I suppose rather than a lung full of -40 degree air Id say your lungs would be exhaling the cabin pressure. I wonder if this rapid exhale is any good for the lungs.
while your are exhaling, one would be doning masks, switch mike audio to mask, activate the "rubber jungle" if it allready hasnt deployed simultaneoulsy emergency descent off the airway and advising ATC your actions, then a cabin announcement after that.All with that one exhaled breath!
Nah only kidding. But the name of the game is to get DOWN ASAP and NOT deal with super chilled Oxygen difficient air.
My 2 cents worth.
Sheep.
P.S used to FLY unpressurised B90 King Airs on long hikes across the Gulf of Mexico and Carribean sea. Its lovely stuff Oxy,makes your mouth dry, and very hard to swallow cake and drink tea. But once you take of the mask off at say 22-26000 ft, the initial symtoms of hypoxia dont take long to develope, tunnel vision etc. From experience its pretty bad stuFF not recommended, only incontrolled decompression chamber conditions.