Impaired pulmonary VO2 kinetics in cystic fibrosis depend on exercise intensity

• Autores: Zoe Louise Saynor, Alan R. Barker, Patrick John Oades
• Localización: Medicine & Science in Sports & exercise: Official Journal of the American College of Sports Medicine, ISSN 0195-9131, Vol. 48, Nº. 11, 2016, págs. 2090-2099
• Idioma: inglés
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• Resumen

  • AB Purpose: This study aimed to investigate the effects of mild-to-moderate cystic fibrosis (CF) on the pulmonary oxygen uptake (V[spacing dot above]O2) kinetics of seven pediatric patients (13.5 +/- 2.8 yr) versus seven healthy matched controls (CON; 13.6 +/- 2.4 yr). We hypothesized that CF would slow the V[spacing dot above]O2 kinetic response at the onset of moderate (MOD) and very heavy (VH) intensity cycling. Methods: Changes in breath-by-breath V[spacing dot above]O2, near-infrared spectroscopy-derived muscle deoxygenation ([HHb]) at the vastus lateralis muscle and thoracic bioelectrical impedance-derived heart rate (HR), stroke volume index, and cardiac index were measured during repeat transitions to MOD (90% of the gas exchange threshold) and VH ([DELTA]60%) intensity cycling exercise. Results: During MOD, the phase II V[spacing dot above]O2 [tau] (P = 0.84, effect size [ES] = 0.11) and the overall mean response time (MRT) (P = 0.52, ES = 0.11) were not significantly slower in CF versus CON. However, during VH exercise, the phase II V[spacing dot above]O2 [tau] (P = 0.02, ES = 1.28) and MRT (P = 0.01, ES = 1.40) were significantly slower in CF. Cardiac function, central O2 delivery (stroke volume index and cardiac index), and muscle [HHb] kinetics were unaltered in CF. However, the arteriovenous O2 content difference ( ) was reduced during VH at 30 s (P = 0.03, ES = 0.37), with a trend for reduced levels at 0 s (P = 0.07, ES = 0.25), 60 s (P = 0.05, ES = 0.28), and 120 s (P = 0.07, ES = 0.25) in CF. Furthermore, significantly correlated with the VH phase II V[spacing dot above]O2 [tau] (r = -0.85, P = 0.02) and MRT (r = -0.79, P = 0.03) in CF only. Conclusion: Impairments in muscle oxidative metabolism during constant work rate exercise are intensity dependent in young people with mild-to-moderate CF. Specifically, V[spacing dot above]O2 kinetics are slowed during VH but not MOD cycling and appear to be mechanistically linked to impaired muscle O2 extraction and utilization.