Predictors of ventilator weaning in individuals with high cervical spinal cord injury

To evaluate which tests best predict the ability of patients with ventilator-dependent tetraplegia to wean from the ventilator.

Retrospective review of patients.

Twenty-six ventilator-dependent patients with tetraplegia admitted to a university inpatient spinal cord-injury rehabilitation unit with American Spinal Injury Association (ASIA) injury levels C2 to C6, A or B.

Failure to wean off the ventilator completely was predicted by absence of motor unit recruitment of one hemidiaphragm or at least moderate decreased recruitment with needle electromyography (EMG) in both hemidiaphragms. Phrenic nerve conduction studies would have predicted that all patients who weaned off the ventilator would have failed. Fluoroscopic examination of the diaphragm and bedside spirometry were not as good predictors of ability to wean, failing to predict accurately in 44% and 19% of cases, respectively. ASIA examination was also not entirely predictive, and any outliers that may have been expected to wean based on ASIA examination (ie, C4 or lower neurological levels) were predicted not to wean by needle electromyography.

Negative inspiration force diaphragm needle EMG best predicted the ability to wean from the ventilator. Bedside spirometry (negative inspiratory force and forced vital capacity) is an accurate bedside measure of a patient's readiness to wean. Fluoroscopic examination of the diaphragm and phrenic nerve conduction studies were not helpful in determining weaning potential in ventilator-dependent patients with cervical spine injury.