BACKGROUND: Postoperative pulmonary complications (PPCs) are associated with postoperative mortality and prolonged hospital stay. Although intraoperative mechanical ventilation (MV) is a risk factor for PPCs, strategies addressing weaning from MV are understudied. In this systematic review, we evaluated weaning strategies and their effects on postoperative pulmonary outcomes.
METHODS: Our protocol was registered on PROSPERO (CRD42022379145). Eligible studies included randomised controlled trials and observational studies of adults weaned from MV in the operating room. Primary outcomes included atelectasis and oxygenation; secondary outcomes included lung volume changes and PPCs. Risk of bias was assessed using the Cochrane Risk of Bias (RoB2) tool, and quality of evidence with the GRADE framework.
RESULTS: Screening identified 14 randomised controlled trials including 1719 patients; seven studies were limited to the weaning phase and seven included interventions not restricted to the weaning phase. Strategies combining pressure support ventilation (PSV) with positive end-expiratory pressure (PEEP) and low fraction of inspired oxygen (FiO2) improved atelectasis, oxygenation, and lung volumes. Low FiO2 improved atelectasis and oxygenation but might not improve lung volumes. A fixed-PEEP strategy led to no improvement in oxygenation or atelectasis; however, individualised PEEP with low FiO2 improved oxygenation and might be associated with reduced PPCs. Half of included studies are of moderate or high risk of bias; the overall quality of evidence is low.
CONCLUSIONS: There is limited research evaluating weaning from intraoperative MV. Based on low-quality evidence, PSV, individualised PEEP, and low FiO2 may be associated with reduced postoperative pulmonary outcomes.
UNASSIGNED: PROSPERO (CRD42022379145).

UNASSIGNED: Patients with acute brain injury (ABI) are a peculiar population because ABI does not only affect the brain but also other organs such as the lungs, as theorized in brain-lung crosstalk models. ABI patients often require mechanical ventilation (MV) to avoid the complications of impaired respiratory function that can follow ABI; MV should be settled with meticulousness owing to its effects on the intracranial compartment, especially regarding positive end-expiratory pressure (PEEP). This scoping review aimed to (1) describe the physiological basis and mechanisms related to the effects of PEEP in ABI; (2) examine how clinical research is conducted on this topic; (3) identify methods for setting PEEP in ABI; and (4) investigate the impact of the application of PEEP in ABI on the outcome.
UNASSIGNED: The five-stage paradigm devised by Peters et al. and expanded by Arksey and O\'Malley, Levac et al., and the Joanna Briggs Institute was used for methodology. We also adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension criteria. Inclusion criteria: we compiled all scientific data from peer-reviewed journals and studies that discussed the application of PEEP and its impact on intracranial pressure, cerebral perfusion pressure, and brain oxygenation in adult patients with ABI. Exclusion criteria: studies that only examined a pediatric patient group (those under the age of 18), experiments conducted solely on animals; studies without intracranial pressure and/or cerebral perfusion pressure determinations, and studies with incomplete information. Two authors searched and screened for inclusion in papers published up to July 2023 using the PubMed-indexed online database. Data were presented in narrative and tubular form.
UNASSIGNED: The initial search yielded 330 references on the application of PEEP in ABI, of which 36 met our inclusion criteria. PEEP has recognized beneficial effects on gas exchange, but it produces hemodynamic changes that should be predicted to avoid undesired consequences on cerebral blood flow and intracranial pressure. Moreover, the elastic properties of the lungs influence the transmission of the forces applied by MV over the brain so they should be taken into consideration. Currently, there are no specific tools that can predict the effect of PEEP on the brain, but there is an established need for a comprehensive monitoring approach for these patients, acknowledging the etiology of ABI and the measurable variables to personalize MV.
UNASSIGNED: PEEP can be safely used in patients with ABI to improve gas exchange keeping in mind its potentially harmful effects, which can be predicted with adequate monitoring supported by bedside non-invasive neuromonitoring tools.

Driving pressure (∆P) is a core therapeutic component of mechanical ventilation (MV). Varying levels of ∆P have been employed during MV depending on the type of underlying pathology and severity of injury. However, ∆P levels have also been shown to closely impact hard endpoints such as mortality. Considering this, conducting an in-depth review of ∆P as a unique, outcome-impacting therapeutic modality is extremely important. There is a need to understand the subtleties involved in making sure ∆P levels are optimized to enhance outcomes and minimize harm. We performed this narrative review to further explore the various uses of ∆P, the different parameters that can affect its use, and how outcomes vary in different patient populations at different pressure levels. To better utilize ∆P in MV-requiring patients, additional large-scale clinical studies are needed.

The determination of optimal positive end-expiratory pressure (PEEP) values in patients undergoing general anesthesia remains controversial. Electrical impedance tomography (EIT) directed individualized PEEP has emerged as a novel approach to PEEP setting and has garnered increasing attention. This meta-analysis aims to systematically assess the effect of EIT-guided PEEP setting compared to traditional fixed PEEP values or other PEEP titration strategies in patients undergoing general anesthesia.
A comprehensive search of electronic databases, including PubMed, Web of Science, EMBASE, and the Cochrane Library, was conducted from inception to January 2023, with no language restrictions. The search terms used were \"EIT\"and \"PEEP\" with their corresponding free words. Two researchers independently conducted literature screening, data extraction, and quality evaluation. The primary outcomes of interest were oxygenation index (OI), lung compliance, and number of postoperative pulmonary complications (PPCs). The secondary outcomes included mean arterial blood pressure (MAP) and number of vasoactive drug injections. RevMan 5.3 software was used to analyze the data and draw the forest plot, and Stata 14.2 software was used to conduct sensitivity analysis to assess the stability of the results.
5 studies involving 272 participants were included in this meta-analysis. Our findings suggest that EIT-guided individualized PEEP setting is superior to traditional fixed PEEP values and other individualized PEEP titration methods in terms of intraoperative OI(OR = 95.73, 95%CI: (49.10, 142.37); P < 0.0001) and lung compliance(OR = 7.69, 95%CI: (5.55, 9.83); P < 0.00001), without affecting intraoperative hemodynamic parameters such as MAP(OR = 2.07, 95%CI: (-1.00, 5.13); P = 0.19) and the number of intravenous vasoactive drugs(OR = 1.22, 95%CI: (0.68, 2.21); P = 0.51) or increasing the incidence of postoperative PPCs(OR = 0.87, 95%CI: (0.41, 1.82); P = 0.71).
Our meta-analysis suggests potential benefits of EIT-guided individualized PEEP setting in improving intraoperative oxygenation and lung compliance in patients undergoing general anesthesia. However, further research is needed to establish conclusive evidence, and caution should be exercised in interpreting these findings as the current literature remains inconclusive regarding the impact on intraoperative hemodynamics and postoperative complications.

Higher positive end-expiratory pressure (PEEP) during laparoscopic surgery may increase oxygenation and respiratory compliance. This meta-analysis aimed to compare the impact of different intraoperative PEEP strategies on arterial oxygenation, compliance, and hemodynamics during laparoscopic surgery in non-obese patients.
We searched RCTs in PubMed, Cochrane Library, Web of Science, and Google Scholar from January 2012 to April 2022 comparing the different intraoperative PEEP (Low PEEP (LPEEP): 0-4 mbar; Moderate PEEP (MPEEP): 5-8 mbar; high PEEP (HPEEP): >8 mbar; individualized PEEP - iPEEP) on arterial oxygenation, respiratory compliance (Cdyn), mean arterial pressure (MAP), and heart rate (HR). We calculated mean differences (MD) with 95% confidence intervals (CI), and predictive intervals (PI) using random-effects models. The Cochrane Bias Risk Assessment Tool was applied.
21 RCTs (n = 1554) met the inclusion criteria. HPEEP vs. LPEEP increased PaO2 (+ 29.38 [16.20; 42.56] mmHg, p < 0.0001) or PaO2/FiO2 (+ 36.7 [+ 2.23; +71.70] mmHg, p = 0.04). HPEEP vs. MPEEP increased PaO2 (+ 22.00 [+ 1.11; +42.88] mmHg, p = 0.04) or PaO2/FiO2 (+ 42.7 [+ 2.74; +82.67] mmHg, p = 0.04). iPEEP vs. MPEEP increased PaO2/FiO2 (+ 115.2 [+ 87.21; +143.20] mmHg, p < 0.001). MPEEP vs. LPEP, and HPEEP vs. MPEEP increased PaO2 or PaO2/FiO2 significantly with different heterogeneity. HPEEP vs. LPEEP increased Cdyn (+ 7.87 [+ 1.49; +14.25] ml/mbar, p = 0.02). MPEEP vs. LPEEP, and HPEEP vs. MPEEP did not impact Cdyn (p = 0.14 and 0.38, respectively). iPEEP vs. LPEEP decreased driving pressure (-4.13 [-2.63; -5.63] mbar, p < 0.001). No significant differences in MAP or HR were found between any subgroups.
HPEEP and iPEEP during PNP in non-obese patients could promote oxygenation and increase Cdyn without clinically significant changes in MAP and HR. MPEEP could be insufficient to increase respiratory compliance and improve oxygenation. LPEEP may lead to decreased respiratory compliance and worsened oxygenation.
CRD42022362379; registered October 09, 2022.

Electrical Impedance Tomography (EIT) is a non-invasive bedside imaging technique that provides real-time lung ventilation information on critically ill patients. EIT can potentially become a valuable tool for optimising mechanical ventilation, especially in patients with acute respiratory distress syndrome (ARDS). In addition, EIT has been shown to improve the understanding of ventilation distribution and lung aeration, which can help tailor ventilatory strategies according to patient needs. Evidence from critically ill patients shows that EIT can reduce the duration of mechanical ventilation and prevent lung injury due to overdistension or collapse. EIT can also identify the presence of lung collapse or recruitment during a recruitment manoeuvre, which may guide further therapy. Despite its potential benefits, EIT has not yet been widely used in clinical practice. This may, in part, be due to the challenges associated with its implementation, including the need for specialised equipment and trained personnel and further validation of its usefulness in clinical settings. Nevertheless, ongoing research focuses on improving mechanical ventilation and clinical outcomes in critically ill patients.

Many RCTs have evaluated the influence of intraoperative tidal volume (tV), PEEP, and driving pressure on the occurrence of postoperative pulmonary complications, cardiovascular complications, and mortality in adult patients. Our meta-analysis aimed to investigate the association between tV, PEEP, and driving pressure and the above-mentioned outcomes.
We conducted a systematic review and meta-analysis of RCTs from inception to May 19, 2022. The primary outcome was the incidence of postoperative pulmonary complications; the secondary outcomes were intraoperative cardiovascular complications and 30-day mortality. Primary and secondary outcomes were evaluated stratifying patients in the following groups: (1) low tV (LV, tV 6-8 ml kg-1 and PEEP ≥5 cm H2O) vs high tV (HV, tV >8 ml kg-1 and PEEP=0 cm H2O); (2) higher PEEP (HP, ≥6 cm H2O) vs lower PEEP (LP, <6 cm H2O); and (3) driving pressure-guided PEEP (DP) vs fixed PEEP (FP).
We included 16 RCTs with a total sample size of 4993. The incidence of postoperative pulmonary complications was lower in patients treated with LV than with HV (OR=0.402, CI 0.280-0.577, P<0.001) and lower in DP than in FP group (OR=0.358, CI 0.187-0.684, P=0.002). Postoperative pulmonary complications did not differ between HP and LP groups; the incidence of intraoperative cardiovascular complications was higher in HP group (OR=1.385, CI 1.027-1.867, P=0.002). The 30-day mortality was not influenced by the ventilation strategy.
Optimal intraoperative mechanical ventilation is unclear; however, our meta-analysis showed that low tidal volume and driving pressure-guided PEEP strategies were associated with a reduction in postoperative pulmonary complications.

BACKGROUND: Newborn resuscitation guidelines recommend positive pressure ventilation (PPV) for newborns who do not establish effective spontaneous breathing after birth. T-piece resuscitator systems are commonly used in high-resource settings and can additionally provide positive end-expiratory pressure (PEEP). Short expiratory time, high resistance, rapid dynamic changes in lung compliance and large tidal volumes increase the possibility of incomplete exhalation. Previous publications indicate that this may occur during newborn resuscitation. Our aim was to study examples of incomplete exhalations in term newborn resuscitation and discuss these against the theoretical background.
METHODS: Examples of flow and pressure data from respiratory function monitors (RFM) were selected from 129 term newborns who received PPV using a T-piece resuscitator. RFM data were not presented to the user during resuscitation.
RESULTS: Examples of incomplete exhalation with higher-than-set PEEP-levels were present in the recordings with visual correlation to factors affecting time needed to complete exhalation.
CONCLUSIONS: Incomplete exhalation and the relationship to expiratory time constants have been well described theoretically. We documented examples of incomplete exhalations with increased PEEP-levels during resuscitation of term newborns. We conclude that RFM data from resuscitations can be reviewed for this purpose and that incomplete exhalations should be further explored, as the clinical benefit or risk of harm are not known.

The optimization of positive end-expiratory pressure (PEEP) according to respiratory mechanics [driving pressure or respiratory system compliance (Crs)] is a simple and straightforward strategy. However, its validity to prevent postoperative pulmonary complications (PPCs) remains unclear. Here, we performed a meta-analysis to assess such efficacy. We searched PubMed, Embase, and the Cochrane Library to identify randomized controlled trials (RCTs) that compared personalized PEEP based on respiratory mechanics and constant PEEP to prevent PPCs in adults. The primary outcome was PPCs. Fourteen studies with 1105 patients were included. Compared with those who received constant PEEP, patients who received optimized PEEP exhibited a significant reduction in the incidence of PPCs (RR = 0.54, 95% CI 0.42 to 0.69). The results of commonly happened PPCs (pulmonary infections, hypoxemia, and atelectasis but not pleural effusion) also supported individualized PEEP group. Moreover, the application of PEEP based on respiratory mechanics improved intraoperative respiratory mechanics (driving pressure and Crs) and oxygenation. The PEEP titration method based on respiratory mechanics seems to work positively for lung protection in surgical patients undergoing general anesthesia.

To determine which method of Positive End-expiratory Pressure (PEEP) titration is more useful, and to establish an evidence base for the clinical impact of Electrical Impedance Tomography (EIT) based individual PEEP setting which appears to be a promising method to optimize PEEP in Acute Respiratory Distress Syndrome (ARDS) patients.
A systematic review and meta-analysis.
4 databases (PUBMED, EMBASE, Web Of Science, and the Cochrane Library) from 1980 to December 2020 were performed.
Randomized clinical trials patients with ARDS.
PaO2/FiO2-ratio and respiratory system compliance.
The quality of the studies was assessed with the Cochrane risk and bias tool.
8 trials, including a total of 222 participants, were eligible for analysis. Meta-analysis demonstrates a significantly EIT-based individual PEEP setting for patients receiving higher PaO2/FiO2 ratio as compared to other PEEP titration strategies [5 trials, 202 patients, SMD 0.636, (95% CI 0.364-0.908)]. EIT-drived PEEP titration strategy did not significantly increase respiratory system compliance when compared to other peep titration strategies, [7 trials, 202 patients, SMD -0.085, (95% CI -0.342 to 0.172)].
The benefits of PEEP titration with EIT on clinical outcomes of ARDS in placebo-controlled trials probably result from the visible regional ventilation of EIT. These findings offer clinicians and stakeholders a comprehensive assessment and high-quality evidence for the safety and efficacy of the EIT-based individual PEEP setting as a superior option for patients who undergo ARDS.