PLM Implementation of a Multiple Closed-Loop Control Strategy for a Microprocessor-Controlled Respirator

This paper describes the control structure for the first microprocessor-based respirator approved by FDA for life support. The respirator offers the conventional mandatory and spontaneous modes of ventilating patient´s lungs. In the mandatory mode, two decoupled feedback loops establish the air and O2 flow levels to deliver breaths based on operator settings for volume, oxygen concentration, peak flow, frequency and wave forms. In the spontaneous mode a pressure control loop establishes the total flow required to maintain patient´s proximal airway pressure at the desired level. The two flow control loops deliver the total desired flow in a proportion determined by the operator entry for oxygen concentration. The respirator control strategy was implemented utilizing PLM language in an 8088 Intel microprocessor.