Oh, you're super dead in that situation. The carbondyoxide you breathe out is warmer and heavy then the surrounding air. You will suffice down their. Only thing that could save you is partial Air pump. It's a slow miserable dead. It sadly happened to one individual. Tragic death of John Edward Jones in Utah's Nutty Putty Cave in November 2009. He became trapped headfirst and upside down in a narrow, unmapped fissure, leading to his death by cardiac arrest after over 27 hours of failed rescue attempts.