Inclusion Criteria:

• Traumatic SCI at levels C3 through C6, ASIA A, B, or C tetraplegia
• Subacute admission to Craig Hospital between 2 weeks and 6 months post-injury
• Completely ventilator-dependent (24 hours a day) at the time of admission to Craig Hospital
• Age 18-55 years
• Informed consent obtained

Exclusion Criteria:

• Concurrent severe traumatic brain injury resulting in inability to cooperate with wean protocol
• Residual severe chest trauma (pneumothorax, recurrent pleural effusion > one third hemithorax, indwelling chest tubes, flail chest, trapped lung, bilateral pulmonary contusions)
• Residual esophageal trauma that may cause ongoing aspiration;
• Current ARDS
• Current VAP unresponsive to antibiotic therapy
• Premorbid cardiomyopathy with ejection fraction <30%, unstable angina, bullous emphysema, obstructive lung disease with forced expiratory volume < 50% predicted, morbid obesity with BMI ≥ 35, increased intracranial pressure, neuromuscular disease, chronic liver disease Child-Pugh Class C, or history of bone marrow or solid organ transplantation
• Critical illness polyneuropathy
• Burns over more than 30 percent of their body-surface area
• Current participation in another clinical trial
• Any condition that, in the judgment of the investigator, precludes successful participation in the study