Donor Age and Recipient-Donor Sex and Height Mismatch Are Associated with Abnormal Pulmonary Reactance (X5) in Stable Recipients After Bilateral Lung Transplantation

Abstract

<h3>Purpose</h3> Respiratory system reactance at 5Hz (X₅) reflects tissue elastance and inertance and is measured using oscillometry, a novel measurement of respiratory mechanics. Abnormal reactance (stiffness) has been observed in baseline and chronic lung allograft dysfunction. This study aims to assess predictors of pulmonary reactance in stable lung transplant (LTx) recipients. <h3>Methods</h3> A cross-sectional study was performed on bilateral lung transplant (LTx) recipients at 2 Australian centres between Jan-20 and Jun-21. Spirometry and oscillometry (TremoFlo C-100) were performed to obtain FEV₁ and FVC and X₅, respectively. Patients with acute and chronic lung allograft dysfunction (LAD) were excluded. Baseline lung allograft dysfunction (BLAD) was defined as failure to achieve FEV₁ or FVC >80%-predicted. Oostveen equations were used to generate predicted X₅ values. Abnormal X₅ was defined as Z-score ≤ -1.64. Logistic regression measured associations between baseline transplant predictors and risk of abnormal X_5. <h3>Results</h3> A total of 326 bilateral lung transplant recipients underwent oscillometry. 173 patients with LAD were excluded and 153 included for final analysis. Patients were at median (IQR) 1.9 (2.7) years after transplant. The median (IQR) concurrent FEV₁ as %-baseline FEV₁ was 96% (7). Abnormal X₅ was detected in 21 (13.7%) and normal X₅ in 132 (86.3%). Increasing donor age (OR 1.03, 95%CI 1.00-1.06, p=0.047), recipient-donor sex mismatch (Male:Female OR 5.15, 95%CI 1.70-15.59, p=0.004), donor-recipient height difference (OR 0.95, 95% CI 0.90-0.99, p=0.027) and spirometric BLAD (OR 7.21, 95%CI 2.59-20.06, p<0.001) were associated with an increased risk of abnormal X_5. <h3>Conclusion</h3> Undersizing of lungs, recipient-donor sex mismatch and increasing donor age are significantly associated with abnormal X₅. Differences in lung volume due to sex and size matching may partly explain this association. Increasing age is associated with decreased lung elastic recoil. Preliminary analysis is limited by the use of recipient anthropometrics to generate predicted values. Longitudinal studies are required to determine if the reactance trajectory may help predict patients at risk of poor outcomes.