Early detection of chronic lung allograft dysfunction with spectral and intrabreath oscillometry

Chronic lung allograft dysfunction (CLAD) is the main obstacle to long-term survival after lung transplantation. CLAD is defined by a sustained >3-month drop in the forced expiratory volume in 1 sec (FEV₁) to ≤80% of the baseline value when other causes are ruled out. Oscillometry is a pulmonary function modality that is sensitive to lung mechanics. This study investigated whether oscillometry at the initial ≥20% drop in FEV₁ is associated with CLAD.

This cross-sectional study analyzed 384 double lung recipients transplanted between December 2017 and January 2023. Patients who recovered within 3 months after the initial FEV₁ drop ≥20% (_{reversible drop}FEV₁, n = 25) and those who developed CLAD (n = 49) were matched by duration post-transplant to patients who had not experienced FEV₁ drop (_stableFEV₁, n = 310). We used Wilcoxon tests with Bonferroni correction for pairwise group comparisons, and logistic regression to analyze the strength of associations between oscillometry and CLAD.

At initial ≥20% FEV₁ drop, _stableFEV₁ patients exhibited significantly better spirometry and oscillometry than CLAD and _{reversible drop}FEV₁ patients. While spirometry could not distinguish between _{reversible drop}FEV₁ and CLAD, oscillometry could. Reactance at 5 Hz (X5) was significantly (p<0.05) worse in the CLAD than _{reversible drop}FEV₁ patients and patients with lower X5 had an increased risk of CLAD (OR = 1.90 [1.01-3.57]).

X5 differentiated between patients who developed CLAD from those whose FEV₁ recovered. Lower X5 (i.e., greater lung stiffness) at time of FEV₁ drop identifies patients who are more likely to develop CLAD.