Optimal flow rates during ex-vivo lung perfusion (EVLP)?
An intriguing but rather limited porcine study suggests a possible advantage of lower flow rates during EVLP of DCD lungs.
Over the last twenty or thirty years, a wealth of literature has been generated on attempts to define the optimal guidelines for temperature, flow, pressures and other evaluation phase parameters during ex-vivo lung perfusion (EVLP). Optimal flow rates in particular have ranged from 20% to 100% of cardiac output although no comparative studies seem to have conclusively shown any difference in post-transplant outcome.
Most of the many studies on optimal EVLP parameters, however, tend to support a flow rate corresponding to 40% of cardiac output (CO), although 100% of CO has been successfully used in the Lund protocol for many years. Occasionally, even flow rates as low as 20% of CO have been evaluated.
One such rather limited experimental study was recently published (8) in which porcine lungs donated after circulatory death (DCD) were subjected to EVLP for four hours at flow rates of either 20% or 40%. The lungs were then transplanted and followed for a further four hours.
After transplant, left lung-specific pulmonary vein partial pressure of oxygen was significantly higher in the low-flow group at three and four hours of reperfusion. The authors claim that their low-flow protocol improved lung function, reduced edema, and attenuated inflammation after transplant. Although the study is interesting there appear to be too many limitations to draw conclusions: there were only four pigs in each group, the warm ischemic times were exceptionally long, and there was no cold preservation time. We do not yet know if there is a cost to low-flow in a human setting.
8. Beller JP et al, Reduced-flow ex vivo lung perfusion to rehabilitate lungs donated after circulatory death J Heart Lung Transplant. 2020 Jan;39(1):74-82. doi: 10.1016/j.healun.2019.09.009. Epub 2019 Sep 18. (link to abstract)
Xvivo Insights PB-2020-02-27