In hot weather dogs keep cool by panting. If I were to do this I would hyperventilate and exhale too much carbon dioxide. How do dogs avoid the effects of respiratory alkalosis?
鈥� Each breath taken by a human (or a dog for that matter) consists of a volume of air that enters the lungs and a smaller volume that only gets as far as the passages that lead to them. This is the 鈥渄ead space鈥�, so called because no exchange of oxygen and carbon dioxide occurs in the mouth, pharynx, trachea or bronchi.
Rapid, shallow breathing can affect just this dead space without hyperventilating the gas-exchange part of the lungs, the alveoli. As air passes through the dead space it produces a cooling effect as moisture lining these passageways evaporates. Dogs, lacking sweat glands, use this method to cool down. Humans have no need of this, though we can do it. Try 鈥渇luttering鈥� your breathing by taking fast, shallow breaths, at least 60 per minute. You will feel a cooling effect in your mouth, but not the dizziness that can accompany hyperventilation. It鈥檚 hard work though鈥�
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John Davies, Anaesthetist, Lancaster, UK