Chest
Volume 124, Issue 6, December 2003, Pages 2215-2219
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Clinical Investigations
CYSTIC FIBROSIS
Longitudinal Determinants of Peak Aerobic Performance in Children With Cystic Fibrosis

https://doi.org/10.1378/chest.124.6.2215Get rights and content

Background

Several cross-sectional studies in patients with cystic fibrosis (CF) have shown that nutritional status and lung function are important determinants of peak aerobic capacity (peak oxygen uptake [

o2peak]). In order to account for individual changes, the aim of this study was to determine the longitudinal relationship of changes in nutritional status, lung function, and
o2peak in children with CF.

Design and methods

Fat-free mass (FFM), lung function, and

o2peak were assessed in 65 children with CF at baseline (mean ± SD age, 10.5 ± 2.9 years; mean FEV1, 92.6 ± 20.5%) and again 2 years later. FFM was calculated using skinfold thickness, and
o2peak was measured using an incremental treadmill test for children < 12 years old or an incremental cycle ergometry test for children ≥ 12 years old. Lung function was measured before the exercise test.

Results

Over the 2-year study period, an increase was found for absolute values of FFM (6.1 kg, p < 0.001), FEV1 (229 mL, p < 0.001), and

o2peak (240 mL, p < 0.001), while a decrease was found for predicted values of FEV1 (– 8.9%, p < 0.001) and
o2peak (– 4.4%, p < 0.05). Δ
o2peak over the 2-year period best correlated with ΔFEV1 (r = 0.619, p < 0.001) and to a lesser degree with ΔFFM (r = 0.506, p < 0.001). Multiple regression analysis demonstrated that ΔFEV1 and ΔFFM explained 47% of the variation of the Δ
o2peak over the 2-year period.

Conclusions

Our results show that longitudinal changes in

o2peak are associated with changes in lung function and to a lesser extent with changes in nutritional status in children with CF. Special consideration should be given to exercise training and nutritional intervention, which might improve long-term clinical outcome in children with CF.

Section snippets

Subjects

Measurement of nutritional status, lung function, and exercise performance is part of the annual medical check-up of the Cystic Fibrosis Center of the Wilhelmina Children's Hospital and University Medical Center at Utrecht. Patients who met the following criteria were approached for the study: age between 4 years and 18 years; stable clinical condition, ie, no need for oral or IV antibiotic treatment in 3 months prior to testing; and ability to perform the tests. One hundred sixty-three

Results

Eight of the 79 children were excluded from the analysis because they did not fulfill the criteria for a maximum exercise test. Six children reached the age of 12 years during the study period and therefore changed from treadmill to cycle ergometer. Several studies202122 have shown higher

o2peak on a treadmill compared to a cycle ergometer. Consecutive annual changes in
o2peak could be the result of different exercise modes, and therefore these six children were also excluded.

Table 1 summarizes

Discussion

We longitudinally studied the effect of changes in FFM and lung function on peak aerobic capacity in children with CF. Our longitudinal data indicate that changes of peak aerobic capacity in children with CF can be ascribed, to a great extent, to changes in lung function. The additional effect of changes in FFM may explain an additional 9% of the variance of changes in

o2peak.

The results of this longitudinal study are in agreement with results from cross-sectional sectional studies showing that

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