Correlation between diaphragmatic ultrasound and pulmonary function in patients after double-lung transplantation

Objective To explore the correlation between diaphragmatic ultrasound and pulmonary function in patients after double-lung transplantation. Methods This is a retrospective observational study. Patients who underwent double-lung transplantation in China-Japan Friendship Hospital from May 2022 to December 2023 were selected. Diaphragmatic ultrasound and pulmonary function test were performed. The end-expiratory(Te) and end-inspiratory(Ti) thickness of bilateral diaphragms were measured, and the thickening fraction of the diaphragm(TFdi) was calculated. The diaphragmatic excursion during quiet breathing(DEq) and deep breathing(DEd) were measured, and the variation of diaphragmatic excursion(ΔDE) was calculated. Vital capacity (VC), Total lung capacity (TLC), forced vital capacity (TLC) were measured. FVC), Forced expiratory volume in one second (FEV₁), and FEV_l/FVC were recorded in lung function test. Spearman's correlation coefficient was used to evaluate the correlation between the parameters. Results A total of 56 patients were included. There was a moderate correlation between the right DEq and TLC, VC, FVC (r = 0.391, 0.371, 0.311, respectively), a moderate correlation between the right DEd and TLC, VC, FVC and FEV₁ (r = 0.419, 0.458, 0.422, 0.387, respectively), a moderate correlation between the right ΔDE and TLC, VC, FVC and FEV₁ (r = 0.356, 0.424, 0.417, 0.432, respectively). The left DEd was moderate correlated with VC and FVC (r= 0.328, 0.315). The left ΔDE was moderate correlated with VC and FVC (r=0.343, 0.314). Conclusion Diaphragmatic ultrasound correlated with pulmonary function after double-lung transplantation, particularly in the right diaphragm.