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正常肺循环具有低阻、低压、高流量、流程短、容量大的特点。当肺动脉压超过30/15mmHg柱或其平均压超过20mmHg柱时,即形成肺动脉高压。由于直径<30μm的肺血管无神经调节,现在多认为肺循环的调节主要是由体液因素进行的。缺氧: Von Euler早在1946年就发现缺氧可使猫产生肺动脉高压。肺泡氧分压降低或动脉血氧分压降低均可使肺血管收缩,前者使肺终末细小动脉及小静脉收缩;后者多引起近端肺动脉收缩。另外pH值降低也可增加肺血管对缺氧的敏感性,促使肺动脉压增高。
Normal pulmonary circulation with low resistance, low pressure, high flow, short process, large capacity. Pulmonary hypertension occurs when pulmonary pressure exceeds 30 / 15mmHg or its mean pressure exceeds 20mmHg. Due to the fact that pulmonary vessels of <30 μm in diameter have no neuromodulation, the regulation of pulmonary circulation is now mostly based on humoral factors. Hypoxia: Von Euler found that hypoxia caused pulmonary hypertension in cats as early as 1946. Lower alveolar oxygen pressure or arterial oxygen partial pressure can reduce pulmonary vasoconstriction, the former pulmonary terminal small arteries and small veins; the latter caused more than the proximal pulmonary artery contraction. In addition the lower pH value can also increase the pulmonary vascular sensitivity to hypoxia, promote pulmonary hypertension.