FINGER-TO-BRACHIAL COMPARABILITY OF MODEL-FLOW STROKE VOLUME IMPROVESAFTER PULSE-WAVE RECONSTRUCTION

Modelflow is a method that determines stroke volume (SV) from central or peripheral continuous blood pressure signals. Pulsewaves are change d along the arterial tree; distortion occurs as the mean pressure leve l gradually declines. These changes might jeopardize the determination of SV from a distal measurement site. Techniques have been assessed t o reconstruct brachial artery pressures (BAPs) from non-invasive finge r blood pressure (FIN) waveforms. In this study, we determined the eff ect of different forms of brachial reconstruction techniques on the co mparability of modelflow SV from FIN and BAP. Supine resting FIN and B AP were measured simultaneously in 57 subjects, covering a wide range of blood pressures and degrees of vascular disease. SV from the two si tes were compared before correction and after correction for pulsewave distortion or pressure gradient. The latter was determined by a regre ssion formula and by a return to flow (RTF) method, using the brachial cuff pressure at the moment of reappearance of FIN during cuff deflat ion. SV from unfiltered FIN exceeded BAP-derived SV by 4.6 (SD 11) ml. This difference was positively related to the subjects' age. Correcti on for pulsewave distortion increased the average difference to 13 (12 ) ml (P<0.05 to the unfiltered condition). Adjustment for the pressure gradient reduced the difference to -2.5 (7) ml (P<0.01). RTF had no a dditional effect. We concluded that the FIN-to-BAP comparability can b e increased by brachial reconstruction techniques, which correct for t he pressure gradient. This can be adequately performed without additio nal measurements, allowing its application to measurements already tak en.