Pulmonary oedema: physiological considerations.

In this paper I propose to attempt to evaluate our knowledge of the mechanisms of acute pulmonary oedema in experimental animals, and to enquire how far it can be applied to our understanding of the phenomenon in man. Our knowledge of the mechanisms of lung oedema is extremely meagre; yet in some respects it may be integrated, with advantage to future investigations. The first issue which should be raised is the relation of pulmonary oedema in man to that produced experimentally. Is there any evidence that clinical pulmonary oedema, which is generally associated with diseases of the cardiovascular system and of the lungs themselves, is produced by similar processes to those which are caused by a variety of means in healthy and in most cases anaesthetized animals? In the former group there is a pathological background, in the latter there is a relatively normal physiological background. I raise this question because we should be extremely cautious in assuming that the chain of biological events which leads to the production of experimental pulmonary oedema is similar to that causing clinical lung oedema. Let me now refer to specific mechanisms which have been regarded as causative factors.