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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, 52patients 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 RVjrLC 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.

Weakness and spasticity of chest wall muscles are known to adversely affect pulmonary function in spinal cord-injured patients. To test the assertion that impaired strength and increased tone contribute to ventilation deficits, 52 patients with recent acute traumatic cervical and high thoracic spinal cord injury underwent complete pulmonary function testing. Regression analyses were performed to determine relationships between spinal cord injury level and pulmonary function test results and between Ashworth scale tone ratings and pulmonary function test results. Level of injury was found to be significantly correlated with expiratory reserve volume (and percent predicted expiratory reserve volume), residual volume/total lung capacity ratio, and negative inspiratory pressure but not with vital capacity, forced expiratory volume in one second, forced expiratory volume in one second/vital capacity ratio, inspiratory capacity, total lung capacity, functional residual capacity, residual volume, or positive expiratory pressure. There were significant correlations between Ashworth Scale tone ratings and negative inspiratory pressure but not between tone ratings and any of the other pulmonary function test results. It appears that muscle strength may be a more important factor than muscle tone in determining pulmonary function in spinal cord-injured patients and that both strength and tone are closely related to negative inspiratory pressure.

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