Yikes!
I'm glad he's on the mend now and hope he will get to come home today.
If you'd like more info on what actually happened to cause this, there's a site I found that explains it in laymans terms. "Spontaneous Pneumothorax" is something we were trained to deal with in my EMT classes. It's pretty frightening for the patient, and their families, but usually has a good outcome if treated promptly.
http://www.lungusa.org/site/pp.asp?c=dvLUK9O0E&b=35772