Evaluation of the alarm reaction induced by blood pressure determination

The purpose of this paper was to evaluate the characteristics of the alarm reaction that induces an increase of blood pressure (BP) above the "basal" when it is measured in the clinic. This "supplemental" increase that is added to the "basal" pressure was analyzed through the decrease of systolic blood pressure (SBP) along ten consecutive measurements separated by 3 minutes intervals in 85 patients with BP values within a wide range (Table I). 91% of the patients showed a decrease in consecutive measurements and only 9% showed increases or no significant change in SBP values. The decrease showed good correlation with the exponential decay (r = 0.99). The asymptote was for the SBP of -8.7 +/- .81 mmHg (P < 0.01) (Fig. 2) with a time constant T (tau) of 4.7 +/- 1.3 minutes. There was no correlation between the magnitude of the decrease and the BP levels, which does not support the idea that this reaction would be increased in hypertensives. The decrease of DBP was lower (3.87 +/- .71 mmHg (P < 0.01) but with similar characteristics (Fig. 3). If we consider the characteristics of the exponential decay and the fact that after 4 or 5 measurements we arrive at values near the asymptote, basal BP could be simply determined by the average of 2 or 3 determinations with 3 minutes intervals measured after discarding the first two or three readings obtained in the same conditions or by calculating the exponential decay from the equation SBP = Po.e-1/T + As (Fig. 6).(ABSTRACT TRUNCATED AT 250 WORDS)