Time to a 90% change in gas concentration: a comparison of three semi-closed anesthesia breathing systems.

Background: The speed with which gas concentration can be changed in the anesthesia breathing system affects the rate of denitrogenation, anesthesia induction, and emergence. Breathing system design also affects the speed at which gas concentration can be changed during maintenance. In this study, we sought to determine the speed of changes in gas concentration in modern semi-closed breathing systems.