C.E.
Go to the health food store and get a small bottle of Peppermint oil. Add a drop or two to the humidifier. You can put a little on his chest and forehead, but be aware it will be very strong and you only need a little if you put it on him. However even putting it in the humidifier or a little on his blankets or sheets will help open him up and make it a bit easier to breath. I use it all the time especially with my asthma.
Good luck and hope he is feeling better soon
Chel E