Assessing Ventilatory Threshold in Individuals With Motor-Complete Spinal Cord Injury

Objective: To assess the feasibility of measuring ventilatory threshold (VT) in higher-level motor-complete spinal cord injury (SCI) using 4 different analysis methods based on noninvasive gas exchange. Design: Observational. Setting: Laboratory testing. Participants: Individuals with C4-T6 motor-complete SCI (16 paraplegia, 22 tetraplegia; American Spinal Injury Association Impairment Scale A/B; 42 +/- 10 years old). Interventions: Not applicable. Main Outcome: VT from a graded arm cycling test to volitional exhaustion using 4 methods: ventilatory equivalents, excess CO2, V-slope, and combined method. Results: VT could be identified in all individuals with paraplegia, but in only 68% of individuals with tetraplegia. Individuals without observable VT completed the graded exercise test with lower ventilatory rate, peak power output, and peak oxygen consumption (Vo(2)peak) (all P<.05), compared to those with a detectable VT. Bland-Altman plots indicate minimal bias between methods (range: 0.01-0.03 L/min), with 95% limits of agreement of the difference within 0.25 L/min. Absolute <(V)over dot>o(2) at VT with individual methods were all correlated to peak power output (r>0.74; P<.01) and Vo(2)peak (r>0.91; P<.01), with negligible differences between methods. Conclusions: The assessment of VT is a feasible alternative to peak exercise testing for aerobic fitness in individuals with higher-level, motor complete SCI, although care should be taken when interpreting VT in individuals with tetraplegia who have lower cardiorespiratory fitness and lower peak power outputs. (C) 2018 by the American Congress of Rehabilitation Medicine