CHANGE IN CHEST-WALL DIMENSIONS ON INDUCTION OF ANESTHESIA - A REAPPRAISAL

We used a linearized magnetometer to measure the changes in rib cage a nd abdominal dimensions which occurred during induction of anesthesia with i.v. methohexitone when spinal movement was prevented. By plottin g the changes on an adaptation of the Konno and Mead plot, we inferred changes in chess wail volume, which decreased in 11, did not change i n two and increased in four patients (n = 17). The mean change was a d ecrease (P < 0.05). These results differ from previous studies using m agnetometry but are consistent with those of three-dimensional imaging . A decrease in chest wail volume could explain the decrease in functi onal residual capacity associated with general anaesthesia.