Accuracy of an automated blood pressure device in stable inpatients: optimum vs routine use

Despite widespread use of the automated blood pressure (BP) device (IVAC model 4200, IVAC Corporation, San Diego, Calif), there is little formal validation in the literature on its accuracy.

To assess the accuracy of the IVAC 4200 device, both under standardized conditions and as routinely used by ward staff, compared with the true indirect BP measured by mercury manometer (MM).

One hundred forty-five stable inpatients were randomly selected for BP measurements by 3 randomly ordered protocols: (1) MM performed by certified investigators, (2) IVAC 4200 BP performed by trained investigators (research automated [RA]), and (3) IVAC 4200 BP performed by ward personnel (ward automated [WA]).

For RA compared with MM ("true" indirect BP), 59% of systolic and 54% of diastolic readings were within 5 mm Hg and 83% of systolic and 86% of diastolic were within 10 mm Hg for a British Hypertension Society grade C for both. For WA compared with MM, 40% of systolic and 50% of diastolic readings were within 5 mm Hg and 70% of systolic and 80% of diastolic readings were within 10 mm Hg for British Hypertension Society grades D and C, respectively. The presence of arrhythmias and/or low K5 values (fifth phase of Korotkoff sounds <30 mm Hg) significantly increased the inaccuracy for diastolic values. Inappropriate cuff selection significantly increased inaccuracy of systolic BP (WA vs MM).

The IVAC 4200 yields substandard estimates of systolic and diastolic BP even under standardized, thus optimum conditions. The presence of arrhythmias or low K5 values and the selection of inappropriate cuff size by the ward staff also contributed to inaccuracy.