发病机理现认为严重肺炎,使肺——毛细血管基底膜的气体弥散功能障碍即换气功能不足所致。同时由于炎症致分泌物多通气功能改变也很严重。这与临床上顽固的喘憋难以解除有密切关系。呼衰的分类一般在静息时有严重缺氧和呼吸性酸中毒,动脉血氧分压(下简写为 paO_2)<50mmHg 或 paCO_2>50mm The pathogenesis is now considered severe pneumonia, lung - capillary basement membrane gas diffusion dysfunction that caused by inadequate ventilation. At the same time due to inflammation caused by secretions ventilation function is also very serious. This is clinically stubborn breathless difficult to lift a close relationship. Classification of respiratory failure is generally at rest, there is a serious hypoxia and respiratory acidosis, arterial partial pressure of oxygen (hereinafter abbreviated as paO_2) <50mmHg or paCO_2> 50mm