The present paper studies a new adaptively controlled artificial respirator which can regulate the arterial blood gas pressures PaO//2 and PaCO//2 independently at predetermined desired levels by adjusting two control inputs: the oxygen concentration of the inspired gas (FiO//2) and the respiration rate (R//f). An adaptive model-matching to a decoupled reference model with the two inputs and two outputs is achieved via constructing a simple model of physiological respiration dynamics of subjects with respiratory insufficiency by use of parameter identification schemes. After decoupling the two-input and two-output respiratory system, the each control input can be designed separately in an optimum manner to compensate modelling errors, variations and disturbances. The validity of the control scheme is examined in numerical simulations and animal experiments using mechanically ventilated dogs.