A NEW PHOTO-OSCILLOMETRIC METHOD EMPLOYING THE DELTA-ALGORITHM FOR ACCURATE BLOOD-PRESSURE MEASUREMENT

Objective To measure blood pressure accurately, by developing a new al gorithm and an indirect method employing a non-elastic cuff with a pho tosensor. Design and methods A non-elastic cuff was wrapped around the brachium. A reflecting plate (10 mm x 40 mm) was sited on the inner c entral part of the cuff on the arterial side. On the opposite side of the cuff, a photosensor consisting of light-emitting and light-receivi ng elements was positioned. Oscillation due to arterial pulsation was measured photologically during cuff inflation. Cessation of oscillatio n was taken as the systolic blood pressure (SEP) and, when the delay t ime between photo-oscillation and cuff-pressure oscillation upstrokes was at its minimum, the transition from rapid to more stable changes i n photo-oscillation was taken as the diastolic blood pressure (DBP; th e delta-algorithm). We compared the blood pressures measured directly in the brachial artery with those obtained by this method and by the c onventional auscultatory method in 10 normotensive and 26 hypertensive subjects [12 women and 24 men, mean age 45 +/- 16 years (mean +/- SD) , with mean brachial circumference 27 +/- 2.6 cm]. The blood pressure of each subject was measured simultaneously by the direct and indirect methods five times. Results Errors (differences from direct blood pre ssure measurements) produced with this new method [SBP -0.8 +/- 3.1 mm Hg, (mean +/- SD) DBP 0.6 +/- 2.8 mmHg] were significantly smaller tha n errors obtained by use of the auscultatory method (SEP -7.4 +/- 5.6 mmHg, DBP 3.0 +/- 7.1 mmHg; P < 0.001, n = 180). The delta-algorithm w as easily applicable to an automatic blood pressure measuring device. Conclusion This new photo-oscillometric method was more accurate than the auscultatory method for measuring blood pressure. The delta-algori thm is logical and will be useful for accurate blood pressure measurem ent. (C) Rapid Science Publishers.