Experimental study of oversized grafts in a canine living-donor lobar lung transplantation model

Background: For infants and small children, organ transplantation is limited by the size discrepancy between donor and recipient. To address this problem, the use of oversized grafts from living-relatative donors could potentially expand the donor pool. The aim of this experimental study was to evaluate the effect of oversized grafts on early pulmonary function and to identify an indicator for acceptable size discrepancy. Methods: Fourteen bilateral lobar lung allotransplant operations were performed without cardiopulmonary bypass in weight mismatched pairs of dogs. Animals were divided into 2 groups: Group I (n = 7), donor/recipient lung volume ratio <2.85; Group II (n = 7), donor/recipient lung volume ratio >2.85. Pulmonary function of the recipient was measured before chest closure, after chest closure, and after the ventilator was removed. Results: Pulmonary vascular resistance and airway pressure significantly increased in Group II after chest closure (1493 ± 195 dynes sec cm^-5 and 14.4 ± 0.9 mm Hg vs 2784 ± 140 dynes sec cm^-5 and 23.4 ± 1.2 mm Hg, p < 0.001). After the ventilator was removed, all recipients in Group I showed PaO2 > 239 mm Hg and PaCO2 < 76 mm Hg, whereas, all recipients in Group II showed PaO2 < 116 mm Hg and PaCO2 > 169 mm Hg. The donor/recipient chest circumference ratio was less than 1.3 in all but 1 dog in Group I. Conclusions: Acceptable, oversized grafts provide adequate pulmonary function, although excessively oversized grafts cause significant impairment in pulmonary function after chest closure. Chest circumference provides useful size-match criteria when oversized grafts are used in this canine experimental model.