C47-05 Early Detection of Antibody- and Cmv-related Allograft Injury Using Impulse Oscillometry After Lung Transplantation

Rationale The development of donor-specific antibodies (DSA’s) and CMV viremia following lung transplantation are significant risk factor for worse outcomes, including chronic lung allograft dysfunction (CLAD) and death. CLAD is the most common cause of mortality in lung transplantations after the first year, emphasizing the importance of early detection and treatment. While transplanted patients complete frequent spirometry, its sensitivity for allograft injury is limited. However, impulse oscillometry (IOS) is a lung function test that utilizes pressure wave dynamics and may be sensitive enough to detect early changes in allograft function. We hypothesize that IOS can help detect DSA- and CMV-related allograft injury earlier than traditional spirometry. Methods Patients receiving a single or double lung transplantation at a single large volume center were enrolled from April 2024 to July 2025. Subjects were offered IOS screening in addition to their routine care for approximately one year postoperatively. IOS metrics, including R5, R20, R5-20, Ax, and X5, were collected along with spirometry and CMV and DSA status. Results A total of 39 patients, including 23 single and 16 double lung transplants, were enrolled. Patients underwent IOS screening every 18 days during the study period following transplant. Linear regression demonstrated that elevated DSA’s significantly predicted changes in R5-20 (β = 0.24, p = 0.012) and X5 (β= -0.57, p < 0.001). A Mann-Whitney U test demonstrated that R5-20 was significantly higher (p = 0.02) in patients with elevated DSA’s, indicating increased small airway resistance. In addition, X5 was significantly lower (p < 0.001) and Ax was significantly higher (p < 0.001) in those with elevated DSA’s suggesting simultaneously reduced lung compliance. However, linear regression demonstrated that CMV viremia significantly predicted inverse changes in R5-20 (β= -0.467, p < 0.001). X5 was significantly higher (p = 0.03) and Ax was significantly lower (p < 0.001) in those with CMV viremia, which suggests increased lung compliance. There were no significant changes in spirometric measurements between groups with normal or elevated DSA’s or CMV levels. Conclusion IOS detected DSA-related allograft injury through elevations in R5-20 and Ax and decrease in X5. These findings suggest an increase in small airway resistance and decrease in lung compliance in affected allografts. In those with CMV viremia, IOS detected opposite changes, which merits further study. These findings, which were spirometrically silent, may be used to augment traditional spirometry in the early detection of allograft dysfunction and prevention of CLAD.