How to use additive animation with a pose

I’m trying to animate a skeletal mesh when it’s idle. I have an animation that is supposed to be an offset to a pose. The animation is supposed to make it look like the person is breathing/making small movements. The idea is that there are multiple idle poses that the animation can be applied to so I don’t have to make an animation for each pose with the small movement. Since the animation is supposed to be an offset to the pose if I preview the animation by itself it looks like the first image. The pose I have is the second image. If someone could point me in the right direction of how to use this animation as an offset that would be great.