Closed-Loop Control of Artificial Ventilation

Abstract

Since 1956, researchers have developed numerous closed-loop controllers to adjust mechanical ventilation [1, 2]. In almost all systems, the end-tidal CO₂ is measured on a breath-to-breath basis and the ventilator’s tidal volume or respiratory rate is adjusted using classical PID control. These systems reach the set end-tidal CO₂ in less than lmin and maintain the end-tidal CO₂ within ±0.1 vol% of the set point. The variability is less than half that seen during periods of open-loop control [3]. Closed-loop control has also been used to adjust the inspired oxygen concentration to maintain the desired arterial oxygen concentration in neonates [4]. Once again, the closed-loop controller out-performs the human operator.