Respiratory System Resistance and Bronchodilator Responsiveness in Paralympic Athletes with Spinal Cord Injury

INTRODUCTION: Cervical spinal cord injury (SCI) may impair autonomic regulation of airway caliber, whereas repeated exposure to high ventilatory loads may modify airway function through mechanical stretch. PURPOSE: To compare airway function and bronchodilator responsiveness between elite athletes with cervical SCI (tetraplegia, TETRA) and thoracic SCI (paraplegia, PARA), with the hypothesis that bronchodilator responsiveness would be greater in TETRA. METHODS: Members of the Great Britain Paralympic team competing in wheelchair rugby (TETRA, C5-C7, n=11) or wheelchair basketball (PARA, T4-T12, n=11) underwent forced oscillation technique (FOT) and spirometry assessments before and 30 min after inhalation of ipratropium bromide (4×40 µg via metered-dose inhaler and spacer). RESULTS: Absolute baseline respiratory system resistance was similar in TETRA and PARA (Rrs4-24: 0.259±0.045 vs. 0.265±0.067 kPa·s·L -1). The between-group comparison of reference-based z-scores showed no significant difference (P = 0.725). Rrs4-24 exceeded the upper limit of normal in only one participant per group. Following ipratropium bromide, reductions in Rrs4-24 and Rrs4-8 were greater in TETRA than PARA (group×condition interaction, P=0.042 and 0.032, respectively). Reductions exceeding the minimal detectable difference (MDD) were observed in 73% of TETRA and 45% of PARA participants for both measures. In contrast, no participant demonstrated an increase in FEV1 that exceeded the MDD. CONCLUSIONS: Although baseline respiratory system resistance was similar in elite athletes with tetraplegia and paraplegia, the greater reductions following ipratropium bromide in TETRA suggest a greater contribution of cholinergic activity to resting bronchomotor tone. In addition, individual changes exceeding measurement error were detected more consistently using FOT than spirometry. The similar baseline resistance between groups may, in part, reflect adaptations associated with repeated exposure to the high ventilatory demands of elite wheelchair sport.