Hypoxaemia created by pulmonary oedema after pulmonary microemboli in dogs

Pulmonary microemboli may play a role in the adult respiratory distress syndrome, creating both pulmonary oedema and hypoxaemia. We measured the time course of pulmonary oedema and hypoxaemia after pulmonary microemboli of 63-74 mu starch were infused into dogs. Dogs were divided into two groups: six dogs that did not develop pulmonary oedema, and seven that did. Immediately after emboli there was no difference between groups in the large fall in PaO2 or the rise in Qs/Qt. Therefore the hypoxaemia of pulmonary embolism is not created by pulmonary oedema. As pulmonary oedema increased with time in the oedematous dogs, PaO2 fell further. There was no further reduction in PaO2 in the dogs who did not develop pulmonary oedema. We conclude that hypoxaemia after pulmonary embolism may be worsened if pulmonary oedema occurs, but the immediate large reduction in PaO2 after embolism is not created by pulmonary oedema.