Inclusion Criteria:  Adult patients ≥ 18 years (Lung volumes and ventilator settings are different for ages <18 years). Traumatic SCI of duration ≤ six months Dependent on mechanical ventilation at the time of admission to The Institute for Rehabilitation and Research (TIRR)  Exclusion Criteria:  Severe dysphagia due to concomitant brain stem injury, which increases the risk of pneumonia ARDS or severe lung disease (required supplemental oxygen or ventilator prior to SCI) at the time of admission (these conditions will not allow patients to randomize because target vt may below) Prolonged antibiotics for > 3 weeks at the time of admission due to infection (e.g., osteomyelitis, epidural abscess, etc.), Presence of diaphragmatic pacemaker.