Accuracy of blood pressure measurement in the family practice center.

BACKGROUND: Equipment, physiologic, and technique factors can influence the accuracy of blood pressure measurement. The current study was designed to isolate certain technique factors and then assess the accuracy of nursing personnel measurements of blood pressure in three residency family practice centers.
METHODS: An experienced registered nurse was trained in applying the American Heart Association recommendations for determining blood pressure by sphygmomanometry; three 1.5-hour practice sessions demonstrated her accuracy. Nine full days were then spent in the family practice centers rechecking as many staff blood pressure readings as possible while controlling for confounding variables.
RESULTS: The following findings were significant: (1) the average absolute differences between control and study nurse systolic and diastolic blood pressure readings were 6.2 mmHg and 4.7 mmHg, respectively; (2) a unidirectional error of 3.8 mmHg in the measurement of diastolic blood pressure was found in one center, possibly because less care was taken with afternoon measurements; (3) variability in systolic blood pressure readings was higher in all three centers (+/- 8.5 mmHg) than attained during the training sessions for the control nurse (+/- 5.8 mmHg); (4) the average errors attributable to technique factors studied that were potentially correctable by training were only 1.8 mmHg for systolic and 0.7 mmHg for diastolic pressures.
CONCLUSIONS: The degree of inaccuracy in ambulatory nursing blood pressure readings attributable to errors in technique is quantified by this study. Training can reduce, but not abolish, this inaccuracy. Careful attention to proper blood pressure measurement technique and such variables as equipment calibration is essential for both nursing and physician observers. Taking multiple blood pressure measurements before making clinical decisions can limit the effect of these inaccuracies.