Spinal cord injury is associated with enhanced peripheral chemoreflex sensitivity

Sleep‐disordered breathing (SDB) is prevalent in individuals with chronic spinal cord injury (SCI), but the exact mechanism is unknown. The aim of this study was to investigate whether peripheral chemoreceptors activity is enhanced in individuals with chronic SCI compared to abled‐bodied control subjects using CO (2) and O(2) chemical tests. In protocol (1) 30 subjects (8 cervical [cSCI], 7 thoracic [tSCI] and 15 able‐bodied [AB]) were studied to determine the ventilatory response to hyperoxia during wakefulness in the supine position. In protocol (2) 24 subjects (6 cSCI, 6 tSCI, and 12 AB subjects) were studied to determine the ventilatory response to a single breath of CO (2) (SBCO (2)). The chemoreflex response to SBCO (2) was calculated as ∆V(E)/∆CO (2) (L/min/mmHg). The ventilatory response to hyperoxia was defined as the % change in V(T) following acute hyperoxia compared to preceding baseline. During hyperoxia SCI subjects had a significant decrease in V(T) and V(E) (63.4 ± 21.7% and 63.1 ± 23.0% baseline, respectively, P < 0.05) compared to AB (V(T): 87.1 ± 14.3% and V(E): 91.38 ± 15.1% baseline, respectively, P < 0.05). There was no significant difference between cSCI and tSCI in the V(T) or V(E) during hyperoxia (P = NS). There was no significant correlation between AHI and V(E)% baseline (r = −0.28) in SCI and AB (n = 30). SCI participants had a greater ventilatory response to an SBCO (2) than AB (0.78 ± 0.42 L/min/mmHg vs. 0.26 ± 0.10 L/min/mmHg, respectively, P < 0.05). Peripheral ventilatory chemoresponsiveness is elevated in individuals with chronic SCI compared to able‐bodied individuals.