Peak systolic velocity and flow volume increase with blood pressure in low resistance systems

This study demonstrates that when vascular resistance is low, peak systolic velocity and peak flow volume increase with increasing blood pressure. We used ischemia with reactive hyperemia to create reproducible low resistance conditions in 32 volunteers. Ischemia resulted in sharp increases in systolic and diastolic velocities, while the difference between these velocities increased minimally. Spontaneous variations in subject's systolic blood pressure were positively correlated with peak systolic volume and peak flow volume (r = 0.40 and 0.59, respectively), but resistive index was not. We conclude that low resistance flow is blood pressure dependent. Because blood pressure increases with age, tumor velocity and frequency shift thresholds may need blood pressure correction if applied over wide age ranges. The resistive index was independent of blood pressure and thus may be preferable.