eupnea

In the mammalian respiratory system, eupnea is normal, good, healthy and unlabored breathing, sometimes known as quiet breathing or a resting respiratory rate. In eupnea, expiration employs only the elastic recoil of the lungs.

Eupnea is the unaffected natural breathing in all mammals, including humans. Eupnea does not require any volitional effort whatsoever, but occurs whenever a mammal is in a natural state of relaxation, i.e. when there is no clear and present danger in their environment and without substantial exertion. When a mammal perceives potential danger or is under exertion, eupnea stops, and a much more limited and labored form of breathing—shallow breathing—occurs.