Abstract: Tracheal gas insufflation (TGI) therapy is performed by a bypass valve and a controller which control a flow of TGI gas to a TGI catheter inserted into an endotracheal tube in the tracheal of a patient. The bypass valve is activated into a pass-through state to admit the TGI gas into the catheter and into a bypass state to divert the TGI gas from the TGI catheter. Potentially dangerous over-pressure may be sensed and the TGI gas flow terminated, but then quickly resumed after the over-pressure condition passes. Selectively applying and diverting the TGI gas allows phasic TGI therapy to be performed using heated and humidified gas and also allows the heat and humidity levels of the TGI gas to be maintained during continuous TGI therapy.