Dead Space: Extraction

You'll unlock the Medical Bay Challenge after completing Chapter 6 of the story mode. The top score is 255,010 so you need more than this to earn the trophy.

This is another really easy challenge and you can make full use of the tactic explained in Overtime Sheet. I got a kill streak of 118 which gave me 536,550 points. You want to aim for a streak of around 70-80 or 3 lots of 45 to hit the target. If you get hit before wave 6 restart. Don't forget if you run low on ammo for the Flame-thrower to make use of other weapons. Early on you can use the Rivet Gun (if it's fully upgraded) and it does some serious damage, saving precious ammo for when you've facing multiple necromorphs. As usual make sure to use stasis on the mothers before they unleash the little necromorphs. If she does get the Flame-thrower out and fry the floor infront of you to stop them jumping on you.