Previous literatures found the incidence of PPCs following liver transplant ranged from 42.1% to 88%.[1-5] Although it might differ depending on PPC definition, the incidence of PPC is much higher than other types of major surgery which ranged from <1 to 23%.[6]
Driving pressure is the difference between plateau pressure and PEEP which represents static compliance. High driving pressure indicates poor lung condition with decreased lung compliance and has been known for poor prognosis in various populations including surgical patient. A recent meta-analysis suggested that driving pressure was the unifying parameter determining the effect of intraoperative mechanical ventilation and the relative importance was much stronger than PEEP or tidal volume.[14] In the same context, recent randomized controlled trials reported that driving pressure-guided ventilation during high-risk surgery reduced PPC compared with conventional ventilation strategy.[15, 16]
High incidence rates of PPC in liver transplant has been known for a link to mortality and morbidity after liver transplantation.[2, 4, 7] Numerous preoperative, intraoperative, and postoperative risk factors have been implicated in the development of PTPCs.[1-5, 10] However, the intraoperative variables were limited to transfusion or surgical technique which were rarely modifiable. The effects of other intraoperative practices including ventilatory strategy on PPC were not fully assessed in liver transplantation.  
Therefore, We aimed to compare the incidence of postoperative pulmonary complications(PPC) after living-donor liver transplantation between Individualized driving pressure guided ventilation and lung protective ventilation with fixed positive end-expiratory pressure during the surgery.


1.	Levesque, E., et al., Pulmonary complications after elective liver transplantation—incidence, risk factors, and outcome. Transplantation, 2012. 94(5): p. 532-538.
2.	Pirat, A., et al. Risk factors for postoperative respiratory complications in adult liver transplant recipients. in Transplantation proceedings. 2004. Elsevier.
3.	Hong, S., et al. Pulmonary complications following adult liver transplantation. in Transplantation proceedings. 2006. Elsevier.
4.	Bozbas, S.S., et al., Pulmonary complications and mortality after liver transplant. Experimental and clinical transplantation: official journal of the Middle East Society for Organ Transplantation, 2008. 6(4): p. 264-270.
5.	Lin, Y., et al., Perioperative risk factors for pulmonary complications after liver transplantation. Journal of International Medical Research, 2010. 38(5): p. 1845-1855.
6.	Miskovic, A. and A. Lumb, Postoperative pulmonary complications. BJA: British Journal of Anaesthesia, 2017. 118(3): p. 317-334.
7.	Yost, C.S., M.A. Matthay, and M.A. Gropper, Etiology of acute pulmonary edema during liver transplantation: a series of cases with analysis of the edema fluid. Chest, 2001. 119(1): p. 219-223.
10.	Feltracco, P., et al., Early respiratory complications after liver transplantation. World Journal of Gastroenterology: WJG, 2013. 19(48): p. 9271.
14.	Neto, A.S., et al., Association between driving pressure and development of postoperative pulmonary complications in patients undergoing mechanical ventilation for general anaesthesia: a meta-analysis of individual patient data. The Lancet Respiratory Medicine, 2016. 4(4): p. 272-280.
15.	Mathis, M.R., et al., Intraoperative mechanical ventilation and postoperative pulmonary complications after cardiac surgery. Anesthesiology, 2019. 131(5): p. 1046-1062.
16.	Park, M., et al., Driving pressure during thoracic surgery: a randomized clinical trial. Anesthesiology, 2019. 130(3): p. 385-393.

Others

(To compare the incidence of postoperative pulmonary complications(PPC) after living-donor liver transplantation between driving pressure guided ventilation and lung protective ventilaton)

<Control group>
1. After the endotracheal intubation, attending clincian should adjust ventilatory parameter according to the guideline for liver transplantation of Samsung Medical Center as follows. 
Tidal volume : predicted body weight * 8ml
Posivie end-expiratory pressure : 6cmH2O
RR : 10~12/min to maintain the EtCO2 between the 30 to 40 cmH2O
Inspiratory pause : 30%
Inspiration : Expiration ratio = 1 : 2

2. Recruitment maneuver : Recruitment maneuver is performed by a trained anesthesiologist at least 4 times during the surgery. 
Immediately after the insertion of Swan-gantz catheter(T1)
immediately after the placement of retractor(T2)
1 hour after the start of anhepatic phase (T3)
1 hour after reperfusion (T4)
PEEP is applied in steps of 6,10,15 and 20 cmH2O every five respiratory breaths; After the plateu pressure reach the pressure of 30cmH2O, it is applied for ten breaths. During the recruitement maneuver, ventilation is set for a tidal volume (Vt) of 8 ml*kg PBW, respiratory rate (RR) of 15 breath/min, inspiratory time (Ti) of 50% with 30% of inspiratory pause. After the recruitement maneuver, 6cmH2O of PEEP is applied again and maintain the same value of ventilatory parameter with initial setting. 

<Experimental group>
1. After the endotracheal intubation, attending clincian should adjust ventilatory parameter according to the guideline for liver transplantation of Samsung Medical Center as follows. 
Tidal volume : predicted body weight * 8ml
Posivie end-expiratory pressure : 6cmH2O
RR : 10~12/min to maintain the EtCO2 between the 30 to 40 cmH2O
Inspiratory pause : 30%
Inspiration : Expiration ratio = 1 : 2

2. Recruitment maneuver : Recruitment maneuver is performed by a trained anesthesiologist at least 4 times during the surgery. 
Immediately after the insertion of Swan-gantz catheter(T1)
immediately after the placement of retractor(T2)
1 hour after the start of anhepatic phase (T3)
1 hour after reperfusion (T4)
PEEP is applied in steps of 6,10,15 and 20 cmH2O every five respiratory breaths; After the plateu pressure reach the pressure of 30cmH2O, it is applied for ten breaths. During the recruitement maneuver, ventilation is set for a tidal volume (Vt) of 8 ml*kg PBW, respiratory rate (RR) of 15 breath/min, inspiratory time (Ti) of 50% with 30% of inspiratory pause. After the recruitement maneuver, PEEP is stepwise reduced, starting from 20 cmH2O, by 2 cmH2O every five breaths. During the decremental PEEP trial, driving pressure is meaused. The PEEP level corresponding to lowest driving pressure during the decremental trial is identified as the “optimal PEEP”. Subsequently, the lungs are recruited again with stepwise recruitment maneuver and after that, the “optimal” PEEP is applied. During the decremental trial, ventilation is set for a tidal volume (Vt) of 8 ml*kg PBW, respiratory rate (RR) of 15 breath/min, inspiratory time (Ti) of 33% with 30% of inspiratory pause. The ventilator is then adjusted to the baseline settings, except that for the “optimal” PEEP level. This setting is maintained until the next time of recruitment maneuver. When the driving pressured is over 15cmH2O, tidal volume is reduced until the driving pressure is reduced to 15cmH2O and tidal volume can be reduced upto a 6 ml*kg PBW.

Arm Label

Target Number of Participant

Arm Type

Arm Description

<Control group>
1. After the endotracheal intubation, attending clincian should adjust ventilatory parameter according to the guideline for liver transplantation of Samsung Medical Center as follows. 
Tidal volume : predicted body weight * 8ml
Posivie end-expiratory pressure : 6cmH2O
RR : 10~12/min to maintain the EtCO2 between the 30 to 40 cmH2O
Inspiratory pause : 30%
Inspiration : Expiration ratio = 1 : 2

2. Recruitment maneuver : Recruitment maneuver is performed by a trained anesthesiologist at least 4 times during the surgery. 
Immediately after the insertion of Swan-gantz catheter(T1)
immediately after the placement of retractor(T2)
1 hour after the start of anhepatic phase (T3)
1 hour after reperfusion (T4)
PEEP is applied in steps of 6,10,15 and 20 cmH2O every five respiratory breaths; After the plateu pressure reach the pressure of 30cmH2O, it is applied for ten breaths. During the recruitement maneuver, ventilation is set for a tidal volume (Vt) of 8 ml*kg PBW, respiratory rate (RR) of 15 breath/min, inspiratory time (Ti) of 50% with 30% of inspiratory pause. After the recruitement maneuver, 6cmH2O of PEEP is applied again and maintain the same value of ventilatory parameter with initial setting.

Arm Label

Target Number of Participant

Arm Type

Arm Description

<Experimental group>
1. After the endotracheal intubation, attending clincian should adjust ventilatory parameter according to the guideline for liver transplantation of Samsung Medical Center as follows. 
Tidal volume : predicted body weight * 8ml
Posivie end-expiratory pressure : 6cmH2O
RR : 10~12/min to maintain the EtCO2 between the 30 to 40 cmH2O
Inspiratory pause : 30%
Inspiration : Expiration ratio = 1 : 2

2. Recruitment maneuver : Recruitment maneuver is performed by a trained anesthesiologist at least 4 times during the surgery. 
Immediately after the insertion of Swan-gantz catheter(T1)
immediately after the placement of retractor(T2)
1 hour after the start of anhepatic phase (T3)
1 hour after reperfusion (T4)
PEEP is applied in steps of 6,10,15 and 20 cmH2O every five respiratory breaths; After the plateu pressure reach the pressure of 30cmH2O, it is applied for ten breaths. During the recruitement maneuver, ventilation is set for a tidal volume (Vt) of 8 ml*kg PBW, respiratory rate (RR) of 15 breath/min, inspiratory time (Ti) of 50% with 30% of inspiratory pause. After the recruitement maneuver, PEEP is stepwise reduced, starting from 20 cmH2O, by 2 cmH2O every five breaths. During the decremental PEEP trial, driving pressure is meaused. The PEEP level corresponding to lowest driving pressure during the decremental trial is identified as the “optimal PEEP”. Subsequently, the lungs are recruited again with stepwise recruitment maneuver and after that, the “optimal” PEEP is applied. During the decremental trial, ventilation is set for a tidal volume (Vt) of 8 ml*kg PBW, respiratory rate (RR) of 15 breath/min, inspiratory time (Ti) of 33% with 30% of inspiratory pause. The ventilator is then adjusted to the baseline settings, except that for the “optimal” PEEP level. This setting is maintained until the next time of recruitment maneuver. When the driving pressured is over 15cmH2O, tidal volume is reduced until the driving pressure is reduced to 15cmH2O and tidal volume can be reduced upto a 6 ml*kg PBW.

Gender

Age

Description

adult recipient who undergo living donor liver transplantation at Samsung Medical Center

(1) pediatric patient under 19 
(2) patient who doesn't agree the consent form of the study
(3) patient with contraindication of positive end-expiratory pressure : increased intracranial pressure, broncho-pleural fistula, hypovolemic shock, modera to severe right ventricular dysfunction
(4) patient with Gr3 or 4 encephalopathy 
(5) patient with preoperative pulmonary complication or history of lung surgery.

the incidence of postoperative pulmonary complication according to Melbourne group scale

from the end of the surgery to postoperative day 7

Duration of mechanical ventilation after the surgery

from the end of the surgery to postoperative day 7

length of ICU stay

30 days after the surgery

length of hopital stay

30 days after the surgery

30-day mortality after the surgery

30 days after the surgery