My DH and I were mtn. biking one day and I went back to the van early, with our wee terrier. The trails were super technical with unforgiving granite---great traction, poor to take a header onto...
DH rode some more, then I noticed he was coming back on the road. Walking. Hmm. Thought at first he had a mechanical failure, but it turned out he'd injured himself in a spectacular landing failure. He was looking queasy and said it hurt to breathe. Thought he'd maybe popped a lung (well, punctured it...) although he'd not hit anything.
I asked which lung he thought it was and he indicated the left one. I asked how he knew, and he said he could feel a bit of heaviness in that side and it was difficult to take a deep breath, as well a painful.
When I was a kid, I used to love exhaling on cold windows to watch my breath steam up the window and then slowly evaporate. So, in my great wisdom-of-the-moment, I heard myself saying something that even as it was coming out of mouth, I knew was wrong. "Well, plug one nostril and see how much air comes out..."
DH was certain I was trying to kill him 'cause it really hurt to laugh, breathe, etc. His retort, "Stop it. You're trying to kill me... [voice fading to a whisper]" And then I couldn't stop laughing. To this day, we get fits of giggles about it. Blessed is the medical system that I didn't go into medicine...
Turns out it he did tear the lung by virtue of the severity of the smack-down landing on his left side. The sheer force of the hit caused the tissue to tear!
Fortunately, after releasing the air and staying close to immobile, he healed well.