Respiratory bypass system

A respiratory bypass system is a part of Gallifreyan physiology which allows them to go without breathing for brief periods of time.

The Doctor used his respiratory bypass system to survive being strangled by an Osirian service robot. (DW: Pyramids of Mars)

The Doctor later used it to avoid inhaling helium. (DW: The Robots of Death)

The Doctor used his respiratory bypass system to survive being hanged. (ST: A Town Called Eternity)

The Doctor used his respiratory bypass system to avoid being overcome by ether. (NA: Timewyrm: Genesys)

Timothy Dean gained a respiratory bypass system when he became infected with the Doctor's DNA. (NA: Human Nature)