Is your air trapping happening on the inhale or exhale? Mine happens when I go to exhale. This is due to having COPD. Other lung diseases can also give you problems with air trapping or impede the ability to breathe normally, for example diaphragm issues. Air trapping can cause that SOB feeling, as well as panic/anxiety attacks. These attacks often occur with patients who have lung issues, and it is a result of a malfunction in the brain. A misfiring of neurons in the brain if you will. They don't know why this happens, but it does. I was told by a Mayo dr that the feeling of oxygen deprivation is the brain not registering the oxygen. I had one such attack and it landed me in the hospital for three days. I feel certain that deep seated subconscious things can bring on these symptoms as well. If you suspect that is your case; you may want to look into hypnotherapy.