Effect of Individualized PEEP Guided by Driving Pressure on Diaphragm Function in Patients Undergoing Laparoscopic Radical Resection of Colorectal Cancer: A Randomized Controlled Trial

Abstract

BACKGROUND The concept of driving pressure (ΔP) has been established to optimize mechanical ventilation-induced lung injury. However, little is known about the specific effects of setting individualized positive end-expiratory pressure (PEEP) with driving pressure guidance on patient diaphragm function. MATERIAL AND METHODS Ninety patients were randomized into 3 groups, with PEEP set to 0 in group C; 5 cmH₂O in group F; and individualized PEEP in group I, based on esophageal manometry. Diaphragm ultrasound was performed in the supine position at 6 consecutive time points from T0-T5: diaphragm excursion, end-expiratory diaphragm thickness (Tdi-ee), and diaphragm thickening fraction (DTF) were measured. Primary indicators included diaphragm excursion, Tdi-ee, and DTF at T0-T5, and the correlation between postoperative DTF and ΔP. Secondary indicators included respiratory mechanics, hemodynamic changes at intraoperative d0-d4 time points, and postoperative clinical pulmonary infection scores. RESULTS (1) Diaphragm function parameters reached the lowest point at T1 in all groups (P<0.001). (2) Compared with group C, diaphragm excursion decreased, Tdi-ee increased, and DTF was lower in groups I and F at T1-T5, with significant differences (P<0.05), but the differences between groups I and F were not significant (P>0.05). (3) DTF was significantly and positively correlated with mean intraoperative ΔP in each group at T3, and the correlation was stronger at higher levels of ΔP. CONCLUSIONS Individualized PEEP, achieved by esophageal manometry, minimizes diaphragmatic injury caused by mechanical ventilation based on lung protection, but its protection of the diaphragm during laparoscopic surgery is not superior to that of conventional ventilation strategies.

Figure 1

(A) Image of probe placement for measuring diaphragm excursion in the supine position. (B) B-mode ultrasound images of the diaphragm showing a C-shaped highlighted arc below the liver window. (C) Images of diaphragm excursion (DE) measurements on M-mode ultrasound. (D) Image of probe placement for measuring diaphragm thickness and diaphragm thickening fraction (DTF) at the diaphragmatic zone of apposition in the supine position. (E) Frozen images of diaphragm thickness at the end of expiration (Tdi-ee). (F) Frozen images of diaphragm thickness at the end of inspiration (Tdi-ei). This figure was created by Adobe lllustrator2024.

Figure 2

CONSORT diagram of patient flow through the study. PEEP – positive end-expiratory pressure. This figure was created with Microsoft® Word 2021.

Figure 3

Comparison of driving pressure (ΔP) values and postoperative clinical pulmonary infection score (CPIS) in the 3 groups. The number at the top indicates the CPIS score and corresponding number of patients in each group, with 4.6±1.4 in group C; 3.5±1.5 in group F; and 2.8±1.4 in group I. * Statistically significant difference at 0.05 level, compared with group C. ^# Statistically significant difference at 0.05 level, compared with group F. This figure was created with GraphPad Prism 9.5.1.

Figure 4

(A) Diaphragm excursion values at each time point. (B) End-expiratory diaphragm thickness values at each time point. (C) Diaphragm thickening fraction (DTF) values at each time point. (D) Significant positive correlation between DTF and mean intraoperative driving pressure (ΔP) at postoperative T3 in the 3 groups, and its correlation was C group >F group >I group. This figure was created with GraphPad Prism 9.5.1.