Airflow Obstruction and Reversibility in Spinal Cord Injury: Evidence for Functional Sympathetic Innervation

Objectives: The first objective was to assess group differences for specific airway conductance (sGaw) among subjects with tetraplegia, high paraplegia (HP: T2-T6), and low paraplegia (LP: T10-L4). The second objective was to determine the significance of responsiveness to ipratropium bromide (IB) by the assessment of the inherent variability of baseline measurements for impulse oscillation (IOS), body plethysmography, and spirometry. Design: Prospective cross-sectional intervention study. Setting: James J. Peters Veterans Administration Medical Center. Participants: Subjects (N=43): 12 with tetraplegia (C4-8), 11 with HP, 11 with LP, and 9 controls. Interventions: Not applicable. Main Outcome Measures: Measurement of IOS, body plethysmography, and spirometry parameters at baseline and 30 minutes after IB. Results: Baseline sGaw was significantly lower in tetraplegia (0.14 +/- 0.03) compared with HP (0.19 +/- 0.05) and LP (0.19 +/- 0.04) patients. By use of minimal difference to evaluate IB responsiveness in tetraplegia, 4 of 12 and 12 of 12 subjects had significant increases in forced expiratory volume in I second and sGaw, respectively, whereas I I of 12 and 10 of 12 subjects had significant decreases in respiratory resistances measured at 5 and 20Hz (R5 and R20), respectively. Conclusions: The finding of group differences for baseline sGaw supports the hypothesis that human lung contains functional sympathetic innervation. Body plethysmography and IOS were comparable in detecting IB-induced bronchodilation in tetraplegia and significantly more sensitive than spirometry.