The effect of pressure drop stabilization in arteries during variations in blood flow rate.

The aim of this study was to clear up whether the flow-induced dilation of arteries is sufficient to ensure invariability of pressure drop along these vessels under many-fold increase in blood flow rate. In anaesthetized rats an arteriovenous shunt was constructed by connecting the saphenous artery and the femoral vein. Resistance of the shunt was changed by a device creating either rectangular flow pulses of different amplitude or slow linear ramps of flow rate. Pressure drop along the arterial cascade, from the aortic arch up to distal saphenous artery, was recorded and the steady-state flow-pressure drop relationship was determined. At low flow rates (< 0.25-0.3 ml min-1) the pressure drop rose proportionally to flow, i.e. as in a system of ordinary tubes with non-regulated diameter. In contrast, at higher flow rates (up to 1.5 ml min-1) the pressure drop either remained unchanged under 3- to 5-fold increases of flow rate or rose far less than the flow. Thus, the pressure drop stabilization effect has been evidenced. The threshold of this effect was about 0.3 ml min-1, corresponding to the 'resting' flow in the saphenous artery, i.e. the narrowest of all the cascade vessels. This coincidence suggests that the pressure drop stabilization is determined by the flow-induced dilation mainly of this artery.