Individualised positive end-expiratory pressure titrated intra-operatively by electrical impedance tomography optimises pulmonary mechanics and reduces postoperative atelectasis

BACKGROUND A protective intra-operative lung ventilation strategy has been widely recommended for laparoscopic surgery. However, there is no consensus regarding the optimal level of positive end-expiratory pressure (PEEP) and its effects during pneumoperitoneum. Electrical impedance tomography (EIT) has recently been introduced as a bedside tool to monitor lung ventilation in real-time. OBJECTIVE We hypothesised that individually titrated EIT-PEEP adjusted to the surgical intervention would improve respiratory mechanics during and after surgery. DESIGN Randomised controlled trial. SETTING First Medical Centre of Chinese PLA General Hospital, Beijing. PATIENTS Seventy-five patients undergoing robotic-assisted laparoscopic hepatobiliary and pancreatic surgery under general anaesthesia. INTERVENTIONS Patients were randomly assigned 2 : 1 to individualised EIT-titrated PEEP (PEEP EIT ; n = 50) or traditional PEEP 5 cmH 2 O (PEEP 5 cmH2O ; n = 25). The PEEP EIT group received individually titrated EIT-PEEP during pneumoperitoneum. The PEEP 5 cmH2O group received PEEP of 5 cmH 2 O during pneumoperitoneum. MAIN OUTCOME MEASURES The primary outcome was respiratory system compliance during laparoscopic surgery. Secondary outcomes were individualised PEEP levels, oxygenation, respiratory and haemodynamic status, and occurrence of postoperative pulmonary complications (PPCs) within 7 days. RESULTS Compared with PEEP 5 cmH2O , patients who received PEEP EIT had higher respiratory system compliance (mean values during surgery of 44.3 ± 11.3 vs. 31.9 ± 6.6, ml cmH 2 O −1 ; P < 0.001), lower driving pressure (11.5 ± 2.1 vs. 14.0 ± 2.4 cmH 2 O; P < 0.001), better oxygenation (mean P a O 2 /FiO 2 427.5 ± 28.6 vs. 366.8 ± 36.4; P = 0.003), and less postoperative atelectasis (19.4 ± 1.6 vs. 46.3 ± 14.8 g of lung tissue mass; P = 0.003). Haemodynamic values did not differ significantly between the groups. No adverse effects were observed during surgery. CONCLUSION Individualised PEEP by EIT may improve intra-operative pulmonary mechanics and oxygenation without impairing haemodynamic stability, and decrease postoperative atelectasis. TRIAL REGISTRATION Chinese Clinical Trial Registry (www.chictr.org.cn) identifier: ChiCTR2100045166.