Chest wall movements in anaesthesia.

This review describes the movements of the parts of the chest wall (rib cage and abdomen) that occur during anaesthesia and operation. Methods of assessing these movements are reviewed and a simple model is used to illustrate the actions of the muscle groups involved, which are: the diaphragm, those of the rib cage, and of the abdomen. The control of these muscle groups, the forces that they generate, and the movements that can result are discussed. It is not possible to infer the action of these muscle groups from surface measurements alone. In particular, rib cage and abdominal movements do not necessarily indicate the separate actions of rib cage muscles and diaphragm. The changes in volume that occur in the chest wall on induction of anaesthesia are reviewed. The pattern of chest wall movement in the conscious subject, during anaesthesia with either spontaneous or artificial ventilation, and after operation is described, and the mechanisms of the changes that occur are discussed. Aspects of movements in respiratory failure and muscle fatigue are introduced.