A clinical evaluation of small airways by ISO method in GVHD patients

<bold>Background:</bold> The small airway disease is a common manifestation of the Graft-versus-host disease (GVHD). As bronchiolitis obliterans syndrome (BOS) develops, the small airways disfunction usually proceeds the proximal airway involvement. Thus, the assessment of the peripheral airways potentially leads to an earlier diagnosis compared to spirometry. Indeed, we aimed at assessing the damage of the distal airways in patients with GVHD, using the Impulse Oscillometry (IOS) and to compare the results to spirometry. <bold>Methods:</bold> We performed a cross-sectional monocentric study, including patients with a diagnosis of pulmonary GVHD. Each enrolled patient underwent both a spirometry and an IOS. For each patient we analysed the FEV1, the Tiffeneau index and FEF25-75 as concerns the spirometry, and ΔR5-R20 and AX to quantify the damage affecting the small airways. <bold>Results:</bold> Our cohort included 9 patients with a diagnosis of GVHD. We found that ΔR5-R20 was higher than 0.07 kPa/L/sec in 6 out of 9 patients. All of them contemporarily had a FEV1 < 80%, a Tiffeneau index < 70%, and reduced values of FEF25-75. We detected a linear increasing in R5-R20 and Ax along with the FEV1 and Tiffeneau index reduction. <bold>Conclusions:</bold> Our results suggest that IOS greatly mirrors spirometry alterations in patients with pulmonary GVHD. As FEF25-75 is not a reliable marker of distal airways involvement, the IOS might be promising for detecting early changes in lung function and obstruction of small airway thanks to ΔR5-R20.