A randomized control trial to compare the effect of conventional and individualized peak end expiratory pressure on kinetics of inflammatory biomarkers in obese patients undergoing laparoscopic surgeries

Globally there is an increase in the incidence of obesity and according to WHO, more than 650 million people were obese in 2016 leading to a proportionate rise in number of obese patients undergoing surgical procedures.Under general anaesthesia and paralysis there is a decrease in lung compliance and  functional residual capacity (FRC) with loss of diaphragmatic tone leading to decrease in oxygen reserve and ventilation-perfusion mismatch. Pneumoperitoneum created for laparoscopic surgery causes a cephalic shift of diaphragm and elevates pleural pressure which increases lung atelectasis and the risk of post operative pulmonary complications(PPCs). The incidence of PPCs in obese patients (18-23%) is almost twice that of normal population. It is widely known that PPCs cause a significant increase in  the length of Intensive care unit (ICU) and hospital stay.

The plasma kinetics of inflammation and lung injury biomarkers such as IL-6, SP-D,TNF-α,  IL-8, sRAGE,  CC-16, and KL6 help in identifying patients at risk of developing PPCs  but the change in the level depends upon various factors such as preoperative lung condition and  intra-operative ventilatory settings. Various lung protective stratergies have been suggested to decrease postoperative pulmonary atelectasis such as low tidal volumes (VT), individualized positive end-expiratory pressure (PEEP), recruitment manoeuvre (RM).

PEEP is the alveolar pressure above atmospheric pressure that exists at the end of expiration. Various advantages of PEEP are increase in lung compliance, prevention of alveolar collapse, improvement of oxygen diffusion thereby improving pulmonary dynamics  and gas exchange. However, PEEP has certain adverse effects such as overdistention of alveoli (barotrauma), decrease in the cardiac output, unintended respiratory alkalosis. Many approaches to titrate PEEP have been proposed such as using PEEP tables (high or low), measuring compliance (static or dynamic), plateau pressure, pressure-volume curve and inflection points and esophageal balloons to measure transpulmonary pressure.

PPCs can be considered as a composite outcome measure which includes respiratory infection, respiratory failure, plueral effusion, atelectasis, etc as per European Perioperative Clinical Outcome(EPCO). Post operative pulmonary atelectasis is best identified using various imaging modalities such as CT, ultrasound or electric impedance tomography but may not be always feasible for every patient.