Bone mineral density in cystic fibrosis: benefit of exercise capacity.

The aim of this study was to evaluate the association between bone mineral density (BMD) and objective maximal exercise measurements in adults with cystic fibrosis (CF). Twenty-five CF patients (19 males, 6 females, mean age 25.5 yr, range: 17-52) underwent BMD assessment and maximal-cycle ergometer exercise testing. We examined the relationship between gas exchange (% peak-predicted O(2) uptake, CO(2) output, O(2) saturation), exercise performance (maximum power, exercise duration), and respiratory mechanics (tidal volume, rate) with lumbar spine and total proximal femur BMD. The strongest clinical correlate with BMD was forced expiratory volume at 1s (lumbar spine Z-score, r=0.36; total proximal femur Z-score, r=0.68, p<0.01). The strongest exercise correlate was % peak-predicted O(2) uptake (lumbar spine Z-score, r=0.44, p<0.01; total proximal femur Z-score, r=0.59, p<0.01). There was a closer association between exercise parameters and total proximal femur BMD (r=0.43-0.60) than with lumbar spine BMD (r=0.04-0.45). Multiple regression analysis revealed VO(2) to be the strongest independent predictor of BMD (R(2)=0.86, p<0.001) followed by petCO(2) and body mass index (R(2)=0.7 and 0.5, respectively, p<0.01). Exercise appears to influence total proximal femur BMD more than lumbar spine BMD in CF. Exercise rehabilitation programs focusing on peripheral strength training may benefit those CF patients with low total proximal femur BMD.

Thin-section CT in patients with cystic fibrosis: correlation with peak exercise capacity and body mass index.

PURPOSE: To evaluate whether thin-section chest computed tomographic (CT) findings correlate with exercise capacity, body mass index (BMI), dyspnea, and leg discomfort in patients with cystic fibrosis (CF). MATERIALS AND METHODS: Institutional ethics committee approval was obtained, and patients provided written informed consent. Twenty-two patients (13 male and nine female patients; mean age, 22 years +/- 5.9; age range, 17-41 years) with stable CF underwent thin-section CT and exercise testing on a cycle ergometer. Three radiologists blinded to the clinical severity of disease and the spirometric findings of all patients independently and randomly scored all scans with a modified Bhalla scoring system. The primary measurement of the outcome of exercise testing was percentage of predicted peak O2 uptake. Univariate (Spearman rank correlation) and multivariate analyses were used to compare thin-section CT, clinical (age, sex, spirometric data, and BMI), and exercise measurements. RESULTS: The correlation between total thin-section CT score and percentage of predicted peak O2 uptake was stronger than the correlation between the percentage of predicted peak O2 uptake and any clinical measurement (R = -0.60, P < .01). The thin-section CT structural abnormalities that had the strongest correlation with percentage of predicted peak O2 uptake were severity of bronchiectasis and presence of sacculations or abscesses (R = -0.70 and -0.71, respectively; P < .01). Multivariate analysis showed total thin-section CT score to be the only significant predictor of exercise capacity, accounting for 42% of the variance in percentage of predicted peak O2 uptake. CONCLUSION: In patients with CF, the correlation between thin-section CT score and exercise limitation is stronger than that between spirometry results or BMI and exercise limitation.