Effects of dynamic individualized PEEP guided by driving pressure in laparoscopic surgery on postoperative atelectasis in elderly patients: a prospective randomized controlled trial

Abstract

Background: Driving pressure (ΔP = Plateau pressure-PEEP) is highly correlated with postoperative pulmonary complications (PPCs) and appears to be a promising indicator for optimizing ventilator settings. We hypothesized that dynamic, individualized positive end-expiratory pressure (PEEP) guided by ΔP could reduce postoperative atelectasis and improve intraoperative oxygenation, respiratory mechanics, and reduce the incidence of PPCs on elderly patients undergoing laparoscopic surgery.

Methods: Fifty-one elderly patients who were subject to laparoscopic surgery participated in this randomized trial. In the PEEP titration group (DV group), the PEEP titration was decremented to the lowest ΔP and repeated every 1 h. Additional procedures were also performed when performing predefined events that may be associated with lung collapse. In the constant PEEP group (PV group), a PEEP of 6 cmH₂O was used throughout the surgery. Moreover, zero PEEP was applied during the entire procedure in the conventional ventilation group (CV group). The primary objective of this study was lung ultrasound score noted at the end of surgery and 15 min after admission to the post-anesthesia care unit (PACU) at 12 lung areas bilaterally. The secondary endpoints were perioperative oxygenation function, expiratory mechanics, and the incidence of the PPCs.

Results: The lung ultrasound scores of the DV group were significantly lower than those in the PV group and CV group (P < 0.05), whereas there was no significant difference between the PV group and CV group (P > 0.05). The lung static compliance (Cstat) and ΔP at all the intraoperative time points in the DV group were significantly better compared to the PV group and the CV group (p < 0.05).

Conclusions: Intraoperative titrated PEEP reduced postoperative lung atelectasis and improved respiratory mechanics in elderly patients undergoing laparoscopic surgery. Meanwhile, standard PEEP strategy is not superior to conventional ventilation in reducing postoperative pulmonary atelectasis in laparoscopic surgery.

Keywords: Atelectasis; Driving pressure; Laparoscopic surgery; Lung ultrasound; Positive end-expiratory pressure.

Fig. 1

Study protocol. Four predefined time points (H0–H3) when intraoperative ventilatory parameters were recorded and arterial blood gas analysis was performed and three-time points of ultrasound examination

Fig. 2

Lung ultrasound scores determined by the number of B lines and subpleural consolidation. A Normal aeration with 0–2 B lines, score = 0, B a small loss of aeration with ≥ 3 B lines, score = 1, C a moderate loss of aeration with multiple coalescent B lines or small subpleural consolidation, score = 2, and D a severe loss of aeration with consolidation or large subpleural consolidation, score = 3. (The yellow letters in the picture are the markings made in the trial. R and L represent the right and left hemithorax, and the numbers represent the subdivisions.)

Fig.3

Flow diagram representing patient enrollment, group assignment, and analysis

Fig. 4

Lung ultrasound scores variations over time among three groups. Data are presented as mean ± SDs. T0: Before surgery; T1: At the end of the surgery but before extubation; T2: 15 min after the PACU admission; ^†compared with the PV group, the difference was significant at 0.05 level; ^‡compared with the CV group, the difference was significant at 0.05 level

Fig. 5

Driving pressure variations over time among three groups. Data are presented as mean ± SDs. H0: 10 min after endotracheal intubation; H1: 10 min after pneumoperitoneum; H2: 1 h after pneumoperitoneum; H3:10 min after pneumoperitoneum stopped. ^†compared with the PV group, the difference was significant at 0.05 level. ^‡compared with the CV group, the difference was significant at 0.05 level

Fig. 6

Cstat variations over time among three groups. Data are presented as mean ± SDs. H0: 10 min after endotracheal intubation; H1: 10 min after pneumoperitoneum; H2: 1 h after pneumoperitoneum; H3:10 min after pneumoperitoneu stopped. ^†compared with the PV group, the difference was significant at 0.05 level. ^‡compared with the CV group, the difference was significant at 0.05 level

Fig. 7

PaO₂ variations over time among three groups. Data are presented as mean ± SDs. H0: 10 min after endotracheal intubation; H1: 10 min after pneumoperitoneum; H2: 1 h after pneumoperitoneum; H3:10 min after pneumoperitoneum stopped. ^†compared with the PV group, the difference was significant at 0.05 level. ^‡compared with the CV group, the difference was significant at 0.05 level

Fig. 8

A-aDO₂ variations over time among three groups. Data are presented as mean ± SDs. H0: 10 min after endotracheal intubation; H1: 10 min after pneumoperitoneum; H2: 1 h after pneumoperitoneum; H3:10 min after pneumoperitoneum stopped. ^†compared with PV group the difference was significant at 0.05 level. ^‡compared with CV group the difference was significant at 0.05 level