The effect of varied fractional inspired oxygen on arm exercise performance in spinal cord injury and able-bodied persons.

OBJECTIVE: To examine the effect of different levels of fractional inspired oxygen (FiO(2)) (15%, 21%, 50%) on peak oxygen consumption (VO(2)peak) during arm exercise in persons with spinal cord injury and in able-bodied controls.

DESIGN: Case-control study.

SETTING: University medical center in the Netherlands.

PARTICIPANTS: Ten able-bodied controls, 6 persons with paraplegia, and 6 persons with tetraplegia.

INTERVENTIONS: Inspiration of 15%, 21%, and 50% oxygen during a 15-minute period before and during arm exercise.

MAIN OUTCOME MEASURES: Oxygen uptake (VO(2)peak, VO(2)peak/kg), power output, ventilation, and base excess.

RESULTS: In the able-bodied controls, significant FiO(2) dependency was seen in power output, VO(2)peak, and VO(2)peak/kg. Persons with paraplegia showed significant FiO(2) dependency in VO(2) and VO(2)/kg. In persons with tetraplegia, no FiO(2) dependency was observed; however, VO(2) and VO(2)/kg were significantly higher at 50% than at 15% FiO(2). Ventilation and base excess did not change in able-bodied controls or in persons with paraplegia with different levels of FiO(2). In persons with tetraplegia, ventilation was significantly higher at 15% than at 50% FiO(2), and base excess did not change. No significant interactions between groups and FiO(2) were observed.

CONCLUSIONS: Oxygen consumption during peak arm-cranking exercise is enhanced with an increased inspiratory oxygen fraction in able-bodied controls as well as in persons with paraplegia and to a lesser extent in persons with tetraplegia, indicating that peak oxygen consumption during arm exercise is limited by oxygen supply rather than by the small muscle mass and related biochemical limitations.