Respiration (breathing) signal movement artifact removal
I figured out how to tackle the problem.

I used the EMD algorithm and then smoothed the signal. I removed the first two IMF[i] and the last IMF[i] and reconstructed the signal again. This removes posture movement.
I then  identified 3sd away outliers and chopped off the signal to pieces. For each piece I calculated the FFT and found the dominant frequency.