Spirometric evaluation of idiopathic pulmonary fibrosis (IPF): forced or slow vital capacity?

Abstract

Forced vital capacity (FVC) is commonly used to evaluate severity, progression, prognosis and therapeutics in IPF. However, FVC has shown significant variability in IPF evaluation leading to differences in the assessment of disease severity and evolution. Slow expiratory vital capacity (SVC) has not been systematically explored in IPF. The aim of the study was to compare baseline FVC and SVC in a group of patients with diagnosis of IPF. Methods: A retrospective study was carried out. Spirometry and plethysmographic lung volumes were obtained according to ATS-ERS Statement. Diagnosis of IPF was based on ATS/ERS/JRS/ALAT 2018 guidelines. Combined IPF-emphysema (CPFE) was excluded. Sign rank Wilcoxon test was used. Results: Fifty four (78% males) patients, age 64 (59-72) years, 40 (74%) ex-smokers with IPF were studied. Table shows PFTs of the studied population. Forty two (78%) patients showed higher SVC than FVC at baseline. SVC was significantly higher than FVC: 110 (20-170) mL (p FVC and the group SVC≤FVC. Conclusions: Spirometric baseline condition of IPF seems to be more accurately assessed by SVC than FVC. The uneven impact of heterogeneous IPF lesions on lung volumes and flows could account for the higher SVC that we found in almost 80% of patients. Prospective studies are needed to determine the utility of SVC for IPF evaluation.