Incidence of tidal expiratory flow limitation in lung transplant patients with and without chronic lung allograft dysfunction

<bold>Background:</bold> Oscillometry (Osc) is an effort-independent test to monitor changes in respiratory mechanics. Detection of the chronic lung allograft dysfunction (CLAD) may be improved by using Osc in the lung function follow-up. <bold>Aims:</bold> To identify the tidal expiratory flow limitation (tEFL) via intra-breath Osc (IB-Osc); we hypothesise that tEFL is more common in the CLAD than in the no-CLAD subjects. <bold>Methods:</bold> IB-Osc measurements at 10 Hz (tremoflo©, Thorasys Inc., Montreal, Canada) were analyzed in 6780 tests from 591 patients receiving lung transplants between 18-11-2017 and 7/12/2022. Criteria of tEFL were based on the reactance (Xrs) values: (a) the expiratory minimum (Xmin,E<2 cmH₂O.s/L) and the area of the Xrs vs. flow loop (AXV’<1.5 cmH₂O) and (b) visual inspection of these IB-Osc loops for the tEFL pattern characteristic of COPD patients (Lorx et. al. ERJ 49: 1601270, 2017). <bold>Results:</bold> CLAD was detected in 198 (33.5%) subjects. The tEFL pattern developed in 38 subjects with CLAD (19.2%), whereas it was detected in 31 subjects (8.5%) without CLAD. The values of Xmin,E were slightly lower in the CLAD group than that in the no-CLAD group (Wilcoxon test: p=0.047); the AXV' values were not different (Fig. 1). <bold>Conclusion:</bold> The high incidence of tEFL in CLAD patients, resembling that of the COPD, may be linked to the small airway mechanical alterations in the bronchiolitis obliterans syndrome. <fig><object-id>erj;64/suppl_68/PA3461/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig>