Even in obligate nasal breathers such as horses, rabbits, and rodents, there is a potential patent path for air to travel from the mouth to the lungs which can be used for endotracheal intubation.
It has been suggested that obligate nasal breathing is an adaptation especially useful in prey species, as it allows an animal to feed while preserving their ability to detect predators by scent.
For example, denervation of the pharyngeal branch of the vagus nerve results in the dorsal displacement of the soft palate (DDSP),[3] and it has been suggested that this leads to a clinical syndrome which may include oral breathing.
[4] However, significant respiratory dysfunction including airway obstruction is observed with DDSP, and the animal cannot function normally in this state.
Like horses, the normal anatomical position of the epiglottis causes it to be engaged over the caudal rim of the soft palate, sealing the oral pharynx from the lower airways.
[13][15][16][17] Nasal breathing is a research interest in orthodontics (and the related field of myofunctional therapy)[18] and for biological anthropologists.
The infant initially attempts to breathe through the nose, and is unable to; hypercapnia occurs, and many babies instinctively begin to cry.
[26] He also observed that mothers repeatedly closed the mouth of their infants while they were sleeping, to instill nasal breathing as a habit.