Hmmm…I tell you what you have experienced is very true. On two occasions my mother experienced that from our cats. Well, the first was from a cat we had from my childhood named Kelly. My mom told me she wasn’t feeling well one day and she was asleep on her back and Kelly climbed on her chest while she was asleep and was literally breathing air into her mouth; almost, like she was trying to make her feel better. You know oxygen is the “key” to good health and life. Also, I know my “Kelpo” and she was very nuturing.
Now, the other incident just happened recently with my cat Nuanawee. My mother was laying on her back in the living room, which she was very tired from working all day. Nana, my mom said, “climbed on my chest put her hand over my mouth then put herself and body in a “V” like shape closed her eyes and started blowing air into her mouth.” What my mom said is it just seemed like to her is, Nana thought she was sick and was trying to help her. I know my Nana and she is very, very, sweet. So, to answer your question maybe they’re just trying to help cause you know they do that to their babies when they are sick but hey, check with a veternarian to get the real answer.