Abstract
Incubator oxygen treatments have been used to prevent newborn respiratory distress. When the oxygen concentration of inhalation (FiO2) is fixed at a rather high level to improve the distress, the newborn arterial oxygen blood pressure (PaO2) sometimes becomes extremely high to bring about the retrolental fibroplasia. This paper investigates the feedback control schemes in an optimal FiO2 inhalation system to maintain PaO2 within normal range. The ventilation behavior of a newborn is shown to be described approximately by a first-order linear model. By modelling the air diffusion in an incubator, as the overall system we have the second-order linear model with dead time lying in a tcPO2 sensor which can monitor PaO2 transcutaneously. The optimal control schemes with the integral action can be given in terms of only the input (FiO2)-output (tcPO2) data sequence. The algorithms are examined through animal experiments in which we simulate anoxia dogs by keeping them in various low ventilated conditions. It is clarified that PaO2 can be maintained within the range ±1.33kPa even if the ventilation is reduced to the one third of the normal rate.
