The Effect of Sensing Site on the Limb Segmental Blood Pressure Determination

The effect of the sensing site on upper-thigh blood pressure readings was studied. We used a multisensing mercury strain gauge (MSG) plethysmographic method and Doppler ultrasound to monitor the upper-thigh blood pressure from the posterior tibial artery and compared the results with those from the popliteal artery. Upper-thigh pressures were measured in 30 limbs of 15 normal subjects and in 60 limbs of 35 patients with multilevel peripheral arterial occlusive disease. Upper-thigh pressures sensed from a thigh MSG placed just distally to the pressure cuff and monitored by the popliteal artery Doppler probe were significantly higher than the upper-thigh pressure readings obtained from an MSG placed on the calf or toe and monitored by a posterior tibial artery Doppler probe in patients with multilevel arterial lesions. In the control group, no significant pressure differences were found. The importance of placing the sensor (MSG or Doppler probe) close to the pressure cuff is critical to obtain accurate thigh pressures in patients with multilevel arterial occlusive disease. Otherwise, erroneous diagnoses, such as nonexistent aortiliac or common femoral artery stenosis, may be made.