When I first had symptoms, there were times when I just felt like "escaping" the environment where I was. Over time I realized that I am not really suffocating so was able to consciously control the sensation and overcome the extreme need to get out of where I was. I cannot really explain the back or kidney pains but would guess (and I am not a medical doctor)  it is more of an issue that is caused by the tightening of muscles from the panic attack.