Special Purpose Timer to Aid in Closed Circuit Anesthesia Delivery

Closed circuit anesthesia systems offer certain advantages over other techniques, but require that gas administration closely foliow the uptake by the body, which is proportional to the square root of time. We have developed a timer which automatically signals the anesthesiologist to readjust the gas flow at selected intervals to provide a stepwise approximation to the square root of time curve. Two additional nonsignaling timers are included to permit timing of total elapsed anesthesia time and a third event.