Revista Española de Cardiología (English Edition) Revista Española de Cardiología (English Edition)
Rev Esp Cardiol. 2007;60:131-8 - Vol. 60 Num.02 DOI: 10.1016/S1885-5857(07)60125-X

Influence of Measurement Duration and Frequency on Ambulatory Blood Pressure Monitoring

Ramón C Hermida a, Diana E Ayala a, José R Fernández a, Artemio Mojón a, Carlos Calvo b

a Laboratorio de Bioingeniería y Cronobiología, Universidad de Vigo, Campus Universitario, Vigo, España,
b Unidad de Hipertensión Arterial y Riesgo Vascular, Hospital Clínico Universitario, Santiago de Compostela, España,

Keywords

Blood pressure. Ambulatory blood pressure monitoring. Measurement schedule. Essential hypertension. Dipper pattern. Non-dipper pattern.

Abstract

Introduction and objectives. Most studies of ambulatory blood pressure monitoring have involved taking measurements every 15-30 minutes over a 24-hour period. We investigated the effect of measurement duration and frequency on the diagnostic blood pressure values obtained by ambulatory monitoring. Methods. The study involved 1450 hypertensive patients and a control group of 378 normotensive volunteers. Blood pressure was measured at 20-minute intervals from 07:00 to 23:00 and at 30-minute intervals at night for 48 consecutive hours. Data were subdivided in such a way as to generate different series of data that were collected at 1-, 2-, 3-, or 4-hour intervals over the 48-hour period. In addition, two data series at the original measurement frequency were derived for the first and second 24-hour periods. The correspondence between the mean blood pressure values derived from the original data series and those from the different subdivided data series was assessed. Results. Variability in the estimated mean blood pressure increased progressively as the measurement frequency decreased: the error range grew from 11 mmHg for hourly data to 28 mmHg for 4-hourly data. The error range was even greater (i.e., 36 mmHg) for data divided into 24-hour series at the original sampling rate. Conclusions. This study demonstrates that the reproducibility of mean blood pressure values depends more on measurement duration than measurement frequency. The findings indicate that monitoring blood pressure for only 24 hours may be insufficient for diagnosing hypertension, identifying a dipper circadian pattern, or assessing treatment efficacy.

1885-5857/© 2007 Sociedad Española de Cardiología. Published by Elsevier España, S.L.U. All rights reserved

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