Characterization of chronic lung allograft dysfunction phenotypes using spectral and intrabreath oscillometry

Area of Science:

• Pulmonary Medicine
• Transplantation Science
• Diagnostic Technologies

Background:

• Chronic lung allograft dysfunction (CLAD) is a primary cause of mortality post-lung transplantation, affecting 50% of patients within five years.
• CLAD diagnosis relies on a sustained 20% decline in forced expiratory volume (FEV1).
• CLAD presents with two phenotypes: bronchiolitis obliterans syndrome (BOS) and restrictive allograft syndrome (RAS).

Purpose of the Study:

• To investigate if spectral and intrabreath respiratory oscillometry can differentiate CLAD-free, BOS-CLAD, and RAS-CLAD states at the onset of CLAD.
• To assess the utility of oscillometry in distinguishing between BOS and RAS phenotypes.

Main Methods:

• Retrospective analysis of 263 double lung transplant recipients with paired oscillometry and spirometry data.
• Data collected between 2017 and 2022 at the Toronto General Pulmonary Function Laboratory.
• Statistical analysis including multiple comparisons and post-hoc analysis.

Main Results:

• Spectral oscillometry patterns differed between RAS (similar to idiopathic pulmonary fibrosis) and BOS (similar to obstructive lung disease) compared to CLAD-free states.
• Significant differences in spectral and intrabreath parameters were observed between BOS, RAS, and CLAD-free groups, primarily driven by BOS.
• Intrabreath reactance at end-inspiration (XeI) distinguished RAS-CLAD from CLAD-free states, while R5 and end-expiratory resistance (ReE) differentiated BOS and RAS.

Conclusions:

• Both spectral and intrabreath oscillometry can differentiate BOS-CLAD from CLAD-free states.
• Intrabreath oscillometry (XeI) uniquely identifies RAS-CLAD compared to CLAD-free states.
• Oscillometry provides complementary data for distinguishing CLAD phenotypes and may aid in prognostication.