Pulmonary function testing in spinal cord injury: correlation with vital capacity.

Spinal cord injury (SCI) causes restrictive ventilatory changes, with reductions in vital capacity, functional residual capacity, and expiratory reserve volume. Vital capacity (VC) often is used as an indicator of overall pulmonary function in these patients. In an effort to determine the extent to which VC correlates with other pulmonary function tests, 52 patients with recent acute traumatic SCI underwent complete pulmonary function testing. Statistical relationships were determined between VC and nine other tests. VC was found to be significantly correlated with forced expiratory volume in 1 s, inspiratory capacity, expiratory reserve volume, functional residual capacity, residual volume (RV), total lung capacity (TLC), and RV/TLC ratio, but not with maximum positive expiratory pressure nor with maximum negative inspiratory pressure. The excellent correlations between vital capacity and nearly all of the other pulmonary function tests support the use of VC as a single global measure of overall ventilatory status in SCI patients.