[Determination of normality limit of blood pressure by home self-measurement]

Home blood pressure (HBP) is frequently used in clinical evaluation; however the interpretation of the data collected is lacked of a precide definition of normal HBP, so we did this study.

A random sample of 1,136 was selected, stratified by gender and age (25 up to 64 years old). Those receiving antihypertensive therapy were excluded. Clinical blood pressure (CBP) consisted of three measurements, with the mercury sphygmomanometer (MS) and with the automatic blood pressure device (Omron 705 CP) (AD). Heart rate (HR), body weight and height were registered. HBP: each participant was asked to obtain 9 home measurements, three in the morning (M), three in the afternoon (A) and three at night (N). Statistical methods included Student's t test for paired comparisons, ANOVA and regression analysis.

CBP and HBP measurements (mmHg) were obtained in 734 participants. The means of S-CBP/D-CBP with the MS were 123.5 +/- 15.1/ 76.4 +/- 10.4 and 122.4 +/- 14.4/75.6 +/- 10.0 and with the AD, 123.4 +/- 16.1/73.7 +/- 10.4. The average of S-HBP/D-HBP in the total sample was 115.0 +/- 14.3/69.2 +/- 9.0. The HBP measurements were significantly lower than CBP (p < 0.05). The mean of clinic HR was 70.3 +/- 10.4. The average of home HR in the whole sample was 67.9 +/- 9.7. The clinic HR and the home HR were significantly different (p < 0.05). The upper limit of normality for HBP obtained from the values that correspond on the mean +2 SD to the CBP value of 140/90 was 135/82. The 95th percentile value of the HBP in the whole sample was 131/80. The upper limit of normality for HBP obtained from the values that correspond on the regression lines in the group with CBP < 140/90 was 125/78, in the group with CBP >or= 140/90 was 130/81 and in the total sample was 128/81.

We consider that the upper limit of normality of home blood pressure is 130/81. Clinic heart rate is higher than home heart rate, which demonstrates a phenomenon of alerting reaction.