Juro Iriuchijima

Indices for the role played by regional flow resistance in blood pressure reflex

SummaryAn index, α = (Δr/r)/(ΔR/R), is proposed for assessment of the relative degree of participation of a regional flow resistance in a blood pressure reflex, wherer andR are regional and total peripheral resistances respectively and Δs refer to their reflexive changes. For actual computation, α =I (iΔP − PΔi)/i(IΔP − PΔI), whereI=cardiac output,i=regional flow rate,P=mean arterial pressure. When the change in cardiac output is neglegible, the above equation is simplified as Δ=1 − PΔi/iΔP. Another index,β = Δg/ΔG = (PΔi − iΔP)/(PΔI − IΔP), is introduced for the degree of contribution of a region to a reflex, whereg andG are regional and total conductances.αi = β1. Some examples of application of the indices are presented.

New technique of measurement of effective capacity changes of total vascular bed

SummaryA simple device was developed which can accurately measure effective changes in total vascular capacity as viewed from the site of the heart. The device consists of a funnel and a suction bottle. It is connected via a single large-bore cannula to the right atrium of an open-chest animal without opening the closed loop of the circulation. It serves to clamp the steady-state level of mean central venous pressure precisely at any desired value and to measure the volume of any displacement of blood out of or into the total vascular bed caused by changes in total vascular capacity. The device was tested in mock and animal experiments and proved to function accurately, except during a short transient phase of less than 1 min following an intervention on the total vascular capacity. Errors in clamp pressure in the steady state, which are theoretically zero, were found to be less than 0.2 mm Hg, and were practically insignificant. Errors in the volume measurement were less than 5 ml.

Circuit parameters of carotid collaterals.

SummaryDuring occlusion of the common carotid artery in the dog, attenuation of AC signals of arterial pressure through collateral channels was greater than that in DC signals: pulse pressure was more attenuated than mean pressure. When treated in a “lumped” fashion, such a frequency dependent pressure attenuation is roughly analogous to the attenuation of voltage in a circuit consisting of two resistors coupled in series with a capacitor parallel to the lower resistor. The upper resistor corresponds to the synthetic resistance of parallel collateral channels, the lower resistor to the peripheral resistance, and the capacitor to the vascular elasticity short-circuiting the pulsation. Calculation of these circuit parameters may be helpful in describing quantitatively the characteristics of the collateral channels. For the left common carotid artery, the collateral resistance was 0.77±0.39 mm Hg/ml/min, the peripheral resistance was 1.26±0.57 mmHg/ml/min, and the capacitor was 0.0069±0.0027 ml/mm Hg, each being the mean and SD obtained from 6 dogs.

Vascular area which most contributes to carotid occlusion reflex

SummaryDuring the carotid occlusion pressor reflex in which elevation of arterial pressure was caused by an increase in total peripheral resistance, the change in local peripheral resistance was compared among various arteries in anesthetized dogs. For the superior mesenteric, femoral and renal arteries, the change in peripheral resistance was below average or at most nearly average. The vascular area which most contributed to the reflex was that in the head and neck supplied by the carotid and vertebral arteries. The conductance (inverse of resistance) change in this area, which unilaterally amounted to about 20% of the total conductance change, was induced by three mechanisms: 1. hemodynamically as a mechanical effect of carotid occlusion, which was however slight due to abundant collaterals, 2. neurally by a sympathetically mediated vasoconstriction especially in the area originally supplied by the occluded carotid arteries, which impeded collateral inflow and contributed to the elevation of systemic pressure, and 3. by autoregulation, which became apparent after the cervical sympathetic nerve had been divided.