Cranio-caudal movement of the sternum on induction of anaesthesia

The cranio-caudal movement of the sternum was studied by the technique of video magnification during induction of anaesthesia with thiopentone 2-4 mg kg-1 i.v. in 20 patients. Anaesthesia produced no consistent change in end-expiratory position of the sternum; there was a range of movement from 3.1 mm cephalad to 5.4 mm caudad. There was a significant relationship between movement and degree of obesity of the patient (P less than 0.01), with the sternum tending to caudal movement in the obese patient.