CHANGES IN CHEST-WALL COMPARTMENT VOLUMES ON INDUCTION OF ANESTHESIA WITH ELTANOLONE, PROPOFOL AND THIOPENTONE

Changes in the expiratory dimensions of the rib cage and abdomen on in duction of anaesthesia with eltanolone, propofol and thiopentone were measured in 76 patients using respiratory inductance bands. Calibratio n of the respiratory inductance plethysmograph was by simultaneous flo w measurement with a pneumotachograph. Movement of the vertebral colum n was restrained with a rigid mattress to allow volume change to be es timated more accurately from rib cage and abdominal dimensions. Rib ca ge volumes decreased by a median of 125 ml, while the median change in the abdominal compartment was O. These findings suggest that a reduct ion in rib cage volume may contribute to the decrease in functional re sidual capacity after induction of anaesthesia, but that changes in th e diaphragmatic-abdominal compartment are not important.