急性呼吸衰竭是肺泡通气与毛细血管血流(V/Q)进展性病理生理失调所造成的最终结果。许多不同的病因可导致气体腔隙消失和间质改变,妨碍局部的气体交换从而形成一种共同形式的肺损害。肺内分流(Q_(sp)/Q_f)过高和肺的机械功能异常主要表现为功能残气量(FRC)减少和透肺顺应性(C_(TP))降低。如果机体内稳态、血流动力学和呼吸机能不能纠正释氧的缺欠,那末这种疾病的自然进程必然有很高的死亡率。V/Q 与分流和/或静脉掺杂的解剖分布单位可以是弥散的或不对称的。X 片则显示单叶、双侧多叶或单侧多叶的浸润。急性呼吸衰竭的治疗手段之一是使用PEEP 来纠正肺脏机械功能的低落,包括FRC 减少和 C_(TP)降低。PEEP 有两项效应:(1)消除区域时间常数的依从性,从而导致局部的过度膨胀;(2)时间和区域时间常数 Acute respiratory failure is the end result of progressive pathophysiology of alveolar ventilation and capillary blood flow (V / Q). Many different causes can result in the disappearance of gas lamellae and interstitial changes, preventing local gas exchange to form a common form of lung damage. Pulmonary shunt (Q sp / Q_f) is too high and mechanical abnormalities of the lung are mainly manifested as reduction of functional residual mass (FRC) and reduction of pulmonary compliance (C TP). If the body’s homeostasis, hemodynamics, and ventilatory function do not correct the lack of oxygen, then the natural course of the disease is bound to have a high mortality rate. The anatomical distribution units of V / Q and shunt and / or vein doping may be diffuse or asymmetric. X-ray showed single leaflets, bilateral leafy or unilateral multi-leaf infiltration. One of the treatments for acute respiratory failure is the use of PEEP to correct low mechanical functions in the lungs, including a decrease in FRC and a reduction in C_ (TP). PEEP has two effects: (1) eliminating the compliance of regional time constants and resulting in local over-expansion; (2) the time and regional time constants