Humans piloting non-pressurized aircraft are required to use supplemental oxygen for flight above ten thousand feet or so. The exact altitude depends on duration of flight and national regulations. Generally we have the choice between two basic styles of supplemental oxygen supply, the nasal cannula (i.e. feel like you have a drinking straw up each nostril) and the mask type (i.e. feel like an extra on Gray's Anatomy). In Canada oxygen must be available to passengers above 10,000' and they are required to supplement oxygen above 13,000'. There are no laws regarding provision of oxygen to dogs.
But now if you want to treat your dog like a passenger, or make it look like at home on Futurama, you can equip it with a dog oxygen mask. 'cause the last thing you want is euphoric basset hound, a cyanotic chow or a chihuahua making poor decisions.
I already knew about dog ear defenders, (and that page has a further link to dog vomit sacks) but the doggie oxygen is new. What's next? Is my dog going to want his own chart holder?