Altered pulmonary gas transfer capacity and capillary blood volume in pediatric Crohn's disease

OBJECTIVES: To describe diffusing capacity for carbon monoxide (DLCO) and its components, that is, membrane diffusing capacity (DmCO) and pulmonary capillary blood volume (Vc) in children with Crohn's disease (CD), and to investigate the correlation between these parameters and disease activity. WORKING HYPOTHESIS: The most common lung function abnormalities are a reduced pulmonary DLCO and small airways disorders which are in many instances, clinically silent. No valid explanations have been proposed regarding the modifications in gas transfer capacity in active CD. METHODS: DLCO, DmCO, and Vc were measured in 25 CD children by the simultaneous single breath lung diffusing capacity method using nitric oxide (NO) and carbon monoxide (CO) transfer. These parameters were analyzed in relation to the CD disease activity index. RESULTS: DLCO (90.7 ± 4.5% vs 128.5 ± 4.7%; P < 0.001), Dm (92.4 ± 5.9% vs 125.6 ± 6.3%; P < 0.001), and Vc (72.6 ± 3.7% vs 104.4 ± 4.0%; P < 0.001) were significantly decreased in the active CD group in comparison with the inactive CD group. DLCO (r = -0.60; P < 0.01), DmCO (r = -0.45; P < 0.01), and Vc (r = -0.60; P < 0.01) were inversely correlated to the PCDAI. In 8 patients who participated to the study at initial diagnosis then during remission, DmCO and Vc increased significantly between the active and the inactive period of the disease. CONCLUSION: Pulmonary diffusing capacity is impaired in children with active CD, mainly because of a decrease of the pulmonary capillary volume.