Forced vital capacity in two large outpatient populations with chronic spinal cord injury

To determine the expected vital capacity in persons with chronic spinal cord injury (SCI) in relation to injury level, completeness of injury, smoking and duration of injury, as an aid to diagnosis and management of respiratory complications. A New York City veterans' hospital and a Los Angeles public rehabilitation hospital. Case series from the two hospitals were pooled. Participants (adult outpatients with SCI of duration >1 year, not ventilator-dependent) were evaluated by conventional forced expiratory spirometry. Cross-sectional analysis was performed, using multiple regression, on the entire population and defined subgroups. The principal outcome measure was forced vital capacity (FVC). In the subjects with complete-motor lesions, FVC ranged from near 100% of normal predicted values in the group with low paraplegia, to less than 50% in those with high tetraplegia. Incomplete lesions mitigated FVC loss in tetraplegia. In subjects with paraplegia, longer duration of injury was associated with greater loss, and smoking-related loss was evident at older but not at younger ages, presumably due to greater pack years in older subjects. Vital capacity/SCI level relationships determined here may have diagnostic and prognostic value. Smoking-related FVC loss is important in persons with SCI as in others, although at higher levels it may be obscured by SCI-related loss.