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一、血流量:一般认为呼吸肌的血流和氧耗量都不多。近年来的研究对此提出了异议。实验证明血压正常时,当吸气有一定的负荷或电刺激膈神经时,膈肌的血流可达200～400ml·100g~(-1)·min~(-1)。休克时,全身各部分血流量均减少,当血压降到50mmHg或心输出量仅为正常对照值的30～40％左右时,膈肌的血供仍有50ml·100g~(-1)·min~(-1)。动物实验还发现心包填塞或感染性休克心输出量下降时,只要呼吸存在,呼吸肌的血供约占心输出量的20％,而使用机械呼吸的动物呼吸肌的血供只占心输出量的3％左右,而自主呼吸动物的呼吸肌占心输出量的分数多,则脑、肝、骨骼肌等的血流减少。对比之下,机械通气的动物心输出量虽然也减少,但分布到呼吸肌的血量却不象自主呼吸时那么多。使用大肠杆菌内毒素制成感染性休克的动物模型其呼吸肌的血运也占心输出量的较大分数。实验证明,尽管心输出量低,血压下降,呼吸肌(特别是膈肌)仍接
First, the blood flow: It is generally believed that respiratory muscle blood flow and oxygen consumption are small. In recent years, research has raised objections. Experiments show that when the blood pressure is normal, when the inspiratory load or electrical stimulation of the phrenic nerve, the diaphragm blood flow up to 200 ~ 400ml · 100g ~ (-1) · min ~ (-1). Shock, all parts of the body blood flow decreased, when the blood pressure dropped to 50mmHg or cardiac output is only about 30 ~ 40% of the normal control value, the diaphragm blood supply is still 50ml · 100g ~ (-1) · min ~ (-1). Animal experiments also found that pericardial or septic shock cardiac output decreased, as long as the presence of breathing, respiratory muscle blood supply accounted for about 20% of cardiac output, while the use of mechanical breathing animal respiratory muscle blood supply only cardiac output Of the 3% or so, and spontaneous breathing animals, respiratory muscles account for more cardiac output, the brain, liver, skeletal muscle and other blood flow decreased. In contrast, cardiac output of mechanically ventilated animals decreased, but the amount of blood distributed to the respiratory muscles was not as much as spontaneous breathing. Animal models of septic shock using E. coli endotoxin also have a greater fraction of cardiac output in their respiratory muscles. Experiments show that, despite low cardiac output, blood pressure, respiratory muscles (especially the diaphragm) is still connected