Automatic control of blood oxygen saturation in premature infants

This paper describes research into the development of a controller that regulates blood oxygen saturation (SaO/sub 2/) in premature infants. The patient's SaO/sub 2/ is measured by a pulse oximeter and fed into the controller which adjusts the neonate's inspired air-oxygen (FiO/sub 2/) mixture by actuating a motorized gas blender. This oxygen therapy is used to prevent incidents of hypoxemia and hyperoxemia. A simplified physiological model is described. The designers use a unique control algorithm based on the sign of the error magnitude, velocity and acceleration as inputs. The algorithm applies these inputs to a state machine that determines the trend of the error. This trend defines the next state and an associated FiO/sub 2/ adjustment and time delay. The controller was verified on eight neonates, each over a six hour study period. During automatic oxygen therapy the controller significantly increased the duration of time the patient spent at normal SaO/sub 2/ levels as compared to manual therapy. The numbers of manual interventions were also greatly reduced when the neonates were under automatic oxygen therapy.<>