[Experimental studies on pulmonary micro-embolism with special reference to the mechanism of initial excessive elevation in pulmonary arterial pressure].
In the experimental pulmonary micro-embolism, pulmonary arterial pressure rises markedly in initial stage, and then falls gradually. For its explanation, some neural and humoral factors, especially those released from aggregated platelets, has been suggested on the basis of many experimental results. A very similar change in perfusion pressure is also observed in micro-embolism of the perfused lung lobe. Present experiment was performed in order to elucidate the mechanism of this initial excessive elevation in pulmonary arterial pressure caused by micro-embolization. An excised canine lung lobe was perfused either forward or retrogradely with pulsatile flow, and embolism was caused by injection of lycopodium spore suspension in saline. After embolization during forward perfusion, the inflow pressure rised rapidly, and reached to a maximal point after 30-60 sec. and then fell gradually. On the other hand, with embolization during retrograde perfusion, the inflow pressure rised immediately, but to a lesser extent compared with that during forward perfusion, then maintained a plateau. When the pulmonary vascular bed was dilated passively by means of elevating the outflow pressure, the basic pattern of the inflow pressure elevation was not remarkably changed during either forward and retrograde perfusion, compared with the control experiment. These results suggest strongly that a gradual fall following initial rise in pulmonary arterial pressure due to microembolization was attributable not to opening new channels, but to resolution of excessive vascular constriction. In conclusion, on the mechanism of initial excessive elevation in pulmonary arterial pressure after microembolization, the importance of local factors, especially the function of small pulmonary muscular artery and pulmonary arteriole, must be emphasized.
D000818:Animals; D001794:Blood Pressure; D004285:Dogs; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000503:physiopathology; D010477:Perfusion; D011651:Pulmonary Artery / Q000503:physiopathology*; D011655:Pulmonary Embolism / Q000503:physiopathology*