Portable Dynamic Digital Radiography for Quantitative Assessment of Diaphragmatic Excursion in Baseline Lung Allograft Dysfunction Among Bilateral Lung Transplant Recipients

OBJECTIVE: To investigate the association between diaphragmatic excursion and both chest computed tomography (CT) findings and baseline lung allograft dysfunction (BLAD) in bilateral lung transplant recipients, using quantitative measurements obtained by portable dynamic digital radiography (pDDR). METHODS: The present prospective study included bilateral lung transplant recipients who received postoperative CT ≥13 weeks after transplantation as well as a pDDR exam within ±14 weeks of their CT exam. BLAD was defined as failure to achieve ≥80% of predicted forced expiratory volume in 1 second and forced vital capacity after lung transplant. Diaphragmatic excursion was measured on pDDR using the maximum vertical displacement of each hemidiaphragm during tidal breathing (mm). Two radiologists independently evaluated the chest CT for pleural thickening, pleural effusion, atelectasis, ground-glass opacity, and diaphragmatic elevation. The resulting data were statistically tested for associations between the measured diaphragmatic excursion values and CT findings and BLAD status. RESULTS: Twenty patients (median age: 63.5 y; 10 males) were recruited with informed consent. Pleural thickening was significantly associated with decreased left diaphragmatic excursion (P=0.023), with a similar trend on the right (P=0.091). Atelectasis was associated with reduced diaphragmatic excursion (right: P=0.018, left: P=0.040). In patients with diaphragmatic elevation at CT, diaphragmatic excursion was significantly decreased on the elevated side (P=0.031). Of 19 patients evaluable for BLAD, 9 met the criteria. Pleural thickening on CT was noted in 78% of BLAD patients compared with 10% in non-BLAD patients (P=0.005). Diaphragmatic excursion was decreased in BLAD patients compared with non-BLAD patients, with a median of 6.8 versus 11.6 mm on the side of less motion, respectively (P=0.072). CONCLUSIONS: In bilateral lung transplant recipients, pleural thickening and atelectasis on CT were associated with decreased diaphragmatic excursion measured by pDDR. Patients with BLAD more frequently showed pleural thickening on CT, with a trend toward decreased diaphragmatic excursion by pDDR, suggesting a structural-functional pathway linking pleura, diaphragm, and lung in transplant recipients.