Reproducibility of the hyperbaric index as a measure of blood pressure excess

The approach of establishing a time-specified tolerance limit reflecting th e circadian variability in blood pressure and then determining the hyperbar ic index, the area of blood pressure excess above the upper limit of the to lerance interval, has been proposed for diagnosing hypertension as: well as for evaluating the patient's response to treatment. The retrospective eval uation of this test provided high sensitivity and specificity in the diagno sis of hypertension, with a threshold value for the hyperbaric index of 15 mm Hg . h. To evaluate the stability and reproducibility of this tolerance- hyperbaric test. we studied 332 previously untreated subjects (218 men) who underwent sequential 48-hour ambulatory blood pressure monitoring for 2 ye ars, providing a total of 1337 blood pressure profiles. Diagnosis of hypert ension was established for each subject on the restricted basis of presenti ng at least 1 blood pressure profile with a hyperbaric index above the prev iously defined threshold. Sensitivity of this tolerance-hyperbaric test was 98.6%, with a negative predictive value of 99.7%. For the same subjects, t he blood pressure load (percentage of values > 140/110/90 mm Hg for systoli c/mean arterial/diastolic blood pressure during activity or >120/95/80 mm N g during resting hours) had a sensitivity of 49% and specificity of 25%. Th e 24-hour mean, still the most common approach for diagnosing hypertension on the basis of ambulatory monitoring, had sensitivities of 40% and 31% for systolic and diastolic blood pressure, respectively. Despite the limitatio ns of ambulatory blood pressure monitoring, the tolerance-hyperbaric test r epresents a reproducible, noninvasive, and high-sensitivity test for the id entification of subjects in need of prophylactic or therapeutic interventio n.