Size Matching Using Body Plethysmography and CT Volumetry for Allocation in Lung Transplantation

Objectives: Organ sizing is a key component of organ allocation in lung transplantation. Currently, lung volumes are calculated based on body size and patient sex (predicted total lung capacity, pTLC). However, lung volumes can also be measured by body plethysmography or CT volumetry. CT possibly reflects size assessment most accurately, based on a transplantation perspective. Rules for listing allow the centers to nominate either pTLC or a corrected volume derived from the mean of pTLC and body plethysmography/CT volumetry (kTLC). Donor organs are then allocated by Eurotransplant within a size range of -10% to +20%, based on the conception that mild oversizing (i.e., 5%) is beneficial for transplant outcomes.

Methods: We measured lung volumes with body plethysmography and CT volumetry in 21 patients with emphysematous lung disease (primarily COPD). We correlated these volumes to pTLC and determined the impact of the alternatively assessed organ volumes on donor organ sizes offered for transplantation into these patients.

Result: Patients were 62 ± 5 years of age (10 males/11 females), height 1.68 ± 7 cm, weight 65± 14 kg, suffered from end-stage obstructive lung disease and were all listed for lung transplantation. pTLC as calculated lung volume was 5.85 ± 0.97l, p < 0.01. Measuring lung volumes resulted in significantly larger values (body plethysmography 7.88 ± 1.92l, p < 0.05, CT volumetry 6.70 ± 1.38l, p < 0.05, kTLC (body plethysmography) 6.86 ± 1.32l, p < 0.05, kTLC (CT volumetry) 6.28 ± 1.11l, p < 0.05). Mean lung volumes that can be nominated as lung volume for the recipient by the center (TLC mean) as well as the range of organ sizes (TLC Min -10% and TLC Max + 20%) offered to the center by the allocation algorithm are: pTLC (Mean 5.85, Min 5.27, Max 7,02), kTLC/Body (Mean 6,86, Min 6,17, Max 8,23) and kTLC/CT (mean 6.28, Min 5.65, Max 7.54). That illustrates, that organs allocated to the same patient may differ significantly in size dependent on the nominated volume for this patient. The findings were the same in men and women.

Conclusion: Lung volumes differ significantly in patients with obstructive lung disease listed for lung transplantation dependent of the method of volume determination (calculated versus measured). If a center nominates the calculated volume for their patients (pTLC), a real oversizing is unlikely to occur in practice.

Publikationsverlauf

Artikel online veröffentlicht:
19. Februar 2021