Oscillometry (Osc) is a non-invasive test of respiratory impedance that is sensitive to small airways, a region not well characterized by conventional pulmonary function tests (PFT). It has been shown to detect early COPD prior to changes in PFT. We posit that Osc could identify small airway obstruction post-lung transplant (LTx) and discriminate between lungs from smoking vs non-smoking donors.
Double LTx recipients who consented were prospectively tested with Osc and PFT during post-LTx follow-up. Osc was conducted according to ERS criteria. Mann-Whitney U test was used to compare Osc and PFT results of recipients of non-smoking vs. smoking donor lungs.
From December 2017 to December 2019, 268 patients were enrolled. 106 received lungs from non- smokers and 147 from smokers, with 36 heavy (> 20 pack years) smokers. We excluded 6 patients with no donor smoking history and 9 who did not undergo any testing.No differences were observed between smoking and non-smoking donor groups overall. However, in the subgroup which received Ltx from heavy smokers, Osc identified small airway obstruction at 8 weeks post-LTx. The main Osc parameters of small airway obstruction, R5-R19, AX (area of reactance) and X5 (reactance at 5 Hz) were significantly different between the 2 groups. In contrast, no differences were observed in the FEV1/FVC or the % predicted FEV1 (Figure 1). The difference in R5-R19 persisted at 3 months but not observed for AX and X5.
Recipients of lungs from donors with heavy smoking history had evidence of small airway obstruction detected by Osc which was not reflected in traditional PFT parameters. This was not observed in donors with a < 20 pack year smoking history, suggesting that moderate smoking is unlikely to affect posttransplant lung function. Longer follow-up is needed to determine whether the observed differences persist over time and lead to graft dysfunction.