Reduction in resting end-expiratory position of the respiratory system with induction of anesthesia and neuromuscular paralysis.

Resting end-expiratory position (REEP) of the respiratory system was monitored continuously using spirometric recording in eleven patients during transition from consciousness to thiopental hypnosis and following subsequent administration of succinylcholine. REEP decreased following thiopental and was little affected by subsequent relaxant in most patients. A fall in REEP was observed within 30 s after thiopental, and a lower, stable level of REEP was attained within approximately 15-45 s. Mean volume of gas expelled from the lungs was 189 (SE 32) ml BTPS. It is concluded that the previously extensively documented decrease in functional residual capacity associated with anesthesia occurs immediately on induction and requires a short, but finite, time for apparent stabilization.