You need to touch the white medical supplies for about half a second continuously for them to collect. Each one has a counter that ticks up while you are touching it and rapidly goes down when not touching it, so to collect one, you need to make this counter reach a certain amount. The best way to do this is usually by freezing the ground below you so that you are touching the supplies continuously. This probably could have been explained more clearly in the game, so my apologies about the unclear mechanic. Thanks for the feedback!