Pain on my left side. the doctor said it could be a collapsed diaphragm but don't want to do pft test until september. should i be concerned?

Sure: Well, you state you have pain, and the dr. is ordering tests, yet you are willing to wait until September-OR is it the DR. who wants to wait? And if so why wait if you still do not have a diagnosis. Get the Pft's done to be safe, and maybe a c-xray, etc. to be safe. Good luck.

Collapse airway: I wonder if you if are referring to an xray finding that shows a segment of the lung that is collapsed above the diaphragm. We call this atelectasis. You could also have pleurisy. A large collapse warrants urgent attention. A lung function test is not designed to specifically address this but can help determine underlying causes. Contact your doctor for clarification and to determine urgency.