Effects of Donor Smoking History on Early Post-Transplant Lung Function Measured by Oscillometry

Abstract

Oscillometry (Osc) is a non-invasive test of respiratory impedance that is sensitive to small airways, a region of lung that is not well characterized by conventional pulmonary function tests (PFT) and has been shown to detect chronic obstructive lung disease (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. All double LTx recipients who consented to the study were prospectively tested with Osc prior to PFT during post-LTx clinic follow-up. Osc was conducted according to ERS criteria. Mann-Whitney U test was used to compare Osc and PFT parameters of recipients of non-smoking vs. smoking donor lungs. From December 2017 to July 2019, 179 patients were enrolled, of whom 102 received lungs from donors with a smoking history (27 had ≥20 pack years) and 68 received lungs from non-smokers. We excluded 33 patients with insufficient data on donor smoking history. No differences were observed between smoking and non-smoking donor groups overall. However, in patients who received donor lungs with ≥20 pack years, Osc identified small airway obstruction 8 weeks post LTx. The main Osc parameters of small airway obstruction, Ax (area of reactance) and X5 (reactance at 5 Hz) were significantly different between the 2 groups. The R5-19 (difference between resistance at 5 and 19 Hz), a measure of small airway obstruction, was increased in smokers, but the difference was not significant. Differences in PFT were not significant (Table 1). Recipients of lungs from donors with a significant smoking history had evidence of small airway obstruction as detected by Osc. Differences in Osc measurements were not detected for donors with a <20 pack year smoking history, suggesting that a moderate smoking history is unlikely to affect post-LTx lung function. Longer follow-up is needed to determine whether the observed differences persist over time and lead to graft dysfunction.