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20 May 2024: Clinical Research  

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

Mingyue Zhang1ABCF, Yongbo Yu1BCD, Cheng Qiu1CE, Xiaoqiong Xia1BCD*, Yuanming Sun1E, Liang Wang1DE, Guifen Ma1BE, Xiang Gao1E

DOI: 10.12659/MSM.944022

Med Sci Monit 2024; 30:e944022

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Abstract

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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.

Keywords: Respiration, Artificial, mechanical ventilation, Driving Pressure, Diaphragm Ultrasound, esophageal manometry, Laparoscopy

Introduction

The diaphragm is the main inspiratory muscle and plays an important role in maintaining proper respiration in the body [1]. It has been established that mechanical ventilation not only damages the lungs but also induces diaphragmatic dysfunction, leading to adverse effects, such as weaning difficulties and respiratory failure [2]. The laparoscopic radical surgery for colorectal cancer is the preferred surgical method [3]. However, since patients are mostly elderly and frail, their physiological functions are declining, and the establishment of pneumoperitoneum and Trendelenburg position for a long time during surgery further elevates the diaphragm and further compresses the lungs, the lung injury and diaphragmatic dysfunction caused by mechanical ventilation are even more severe, which seriously reduces the quality of patients’ postoperative recovery [4]. With the development of comfortable medical technology, diaphragm ultrasound is becoming the first-line technique for clinical diaphragm function monitoring due to its noninvasive, portable, intuitive, and repeatable nature [5].

Currently, diaphragm ultrasound is mainly used to measure diaphragm excursion, diaphragm thickness, and diaphragm thickening fraction (DTF). Diaphragm excursion is an index for assessing lung ventilation in humans and is related to the ability of the diaphragm to contribute to respiration. Diaphragm thickness, commonly used to assess whether atrophy of the diaphragm has occurred, and the DTF reflect the active contractile capacity of the diaphragm. Diaphragm thickness and DTF are often used together with diaphragm excursion to assist in the diagnostic workup of bedside dyspnea or withdrawal of mechanical ventilation. Studies have shown that ultrasound diaphragm measurements of thickness, diaphragm excursion, and DTF are highly feasible, reproducible, and accurate [6]. Another meta-analysis [7] indicated that DTF has high sensitivity and specificity and is the most accurate predictor of withdrawal outcome.

The concepts of driving pressure (ΔP) and transpulmonary ΔP are now increasingly used for lung protection in the operating room [8]. Esophageal manometry, as a minimally invasive monitoring method to assess respiratory mechanics, not only calculates transpulmonary ΔP to guide individualized positive end-expiratory pressure (PEEP) settings but also reflects patient inspiratory effort and compliance with the machine [9], providing a new mode of thinking for current lung and diaphragm protective ventilation.

The aim of this study is to analyze the specific effects of individualized ΔP-directed PEEP on diaphragm function in patients undergoing laparoscopic radical colorectal surgery. The final exploration and primary outcome of the study was the correlation between postoperative DTF and ΔP. We hypothesized that esophageal manometry to achieve ΔP-guided individualized PEEP would similarly reduce mechanical ventilation-induced diaphragmatic injury on the basis of lung protection. We believe that this study will further validate the efficacy of ΔP ventilation strategies for lung protection and identify a ventilation method that can simultaneously achieve diaphragm protection.

Material and Methods

RANDOMIZATION AND BLINDING:

According to the results of the pre-experiment, the mean values of DTF for postoperative T3 in the 3 groups were 35.01, 32.22, and 31.99, respectively, with a standard deviation of 3.14. With a degree of certainty of 1-β=0.9, a test level of α=0.05, and equal sample sizes of the 3 groups, sample size estimation was conducted by using PASS 2021 software according to the following formula:

According to the pre-set parameters, the calculation using PASS 2021 software showed that the minimum required sample size for all 3 groups was 24 patients. Considering a dropout rate of 20%, 30 patients were included in all 3 groups. Finally, a total of 90 screening numbers were generated in this study, and the first letter of the screening number represented the group, which were evenly divided into 3 groups at a ratio of 1: 1: 1. Numbers were assigned by means of random serial numbers generated by the computer, and groups were enrolled according to the selected screening numbers (group C, F, and I). The intervention protocol was kept in a sealed, opaque envelope to conceal allocation. An anesthesiologist not involved in the design of the study protocol opened the envelope, administered anesthesia, and performed the ventilation protocol. The researcher who performed diaphragm ultrasound measurements and collected intraoperative respiratory mechanics, hemodynamic data, perioperative diaphragm function, and postoperative clinical pulmonary infection score (CPIS) results was blinded to the patient allocation.

PARTICIPANTS:

The inclusion criteria used were as follows: (i) fulfillment of the diagnostic criteria for colorectal cancer and presence of an indication for surgery; (ii) age >65 years and body mass index <35 kg/m2; (iii) American Society of Anesthesiologists’ (ASA) physical status I–II; and (iv) the patient signed an informed consent form.

The exclusion criteria were as follows: (i) pulmonary infection, pulmonary abscess within 1 month before surgery, history of chronic obstructive pulmonary disease, asthma, and other respiratory diseases; (ii) previous history of septal paralysis, cervical pulp injury, neuromuscular junction disease, and extracorporeal diaphragm pacemaker treatment; (iii) presence of chest trauma or severe cardiac or renal dysfunction; and (iv) combination of other malignancies, immune system disorders, and other chronic systemic diseases. Inability to complete the study protocol or life-threatening postoperative complications were considered as withdrawal.

To summarize, 90 patients were included in the analysis and randomized into 30 in group C, 30 in group F, and 30 in group I. The intention-to-treat analysis approach was used in our study. All efficacy analyses were performed in the intention-to-treat population, which was defined as all randomized participants.

ANESTHETIC PROTOCOL:

Patients were routinely monitored on admission with electrocardiogram and bispectral index, and after intravenous access was established, a radial artery puncture tube was placed for continuous arterial pressure measurement and blood gas collection. Induction of anesthesia was performed as follows: esketamine hydrochloride 0.25 mg/kg, etomidate 0.3 mg/kg, sufentanil 0.3 μg/kg, and cis-atracurium 0.2 mg/kg. Maintenance of anesthesia was as follows: target-controlled infusion of propofol 2–4 μg/mL and remifentanil 3–5 μg/mL were used to maintain mean arterial pressure (MAP) and heart rate (HR) fluctuations within 20% of basal values and the bispectral index (40–60). Intraoperative cisatracurium at 0.08–0.1 mg/kg/h was pumped, and myorelaxant antagonists were routinely used during resuscitation. During the postoperative period, all patients received usual physiotherapy according to our standard of care.

VENTILATION PROTOCOL:

Ventilation was performed immediately after tracheal intubation (ventilator: Datex-Ohmeda Corp, USA). Intraoperative volume-controlled ventilation mode was used with tidal volume 6–8 mL/kg, oxygen flow 2 L/min, FiO2 60%, inspiratory pause 20%, and inspiratory: expiratory ratio 1: 2, and ventilation frequency was adjusted to maintain PetCO2 35–45 mmHg. The tidal volume was set based on ideal body weight, and permissive hypercapnic ventilation was used when necessary. No PEEP was set in the conventional group, 5 cmH2O was set in the fixed PEEP group, and individualized PEEP based on esophageal pressure was set in the individualized PEEP group.

The 5 steps were as described in the literature [7]. Step 1: Check the airtightness of the esophageal manometry catheter (Mindray Corp, China) and estimate the required length. Step 2: Insert the catheter through the nose to reach the stomach and connect the catheter to the interface of the pressure sensor of the monitor using a 3-way stopcock. Step 3: Turn the button of the 3-way stopcock to equalize the pressure sensor with ambient pressure for calibration zero, and use a syringe to inflate the balloon. Close the three-way stopcock so that the esophageal manometry catheter is linked to the pressure sensor of the monitor and the esophageal pressure waveform can be displayed on the monitor. Step 4: Slowly withdraw the catheter until the esophageal pressure waveform showed cardiac oscillations., which means that the catheter has moved from the abdomen to the ideal position, which is the lower one-third of the esophagus. Step 5: Test examination: gently squeeze the patient’s chest to see if the airway pressure and esophageal pressure change synchronously; if the fit is good, the esophageal pressure is successfully calibrated.

Plateau pressure (Pplat) was measured by setting a 20% inspiratory pause during mechanical ventilation. At this time, Pplat was equivalent to alveolar pressure (Plar), and esophageal pressure (Pes) simulated as equivalent to pleural pressure (Ppl), whereas the transpulmonary ΔP, which causes the lung to truly inflate, was the difference between Plar and Ppl, or the difference between Pplat and Pes, and was calculated as transpulmonary ΔP=Pplat-Pes+5 cmH2O. After lung recruitment, the transpulmonary ΔP would be monitored during PEEP decrement to find the lowest PEEP value that satisfied 0 mmHg ≤ transpulmonary ΔP ≤10 mmHg (1 mmHg=0.133 kpa), which was the optimal PEEP value. This individualized PEEP value was then maintained throughout the procedure, and the esophageal pressure variation was maintained at 3–8 cmH2O. (dynamic compliance [Cdyn]=tidal volume/(Ppeak-PEEP), ΔP=Pplat-PEEP, oxygenation index [OI]=PaO2/FIO2).

MEASUREMENT OF DIAPHRAGM EXCURSION: Based on the literature [10], the low-frequency convex array probe was placed at the right rib margin, with the patient in the supine position (Figure 1A). The dark isodense area is the liver window, and the C-shaped highlighted arc below it is the diaphragm (Figure 1B). The patient was switched to M mode and asked to breathe by sniffing. The vertical distance between the peak during inspiration and the low peak during expiration in the sinusoidal waveform was measured as the diaphragm excursion (Figure 1C). The average of the 3 respiratory cycles was the recorded result.

Diaphragm excursion less than 1 cm can indicate diaphragm dysfunction.

MEASUREMENT OF DIAPHRAGM THICKNESS AND DTF: Based on the literature [10], the high-frequency line array probe was placed in the diaphragmatic zone of apposition (Figure 1D) in a supine patient, and 2 hyperechoic parallel lines, the peritoneum and pleura, were visible. The distance between them was the diaphragm thickness. The end-expiratory diaphragm thickness (Tdi-ee) (Figure 1E) and the end-inspiratory diaphragm thickness (Tdi-ei) (Figure 1F) were measured and averaged over 3 respiratory cycles. The DTF was calculated as DTF=(Tdi-ei-Tdi-ee)/Tdi-ee×100%.

A DTF of less than 20% on maximal effort inspiration has been shown to be a reliable predictor of diaphragm dysfunction.

OBSERVED INDICATORS AND MONITORING AT DIFFERENT TIME POINTS:

Primary indicators included DE, end-expiratory diaphragm thickness, and DTF at T0–T5, and the correlation between postoperative DTF and ΔP. The time points T0 to T5 were defined as follows: T0: during spontaneous respiration before anesthesia; T1: 5 min after pneumoperitoneum; T2: 5 min before pneumoperitoneum withdrawal; T3: 15 min after extubation; T4: 30 min after extubation; and T5: 1 day after surgery.

Secondary indicators included respiratory mechanics (Ppeak, Pplat, PEEP, ΔP, Cdyn, PaCO2, OI), hemodynamic changes (MAP, HR) at the intraoperative d0–d4 time points, and postoperative CPIS scores. The d0 to d4 time points were defined as follows: d0: after tracheal intubation; d1: 5 min after pneumoperitoneum; d2: 1 h after Trendelenburg position; d3: 2 h after Trendelenburg position; and d4: 5 min before pneumoperitoneum withdrawal. The basic CPIS consists of 5 measures: temperature, white blood cell count, airway secretions, oxygenation, and pulmonary exudative shadows on chest radiographs; a CPIS of 6 or more indicates a high likelihood of pulmonary complications.

STATISTICAL METHODS:

PASS21.0 software was used for sample size estimation of multiple group means based on pre-experimental results. Data were statistically analyzed using SPSS 26.0 software, and normality was tested using the Shapiro-Wilk test. Measures that conformed to a normal distribution are expressed as the mean±standard deviation (x±s), and counts are expressed as frequencies. Categorical variables were compared using the chi-square test, one-way ANOVA for between-group comparisons, and repeated-measures ANOVA for within-group comparisons, with P<0.05 considered a statistically significant difference. Graphs were plotted using GraphPad Prism 9.5.1, and a linear regression model was developed to analyze the correlation between DTF at T3 and mean intraoperative ΔP for each patient group. The null hypothesis was that there would be no positive correlation between DTF at T3 and mean intraoperative ΔP. The alternative hypothesis was that there would be a moderate positive correlation between DTF at T3 and mean intraoperative ΔP.

Results

COMPARISON OF BASIC CHARACTERISTICS OF PATIENTS IN THE 3 GROUPS:

The differences in sex, age, BMI, ASA classification, site of colorectal cancer, preoperative FEV1/FVC, train-of-four (TOF) ratio before extubation and operation time were not statistically significant (P>0.05) among the 3 groups (Table 1).

COMPARISON OF SECONDARY INDICATORS BETWEEN THE 3 GROUPS:

The mean PEEP value in group I was 10.8±1.4 cmH2O, and Ppeak and Pplat were higher in both groups I and F than in group C at d1–d4, while ΔP was lower in both group I and group F than in group C (P<0.05) (Figure 3A). Cdyn and OI were better in both groups I and F than in group C at d2–d4 and were better in group I than in group F (P<0.05). In contrast, PaCO2 was higher in both groups I and F than in group C at d2–d4 and higher in group I than in group F (P<0.05). The differences in MAP and HR between the groups were not statistically significant (P>0.05) (Table 2).

The CPIS scores of the 3 groups of patients 1 day after surgery were 4.6±1.4 in group C, 3.5±1.5 in group F, and 2.8±1.4 in group I. The difference between the groups was statistically significant (P<0.05) (Figure 3B).

COMPARISON OF PRIMARY INDICATORS BETWEEN THE 3 GROUPS:

There was a time-group interaction for diaphragm excursion, diaphragm thickness, and DTF, and all 3 groups had the lowest diaphragm parameters at T1 (P<0.001) (Figure 4).

There was a statistically significant difference in diaphragm excursion between groups at T1 and T2, with group C > group F > group I (P<0.01). Group F and group I had lower excursion than group C at T3–T5 (P<0.01), while the difference between group F and group I was not statistically significant (P3=0.098, P4=0.063, P5=0.209) (Figure 4A).

The difference in end-expiratory diaphragm thickness between groups at T2 and T3 was statistically significant, with group I > group F > group C (P<0.05). At T4 and T5, the thickness of both groups F and I was higher than that of group C (P<0.05), while the difference between group F and group I was not statistically significant (P4*=0.169, P5*=0.470) (Figure 4B).

DTF at T2–T5 was lower in both groups F and I than in group C (P<0.01), while the difference between groups F and I was not statistically significant (P2#=0.089, P3#=0.054, P4#=0.283, P5# =0.741) (Figure 4C).

COMPARISON OF CORRELATION ANALYSIS BETWEEN POSTOPERATIVE T3 DTF AND INTRAOPERATIVE ΔP MEANS IN THE 3 GROUPS:

The correlation between DTF and intraoperative ΔP mean values was significantly positive in each group at T3, and the correlation was stronger at higher ΔP values. r2=0.613, 95% BCa CI [1.655,3.126], P=0.000 for group C; r2=0.310, 95% BCa CI [0.460,1.717], P=0.001 for group F; r2=0.135, 95% BCa CI [0.017,1.841], P=0.046 for group I (Figure 4D).

Discussion

The main findings of this study can be summarized as follows. (1) Reducing ΔP with PEEP augmentation significantly improved respiratory mechanics and oxygenation in laparoscopic patients, thus achieving lung protection, but may have had a negative effect on diaphragm function. (2) The end-expiratory diaphragm thickness was relatively thickened by PEEP increments to reduce ΔPs, while diaphragm excursion and DTF were reduced. (3) Postoperative DTF correlated well with ΔP, and its correlation was stronger at higher ΔP.

In recent years, a better understanding of the physiological and biological effects of mechanical ventilation has led to the development of the concept of ΔP [11]. Studies have also confirmed that ΔP is the indicator of the most direct benefit in terms of morbidity and mortality in mechanically ventilated patients [11] and that the beneficial effect of a lung-protective ventilation strategy may depend on the level of ΔP. Indeed, in our study, as expected, the establishment of pneumoperitoneum (d1) was accompanied by a decrease in patient thoracic compliance and an increase in ΔP levels, and this effect was amplified by the Trendelenburg position. Reducing the ΔP by increasing PEEP at this time reduced the strain on the lung parenchyma during the ventilation cycle when Cdyn was improved. OI also increased significantly, and postoperative CPIS scores were significantly reduced (Figure 3). The results are consistent with a recent multicenter retrospective trial [12] and the findings of Zhang et al [13]. This further verifies that the effect of low ΔP on lung protection is evident.

Protective ventilation strategies promote lung injury while ignoring the effects on the diaphragm, leading to an increased risk of diaphragmatic dysfunction [2]. It has been shown that diaphragmatic dysfunction occurs early during mechanical ventilation and worsens with the duration of ventilation [14]. However, the mechanism of diaphragmatic dysfunction is not clear, and it is now widely believed that disuse atrophy and microstructural changes in the diaphragm caused by diaphragmatic deloading are the main factors in its development [15]. From a cytological point of view, it is believed that the atrophied state of the diaphragm depresses Ca2+ release from myocytes [16] and that induced pro-inflammatory factors, such as IL-6 and IL-24, induce apoptosis [17], further causing diaphragm dysfunction. Goligher et al [18] suggested that diaphragmatic loading is directly related to mechanical ventilation parameter settings and respiratory effort and that optimizing mechanical ventilation parameter settings and reducing man-machine asynchrony can reduce diaphragmatic injury.

In addition to calculating transpulmonary ΔPs and rapidly titrating PEEP, esophageal manometry can reflect the risk of injury during spontaneous breathing by dynamic changes in esophageal pressure [19]. Changes in esophageal pressure of 3–8 cmH2O are considered an appropriate level of respiratory effort, comparable to quiet breathing [20]. There is also increasing evidence of a good correlation between diaphragm ultrasound, a noninvasive technique, and various invasive indicators of diaphragm function monitoring [21].

The mean value of individualized PEEP set in this study based on esophageal manometry was 10.8±1.4 cmH2O, which was significantly higher than that in other groups. Additionally, Goligher et al found that the right diaphragm was better defined in most patients during mechanical ventilation, ultrasound monitoring of its thickness and DTF was highly feasible and reproducible [22], and diaphragmatic weakness was more easily detected in the supine position [23]. We also ensured that the TOF ratio was >90% at the time of extubation to avoid the effect of postoperative musculoskeletal residuals on the measurements. The results revealed that postoperative diaphragmatic function decreased in all 3 groups but did not meet the criteria for diaphragmatic dysfunction, or more precisely, a state of diaphragmatic weakness [24], which could be due to insufficient time of mechanical ventilation. Interestingly, all 3 groups showed a general trend of decreasing and then slowly increasing diaphragm function parameters, with the lowest values at T1, which was considered mainly due to the depression of the respiratory center after the pushing of anesthetic and inotropic drugs, as confirmed by the study of Testelmans et al [25]. Unlike the chronic damage to the diaphragm caused by mechanical ventilation, the effects of drugs on diaphragm function are more rapid.

Diaphragm excursion is the displacement of the diaphragm between the end of expiration and the end of inspiration during breathing and is representative of pulmonary ventilatory capacity [10]. In our study, importantly, diaphragm excursion at T1 and T2 differed between the 3 groups of patients (P<0.05), which we analyzed because as PEEP increased to achieve low ΔP, its distending effect on the lungs also increased, resulting in a lower diaphragm position and a reduction in excursion. However, a gradual increase in excursion was observed from T2 to T4, suggesting that the muscle relaxing drugs had worn off and that the patient’s voluntary breathing was gradually restored. DTF is an indicator of the efficiency of diaphragm contraction and can represent the strength of the diaphragm. It is not affected by the state of ventilation. A DTF of less than 20% on maximal effort inspiration has been shown to be a reliable predictor of diaphragm dysfunction. End-expiratory diaphragm thickness is more stable than end-inspiratory diaphragm thickness, and its assessment of diaphragm recovery is more meaningful [10]. In our study, end-expiratory diaphragm thickness was found to be relatively thicker in the F and I groups at T2–T5 when PEEP was increased to reduce ΔP. This may be due to the lowering of the position of the diaphragm, which is forced to shorten and thicken, as also found by Lindqvist et al [26], and suggests that this may also stem from the easily overlooked mechanism of longitudinal atrophy, which is different from disuse atrophy and is mainly because PEEP expands the lung while the diaphragm is forced to shorten over time to adapt to this state. Diaphragm fibers adapt by reducing the number of tandem muscle segments to maintain an optimal overlap of filaments, hence the increased thickness of the diaphragm at the end of expiration, which can better explain why this difference persists postoperatively. Despite the different mechanisms causing atrophy, all resulted in a decrease in DTF. Schepens [27] also states that an early and rapid increase in diaphragm thickness predicts a prolonged ventilation time, increasing the likelihood of diaphragmatic injury during ventilation.

Ideally, esophageal manometry gives optimal PEEP titration and maintains an appropriate level of respiratory effort, which can maintain diaphragmatic autonomic activity while improving lung injury, and diaphragmatic contraction efficacy will increase [28]. However, our results showed that the DTF remained reduced, compared with the C group. We speculate that this can be due to the following factors. (1) The contractile efficacy of the diaphragm cannot be significantly improved by improving the level of respiratory effort alone, and the risk of longitudinal atrophy from PEEP increments cannot be ignored. (2) Compared with open surgery, the combined forces of pneumoperitoneum and PEEP in the opposite direction may increase the degree of inhibition of the diaphragm, accelerating the process of disuse atrophy. Additionally, our results showed no significant difference in DTF between the I and F groups, while there was a difference in the pulmonary protective effect between these 2 groups. This suggests that the benefit of improved respiratory effort does exist. However, its benefits do not reverse the adverse effects caused by PEEP or are not significant in the short term. Finally, we averaged the ΔPs at each time point and considered them as continuous variables in an attempt to analyze their correlation with DTF at the patient’s postoperative T3 time point, showing a significant positive correlation, which was stronger at higher levels of ΔP.

The innovations of this study are as follows. (1) Most studies have focused on the optimization of lung injury with a ΔP-directed ventilation strategy, but our study focused on the evolution of diaphragm function under this strategy. (2) For PEEP titration in laparoscopic surgery, esophageal manometry is more accurate than other PEEP titration methods because it eliminates the effects of pneumoperitoneum and position on patient chest wall compliance and directly measures the pressure that truly indicates pulmonary strain, namely, transpulmonary ΔP. However, limitations of this study remain. (1) The individualized PEEP in this study was titrated immediately after intubation and throughout the procedure, failing to achieve dynamic real-time changes. This can lead to deviations between optimal PEEP values and actual values. (2) Individual differences and measurement errors during diaphragm ultrasound could not be avoided. (3) The small sample size can lead to biased conclusions, which still need to be verified by a multicenter trial at a later stage.

Conclusions

Individualized PEEP achieved by esophageal manometry allows lung protection while balancing respiratory effort to maximize diaphragm protection but is not superior to conventional ventilation strategies for diaphragm protection during laparoscopic surgery. This suggests that we need to be alert to the potential for diaphragmatic injury when implementing a low ΔP ventilation strategy for lung protection.

Figures

(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 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. CONSORT diagram of patient flow through the study. PEEP – positive end-expiratory pressure. This figure was created with Microsoft® Word 2021.Figure 2. CONSORT diagram of patient flow through the study. PEEP – positive end-expiratory pressure. This figure was created with Microsoft® Word 2021. 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 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. (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.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.

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Figures

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.

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Medical Science Monitor eISSN: 1643-3750
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