteers in sitting position. The results confirmed the objective of the study. All narrow cuff BPs were higher than either the reference BPs or wide cuff BPs. Wide cuff algorithmic BPs were similar to the reference BPs. Wider wrist cuffs appear to be desirable for improved accuracy and reliability of wrist BP monitors