Before the creation of the patch, Terran research found the old life support protocols of CMC armor to be counter productive in the face of unforeseen alien threats. Normally, the old systems would inject stabilization medicines to prevent users from overexertion in combat (Starcraft Novels: Liberty's Crusade). This would be unhelpful when one of the most dangerous alien threats is known for infecting near dead soldiers to bolster their own forces.
Basically, the Lazarus patch causes power armor to build up an electrical charge to fibrillate users when they begin to flat line (Capcom/Universal Pictures: Street Fighter; Crysis 2: Nanosuit 2; Ultimate Spiderman: Flight of the Iron Spider). This causes a type of artificial CPR to revive users as fast as possible.
- 15% chance of reviving an infantry unit with 5 HPs