T.M.
I have terrible coughing spells like that. I cannot imagine a child going through it :( When i shut the bathroom door, i steam the shower and the sink, and also shove a towel under the door. My inhaler helps a little. Also, when i get steriods they help too. Hopefully the dr can give him something like that to help. I keep a humidifier in my room and sleep on a ton of pillows to keep me proped up. (i also put the "tootsie roll" pillows under my arms to keep me propped up). A fan blowing near my face helps too. A hot cup of decaf tea, sipped slowly sometimes helps also.
I am so sorry. I hope i helped a little. It really is terrible :( I hope he feels better soon!!