Lungs maintained in the atelectatic state, hyperinflated state or with 100% FIO2 have increased capillary permeability and alveolar edema, with worsened gas exchange when compared to normally inflated lungs with 50% FIO2.15,16 Even segmental atelectasis should be assiduously avoided as it causes significant maldistribution of lung preservation solutions regardless of the route of delivery. The presence of a higher than ambient FIO2 in the alveoli during the ischemic phase of procurement and transport allows the lung to uniquely have an O2 source for continued aerobic metabolism despite the fact that the blood supply has been
Table 9.1. Preservative composition
Component Modified Low Potassium University of
(mmol/L) Euro-Collins (EC) Dextran (LPD) Wisconsin (UW)
Glucose (gm/L) 35
(Hydroxyethyl starch, HES)
halted.17 Indeed, data reported three decades ago demonstrated that canine lungs can tolerate 3-4 hours of warm ischemia in situ as long as ventilation was maintained.18 Preservation temperature at 10°C induced by core perfusion was found to be superior to 4°C and to topical cooling methods in an ex vivo rabbit lung model. Nevertheless, topical cooling as an adjunct to core cooling is felt to be essential to lung preservation during the transport period in the ischemic phase.19 Excessive hypothermia may be injurious due to cold injury, cryodessication, or by eliminating the low level of metabolic activity required for membrane ho-meostasis. Topical cooling of the inflated lung during transport in the ischemic, postharvest phase has been hampered by inhomogenous cooling of the graft due to buoyancy of the lung. A non-slush, non-immersion technique of graft cooling was investigated using cold air storage, and compared to slush immersion stor-age.20 After 8 hours, lung grafts from cold air storage at 4°C, 8°C, and 12°C demonstrated improved gas exchange and less lung edema than those grafts immersed in iced slush.
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