I thought this was going to be very difficult but the blue sphere secret by blue key made it possible for me.

Could normally get down all elevators in opening with 100% health. I kill a lot of enemies because they can mess you up quick. I use a trick of going by the yellow door to open a secret door.

Grabbing the yellow key is not easy without taking huge damage and this was my best by far. I turn 180 after portal to open secret door, drop elevator, grab yellow key then enter secret door grab blue sphere then exit portal. Tried other things and got wrecked.

Had a ton of health going to red key so I skip beserk on way in and go for a quick key grab after killing one chaingunner. Am able to run to exit pretty cleanly from here.