Acute cellular rejection (ACR) is common during the initial 3 months after lung transplant. Patients are monitored with spirometry and routine surveillance transbronchial biopsies. However, many centres monitor patients with spirometry only due to the risks and insensitivity of transbronchial biopsy for detecting ACR. Airway oscillometry (OSc) is a lung function test that detects peripheral airway inhomogeneity with greater sensitivity than spirometry. Little is known about the role of oscillometry in patient monitoring post-transplant.
To characterize oscillometry measurements in biopsy-proven clinically significant (grade ≥ 2 ACR) in the first 3 months post-transplant. Methods: We enrolled 156 of the 209 double lung transplant recipients between December 2017 and March 2019. Weekly outpatient oscillometry and spirometry and surveillance biopsies at weeks 6 and 12 were conducted at our centre.
Of the 138 patients followed for ≥3 months, 15 patients had 16 episodes of grade 2 ACR (AR2) and 44 patients had 64 episodes of grade 0 rejection associated with stable/improving spirometry (AR0). In 15/16 episodes of AR2, spirometry was stable or improving in the weeks leading to transbronchial biopsy. However, oscillometry was markedly abnormal, and significantly different to AR0 (p<0.05), particularly in Ax and R5-19, the indices of peripheral airway obstruction. By 2 weeks post- biopsy, after treatment for AR2, oscillometry in the AR2 group improved and was similar to the AR0 group.
Oscillometry identified physiological changes associated with AR2 that were not discernible by spirometry and is useful for graft monitoring post-lung transplant.