Blood pressure measurement in childhood epidemiological studies.

BACKGROUND: Accurate measurement of blood pressure in childhood epidemiological studies requires standardized conditions, valid instruments, and multiple measurements. METHODS AND
RESULTS: We used published literature and our own data to make recommendations on the reduction of biases caused by various technical factors, to discuss the advantages and disadvantages of selected measurement devices, and to evaluate the optimal number of visits and measurements per visit for accurate estimation of a child's blood pressure level. The conditions under which blood pressure is measured should be standardized. This includes training and certification to minimize observer biases; equipment factors such as use of an appropriate cuff bladder size, subject factors such as minimizing activities before and during the reading, environmental factors such as accounting for the time of day and ambient temperature, and technique factors such as recording both the fourth and fifth Korotkoff sounds. The choice of instrument for measuring blood pressure depends on the goals of the study and the resources available to the investigators.
CONCLUSIONS: Although relatively economical and easy to use, the standard mercury sphygmomanometer is subject to the bias resulting from knowledge of earlier readings. The random-zero sphygmomanometer overcomes this bias, but it is more expensive and difficult to use and may underestimate blood pressure levels. In contrast to auscultatory devices, automated oscillometric devices are not subject to observer biases. They are gaining wider use and may be especially appropriate for younger children. However, they are expensive, and each model requires validation before use in epidemiological studies. Ambulatory blood pressure monitoring represents a potentially useful technique for future epidemiological studies. Multiple measurements are vital in estimating a child's blood pressure, and the number of visits, days or weeks apart, is at least as important as the number of measurements per visit.