Sleep Apnea in Patients with Cervical Spinal Cord Injury

Eligibility Details: Inclusion Criteria: 1. healthy adults between the ages of 18 - 89 2. chronic spinal cord injury patients (T6 and above), > 3 months since injury and not on mechanical ventilation, and have not received mechanical ventilation via tracheostomy in the past. Exclusion Criteria: 1. subjects ≤ 17 yrs old 2. Pregnant and lactating females 3. History of head trauma that resulted in neurological symptoms or loss of consciousness 4. advanced heart, lung, metabolic, liver or chronic kidney disease. 5. severe obstructive or restrictive respiratory defect by PFTs or history of tracheostomy 6. extreme obesity defined for this protocol as BMI ≥ 40 kg/m2 (to avoid the effect of morbid obesity on ventilation.