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

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