Lumbar (spinal region) tension preventing full, deep breath, can anyone recommend an effective exercise?

I need something other than the typical deep breathing exercises, as they aren't enough. I'm doing yoga and tai chi as well, which help, but also aren't enough. I need a more conveniently specific exercise, yoga pose, whatever. This is not only causing rosacea but also improper spinal alignment which are affecting my arms and hands, a vital key to my job.