Abstract
BackgroundThe flow-volume (FV) curve pattern in the pulmonary function test (PFT) for obstructive lung diseases is widely recognized. However, there are few reports on FV curve pattern in idiopathic pulmonary fibrosis (IPF). In this study, we investigated the relationship between FV curve pattern and clinical or radiological features in IPF.MethodsThe FV curves on PFTs and chest high-resolution computed tomography (HRCT) images of 130 patients with IPF were retrospectively evaluated. The FV curves were divided into four groups based on the presence or absence of the convex and concave patterns: convex/concave, non-convex/concave, convex/non-concave, and non-convex/non-concave. Using a computer-aided system, CT honeycombing area (%HA) and subtracted low attenuation area (%sLAA) were quantitatively measured. To assess the distribution of CT findings, the lung area was divided into upper, lower, central, and peripheral areas. The relationships of FV curve patterns with patient characteristics, spirometry results, and quantitative CT findings were evaluated.ResultsThe patients with convex pattern was identified in 93 (71.5%) and concave pattern in 72 (55.4%). Among the four groups, patients with the convex/non-concave pattern had significantly lower forced vital capacity (FVC) and higher %HA of the upper/peripheral lung area (p = 0.018, and p = 0.005, respectively). The convex/non-concave pattern was a significant predictor of mortality for IPF (hazard ratio, 2.19; p = 0.032).ConclusionsPatients with convex/non-concave pattern in FV curve have lower FVC and poorer prognosis with distinct distribution of fibrosis. Hence, FV curve pattern might be a useful predictor of mortality in IPF.
Highlights
The flow-volume (FV) curve pattern in the pulmonary function test (PFT) for obstructive lung diseases is widely recognized
Patient characteristics Of the 191 consecutive patients with idiopathic pulmonary fibrosis (IPF) who visited the outpatient clinic of our hospital between April 2012 and March 2015, 30 patients were excluded because of the absence of high-resolution computed tomography (HRCT) images or PFT results obtained within three months from the first visit
Our results demonstrated that the patients in C group, with a convex/non-concave pattern, had higher mortality rates than those in the other groups, and suggested that this pattern may be a prognostic factor in IPF
Summary
The flow-volume (FV) curve pattern in the pulmonary function test (PFT) for obstructive lung diseases is widely recognized. In patients having both IPF and expansive emphysema, FVC may not be an appropriate indicator of the severity of IPF [9]. In another aspect of the PFT, the flow-volume (FV) curve demonstrates a portion of the respiratory dynamics. A previous study reported the presence of increased elastic recoil forces and decreased dynamic airway compression in the large bronchi in ILD [12]. These patterns have been classified by visual inspection without clear definition. In patients having both expansive fibrosis and emphysema, we cannot visualize the pattern of the FV curve
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