Dear Vigilant Watchman:

Circulatory and respiratory systems are vitals (heart and lungs).  Knowing how to protect
and revive them is important.  Prevention is best.  I read that the average
ambient temperature for hypothermia (general body cooling) is 58 degrees. 
A survival bed and shelter are critical.  Much heat is released from the head. 
Keep it covered.  Shock is a killer.

Mephibosheth