The value of high-resolution computed tomography (HRCT) to determine exercise ventilatory inefficiency and dynamic hyperinflation in adult patients with cystic fibrosis

IntroductionIn Cystic Fibrosis (CF), exercise ventilatory inefficiency and dynamic hyperinflation (DH) cause exercise limitation and induce poor exercise tolerance. High-resolution computed tomography (HRCT) of the lung can detect pulmonary abnormalities in CF patients. We aimed to identify the determinants of exercise ventilatory inefficiency and DH using HRCT-derived metrics.MethodsFifty-two adult CF patients were prospectively enrolled; all participants underwent cardio-pulmonary exercise test (CPET) and HRCT. Radiological impairment was evaluated by the Brody II scoring system. Slope and intercept of the minute ventilation/CO2 production (V'(E)/V'(CO2)) regression line and the ratio of inspiratory capacity/total lung capacity (IC/TLC) at rest and at peak of exercise were measured.ResultsFour groups of patients were identified based on the combination of ventilatory efficiency (Vef) or inefficiency (Vin) and the presence/absence of DH. Compared to other groups, CF adults with Vin and DH had worse functional status and higher total (T), bronchiectasis (B) and air trapping (AT) scores at HRCT. Significant correlations were found between V'(E)/V'(CO2 intercept) and V'(E)/V'(CO2 slope) ( -0.455, p=0.001) and between V'(E)/V'(CO2 intercept) and inspiratory capacity (IC) ( -0.334, p=0.015). Regression analysis identified AT score (cut-off 7.9, odds ratio-OR 3.50) as the only independent predictor of Vin and T (cut-off 53.6, OR 4.98), B (cut-off 16.1, OR 4.88), airways wall thickening (AWT) (cut-off 13, OR 3.41), and mucous plugging (MP) scores (cut-off 11.7, OR 4.18) as significant predictors of DH.ConclusionIn adult CF cohort, values of HRCT metrics are determinants of Vin (AT) and DH (T, B, AWT, MP).