The phrase "upper airway" refers to the section of our breathing system that is located at the top. It includes our nose, mouth, throat, and voice box, where air enters and moves into our lungs when we breathe. Full definition
Bostons are predisposed to a variety of heart ailments, respiratory problems and heatstroke caused by partial upper airway obstruction and the pushed - in nose anatomy. (soonervet.net)
Brachycephalic means short - headed, and when shortened to some extremes like we witness today with Bulldogs, this respiratory problem also called congenital obstructive upper airway disease leads to a series of related problem. (breedingbusiness.com)
When breathed in by a susceptible dog, the viruses attach to the lining of upper airway passages where the warm, moist conditions allow them to reproduce and sicken the pet. (roverstayover.net)