Non-invasive measurement of instantaneous blood pressure in dorsalis pedis artery based on the volume-compensation technique

Instantaneous non-invasive blood pressure (BP) measurement in dorsalis pedis artery as a measuring site, which can be applied to the patient monitoring in a hospital bed, was attempted based on previously proposed the volume-compensation technique. The measurement system mainly consists of a partial pressurization cuff with a pair of LED and photo-diode for the detection of arterial volume, a micro-computer-based PID servo control circuitry, a hydrostatic compensator of the pressure difference between the dorsal artery of foot and the heart level to obtain the dorsal arterial BP at heart level. Using healthy subjects, the performance and accuracy of this system were evaluated through comparison experiments with the indirect BP simultaneously measured from the radial artery. It was demonstrated that the compensated BP values in dorsal artery of foot were well coincident with those in radial artery and that the short-term BP responses such as instantaneous slight hypotension and its recovery during the changes in body positions from supine to sitting were clearly observed in both measuring sites. Dorsal BP was also measured during the Valsalva maneuver test then showed typical BP response in the maneuver. The mean error of BP measured in dorsalis pedis from radial artery are -3.0α6.88 mmHg in SBP and 0.4α6.84 mmHg in DBP. The Bland-Altman plots of systolic (SBP) and diastolic BP (DBP) values in dorsalis pedis and radial artery showed almost consistent results. The instantaneous BP measurement technique in dorsalis pedis artery appears promising as a useful means for the patients restrained in a bed during hemodialysis, bedridden patients with spinal cord injuries and with severe diseases, and others.