Purpose: To document the matching of muscle O2 delivery-to-O2 utilisation in young cystic fibrosis (CF) patients from muscle deoxygenation (HHb) dynamics during ramp exercise.
Methods: Ten patients with stable, mild-to-moderate CF (12.7 +/- 2.8 y) and 10 healthy controls (CON; 12.8 +/- 2.8 y) completed a combined ramp and supramaximal cycling test to determine maximal O2 uptake (V[spacing dot above]O2max). Changes in gas exchange and ventilation, heart rate and m. vastus lateralis HHb (near-infrared spectroscopy) were assessed. [DELTA][HHb]-work rate and [DELTA][HHb]-V[spacing dot above]O2 profiles were normalised and fit using a sigmoid function.
Results: Aerobic function was impaired in CF, indicated by very likely reduced fat-free mass normalised V[spacing dot above]O2max (mean difference, +/-90% CI: -7.9 mL[middle dot]kg-1[middle dot]min-1, +/-6.1), very likely lower V[spacing dot above]O2 gain (-1.44 mL[middle dot]min-1[middle dot]W-1, +/-1.12) and a likely slower V[spacing dot above]O2 mean response time (11 s, +/-13). An unclear effect was found upon the absolute and relative WR (-14 W, +/-44 and -0.7 %PPO, +/-12.0, respectively) and the absolute and percentage (-0.10 L[middle dot]min-1, +/-0.43 and 3.3 %V[spacing dot above]O2max, +/-6.0) V[spacing dot above]O2 corresponding to 50% [DELTA][HHb] amplitude, respectively, between groups. However, arterial hypoxemia was very likely lower in CF (-1%, +/-1) and demonstrated moderate-very large relationships with parameters of aerobic function.
Conclusion: Young patients with mild-to-moderate CF present with impaired aerobic function during ramp incremental cycling exercise. Since the rate of fractional O2 extraction during ramp cycling exercise was not altered by CF, yet arterial hypoxaemia was greater, the present findings support the notion of centrally mediated oxygen delivery principally limiting the aerobic function of paediatric CF patients during ramp incremental cycling exercise.
(C) 2014 American College of Sports Medicine