Recent advances in blood pressure measurement technology: normalized blood pressure measurement with a double-cuff sphygmotonometer.
BACKGROUND
In our previous studies of 24-h blood pressure measurement, basal blood pressure (minimum sleep-time blood pressure) showed the strongest correlation with hypertensive target-organ damage. We have currently devised a new accurate method of blood pressure measurement that entails recording casual blood pressure waves by means of a double-cuff sphygmotonometer, and attempted to normalize casual blood pressure to basal blood pressure.


METHODS
The double-cuff sphygmotonometer records the arterial pressure wave, from which, using the formula (P0 = phi(-1)(i) x Pi), we attempted a normalization of casual blood pressure (Pi) to values close to those of the basal blood pressure (P0). True basal blood pressure was measured by an indirect ambulatory blood pressure monitoring device (TM2425, A&D Co. Ltd., Tokyo, Japan). The subjects were 54 normotensive volunteers and 156 out-patients with essential hypertension [63 with World Health Organization (WHO)-II stage and 93 with WHO-I stage, including 47 subjects with white-coat hypertension] not receiving medication.


RESULTS
The coefficient of correlation (r) between normalized diastolic blood pressure (Pd0') and true diastolic basal blood pressure (Pd0) was 0.82 (mean difference = 1 +/- 9.8 mmHg), that between normalized systolic blood pressure (Ps0') and true systolic basal blood pressure (Ps0) being 0.78 (1 +/- 13 mmHg) in 210 subjects. When an office mean blood pressure (MBP) of 116 mmHg was taken as the standard for identifying the WHO-I group, the sensitivity was 70% (65/93) and the specificity 67% (42/63), but when an MBP0 [MBP0' = (Ps0'-Pd0')/3 + Pd0'] of 89 mmHg was the standard, the sensitivity was 82% (76/93) and the specificity 90% (57/63), both significantly higher than the corresponding values for office MBP (P < 0.05).


CONCLUSIONS
We devised a new double-cuff sphygmotonometer and normalizing function (phi(-1)) and, using these methods, calculated the normalized blood pressure in hypertensive out-patients, which may make it possible to identify degrees of severity of hypertension in terms of WHO stages.
Tochikubo
O
O
Department of Public Health, Yokohama City University School of Medicine, Japan. tocchi@med.yokohama-cu.ac.jp
Kimura
K
K
D000465:Algorithms; D001795:Blood Pressure Determination / Q000295:instrumentation* / Q000379:methods / Q000592:standards; D015924:Blood Pressure Monitors / Q000592:standards*; D016022:Case-Control Studies; D002940:Circadian Rhythm / Q000502:physiology; D003627:Data Interpretation, Statistical; D004867:Equipment Design; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D009991:Oscillometry; D012680:Sensitivity and Specificity