VASCULAR-RESISTANCE QUANTIFICATION IN HIGH-FLOW RESISTANCE AREAS USING THE DOPPLER METHOD

The objective of the present study is to define and validate on an ani mal model (ewe) a new Doppler parameter for the assessment and monitor ing of the vascular resistances in high resistance to flow areas (lowe r limbs, placenta with vascular disease). The high resistance index (H RI) was derived from the transmission line theory and defined as: HRI = D/S with S the amplitude of the systolic peak and D that of the dias tolic reverse flow, Validation of the HRI was performed on adult ewes. Distal lower limb vascular resistances were evaluated from the Dopple r femoral waveform (HRI) and compared with the classic vascular resist ances (Rv), calculated from pressure and flow (mmHg/mL/min). The femor al flow variations were measured by duplex (echo-Doppler) method and t he mean pressure through an arterial catheter inserted into the abdomi nal aorta, Two tests were used in this study: (1) A calibrated venous compression of the lower limbs extremity: The femoral Row dropped by 2 9%, the pressure and heart rate did not change, the HRT increased by 3 7% (p < 0.01), and the vascular resistances (Rv) by 46% (p < 0.01), (2 ) The intravenous injection of 1 mg adrenaline: The arterial pressure increased by 70% (p < 0.001), the heart rate and femoral flow dropped by 50% (p < 0.001), acid 35% (p < 0.001), the HRI increased by 70% (p < 0.01) and the vascular resistances (Rv) by 140% (p < 0.01). During t he two tests, the HRI changed in proportion with the ''classic'' vascu lar resistances. Comparison of the absolute values of HRI and Rv showe d a good correlation in the two tests (r = 0.82). The present animal e xperiment and other human experiments have demonstrated the high sensi tivity of the HRI for the assessment of vascular resistance changes.