Usefulness of the Impulse Oscillometry System in Graft Function Monitoring in Lung Transplant Recipients

Abstract

BackgroundAfter successful lung transplantation, patients are monitored for chronic lung allograft dysfunction. Pulmonary function tests and 6-minute-walk tests are commonly used for functional graft monitoring. As these methods require substantial effort, however, many patients are unable to complete testing fully. The impulse oscillometry system is a noninvasive method that requires minimal patient cooperation and is suitable for use for patients incapable of strenuous activity. We compared impulse oscillometry system with pulmonary function tests and 6-minute-walk tests to determine if impulse oscillometry system could serve as a substitute measure. MethodsThis prospective, observational study evaluated 25 consecutive patients (19 men, median age 54.5 years) admitted to a single institution from January to October 2016 (double-lung = 13, single-lung = 13). Patients were assessed using pulmonary function tests, impulse oscillometry system, and 6-minute-walk tests. ResultsEighty-eight percent of patients reached high-resonance frequency (Fres) and, in 84% of patients, the value of Ax (area of reactance) increased above the norm (N < 0.33 kPa/L) indicating peripheral airways obstruction. High resistance of small airways, measured with an R5 – R20 difference, followed higher Ax values. The increase of resistance at 5 Hz in 31% of patients (R5 >150% predicted value) also indicated small airway obstruction. Airway obturation in patients with elevated Ax and R5 was confirmed by decreased FEV1 (<75% predictive value) and FEV1/FVC ratio in 38% of patients. ConclusionsStudy results confirm the impulse oscillometry system method could be a substitute for pulmonary function tests in determining the occurrence of chronic lung allograft dysfunction. 6-minute-walk tests showed neither strong correlations regarding impulse oscillometry system and pulmonary function tests nor any base for differentiation of results regarding main factor codes.