Abstract:

Introduction
To compensate the lack of pulmonary grafts, ex-vivo lung perfusion techniques (EVLP) have been developed. The evaluation criteria are based on physiological parameters such as the quality of gas exchange, pulmonary vascular resistance, edema formation, and the general appearance of the lungs. The endogenous production of carbon monoxide (CO) is influenced by inflammatory phenomena and is more particularly linked to the mechanisms of ischemia-reperfusion.
The measurement of exhaled CO (eCO) is possible thanks to a laser spectrometer (ProCeas®). This device is precise (concentrations lower than Ppmv) and fast allowing cycle-to-cycle monitoring, in real time.
The aim of the study was to assess the eCO level of human lung grafts during the EVLP procedure and to compare it with the acceptance of the grafts, the other parameters tested and the short-term outcome of the recipients.
Material and method
Lung grafts have been optimized and evaluated in normothermic EVLP. The lungs were gradually warmed, perfused and ventilated. This was followed by an evaluation phase (including recruitment maneuvers) lasting two to four hours.
The ProCeas® was connected in bypass to the ventilation circuit. CO production was averaged over five minutes at the end of each recruitment procedure.
At the end of the EVLP procedure, the decision to transplant the lungs was taken according to the usual criteria of the surgical team without knowing the value of eCO.
Results and discussion
21 procedures took place at Foch Hospital in Suresnes from December 2018 to July 2019, including 13 grafts with extended criteria (EC) and 8 from donors after cardiac arrest (Category III of Maastricht) (DDCA-M3).
The presence of blood in the airways distorted the eCO results, so three procedures were excluded.
There was no difference in eCO based on the EC or DDCA-M3 origin of the lungs.
Of the 18 grafts, two were definitively rejected at the graft. There was a tendency for higher eCO for the recused lungs (p=0.068). This trend was present from the start of the procedures.
Regarding the physiological parameters tested during EVLP procedures, eCO was correlated with glucose consumption (r=0.64; p=0.04) and lactate production (r=0.53; p=0.025). There was a non-significant relationship with vascular resistance (p = 0.062). There was no link between eCO and edema formation or the PaO2/FiO2 relationship per PPEV.
Concerning the post-operative data, by separating the grafts into 2 groups (low eCO Vs high eCO, limit fixed at 0,235 Ppmv), there was a tendency to better capacities of hemostasis (PaO2/FiO2) at 24h (p=0.052) for those with a low eCO level. All lungs with high eCO levels presented a PGD score of 3 within 72 hours (p=0.088). There was also a tendency for longer durations of resuscitation (6 days (+-3.25) vs 15 days (+-3.83), p = 0.06) and total duration in the continuing care unit (resuscitation + intensive care) (14.5 days (+-2.34) vs 19 days (+-3.4) (p = 0.07)) for grafts with a high COe level.
Conclusion
The eCO level per EVLP could be an additional and early aid in the evaluation of the lungs.
It also seems to be able to provide prognostic help to anticipate post-operative resuscitation care.