Resumen de Impaired Aerobic Function in Patients with Cystic Fibrosis during Ramp Exercise.
Zoe Louise Saynor, Craig A. Williams, Alan R. Barker, Patrick John Oades
AB Purpose: This study aimed to document the matching of muscle O2 delivery to O2 use in young patients with cystic fibrosis (CF) from muscle deoxygenation (HHb) dynamics during ramp exercise. Methods: Ten patients with stable, mild-to-moderate CF (12.7 +/- 2.8 yr) and 10 healthy controls (CON, 12.8 +/- 2.8 yr) completed a combined ramp and supramaximal cycling test to determine maximal O2 uptake (V[spacing dot above]O2max). Changes in gas exchange and ventilation, HR, and m. vastus lateralis HHb (near-infrared spectroscopy) were assessed. [DELTA][HHb]-work rate and [DELTA][HHb]-V[spacing dot above]O2 profiles were normalized and fit using a sigmoid function. Results: Aerobic function was impaired in CF, indicated by very likely reduced fat-free mass-normalized V[spacing dot above]O2max (mean difference, +/-90% confidence interval: -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 work rate (-14 W, +/-44, and -0.7% peak power output, +/-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 oxygen saturation (SpO2) was very likely lower in CF (-1%, +/-1) and demonstrated moderate-to-very large relations with parameters of aerobic function. Conclusions: Young patients with mild-to-moderate CF present with impaired aerobic function during ramp incremental cycling exercise. Because the rate of fractional O2 extraction during ramp cycling exercise was not altered by CF, yet SpO2 was lower, the present findings support the notion of centrally mediated oxygen delivery to principally limit the aerobic function of pediatric patients with CF during ramp incremental cycling exercise.
