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目的:通过理论推导，理清通气/血流(V/Q)增大与低氧血症的关系、肺动脉栓塞与V/Q增大及低氧血症的关系。方法:从整体而言，造成V/Q增大的原因主要见于V增大(过渡通气)或Q减小(右心输出量下降)，分析这2种情况与低氧血症的关系。将发生肺栓塞后的肺分为两部分，所有发生栓塞的肺组织组合称为A，所有未栓塞部分的组合称为B；将A、B对应的栓塞前部分分别称为a、b。分别将“a、b的V/Q、B的动脉供血量、B的通气”以不同方式组合，推理可能出现的PaOn 2结果。n 结果:(1)常见的V/Q增大的病理生理类型(过度通气、低右心排)与低氧血症在临床上并无关联。(2)单纯从V/Q角度分析，不同的组合下，PaOn 2的结果均是由B的V/Q状态决定，且只有当其V/Q下降，处于“血多气少”的状态，患者方可能会出现PaOn 2下降；而B的V/Q是由B的前期状态“b”的V/Q、B的通气代偿程度及B的血流反应程度三者决定。n 结论:就整体而言，将V/Q增大与PaOn 2降低相关联具有一定的误导性。对于肺栓塞而言，导致PaOn 2下降的机制复杂；单纯从V/Q角度，导致PaOn 2下降的根本原理是未栓塞肺的V/Q减小，而非总体肺的V/Q增大。临床上应理清其中的逻辑关系。n “,”Objective:To clarify the relationships among the ventilation/blood (V/Q) increase, pulmonary embolism and hypoxemia by theoretical deduction.Methods:As a whole, V/Q increase was mainly due to the increase of V (transitional ventilation) or the decrease of Q (decrease of right cardiac output). The relationship with hypoxemia was analyzed.The lung after pulmonary embolism was divided into two parts.The combination of all embolic lung tissues was called “ A” , and the combination of all non-embolic parts was called “ B” . The corresponding pre-embolic parts of “ A” and “ B” were respectively called “ a” and “ b” . The V/Q of “ a” and “ b” , the arterial blood flow of “ B” , and the ventilation of “ B” were combined in different ways, the possible results of PaO n 2 could be inferred.n Results:The common pathophysiological types of V/Q increase (transition ventilation, low right cardiac output) were not associated with hypoxemia.Just from the view of V/Q, the results of PaOn 2 in different combinations were determined by the V/Q of “ B” . Only when the V/Q of “ B” decreased (meaning “ more blood and less gas” ), the PaO n 2 would decrease.And the V/Q of “ B” was determined by the V/Q of “ b” , the degree of ventilation compensation of “ B” , and the degree of blood flow response of “ B” .n Conclusions:As a whole, the increase of V/Q is not related to the decrease of PaOn 2.For pulmonary embolism, the mechanism of PaOn 2 decrease is complex.Just from the perspective of V/Q, the basic principle of PaOn 2 decrease is the decrease of V/Q in non-embolism lung, rather than the increase of V/Q in the whole lung.The logical relationship should be clarified in clinic.n