A method of operating a ventilator assembly having inhalation and exhalation passages communicating with one another, and a respiration assembly that can perform repetitive respiratory cycles. The method includes (a) repetitively cycling the respiration assembly so that during the inhalation phase, gas in the inhalation passage flows to the patient, and during the exhalation phase, an exhalation valve is maintained relatively closed and the exhaled gases flow pass the vocal cords and out of the mouth thereby facilitating the patients ability to speak, (c) monitoring the pressure within at least one of the passages during the exhalation phase, and (d) determining whether a circuit disconnect or an occlusion exists based on the pressure monitoring.
