Is static hyperinflation a limiting factor during exercise in adolescents with cystic fibrosis?

Increased work of breathing is considered lobe a limiting factor in patients with cystic fibrosis (CF) performing aerobic exercise. We hypothesized that adolescents with CF and with static hyperinflation are more prone to a ventilatorily limited exercise capacity than non-static hyperinflated adolescents with CF .

Exercise data of 119 adolescents with CF [range 12-18 years), stratified for static hyperinflation, defined as ratio of residual volume to total lung capacity (RV/TLC) > 30%, were obtained during a progressive bicycle ergometer test with gas analysis and analyzed for ventilatory limitation.

Static hyperinflation showed a significant, though weak association (Phi 0.38; P <0.001) with a ventilatorily limited exercise capacity (breathing reserve index at maximal effort >0.70; FEV(1) 50%. In adolescents with static hyperinflation, peak work rate (W(peak), 3.1 +/- 0.7 W/kg (75.1 +/- 17.3% of predicted), peak oxygen uptake (VO(2peak)/kg (ml/min/kg); 39.2 +/- 9.2 ml/min/kg (91.0 +/- 20.3% of predicted), peak heart rate (HR(peak); 176 +/- 19 beats/min) were significantly (P <0.05) decreased when compared with non-static hyperinflated adolescents (W(peak) 3.5 +/- 0.5 W/kg (81.4 +/- 10.0% of predicted)); VO(2peak)/kg (ml/min/kg); 43.1 +/- 7.5 ml/min/kg (98.0 +/- 15.1% of predicted); and HR(peak) 185 +/- 14 beats/min). Additionally, no difference was found in the degree of association of FEV(1) (%) and RV/TLC (%) with VO(2peak)/kg(pred) and W(peak)/kg(Pred), but we found the RV/TLC (%) to be a slightly stronger predictor of VO(2peak)/kg(pred) and W(peak)/kg(Pred) than FEV(1) (%).

These results indicate that the presence of static hyperinflation in adolescents with CF by nnitself does not strongly influence ventilatory constraints during exercise and that static hyperinflation is only a slightly stronger predictor of W(peak)/kg(Pred) and VO(2peak)/kg(Pred) than airflow obstruction (FEV(1) (%)). Pediatr Pulmonol. 2011; 46:119-124. (C) 2011 Wiley-Liss, Inc.