I have...on a few occasions. Here's the latest. In the recovery room after a knee replacement. 3rd operation on this knee and it was rough. Woke up in extreme pain...evidenced by my blood pressure being very high...and me saying, "OW,OW,OWWWWWW" of course. They pumped me so full of pain killers, I started to have trouble breathing. Classic opiate/opiod OD. Now I have a nervous nurse shaking me to keep me awake and barking "BREATHE" at me while another gets an oxygen mask. Still struggling to stay awake and breathe enough for Nurse Nervous. I hear her saying to another nurse, I have "situational anxiety." I can barely talk because I'm half knocked out and have air blowing IN to my throat, so it's hard to get words out, but I tell her that's because the SITUATION is, I can't freakin' BREATHE. So I spend the whole night with a mask and a blood oxygen monitor that beeps every 30 seconds when the oxygen level drops and I have to breathe deep. As if a knee replacement isn't enough!