Abstract
INTRODUCTION: Interstitial lung diseases (ILD) are a heterogeneous group of disorders generally sharing physiologic abnormalities such as restrictive ventilatory defect andreduced diffusing capacity for carbon monoxide (DLCO). In idiopathic pulmonary fibrosis (IPF), DLCO, product of two primary measurements during breath-holding: CO transfer coefficient (kCO) and alveolar volume (VA), is considered to be more informative than kCO in predicting gas exchange modifications. We aimed at comparing the relevance of both kCO and DLCO in IPF and other ILDs.
MATERIAL AND METHODS: We retrospectively studied 84 patients with ILD: groups 1 (IPF: n=26), 2 (stage IV sarcoidosis: n=17), and 3 (other fibrosing ILD: n=41). All had performed HRCT and pulmonary function tests (PFT) including spirometry, plethysmography, kCO and VA measurements. Statistical analysis was performed using Kruskall-Wallis test.
RESULTS: IPF pts were older (73±13 yrs) than the 2 other groups (p<0.0001). TLC and FVC were similar in the 3 groups : TLC = 70+21%, 72+20% and 80+18% predicted, respectively, and ; FVC = 75±25, 69±24%, 74±20% predicted, respectively, in gr 1, 2 and 3 (NS). In contrast, while DLCO was also similar in the 3 groups, kCO was clearly decreased in IPF alone (p<0.01). A marked basal predominance of fibrotic lesions on HRCT was associated with a lower kCO but with no difference in DLCO.
CONCLUSION: IPF is associated with a preferential alteration of kCO rather than of DLCO, reflecting the major implication of alveolo-capillary membrane disorders in this disease. kCO provides more hints to IPF pathophysiology and might be helpful to differential diagnosis of ILD with no CT scan pattern typical of IPF.
- © 2014 ERS