If you type in the 'Chris Barnes' code first when you make the optical disc in Episode 2 you will get a first aid kit. Just keep repeating the process to get your desired amount of first aid kits.

Try entering these codes if you are struggling and need help progressing in the game.

Unlock ALL Acts:
Enter R2, Right, L2, Up, Square.

Unlock ALL Bonus Features:
Enter Left, R1, L1, Down, Circle.

Unlock Invincible Player:
Enter Up, Square, Circle, X, Down.

Unlock One-Shot Kills:
Enter Circle, L2, Down, R1, X.

Unlock Infinite Ammunition:
Enter L1, L2, X, R2, R1.

Unlock Grenade Bullets:
Enter X, Circle, Square, L2, R1.