This is a serious respiratory infection that will need prescribed antibiotics to treat. I'll warn you...by the time a cham starts bubbling it is very serious. You need an experienced herp vet NOW. Most vets prescribe Baytril as it is broad spectrum, but it is also tough on kidneys so you will need to be very careful to hydrate him well during treatment. If the vet gives you an subcutaneous injectable form be sure you don't inject it in the back half of the body...too close to kidneys. If it is to be given orally you may find it is easier to give mixed with a little warm Pedialyte...not so bitter and again will help with rehydration. If your vet can't show you how to give it here's a tip. Tip the cham's head back and squirt it down the BACK of the throat to avoid getting any liquid down the trachea. The trachea opens in the throat near the base of the tongue. The next thing to do is review your setup and husbandry to find out why he got the infection in the first place. He will be very suseptible to another or this one will get worse if you don't. Descibe your setup, temps, lighting, humidity levels, gutloads, dusting schedule, etc. Also have the vet check his lips, gums, and inside the mouth for any possible local infection just in case.