The Measurement of Digital Systolic Blood Pressure by Strain Gauge Technique

Abstract

The systolic blood pressure on the finger, toe, and ankle has been measured by a strain gauge technique in 10 normal subjects aged 17–31 years and 14 normal subjects aged 43–57 years. The standard deviation in repeated measurements lies between 2 and 6 mm Hg. The finger pressure in the younger group was significantly higher than the corresponding arm pressure (+ 9.3 mm Hg, S.D. 6.8), but equalled this in the older group (– 0.5 mm Hg, S.D. 6.6). In the two groups the ankle pressures were + 19.3 mm Hg (S.D. 7.5) and + 23.6 mm Hg (S.D. 9.5) higher than the systolic arm pressures. The toe pressures were lower than the arm pressures, in the two groups – 4.8 mm Hg (S.D. 6.6) and – 9.8 mm Hg (S.D. 10.7) respectively. The ankle-toe gradient was in the younger group 24.3 mm Hg (S.D. 7.3) and in the older group 33.3 mm Hg (S.D. 12.1). Using mean minus 2.5 X S.D. as the lower limit of normality, arterial stenosis or occlusion in the leg is suggested by ankle pressure below the systolic arm pressure and in the foot by ankle-toe gradient exceeding 43 and 64 mm Hg in the two age groups respectively.

Key Words:

• Ankle pressure
• digital blood pressure (normal values)
• finger pressure
• strain-gauge
• toe pressure