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Frontiers in Anesthesiology ·

Volume 5 - 2026 | https://doi.org/10.3389/fanes.2026.1758421

Individualized PEEP guided by electrical impedance tomography versus fixed PEEP in laparoscopic surgery: a systematic review and meta-analysis of effects on postoperative pulmonary complications

  • Abdelrhman H. Mohamed1
  • Mohamed Fawzi Hemida2
  • Ahmad Omar Saleh3
  • Ahmed A. Abdelfattah4
  • Mohammed M. Alamin5
  • Ehsanullah Alokozay6*corresponding author
  • Walid Bechichi7
  • Sampana Fatima8
  • Tushar K. Bhadra9
  • Mariam M. Mohammed10
  • Raghad Alasali11
  • Abdelrahman A. Mohamed12
  • Mahera Habibi13
  • Irfan Ullah14
  1. 1Faculty of Medicine, Luxor University, Luxor, Egypt
  2. 2Faculty of Medicine, Alexandria University, Alexandria, Egypt
  3. 3Department of Medicine, The University of Jordan, Amman, Jordan
  4. 4Faculty of Medicine, Tanta University, Tanta, Egypt
  5. 5Faculty of Medicine, Assiut University, Assiut, Egypt
  6. 6Faculty of Medicine, Kandahar University, Kandahar, Afghanistan
  7. 7Faculty of Medicine, University of Constantine 3, Salah Boubnider, Constantine, Algeria
  8. 8Department of Medicine, Shahida Islam Medical and Dental College, Lodhran, Pakistan
  9. 9Department of Medicine, Dhaka Medical College and Hospital, Dhaka, Bangladesh
  10. 10Faculty of Pharmacy, Fayoum University, Fayoum, Egypt
  11. 11School of Medicine, University of Jordan, Amman, Jordan
  12. 12Faculty of Medicine, October 6 University, Giza, Egypt
  13. 13Faculty of Medicine, Ghalib University, Herat, Afghanistan
  14. 14Department of Cardiovascular Medicine, University Hospitals Harrington Heart and Vascular Institute, Cleveland, OH, United States
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Abstract

Optimal positive end-expiratory pressure (PEEP) is essential for maintaining alveolar recruitment and preventing postoperative pulmonary complications (PPCs). Traditional fixed PEEP strategies may not account for individual variations in lung recruitability. Electrical impedance tomography (EIT) offers real-time assessment of regional ventilation, enabling individualized PEEP titration that balances alveolar collapse and overdistension. This systematic review and meta-analysis evaluated the effectiveness of individualized EIT-guided PEEP compared with fixed PEEP in reducing postoperative atelectasis and improving perioperative outcomes. This review followed PRISMA guidelines and was prospectively registered in PROSPERO (CRD420251169858). Randomized controlled trials (RCTs) involving patients undergoing laparoscopic surgery under general anesthesia were eligible if they compared EIT-guided individualized PEEP with fixed PEEP (5 cmH₂O). Primary outcome was postoperative atelectasis assessed by lung ultrasound. Secondary outcomes included mean arterial pressure (MAP), PaO₂/FiO₂ ratio, PaCO₂, pH, dynamic lung compliance, crystalloid use, urine output, length of hospital stay (LOS), intraoperative blood pressure complications, bradycardia during recruitment maneuvers or PEEP titration phases. Data were synthesized using a random-effects model, and heterogeneity was assessed using I² statistics. Leave-one-out sensitivity analyses evaluated the robustness of results. Five RCTs (n = 290) met inclusion criteria. Individualized EIT-guided PEEP significantly reduced postoperative atelectasis (OR: 0.18, 95% CI: 0.06–0.51) and improved oxygenation (PaO₂/FiO₂ ratio SMD 1.72, 95% CI: 0.45–2.98). MAP was modestly higher in the EIT group, while bradycardia during recruitment or titration phases occurred more frequently. No significant differences were observed in lung compliance, hospital stay, urine output, or metabolic parameters. Sensitivity analyses confirmed the stability of key findings. Individualized PEEP titration guided by EIT reduces postoperative atelectasis and enhances oxygenation without adversely affecting most perioperative outcomes. Despite encouraging results, larger multicenter trials are needed to validate these findings and guide clinical implementation.

Keywords

1 Introduction

Positive end-expiratory pressure (PEEP) is frequently utilized in acute respiratory distress syndrome (ARDS) with the goal of opening collapsed lung areas and keeping the lung open (1, 2). According to the Berlin definition of acute respiratory distress syndrome (ARDS), optimizing PEEP is one of the most important measures in ARDS management (2). PEEP-based protective breathing strategy in high-risk patients undergoing major surgery has been linked to better clinical outcomes (3). However, establishing the “optimum” PEEP is still difficult. Excessive PEEP causes overdistension, whereas insufficient PEEP can result in alveolar collapse. The conventional ARDS network PEEP selection table, which is based on the ratio of arterial oxygen partial pressure to fractional inspired oxygen (PaO2/FiO2), is a feasible technique in this respect. However, it might not always yield good outcomes as lung recruitability varies greatly among individuals. Individualized PEEP is therefore required for critically ill patients (4–7). Although PEEP optimization is well established in ARDS, its role in intraoperative ventilation and prevention of postoperative pulmonary complications remains an area of ongoing investigation. In surgical patients, particularly during laparoscopic procedures, anesthesia and pneumoperitoneum contribute to atelectasis formation, highlighting the need for individualized ventilatory strategies. A commonly used clinical strategy hinges on the degree of hypoxemia, using the PaO2/FiO2 tables. Other methods for choosing individualized PEEP concentrate on how it affects respiratory mechanics, with an emphasis on transpulmonary pressure, stress index, or plateau pressure. However, these approaches lack consistent results and have the drawback of combining various lung processes into a single measurement and employing intermediary rather than direct measurements for PEEP-induced lung recruitment (8–11).

Electrical impedance tomography (EIT) is a non-invasive, radiation-free technique that provides bedside, real-time dynamic monitoring of lung function. With real-time tomographic functional pictures of the lungs taken through a thoracic belt, medical personnel can view and evaluate the distribution of ventilation at different ventilation settings in this technique. It can aid in determining the optimum PEEP, which shows a balance between recruitment and overdistension (12–15). Furthermore, local lung perfusion can be estimated using this method, and regional ventilation-perfusion ratios can be mapped by connecting these data with the ventilation signal (14). Therefore, the best and most promising areas of application for EIT are lung function and central hemodynamics monitoring (15).

During anesthesia, during lung-protective ventilation using low tidal volume strategies, EIT can be utilized to guide PEEP titration to establish the nearest PEEP value above the intersection of the lung hyperdilation and collapse curves as the optimal PEEP, which might decrease the risk of postoperative pulmonary atelectasis (15). This systematic review and meta-analysis attempted to provide in-depth insights into the effectiveness of tailored EIT-guided PEEP vs. fixed PEEP in reducing postoperative atelectasis.

2 Methods

3. This systematic review and meta-analysis were conducted according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) Guidelines (16). The study protocol has been submitted to the PROSPERO website, along with its registration number CRD420251169858. Ethical considerations were not necessary because this meta-analysis was conducted by collecting data from previously published clinical trials.

2.1 Inclusion and exclusion criteria

The following criteria must be fulfilled by the clinical trials to be included in our study: (1) Population: Patients who are undergoing laparoscopic surgery under general anesthesia without restriction to their age. (2) Intervention: Individualized positive end-expiratory pressure (PEEP) titrated by electrical impedance tomography (EIT) during pneumoperitoneum mechanical ventilation. (3) Comparator: Fixed positive end-expiratory pressure (PEEP) of 5 cmH₂O during pneumoperitoneum mechanical ventilation. (4) Outcome: Primary outcome: Incidence of postoperative atelectasis assessed by lung ultrasound. Secondary outcomes: mean arterial pressure (MAP), PaO₂/FiO₂ ratio, PaCO₂, pH, dynamic lung compliance, crystalloid use, urine output, length of hospital stay (LOS), intraoperative blood pressure complications, bradycardia during recruitment maneuvers or PEEP titration phases. (5) Study Design: randomized controlled trials (RCTs) that were published in English. The exclusion criteria are different study designs, interventions, or comparators, as well as different outcomes or non-English studies. In addition to that, all studies with incomplete data or unavailable full text would be excluded.

2.2 Search strategy

A comprehensive search on different databases, such as PubMed, Scopus, and Web of Science, was conducted from database inception to the date of the final search, including keywords as “positive end-expiratory pressure”, “electrical impedance tomography”, and “laparoscopic surgery”. The comprehensive search strategy was presented in the (Supplementary Table S1).

2.3 Study selection and data extraction

Finding possibly eligible studies was conducted through titles and abstracts screening, which was done by two independent reviewers (AAA and AOS). The selected papers then underwent a full-text screening, and disagreements between authors were resolved by discussion until an agreement was achieved. A third independent author (AHM) was consulted for further opinions if consensus could not be reached. Two previously created Excel sheets were used to extract relevant data from the papers included. Data was extracted by two reviewers (RA and YS) separately, and the items were grouped into two sheets: one for the study summary and the patients' baseline characteristics, and the outcome measures were the primary focus of the second sheet.

2.4 Risk of bias assessment

The quality and risk of bias of the included papers were assessed by two authors (MMA and MMM) who worked independently, and the updated Cochrane Collaboration's tool for evaluating risk of bias in randomized clinical trials (RoB 2) was used to evaluate the quality and risk of bias of the included studies (17). This tool investigates possible bias through five domains, including domain one for the randomization process, with three subcategorical items; domain two for deviations from intended interventions, with seven subcategorical items; domain three for missing outcome data, with four subcategorical items; domain four, which is used to assess measurement of the outcome with five subcategorical items; as well as domain five, which is used for selection of the reported results. Each domain judgment depended on different subcategorical items, which were finally defined as “low risk of bias”, “some concerns”, or “high risk of bias”. The overall risk of bias for every included clinical trial depended on the judgment of all five domains, in which a low risk of bias was considered the overall risk of bias if all five domains were judged as “low risk”. If one domain was rated as “some concern”, and the other four domains' judgments were “low risk”, the overall risk of bias was rated as “some concern”. Furthermore, if more than one domain was rated as “some concern” or only one domain was “high risk”, the overall risk of bias was rated as “high risk”.

2.5 Statistical analysis

A statistical analysis was conducted using RStudio (version 4.5.1) (16, 18). Forest plots were generated using Standardized Mean Difference (SMD) or Mean Difference (MD) for continuous outcomes, and Odds Ratio (OR) for dichotomous outcomes, along with their respective 95% confidence intervals (CI). A random-effects model was adopted rather than a fixed-effect model, yielding a more conservative estimate of the pooled effect and more generalizable results. Leave-one-out sensitivity analysis was performed to assess the robustness of results by exploring the contribution of each study to the pooled effect and heterogeneity. Statistical heterogeneity was assessed via I² statistic and Cochrane Q test values, where an I² value of <25% indicates a low degree of heterogeneity, 25%–50% indicates a moderate degree of heterogeneity, and >75% indicates a high degree of heterogeneity (19, 20). Cochrane Q test with a p-value of <0.05 was considered significant for heterogeneity. The random-effects model was used in all analyses, regardless of heterogeneity, as recent evidence suggests that it provides a more robust outcome than alternative fixed-effect models.

3 Results

3.1 Study selection

The systematic literature search across multiple databases identified 847 records. After removal of 203 duplicates, 644 records underwent title and abstract screening. Of these, 598 were excluded, leaving 46 full-text articles assessed for eligibility. Following full-text review, 41 articles were excluded for the following reasons: inappropriate study design (n = 15), lack of EIT-guided PEEP titration as the intervention (n = 12), mixed or undefined patient populations (n = 8), and absence of relevant outcome measures (n = 6). Ultimately, five randomized controlled trials were included in the systematic review and meta-analysis. These studies comprised 290 participants, with 145 allocated to the EIT-guided PEEP group and 145 to the fixed PEEP group. Four studies enrolled adult surgical populations, whereas one study included pediatric patients undergoing laparoscopic surgery. The included studies were published between 2017 and 2025 and originated from Germany (n = 2), China (n = 2), and Brazil (n = 1). The full study selection process is shown in Figure 1.

PRISMA flowchart of the study screening and selection.
Figure 1. PRISMA flowchart of the study screening and selection.

All included studies compared individualized PEEP titrated by electrical impedance tomography against conventional fixed PEEP strategies (4–5 cm H₂O) during mechanical ventilation under general anesthesia. The complete study selection process is detailed in the PRISMA flow diagram (Figure 1).

3.2 Summary and baseline characteristics

Our meta-analysis included five RCTs published between 2017 and 2025 from three countries (Germany, China, Brazil), comprising a total of 290 patients who met our inclusion criteria. Of these, 145 were allocated to the PEEP EIT group and 145 to the fixed PEEP group. A summary of included studies and baseline characteristics of the patients included is presented in (Tables 1, 2A,B). The mean PEEP levels in the EIT-guided groups varied across studies and were not consistently reported, precluding pooled analysis.

Table 1. Characteristics of included studies.

Study IDCountrySample size (control/intervention)Inclusion criteriaExclusion CriteriaOutcomes Measured
Girrbach et al. (32)Germany20/20Males ≥18 y, BMI <30 or >18.5 kg/m², ARISCAT score indicating intermediate–high risk; scheduled for robotic radical prostatectomy.Implanted cardiac devices, chronic pulmonary disease, CHF (NYHA III–IV), severe hemodynamic instability after induction.PaO₂/FiO₂ ratio before last RM (primary); EELV and PaO₂/FiO₂ at different time points; vasopressor use; cardiovascular effects.
Nestler et al. (25)Germany25/25Obese pts (BMI ≥35 kg/m²), ≥18 y, medium/high ARISCAT score (≥26), elective laparoscopic surgery.None.PaO₂/FiO₂ ratio before last RM; EELV, SOFA score, ICU/hospital LOS, PPCs (e.g., pneumonia, ARF).
Wang et al. (24)China25/25Age 2–7 y, ASA I–II, laparoscopic surgery.Hemodynamic instability; lung, heart, or chest wall disease; obesity/overweight; op >2 h or mode change.Incidence of atelectasis, lung compliance, B-lines, MAP, HR, SPO₂ <95%.
Ma et al. (31)China24/48≥18 y, elective surgery >180 min, ASA I–II, BMI 18–35 kg/m².Pregnancy, other trials, pneumonia <30 d, lung fibrosis, bullae, prior lung surgery.Respiratory system compliance (CRS); individualized PEEP; PaO₂/FiO₂, driving pressure, hemodynamics (MAP, CO, SVV); PPCs within 7 d.
Pereira et al. (30)Brazil20/20>18 y, abdominal surgery.ASA ≥3, moderate–severe restrictive or obstructive pulmonary disease.Atelectasis, driving pressure, plateau P, oxygenation (Vt/kg), ΔP at PEEP, anesthesia time, LOS, PPCs, vasopressor use.

ARISCAT, assess respiratory risk in surgical patients in catalonia; ASA, American society of anesthesiologists; BMI, body mass index; CHF, congestive heart failure; CO, cardiac output; CRS, compliance of respiratory system; EELV, end-expiratory lung volume; FiO₂, fraction of inspired oxygen; HR, heart rate; ICU, intensive care unit; LOS, length of stay; MAP, mean arterial pressure; NYHA, New York heart association; PaO₂, arterial oxygen pressure; PEEP, positive end-expiratory pressure; PPCs, postoperative pulmonary complications; RM, recruitment maneuver; SOFA, sequential organ failure assessment; SPO₂, oxygen saturation; SVV, stroke volume variation; Vt, tidal volume; ΔP, driving pressure.

Table 2A. Baseline characteristics of the included studies.

Study IDAge (yrs, mean ± SD)Sex (males n, %)BMI (mean ± SD)
ControlInterventionControlInterventionControlIntervention
Girrbach et al. (32)64.2 ± 762.6 ± 7.220 (100%)20 (100%)25.6 ± 2.525.3 ± 2.3
Nestler et al. (25)46.2 ± 11.244.9 ± 9.98 (32%)8 (32%)53.8 ± 8.248.3 ± 7.1
Wang et al. (24)4 ± 14 ± 11819NRNR
Ma et al. (31)57.3 ± 14.553.7 ± 14.014 (58.3%)22 (45.8%)24.2 ± 3.123.9 ± 3.0
Pereira et al. (30)51.73 ± 2750.2 ± 38.38 (40%)10 (50%)30.6 ± 4.228.3 ± 4.2

Table 2B. Baseline clinical characteristics of included studies.

VariableGirrbach et al. (32)Nestler et al. (25)Wang et al. (24)Ma et al. (31)Pereira et al. (30)
ARISCAT (Control)35.0 ± 4.033.4 ± 4.1NRNRNR
ARISCAT (Intervention)36.1 ± 5.333.5 ± 4.7NRNRNR
Smoking—Never8 (42%)11 (44%)NR13 (54%)16 (80%)
Smoking—Former4 (21%)5 (20%)NR3 (13%)2 (10%)
Smoking—Current7 (37%)9 (36%)NR8 (33%)2 (10%)
Hypertension (Control)NRNRNR8 (33%)8 (40%)
Hypertension (Intervention)NRNRNR17 (35%)10 (50%)
Diabetes (Control)2 (10%)16 (64%)NR5 (21%)2 (10%)
Diabetes (Intervention)0 (0%)13 (52%)NR7 (15%)5 (25%)
IHD (Control)3 (16%)1 (4%)NR3 (13%)NR
IHD (Intervention)1 (5%)1 (4%)NR4 (8%)NR
Surgery Duration (Control)NRNR29 ± 8228.0 ± 48.7177.6 ± 29.5
Surgery Duration (Intervention)NRNR29 ± 3214.7 ± 49.4140.3 ± 42.2
Anesthesia Duration (Control)NRNR57 ± 14273.2 ± 47.5234.3 ± 22.3
Anesthesia Duration (Intervention)NRNR55 ± 13251.6 ± 52.1206.6 ± 51.8
Pneumoperitoneum (Control)NRNR21 ± 7199.7 ± 43.8NR
Pneumoperitoneum (Intervention)NRNR21 ± 3185.9 ± 46.5NR
Sleep Apnea (Control)0 (0%)5 (20%)NRNRNR
Sleep Apnea (Intervention)1 (5%)4 (16%)NRNRNR
Bronchitis (Control)1 (5%)1 (4%)NRNRNR
Bronchitis (Intervention)1 (5%)1 (4%)NRNRNR
ASA I (Control)2 (10%)0 (0%)NR11 (46%)6 (30%)
ASA I (Intervention)7 (35%)1 (4%)NR19 (40%)6 (30%)
ASA II (Control)16 (80%)11 (44%)NR13 (54%)14 (70%)
ASA II (Intervention)12 (60%)16 (64%)NR29 (60%)14 (70%)
ASA III (Control)2 (10%)14 (56%)NRNRNR
ASA III (Intervention)1 (5%)8 (32%)NRNRNR
Alcohol—None1 (6%)12 (50%)NRNRNR
Alcohol—Rare7 (39%)0 (0%)NRNRNR
Alcohol—Current10 (56%)12 (50%)NRNRNR

3.3 Risk of bias

The quality of the five RCTs was assessed using RoB 2. The overall risk of bias was low in two studies, some concerns in one study, and high risk in two studies. Domain 1, the risk of bias arising from the randomization process, showed a high risk in two studies due to no description about allocation concealment. Domain 4, the risk of bias arising from measurement of the outcomes, showed some concerns in two studies due to the lack of information about assessors' blinding. Full domain-level risk-of-bias judgments are summarized in (Figures 2a,b).

Full domain-level risk-of-bias **(a)** table **(b)** graph. **(a)** RoB2 Table. **(b)** Rob2 graph.
Figure 2. Full domain-level risk-of-bias (a) table (b) graph. (a) RoB2 Table. (b) Rob2 graph.

3.4 Outcomes

Although postoperative atelectasis assessed by lung ultrasound was predefined as the primary outcome, only three of the included studies reported this outcome; therefore, the analysis was limited to available data.

3.4.1 Mean arterial pressure (MAP)

Positive End-Expiratory Pressure by Electrical Impedance Tomography (PEEP EIT) within the normal range was associated with a significantly higher MAP compared to PEEP 5 cmH2O (MD: 2.12, 95% CI: 0.93 to 3.31, p = 0.0005), with no observed heterogeneity (I2 = 0%) (Figure 3a). Leave-one-out sensitivity analysis demonstrated that the significance and direction of the effect remained consistent after sequential exclusion of individual studies, except when Wang 2025 was excluded, at which point the result became non-significant, although still favored PEEP-EIT (Figure 3b). No subgroup difference was observed based on the age subgroup (adult vs. children) (p = 0.6823).

**(a)** Pooled effect of EIT-guided PEEP on mean arterial pressure. **(b)** Leave -one-out sensitivity analysis for mean arterial pressure.
Figure 3. (a) Pooled effect of EIT-guided PEEP on mean arterial pressure. (b) Leave -one-out sensitivity analysis for mean arterial pressure.

3.4.2 Postoperative atelectasis

PEEP EIT was significantly demonstrated to have lower odds of postoperative atelectasis compared to PEEP 5 cmH2O (OR: 0.18, 95% CI: 0.06 to 0.51, p = 0.0013), with no observed heterogeneity (I2 = 0%) (Figure 4a). Leave-one-out sensitivity analysis demonstrated that the significance and direction of the effect remained consistent after sequential exclusion of individual studies (Figure 4b). No subgroup difference was observed based on the age subgroup (adult vs. children) (p = 0.8213).

**(a)** Pooled effect of EIT-guided PEEP on postoperative atelectasis. **(b)** Leave-one-out sensitivity analysis for postoperative atelectasis.
Figure 4. (a) Pooled effect of EIT-guided PEEP on postoperative atelectasis. (b) Leave-one-out sensitivity analysis for postoperative atelectasis.

3.4.3 Crystalloid

There was no significant difference between PEEP EIT and PEEP 5 cmH2O (SMD: −0.05, 95% CI: −0.81 to 0.71, p = 0.9014), with substantial heterogeneity (I2 = 81.4%) (Supplementary Figure S1). Leave-one-out sensitivity analysis demonstrated that the result showed a significant reduction in the use of crystalloid in PEEP EIT compared to PEEP 5 cmH2O (SMD: −0.43, 95% CI: −0.82 to −0.04, p = 0.0297), and heterogeneity dropped to I2 = 0% after excluding Nestler 2017 (Supplementary Figure S2).

3.4.4 Pao₂/FiO₂ ratio

PEEP EIT was significantly associated with a higher PaO₂/FiO₂ ratio compared with PEEP 5 cmH₂O (SMD 1.72, 95% CI: 0.45 to 2.98, p = 0.0078), although heterogeneity was substantial (I2 = 82.3%) (Figure 5).

Pooled effect of EIT-guided PEEP on PaO₂/FiO₂ ratio.
Figure 5. Pooled effect of EIT-guided PEEP on PaO₂/FiO₂ ratio.

3.4.5 pH

No significant difference was found between PEEP EIT and PEEP 5 cmH₂O (MD: 0.00, 95% CI: −0.03 to 0.02, p = 0.8190), and no heterogeneity was observed (I2 = 0%) (Supplementary Figure S3).

3.4.6 PaCO2 (mmHg)

No significant difference was found between PEEP EIT and PEEP 5 cmH2O (MD: −0.75, 95% CI: −6.33 to 4.84, p = 0.7935), though substantial heterogeneity (I2 = 82.9%) (Supplementary Figure S4). Due to the limited number of included studies, leave-one-out sensitivity analysis was not feasible.

3.4.7 Urine output (mL)

No significant difference was found between PEEP EIT and PEEP 5 cmH2O (MD: −23.55, 95% CI: −78.90 to 31.80, p = 0.4043), with no observed heterogeneity (I2 = 0%) (Supplementary Figure S5). Due to the limited number of included studies, leave-one-out sensitivity analysis was not feasible.

3.4.8 Length of hospital stay, days (LOS)

No significant difference was found between PEEP EIT and PEEP 5 cmH2O (MD: −0.00, 95% CI: −0.49 to 0.49, p = 0.9978), no observed heterogeneity (I2 = 0%) (Supplementary Figure S6). Due to the limited number of included studies, leave-one-out sensitivity analysis was not feasible.

3.4.9 Lung compliance (mL/cmH₂O)

PEEP EIT resulted in a non-significant increase in lung compliance (mL/cmH₂O) compared with PEEP 5 cmH₂O (MD: 10.20, 95% CI: −5.73 to 26.14, p = 0.2096), with considerable heterogeneity (I2 = 92.7%) (Supplementary Figure S7).

3.4.10 Blood pressure complications during surgery

No significant difference was found between PEEP EIT and PEEP 5 cmH₂O (OR: 1.33, 95% CI: 0.56 to 3.17, p = 0.5184), with no observed heterogeneity (I2 = 0%) (Supplementary Figure S8). For this meta-analysis, blood pressure complications were analyzed according to the original trial reports of intraoperative hemodynamic adverse events, including vasopressor requirement and other cardiovascular/hemodynamic complications as reported by each study. Because these definitions were not fully uniform across trials, this outcome should be interpreted cautiously (Supplementary Figure S8).

3.4.11 Bradycardia during RM or PEEP titration phases

PEEP EIT had significantly higher odds of bradycardia during RM or PEEP titration phases compared with PEEP 5 cmH₂O (OR: 38.90, 95% CI: 4.88 to 309.76, p = 0.005), with no observed heterogeneity (I2 = 0%) (Supplementary Figure S9).

4 Discussion

In patients undergoing abdominal surgery, the use of individually titrated EIT-guided PEEP appears to be a promising bedside strategy associated with improved perioperative lung aeration and reduced atelectasis. In our study, individualized EIT-titrated PEEP was compared with a low fixed PEEP. Significant differences were observed between the intervention and control groups regarding postoperative atelectasis, PaO₂/FiO₂ ratio, mean arterial pressure (MAP), and bradycardia during the recruitment manoeuvre or PEEP titration phases. Leave-one-out sensitivity analyses confirmed the consistency of these results across subgroups, except for MAP, which still favoured the EIT-PEEP group. No significant differences were found between groups concerning lung compliance, hospital stay, intraoperative hemodynamic instability, urine output, pH, or PaCO₂.

This pooled study aligns with previous studies by highlighting the potential role of individualized PEEP titration in improving perioperative outcomes (1, 7, 15, 21–23). It helps identify a PEEP level that balances alveolar collapse and overdistension (1, 7, 15, 21, 22). EIT provides real-time monitoring of regional lung aeration, allowing identification of the PEEP level that minimizes both collapse and overinflation, particularly in dorsal regions of the lungs (24). This observation is consistent with other authors who demonstrated improved lung aeration with individualized PEEP strategies (22–25).

Postoperative atelectasis is a common and potentially harmful complication that may persist for several days after surgery, which may compromise respiratory function and prolong hospital stay (26–29). In our meta-analysis, individualized EIT-titrated PEEP was associated with a lower incidence of postoperative atelectasis (OR: 0.18, 95% CI: 0.06 to 0.51). Consistent with our pooled analysis, Wang et al. reported a lower incidence of postoperative atelectasis in the intervention group compared to the control group (64% vs. 92%) (21). In contrast, both Pereira et al. and Ma et al. demonstrated no association between individualized EIT-titrated PEEP and incidence of atelectasis (30, 31). However, these trials were limited by small sample sizes and single-center designs, which may restrict the generalizability of their findings.

Beyond its association with reduced postoperative atelectasis, individualized EIT-guided PEEP was also associated with improved oxygenation. In our meta-analysis, the PaO₂/FiO₂ ratio was significantly higher in the intervention group compared with the fixed low PEEP group (SMD 1.72, 95% CI: 0.45 to 2.98), indicating improved alveolar recruitment and more effective gas exchange.

This finding is consistent with previous studies that reported improved oxygenation when PEEP was titrated individually based on EIT measurements. Girrbach et al. and Pereira et al. both reported significant improvements in the PaO₂/FiO₂ ratio following EIT-guided PEEP adjustment, supporting the concept that individualized PEEP settings may reduce ventilation-perfusion mismatch and intrapulmonary shunt (30, 32).

Justification: Standardizes terminology and softens mechanistic certainty. Also corrects the spelling of Girrbach to match the reference list in the current manuscript.

A considerable degree of heterogeneity was observed among the included studies for this outcome. Although a leave-one-out sensitivity analysis was performed to explore potential sources of heterogeneity, the limited number of available trials precluded further subgroup analyses. The heterogeneity among studies may be explained by differences in patient characteristics, surgical types, and PEEP titration protocols. Nevertheless, the direction of effect remained consistent across studies, supporting the robustness of the overall result.

Regarding hemodynamic outcomes, these discrepancies may be related to variations in applied PEEP levels, anaesthesia depth, pneumoperitoneum, and patient characteristics across trials, as well as the small sample sizes of the individual studies. Overall, individualized PEEP titration appeared to preserve hemodynamic stability without evidence of increased overall intraoperative blood pressure complications, but the underlying mechanism remains uncertain and should not be attributed solely to reduced intrathoracic pressure or improved venous return.

Regarding bradycardia during recruitment manoeuvre (RM) or PEEP titration phases, our meta-analysis demonstrated a significantly higher incidence in patients receiving individualized EIT-guided PEEP. Consistent with this finding, Girrbach et al. and Nestler et al. also reported significant bradycardia during recruitment or PEEP titration (22, 30).

No significant differences were found between groups regarding lung compliance, duration of hospital stay, intraoperative hemodynamic complications, or metabolic parameters such as pH and PaCO₂. Similarly, intraoperative fluid administration and urine output were comparable between groups. These findings suggest that no clear differences were observed between groups in lung mechanics, overall hemodynamic complications, or postoperative recovery outcomes within the available evidence base.

Taken together, these trials and our pooled analysis suggest that individualized EIT-guided PEEP was associated with reduced postoperative atelectasis and improved oxygenation compared with fixed low PEEP strategies. Mean arterial pressure was also higher in the EIT-guided PEEP group, although this finding should be interpreted cautiously given the limited number of studies and variation in intraoperative conditions.

The strength of this pooled study is that it evaluates the efficacy and safety of individualized EIT-guided PEEP to reduce postoperative atelectasis. The reliability of the findings was confirmed through leave-one-out sensitivity analyses, ensuring the robustness of the results.

An additional limitation relates to the inclusion of the Nestler 2017 trial, in which the PulmoVista 500 system was used in an obese surgical population that may have included patients with BMI >50. Poor-quality EIT images have been reported as a potential concern in morbidly obese patients with BMI above 50. However, this issue should be interpreted cautiously rather than considered sufficient grounds for automatic exclusion. EIT-guided PEEP titration is generally based on time-difference imaging, which tracks relative within-patient changes in conductivity between ventilatory states rather than relying on absolute chest images; accordingly, even if body habitus affects electrode contact or image quality to some extent, the relative changes used for PEEP guidance may remain clinically informative. This interpretation is supported by contemporary reviews of EIT principles and applications, as well as more recent evidence showing comparable EIT performance for lung function measurement in obese and non-obese subjects. In addition, Nestler and colleagues developed the regional ventilation delay index specifically to guide PEEP in obese patients under general anaesthesia, supporting the clinical relevance of EIT-derived guidance in this population. Importantly, in our review, leave-one-out sensitivity analysis for mean arterial pressure showed that exclusion of Nestler 2017 did not reverse the direction of effect, which supports the robustness of that finding independent of this study. Future studies in morbidly obese patients should ideally report EIT signal-quality metrics alongside clinical outcomes.

5 Conclusion

This systematic review and meta-analysis suggest that individualized PEEP guided by electrical impedance tomography may offer clinical advantages over fixed low PEEP strategies during general anesthesia. EIT-guided PEEP was associated with reduced postoperative atelectasis and improved oxygenation, while no clear differences were observed for most other perioperative outcomes, although mean arterial pressure was higher and bradycardia during recruitment or titration phases was more frequent. These findings suggest that EIT may be a useful bedside tool for optimizing PEEP selection by balancing alveolar recruitment and overdistension. Larger multicenter randomized trials are needed to validate these findings and inform future perioperative ventilatory recommendations.

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Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fanes.2026.1758421/full#supplementary-material

Supplementary material Supplementary material at the source

Footnotes

Edited by: José Eduardo Guimarães Pereira, Hospital Central do Exercito, Brazil

Reviewed by: Serge Heines, Maastricht University Medical Centre, Netherlands

Myrte Wennen, Academic Medical Center, Netherlands

Statements

Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Funding

The author(s) declared that financial support was not received for this work and/or its publication.

Author contributions

AM: Methodology, Visualization, Formal analysis, Writing – review & editing, Data curation, Validation, Conceptualization, Project administration, Supervision, Investigation, Resources. MH: Writing – review & editing, Supervision, Data curation, Investigation, Project administration, Conceptualization, Visualization, Validation, Methodology. AO: Supervision, Methodology, Software, Validation, Investigation, Writing – review & editing, Formal analysis, Resources. AA: Methodology, Validation, Project administration, Investigation, Writing – review & editing, Visualization, Software, Resources. MA: Investigation, Software, Writing – original draft, Resources, Visualization, Validation, Methodology, Project administration. EA: Methodology, Supervision, Writing – review & editing, Investigation, Validation, Software, Writing – original draft, Visualization, Project administration, Resources. WB: Writing – review & editing, Methodology. SF: Methodology, Writing – review & editing, Resources, Visualization, Validation, Project administration. TB: Project administration, Validation, Writing – original draft, Visualization, Software, Resources. MM: Validation, Methodology, Project administration, Software, Visualization, Writing – original draft. RA: Visualization, Validation, Writing – original draft, Software. AM: Writing – review & editing, Validation, Software, Visualization. MH: Writing – original draft, Visualization, Validation, Writing – review & editing. IU: Writing – original draft, Validation, Supervision.

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Citation

Mohamed, A. H., et al. (2026). Individualized PEEP guided by electrical impedance tomography versus fixed PEEP in laparoscopic surgery: a systematic review and meta-analysis of effects on postoperative pulmonary complications. Frontiers in Anesthesiology, Volume 5. https://doi.org/
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5 - 2026

Copyright

© 2026 Mohamed, Hemida, Omar Saleh, Abdelfattah, Alamin, Alokozay, Bechichi, Fatima, Bhadra, Mohammed, Alasali, Mohamed, Habibi and Ullah.

License: https://creativecommons.org/licenses/by/4.0/

*Correspondence: Ehsanullah Alokozay

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