Proctor K G, Damon D N, Duling B R
Microvasc Res. 1984 Jul;28(1):23-36. doi: 10.1016/0026-2862(84)90026-8.
The effect of vasomotor tone on blood flow estimates was evaluated in the hamster cheek pouch and cremaster muscle microcirculation. The products of arteriolar cross-sectional area and red blood cell velocity were calculated in three different cases: (1) at arteriolar bifurcations, (2) in short segments of an arteriole constricted by iontophoretic application of norepinephrine, and (3) at randomly selected second- and third-order arterioles. Vasodilation of the microcirculation was induced by topical application of adenosine. Vasoconstriction was induced by elevation of superfusion solution PO2. If true volume flow is accurately estimated by this method then: the sum of measured branch flows at a bifurcation should equal feed flow; measured flow through constricted arteriolar segments should equal flow proximal or distal to the constricted segment; and, following experimental manipulations, relative changes in estimated flow in second- and third-order arterioles should be equal. Our findings suggest that the blood flow estimates were not always accurate. The sum of branch flows was equal to feed flow only across bifurcations with low or resting vascular smooth muscle tone. During vasoconstriction, feed flow averaged 40% higher than the sum of downstream flows. In addition, estimated flow was 15% lower in constricted segments of an arteriole compared to dilated contiguous segments of the vessel. During alterations in vasomotor state, estimated fractional changes in flow in second- and third-order arterioles differed by more than sixfold. Therefore, blood flow estimates with the dual-slit method may not be reliable under conditions of high vasomotor tone. We speculate that the error may result largely from uncertainties in the diameter measurement.
在仓鼠颊囊和提睾肌微循环中评估了血管运动张力对血流估计值的影响。在三种不同情况下计算小动脉横截面积与红细胞速度的乘积：（1）在小动脉分叉处；（2）在通过去甲肾上腺素离子电渗法收缩的小动脉短节段中；（3）在随机选择的二级和三级小动脉处。通过局部应用腺苷诱导微循环血管舒张。通过提高灌注溶液的PO2诱导血管收缩。如果通过该方法能准确估计真实的容积流量，那么：分叉处测量的分支血流总和应等于供血血流；通过收缩小动脉节段测量的血流应等于收缩节段近端或远端的血流；并且，在实验操作后，二级和三级小动脉中估计血流的相对变化应相等。我们的研究结果表明血流估计值并不总是准确的。仅在血管平滑肌张力低或处于静息状态的分叉处，分支血流总和才等于供血血流。在血管收缩期间，供血血流平均比下游血流总和高40%。此外，与血管扩张的相邻节段相比，小动脉收缩节段的估计血流低15%。在血管运动状态改变期间，二级和三级小动脉中估计的血流分数变化相差超过六倍。因此，在血管运动张力高的情况下，双缝法估计的血流可能不可靠。我们推测误差可能主要源于直径测量的不确定性。
