Noninvasive blood pressure measurement by impedance plethysmography

A tetrapolar electrical impedance Plethysmograph has heen used for noninvasive hlood pressure measurement on the human fingen. The pulsatile impedance variations (δZ) during a gradual decrease in the pressure of an occluding cuff wrapped around the finger of the subject were recorded and the systolic pressure (P) and mean arterial pressure (p) were determined. The diastolic pressure (P) was calculated from the systolic and mean arterial pressures. A I-c hased system for automatic blood pressure monitoring has been designed based on this approach. The results obtained with this system agree well with those obtained from the conventional cuff method of blood pressure measurement. This system is expected to have wide applications in continuous and noninvasive blood pressure monitoring during surgery and under such situations wherein it is difficult to use the conventional cuff method.