Have you had a sleep apnea study?
Have you had a phrenic nerve EMG?
Have you had inspiratory/expiratory Xrays to assess your diaphragm position on either side of your chest during breathing?
Has central (brain) apnea been ruled out?

You may want to post on a forum for people with spinal cord injury (not spine disorders). Since they have failed to open such a forum here (unlike the original BT) you may want to post over at the www.CareCure.org website which is specifically for those with spinal cord injuries (SCI).