Man, I love this place because I’m always learning something new.
You’re right about the importance of tidal volume. Panting involves moving air in the upper respiratory pathway, where oxygen exchange is minimal. This reduces the rate at which a dog will go into respiratory alkalosis (the increase of bicarbonates in the bloodstream). But the dog will have to take regular breaths to get air into the aveolar sacs so that oxygen exchange can occur. So, he “pantspantspantspantspants” stops and breathes regularly for a bit, then “pantspantspantspantspants.” And so on. Those big, slobbery dog tongues (which are highly vascular) provide a nice large surface for heat transfer via evaporation.
This I already knew from physiology classes. What I didn’t know was that the act of panting does not require a lot of muscular work. Muscular work generates heat, and could be counter-productive if the idea is to blow off heat. But panting is done at a rate that is the natural oscillation frequency of the chest cavity, and this means very little muscular work to move air during the pant breaths. This is pretty cool, so thanks for asking the question!
(And like **CCL ** suggests, sometimes behavioral/physiological actions fail to counteract high body heat. Denatured proteins trump respiratory alkalosis. :eek: )