Optimal Positive End-expiratory Pressure Research Articles

Effect of Prone Positioning With Individualized Positive End-Expiratory Pressure in Acute Respiratory Distress Syndrome Using Electrical Impedance Tomography.

Background: Positive end-expiratory pressure (PEEP) optimization during prone positioning remains under debate in acute respiratory distress syndrome (ARDS). This study aimed to investigate the effect of prone position on the optimal PEEP guided by electrical impedance tomography (EIT). Methods: We conducted a retrospective analysis on nineteen ARDS patients in a single intensive care unit. All patients underwent PEEP titration guided by EIT in both supine and prone positions. EIT-derived parameters, including center of ventilation (CoV), regional ventilation delay (RVD), percentage of overdistension (OD) and collapse (CL) were calculated. Optimal PEEP was defined as the PEEP level with minimal sum of OD and CL. Patients were divided into two groups: 1) Lower Optimal PEEPPP (LOP), where optimal PEEP was lower in the prone than in the supine position, and 2) Not-Lower Optimal PEEPPP (NLOP), where optimal PEEP was not lower in the prone compared with the supine position. Results: Eleven patients were classified as LOP (9 [8-9] vs. 12 [10-15] cmH2O; PEEP in prone vs. supine). In the NLOP group, optimal PEEP increased after prone positioning in four patients and remained unchanged in the other four patients. Patients in the LOP group had a significantly higher body mass index (26 [25-28] vs. 22 [17-25] kg/m2; p = 0.009) and lower ICU mortality (0/11 vs. 4/8; p = 0.018) compared with the NLOP group. Besides, PaO2/FiO2 increased significantly during prone positioning in the LOP group (238 [170-291] vs. 186 [141-195] mmHg; p = 0.042). CoV and RVD were also significantly improved during prone positioning in LOP group. No such effects were found in the NLOP group. Conclusion: Broad variability in optimal PEEP between supine and prone position was observed in the studied ARDS patients. Not all patients showed decreased optimal PEEP during prone positioning. Patients with higher body mass index exhibited lower optimal PEEP in prone position, better oxygenation and ventilation homogeneity.

Early Physiologic Effects of Prone Positioning in COVID-19 Acute Respiratory Distress Syndrome.

The mechanisms underlying oxygenation improvement after prone positioning in COVID-19 acute respiratory distress syndrome have not been fully elucidated yet. The authors hypothesized that the oxygenation increase with prone positioning is secondary to the improvement of ventilation-perfusion matching. In a series of consecutive intubated COVID-19 acute respiratory distress syndrome patients receiving volume-controlled ventilation, the authors prospectively assessed the percent variation of ventilation-perfusion matching by electrical impedance tomography before and 90 min after the first cycle of prone positioning (primary endpoint). The authors also assessed changes in the distribution and homogeneity of lung ventilation and perfusion, lung overdistention and collapse, respiratory system compliance, driving pressure, optimal positive end-expiratory pressure, as assessed by electrical impedance tomography, and the ratio of partial pressure to fraction of inspired oxygen (Pao2/Fio2; secondary endpoints). Data are reported as medians [25th to 75th] or percentages. The authors enrolled 30 consecutive patients, all analyzed without missing data. Compared to the supine position, prone positioning overall improved ventilation-perfusion matching from 58% [43 to 69%] to 68% [56 to 75%] (P = 0.042), with a median difference of 8.0% (95% CI, 0.1 to 16.0%). Dorsal ventilation increased from 39% [31 to 43%] to 52% [44 to 62%] (P < 0.001), while dorsal perfusion did not significantly vary. Prone positioning also reduced lung overdistension from 9% [4 to 11%] to 4% [2 to 6%] (P = 0.025), while it did not significantly affect ventilation and perfusion homogeneity, lung collapse, static respiratory system compliance, driving pressure, and optimal positive end-expiratory pressure. Pao2/Fio2 overall improved from 141 [104 to 182] mmHg to 235 [164 to 267] mmHg (P = 0.019). However, 9 (30%) patients were nonresponders, experiencing an increase in Pao2/Fio2 less than 20% with respect to baseline. In COVID-19 acute respiratory distress syndrome patients, prone positioning overall produced an early increase in ventilation-perfusion matching and dorsal ventilation. These effects were, however, heterogeneous among patients.

Clinical Implications of Determining Individualized Positive End-Expiratory Pressure Using Electrical Impedance Tomography in Post-Cardiac Surgery Patients: A Prospective, Non-Randomized Interventional Study.

Optimal positive end-expiratory pressure (PEEP) can induce sustained lung function improvement. This prospective, non-randomized interventional study aimed to investigate the effect of individualized PEEP determined using electrical impedance tomography (EIT) in post-cardiac surgery patients (n = 35). Decremental PEEP trials were performed from 20 to 4 cmH2O in steps of 2 cmH2O, guided by EIT. PEEP levels preventing ventilation loss in dependent lung regions (PEEPONLINE) were set. Ventilation distributions and oxygenation before the PEEP trial, and 5 min and 1 h after the PEEPONLINE setting were examined. Furthermore, we analyzed the saved impedance data offline to determine the PEEP levels that provided the best compromise between overdistended and collapsed lung (PEEPODCL). Ventilation distributions of dependent regions increased at 5 min after the PEEPONLINE setting compared with those before the PEEP trial (mean ± standard deviation, 41.3 ± 8.5% vs. 49.1 ± 9.3%; p < 0.001), and were maintained at 1 h thereafter (48.7 ± 9.4%, p < 0.001). Oxygenation also showed sustained improvement. Rescue oxygen therapy (high-flow nasal cannula, noninvasive ventilation) after extubation was less frequent in patients with PEEPONLINE ≥ PEEPODCL than in those with PEEPONLINE < PEEPODCL (1/19 vs. 6/16; p = 0.018). EIT-guided individualized PEEP stabilized the improvement in ventilation distribution and oxygenation. Individual PEEP varies with EIT measures, and may differentially affect oxygenation after cardiac surgery.

The respiratory and hemodynamic effects of alveolar recruitment in cirrhotic patients undergoing liver resection surgery: A randomized controlled trial.

Extensive surgical retraction combined with general anesthesia increase alveolar collapse. The primary aim of our study was to investigate the effect of alveolar recruitment maneuver (ARM) on arterial oxygenation tension (PaO2). The secondary aim was to observe its effect on hemodynamics parameters in hepatic patients during liver resection, to investigate its impact on blood loss, postoperative pulmonary complications (PPC), remnant liver function tests, and on the outcome. Adult patients scheduled for liver resection were randomized into two groups: ARM (n = 21) and control (C) (n = 21). Stepwise ARM was initiated after intubation and was repeated post-retraction. Pressure-control ventilation mode was adjusted to deliver a tidal volume (Vt) of 6 mL/kg and an inspiratory-to-expiratory time (I:E) ratio of 1:2 with an optimal positive end-expiratory pressure (PEEP) for the ARM group. In the C group, a fixed PEEP (5 cmH2O) was applied. Invasive intra-arterial blood pressure (IBP), central venous pressure (CVP), electrical cardiometry (EC), alanine transaminase (ALT, U/L), and aspartate aminotransferase (AST, U/L) blood levels were monitored. ARM increased PEEP, dynamic compliances, and arterial oxygenation, but reduced ventilator driving pressure compared to group C (P < 0.01). IBP, cardiac output (CO), and stroke volume variation were not affected by the higher PEEP in the ARM group (P > 0.05) but the CVP increased significantly (P = 0.001). Blood loss was not different between the ARM and C groups (1700 (1150-2000) mL vs 1110 (900-2400) mL, respectively and P = 0.57). ARM reduced postoperative oxygen desaturation; however, it did not affect the increase in remnant liver enzymes and was comparable to group C (ALT, P = 0.54, AST, P = 0.41). ARM improved intraoperative lung mechanics and reduced oxygen desaturation episodes in recovery, but not PPC or ICU stay. ARM was tolerated with minimal cardiac and systemic hemodynamic effects.

Evidence-Based Mechanical Ventilatory Strategies in ARDS.

Acute respiratory distress syndrome (ARDS) remains one of the leading causes of morbidity and mortality in critically ill patients despite advancements in the field. Mechanical ventilatory strategies are a vital component of ARDS management to prevent secondary lung injury and improve patient outcomes. Multiple strategies including utilization of low tidal volumes, targeting low plateau pressures to minimize barotrauma, using low FiO2 (fraction of inspired oxygen) to prevent injury related to oxygen free radicals, optimization of positive end expiratory pressure (PEEP) to maintain or improve lung recruitment, and utilization of prone ventilation have been shown to decrease morbidity and mortality. The role of other mechanical ventilatory strategies like non-invasive ventilation, recruitment maneuvers, esophageal pressure monitoring, determination of optimal PEEP, and appropriate patient selection for extracorporeal support is not clear. In this article, we review evidence-based mechanical ventilatory strategies and ventilatory adjuncts for ARDS.

Unsuccessful and Successful Clinical Trials in Acute Respiratory Distress Syndrome: Addressing Physiology-Based Gaps.

The acute respiratory distress syndrome (ARDS) is a severe form of acute hypoxemic respiratory failure caused by an insult to the alveolar-capillary membrane, resulting in a marked reduction of aerated alveoli, increased vascular permeability and subsequent interstitial and alveolar pulmonary edema, reduced lung compliance, increase of physiological dead space, and hypoxemia. Most ARDS patients improve their systemic oxygenation, as assessed by the ratio between arterial partial pressure of oxygen and inspired oxygen fraction, with conventional intensive care and the application of moderate-to-high levels of positive end-expiratory pressure. However, in some patients hypoxemia persisted because the lungs are markedly injured, remaining unresponsive to increasing the inspiratory fraction of oxygen and positive end-expiratory pressure. For decades, mechanical ventilation was the only standard support technique to provide acceptable oxygenation and carbon dioxide removal. Mechanical ventilation provides time for the specific therapy to reverse the disease-causing lung injury and for the recovery of the respiratory function. The adverse effects of mechanical ventilation are direct consequences of the changes in pulmonary airway pressures and intrathoracic volume changes induced by the repetitive mechanical cycles in a diseased lung. In this article, we review 14 major successful and unsuccessful randomized controlled trials conducted in patients with ARDS on a series of techniques to improve oxygenation and ventilation published since 2010. Those trials tested the effects of adjunctive therapies (neuromuscular blocking agents, prone positioning), methods for selecting the optimum positive end-expiratory pressure (after recruitment maneuvers, or guided by esophageal pressure), high-frequency oscillatory ventilation, extracorporeal oxygenation, and pharmacologic immune modulators of the pulmonary and systemic inflammatory responses in patients affected by ARDS. We will briefly comment physiology-based gaps of negative trials and highlight the possible needs to address in future clinical trials in ARDS.

Electrical Impedance Tomography to Set Positive End Expiratory Pressure During Pediatric Extracorporeal Membrane Oxygenation for Respiratory Failure... Is it Feasible?

Electrical Impedance Tomography to Set Positive End Expiratory Pressure During Pediatric Extracorporeal Membrane Oxygenation for Respiratory Failure... Is it Feasible?

Is There an Optimal Positive End-expiratory Pressure to Measure the Internal Jugular Vein Collapsibility Index? A Pilot Study in Mechanically Ventilated Patients

Background: Hemodynamic monitoring its early stabilization is very important in critically ill patients. Evaluating the Internal jugular vein diameter during respiratory cycles by the means of Point-of care ultrasound provides an important, easily available and precise index for monitoring hemodynamic status; a new method which is called Internal Jugular Vein Collapsibility Index (IJV-CI). Any events that alters intrathoracic volumes and pressures may affect this index. In this study we investigate the effects of various levels of positive end-expiratory pressure on this index. Methods: Thirty mechanically ventilated patients were studied. We used three different PEEP levels (0, 5 and 10 cmH2o) and point-of-care ultrasound evaluation of IJV (Internal Jugular Vein) diameter to determine the IJV-CI. The analysis were performed using SPSS V.25.0. Results: Patients were included men (76.6%) and women (33.3%). The mean age of patients was 39.65±3.4 for men and 42.71± 9.34 for women. The IJV-CI were 20.71±11.77 and 24.25±11.46 in PEEP=0 and PEEP=10 cmH20 groups respectively. In 5cmH20-PEEP group median and interquartile range were 16.45(14.8). The IJV-CI in three different PEEP levels were not statistically significantly different. Conclusion: According to the finding of this study, we found no evidence of an optimal PEEP level to measure The IJV-CI.

Determining optimal positive end-expiratory pressure and tidal volume in children by intratidal compliance: a prospective observational study

BackgroundLimited data exist regarding optimal intraoperative ventilation strategies for the paediatric population. This study aimed to determine the optimal combination of PEEP and tidal volume (VT) based on intratidal compliance profiles in healthy young children undergoing general anaesthesia. MethodsDuring anaesthesia, infants (1 month–1 yr), toddlers (1–3 yr), and children (3–6 yr) were assigned serially to four ventilator settings: PEEP 8 cm H2O/VT 8 ml kg−1 (PEEP8/VT8), PEEP 10 cm H2O/VT 5 ml kg−1 (PEEP10/VT5), PEEP 10 cm H2O/VT 8 ml kg−1 (PEEP10/VT8), and PEEP 12 cm H2O/VT 5 ml kg−1 (PEEP12/VT5). The primary outcome was intratidal compliance profile, classified at each ventilator setting as horizontal (indicative of optimal alveolar ventilatory conditions), increasing, decreasing, or combinations of increasing/decreasing/horizontal compliance. Secondary outcomes were peak inspiratory, plateau, and driving pressures. ResultsIntratidal compliance was measured in 15 infants, 13 toddlers, and 15 children (15/43 [35%] females). A horizontal compliance profile was most frequently observed with PEEP10/VT5 (60.5%), compared with PEEP10/VT8, PEEP8/VT8, and PEEP12/VT5 (23.3–34.9%; P<0.001). Decreasing compliance profiles were most frequent when VT increased to 8 ml kg−1, PEEP increased to 12 cm H2O, or both. Plateau airway pressures were lower at PEEP8/VT8 (16.9 cm H2O [2.2]) and PEEP10/VT5 (16.7 cm H2O [1.7]), compared with PEEP10/VT8 (19.5 cm H2O [2.1]) and PEEP12/VT5 (19.0 cm H2O [2.0]; P<0.001). Driving pressure was lowest with PEEP10/VT5 (4.6 cm H2O), compared with other combinations (7.0 cm H2O [2.0]–9.5 cm H2O [2.1]; P<0.001). ConclusionsVT 5 ml kg−1 combined with 10 cm H2O PEEP may reduce atelectasis and overdistension, and minimise driving pressure in the majority of mechanically ventilated children <6 yr. The effect of these PEEP and VT settings on postoperative pulmonary complications in children undergoing surgery requires further study. Clinical trial registrationNCT04633720.

Use of Lung Ultrasound for Assessment of Lung Recruitment Maneuvers in Patients with ARDS

BACKGROUND: Positive pressure mechanical ventilation is a non-physiological intervention that saves lives but is not free of important side effects. It invariably results in different degrees of collapse of small airways. Recruitment maneuver (RM) aims to resolve lung collapse by a brief and controlled increment in airway pressure while positive end-expiratory pressure (PEEP) afterward keeps the lungs open. Therefore, ideally RM and PEEP selection must be individualized and this can only be done when guided by specific monitoring tools since lung’s opening and closing pressures vary among patients with different lung conditions. AIM: The aim of this study was to explore the clinical value of ultrasonic monitoring in the assessment of pulmonary recruitment and the best PEEP. PATIENTS AND METHODS: This study was conducted on 120 patients, 30 were excluded as in whom lung collapse cannot be confirmed then the rest were 90 patients from whom another 25 patients excluded as they were hemodynamically unstable the rest 65 patients were divided into two groups: Group A: Included 50 mechanically ventilated patients with ARDS, underwent lung recruitment using lung ultrasound and Group B: Included 15 mechanically ventilated patients with ARDS, underwent lung recruitment using oxygenation index. This prospective study was held at many critical care departments around Egypt. RESULTS: We noticed that lung recruitment in both groups significantly increased Pao2/Fio2 ratio immediately after recruitment compared with basal state and also significantly increase dynamic compliance compared with basal state. The increase in PF ratio immediately was significantly more in ultrasound group than in oxygenation group. Furthermore, we noticed that that P/F ratio 12 h after recruitment decreased compared with P/F ratio immediately after recruitment but significantly increased compared with basal state before recruitment and also we found that the increase in P/F ratio 12 h after recruitment was more significantly in lung ultrasound group than in oxygenation group. Furthermore, we noticed that lung recruitment (both lung ultrasound and oxygenation group) significantly increase RV function using TAPSE compared with basal state. Both opening pressure and optimal PEEP were significantly higher in lung ultrasound group than in oxygenation group. In our study, opening pressure was 37.28 ± 1.25 in lung ultrasound group and was 36.67±0.98 in oxygenation group and optimal PEEP was 14.64 ± 1.08 in lung ultrasound group and was 13.13 ± 0.74 in oxygenation group. CONCLUSION: Lung US is an effective mean of evaluating and guiding alveolar recruitment in ARDS. Compared with the maximal oxygenation–guided method, the protocol for reaeration in US-guided lung recruitment achieved a higher opening pressure, resulted in greater improvements in lung aeration, and substantially reduced lung heterogeneity in ARDS.

Role of proning and positive end-expiratory pressure in COVID-19.

The novel coronavirus, which was declared a pandemic by the World Health Organization in early 2020 has brought with itself major morbidity and mortality. It has increased hospital occupancy, heralded economic turmoil, and the rapid transmission and community spread have added to the burden of the virus. Most of the patients are admitted to the intensive care unit (ICU) for acute hypoxic respiratory failure often secondary to acute respiratory distress syndrome (ARDS). Based on the limited data available, there have been different opinions about the respiratory mechanics of the ARDS caused by coronavirus disease 2019 (COVID-19). Our article provides an insight into COVID-19 pathophysiology and how it differs from typical ARDS. Based on these differences, our article explains the different approach to ventilation in COVID-19 ARDS compared to typical ARDS. We critically analyze the role of positive end-expiratory pressure (PEEP) and proning in the ICU patients. Through the limited data and clinical experience are available, we believe that early proning in COVID-19 patients improves oxygenation and optimal PEEP should be titrated based on individual lung compliance.

Optimal Positive End Expiratory Pressure Levels in Ventilated Patients Without Acute Respiratory Distress Syndrome: A Bayesian Network Meta-Analysis and Systematic Review of Randomized Controlled Trials

Background: To find the optimal positive end expiratory pressure (PEEP) in mechanical ventilated patients without Acute Respiratory Distress Syndrome (ARDS), we conducted a Bayesian network meta-analysis and systematic review of randomized controlled trials (RCTs) comparing different level of PEEP based on a novel classification of PEEP level: ZEEP group (PEEP = 0 cm H2O); lower PEEP group (PEEP = 1–6 cm H2O); intermediate PEEP group (PEEP = 7–10 cm H2O); higher PEEP group (PEEP > 10 cm H2O).Result: Twenty eight eligible studies with 2,712 patients were included. There were no significant differences in the duration of mechanical ventilation between higher and intermediate PEEP (MD: 0.020, 95% CI: −0.14, 0.28), higher and lower PEEP (MD: −0.010, 95% CI: −0.23, 0.22), higher PEEP and ZEEP (MD: 0.010, 95% CI: −0.40, 0.22), intermediate and lower PEEP (MD: −0.040, 95% CI: −0.18, 0.040), intermediate PEEP and ZEEP (MD: −0.010, 95% CI: −0.42, 0.10), lower PEEP and ZEEP (MD: 0.020, 95% CI: −0.32, 0.13), respectively. Higher PEEP was associated with significantly higher PaO2/FiO2 ratio(PFR) when compared to ZEEP (MD: 73.24, 95% CI: 11.03, 130.7), and higher incidence of pneumothorax when compared to intermediate PEEP, lower PEEP and ZEEP (OR: 2.91e + 12, 95% CI: 40.3, 1.76e + 39; OR: 1.85e + 12, 95% CI: 29.2, 1.18e + 39; and OR: 1.44e + 12, 95% CI: 16.9, 8.70e + 38, respectively). There was no association between PEEP levels and other secondary outcomes.Conclusion: We identified higher PEEP was associated with significantly higher PFR and higher incidence of pneumothorax. Nonetheless, in terms of other outcomes, no significant differences were detected among four levels of PEEP.Systematic Review Registration: The study had registered on an international prospective register of systematic reviews, PROSPERO, on 09 April 2021, identifier: [CRD42021241745].

Association of different positive end-expiratory pressure selection strategies with all-cause mortality in adult patients with acute respiratory distress syndrome

BackgroundThe acute respiratory distress syndrome (ARDS) has high morbidity and mortality. Positive end-expiratory pressure (PEEP) is commonly used in patients with ARDS but the best method to select the optimal PEEP level and reduce all-cause mortality is unclear. The primary objective of this network meta-analysis is to summarize the available evidence and to compare the effect of different PEEP selection strategies on all-cause mortality in adult patients with ARDS.MethodsWe will search MEDLINE, Cochrane Central Register of Controlled Trials, PubMed, EMBASE, and LILACS from inception onwards for randomized controlled trials assessing the effect of PEEP selection strategies in adult patients with moderate to severe ARDS. We will exclude studies that did not use a lung-protective ventilation approach as part of the comparator or intervention strategy. The primary outcome will be all-cause mortality (at the longest available follow-up and up to 90 days). Secondary outcomes will include barotrauma, ventilator-free days, intensive care unit and hospital length of stay, and changes in oxygenation. Two reviewers will independently screen all citations, full-text articles, and extract study-data. We will assess the risk of bias for each of the outcomes using version 2 of the Cochrane risk of bias tool for randomized controlled trials. If feasible, Bayesian network meta-analyses will be conducted to obtain pooled estimates of all potential head-to-head comparisons. We will report pairwise and network meta-analysis treatment effect estimates as risk ratios and risk differences, together with the associated 95% credible intervals. We will assess certainty in effect estimates using GRADE methodology.DiscussionThe present study will inform clinical decision-making for adult patients with ARDS and will improve our understanding of the limitations of the available literature assessing PEEP selection strategies. Finally, this information may also inform the design of future randomized trials, including the selection of interventions, comparators, and predictive enrichment strategies.Trial registrationPROSPERO 2020 CRD42020193302.

Management of Intraoperative Mechanical Ventilation to Prevent Postoperative Complications after General Anesthesia: A Narrative Review.

Mechanical ventilation (MV) is still necessary in many surgical procedures; nonetheless, intraoperative MV is not free from harmful effects. Protective ventilation strategies, which include the combination of low tidal volume and adequate positive end expiratory pressure (PEEP) levels, are usually adopted to minimize the ventilation-induced lung injury and to avoid post-operative pulmonary complications (PPCs). Even so, volutrauma and atelectrauma may co-exist at different levels of tidal volume and PEEP, and therefore, the physiological response to the MV settings should be monitored in each patient. A personalized perioperative approach is gaining relevance in the field of intraoperative MV; in particular, many efforts have been made to individualize PEEP, giving more emphasis on physiological and functional status to the whole body. In this review, we summarized the latest findings about the optimization of PEEP and intraoperative MV in different surgical settings. Starting from a physiological point of view, we described how to approach the individualized MV and monitor the effects of MV on lung function.

Driving Pressure-Guided Individualized Positive End-Expiratory Pressure in Abdominal Surgery: A Randomized Controlled Trial.

The optimal positive end-expiratory pressure (PEEP) to prevent postoperative pulmonary complications (PPCs) remains unclear. Recent evidence showed that driving pressure was closely related to PPCs. In this study, we tested the hypothesis that an individualized PEEP guided by minimum driving pressure during abdominal surgery would reduce the incidence of PPCs. This single-centered, randomized controlled trial included a total of 148 patients scheduled for open upper abdominal surgery. Patients were randomly assigned to receive an individualized PEEP guided by minimum driving pressure or an empiric fixed PEEP of 6 cm H2O. The primary outcome was the incidence of clinically significant PPCs within the first 7 days after surgery, using a χ2 test. Secondary outcomes were the severity of PPCs, the area of atelectasis, and pleural effusion. Other outcomes, such as the incidence of different types of PPCs (including hypoxemia, atelectasis, pleural effusion, dyspnea, pneumonia, pneumothorax, and acute respiratory distress syndrome), intensive care unit (ICU) admission rate, length of hospital stay, and 30-day mortality were also explored. The median value of PEEP in the individualized group was 10 cm H2O. The incidence of clinically significant PPCs was significantly lower in the individualized PEEP group compared with that in the fixed PEEP group (26 of 67 [38.8%] vs 42 of 67 [62.7%], relative risk = 0.619, 95% confidence intervals, 0.435-0.881; P = .006). The overall severity of PPCs and the area of atelectasis were also significantly diminished in the individualized PEEP group. Higher respiratory compliance during surgery and improved intra- and postoperative oxygenation was observed in the individualized group. No significant differences were found in other outcomes between the 2 groups, such as ICU admission rate or 30-day mortality. The application of individualized PEEP based on minimum driving pressure may effectively decrease the severity of atelectasis, improve oxygenation, and reduce the incidence of clinically significant PPCs after open upper abdominal surgery.

Effects of positive end-expiratory pressure setting of mechanical ventilation guided by esophageal pressure in the treatment of patients with traumatic craniocerebral injury combined with acute respiratory distress syndrome

Objective: To investigate the effects of positive end-expiratory pressure (PEEP) setting of mechanical ventilation guided by esophageal pressure in the treatment of patients with traumatic craniocerebral injury combined with acute respiratory distress syndrome (ARDS). Methods: The retrospective cohort study was conducted. From June 2016 to June 2018, 55 patients with traumatic craniocerebral injury combined with ARDS who met the inclusion criteria were admitted to Zhengzhou Central Hospital Affiliated to Zhengzhou University. According to PEEP setting method, 28 patients were allocated to esophageal pressure group (17 males and 11 females, aged (40±13) years) and 27 patients were allocated to PEEP-fractional concentration of inspired oxygen (FiO2) table group (18 males and 9 females, aged (38±10) years). Patients in the 2 groups were treated with mechanical ventilation guided by lung protective ventilation strategy, and the optimal PEEP at 0 (immediately), 24, 48, and 72 h after treatment was determined according to esophageal pressure and PEEP-FiO2 table, respectively. The mechanical ventilation parameters in the 2 groups were adjusted according to the optimal PEEP. The transpulmonary end-expiratory pressure, pulmonary compliance, oxygen index, central venous pressure, mean arterial pressure, and intracranial pressure at 24, 48, and 72 h after treatment were recorded. Data were statistically analyzed with analysis of variance for repeated measurement, chi-square test, independent sample t test, and Bonferroni correction. Results: The optimal PEEP of patients in esophageal pressure group at 0, 24, 48, and 72 h after treatment was (12.4±3.9), (11.2±3.5), (13.4±2.6), and (13.2±3.6) cmH2O (1 cmH2O=0.098 kPa), respectively, which was significantly higher than (8.2±2.5), (7.4±2.2), (8.3±2.3), and (8.5±2.5) cmH2O in PEEP-FiO2 table group, respectively (t=4.702, 4.743, 7.849, 5.623, P<0.01). The transpulmonary end-expiratory pressure and pulmonary compliance at 24, 48, and 72 h after treatment and oxygen index at 48 and 72 h after treatment of patients in esophageal pressure group were significantly higher than those in PEEP-FiO2 table group (t=17.852, 20.586, 19.532, 4.752, 5.256, 7.446, 2.342, 4.178, P<0.05 or P<0.01). The central venous pressure of patients in esophageal pressure group at 24, 48, and 72 h after treatment was significantly higher than that in PEEP-FiO2 table group (t=12.632, 5.247, 8.994, P<0.01), and there was no statistically significant difference in mean arterial pressure of patients between the 2 groups at 24, 48, and 72 h after treatment (P>0.05). The intracranial pressure of patients in esophageal pressure group was higher than that in PEEP-FiO2 table group at 24, 48, and 72 h after treatment, but there was no statistically significant difference between the 2 groups (P>0.05). Conclusions: For patients with traumatic craniocerebral injury combined with ARDS, the optimal PEEP can be set under the guidance of esophageal pressure method, and the mechanical ventilation parameters adjusted according to the optimal PEEP can improve lung compliance and accelerate recovery of lung function more effectively, with no adverse effect in mean arterial pressure and intracranial pressure.

Protective mechanical ventilation with optimal PEEP during RARP improves oxygenation and pulmonary indexes

BackgroundThis trial aimed to evaluate the effects of a protective ventilation strategy on oxygenation/pulmonary indexes in patients undergoing robot-assisted radical prostatectomy (RARP) in the steep Trendelenburg position.MethodsIn phase 1, the most optimal positive end-expiratory pressure (PEEP) was determined in 25 patients at 11 cmH2O. In phase 2, 64 patients were randomized to the traditional ventilation group with tidal volume (VT) of 9 ml/kg of predicted body weight (PBW) and the protective ventilation group with VT of 7 ml/kg of PBW with optimal PEEP and recruitment maneuvers (RMs). The primary endpoint was the intraoperative and postoperative PaO2/FiO2. The secondary endpoints were the PaCO2, SpO2, modified clinical pulmonary infection score (mCPIS), and the rate of complications in the postoperative period.ResultsCompared with controls, PaO2/FiO2 in the protective group increased after the second RM (P=0.018), and the difference remained until postoperative day 3 (P=0.043). PaCO2 showed transient accumulation in the protective group after the first RM (T2), but this phenomenon disappeared with time. SpO2 in the protective group was significantly higher during the first three postoperative days. Lung compliance was significantly improved after the second RM in the protective group (P=0.025). The mCPIS was lower in the protective group on postoperative day 3 (0.59 (1.09) vs. 1.46 (1.27), P=0.010).ConclusionA protective ventilation strategy with lower VT combined with optimal PEEP and RMs could improve oxygenation and reduce mCPIS in patients undergoing RARP.Trial registrationChiCTR ChiCTR1800015626. Registered on 12 April 2018.

Individualized positive end-expiratory pressure in patients undergoing thoracoscopic lobectomy: a randomized controlled trial

Background and objectivesWith the intensive study of lung protective ventilation strategies, people begin to advocate the individualized application of positive end-expiratory pressure (PEEP). This study investigated the optimal PEEP in patients during one-lung ventilation (OLV) and its effects on pulmonary mechanics and oxygenation. MethodsFifty-eight patients who underwent elective thoracoscopic lobectomy were randomly divided into two groups. Both groups received an alveolar recruitment maneuver (ARM) after OLV. Patients in Group A received optimal PEEP followed by PEEP decremental titration, while Group B received standard 5 cmH2O PEEP until the end of OLV. Relevant indexes of respiratory mechanics, pulmonary oxygenation and hemodynamics were recorded after entering the operating room (T0), 10 minutes after intubation (T1), pre-ARM (T2), 20 minutes after the application of optimal PEEP (T3), at the end of OLV (T4) and at the end of surgery (T5). Postoperative outcomes were also assessed. ResultsThe optimal PEEP obtained in Group A was 8.8 ± 2.4 cmH2O, which positively correlated with BMI and forced vital capacity (FVC). Group A had a higher CPAT than Group B at T3, T4, T5 (p < 0.05) and a smaller ΔP than Group B at T3, T4 (p < 0.01). At T4, PaO2 was significantly higher in Group A (p < 0.01). At T3, stroke volume variation was higher in Group A (p < 0.01). Postoperative outcomes did not differ between the two groups. ConclusionsOur findings suggest that the individualized PEEP can increase lung compliance, reduce driving pressure, and improve pulmonary oxygenation in patients undergoing thoracoscopic lobectomy, with little effect on hemodynamics.

Respiratory and Hemodynamic Effects of Prophylactic Alveolar Recruitment During Liver Transplant: A Randomized Controlled Trial.

Prolonged surgical retraction may cause atelectasis. We aimed to recruit collapsed alveoli, stepwise, monitored by lung dynamic compliance and observe effects on arterial oxygenation and systemic and graft hemodynamics. Secondarily, we observed alveolar recruitment effects on postoperative mechanical ventilation, international normalized ratio, and pulmonary complications. For 58 recipients (1 excluded), randomized with optimal positive end-expiratory pressure (n = 28) versus control (fixed positive end-expiratory pressure, 5 cm H₂O; n = 29), alveolar recruitment was initiated (pressure-controlled ventilation guided by lung dynamic compliance) to identify optimal conditions. Ventilation shifted to volume-control mode with 0.4 fraction of inspired oxygen, 6 mL/kg tidal volume, and 1:2 inspiratory-to-expiratory ratio. Alveolar recruitment was repeated postretraction and at intensive care unit admission. Primary endpoints were changes in lung dynamic compliance, arterial oxygenation, and hemodynamics (cardiac output, invasive arterial and central venous pressures, graft portal and hepatic vein flows). Secondary endpoints were mechanical ventilation period and postoperative international normalized ratio, aspartate/alanine aminotransferases, lactate, and pulmonary complications. Alveolar recruitment increased positive end-expiratory pressure, lung dynamic compliance, and arterial oxygenation (P < .01) and central venous pressure (P = .004), without effects on corrected flow time (P = .7). Cardiac output and invasive arterial pressure were stable with (P = .11) and without alveolar recruitment (P = .1), as were portal (P = .27) and hepatic vein flow (P = .30). Alveolar recruitment reduced postoperative pulmonary complications (n = 0/28 vs 8/29; P = .001), without reduction in postoperative mechanical ventilation period (P = .08). International normalization ratio, aspartate/alanine aminotransferases, and lactate were not different from control (P > .05). Stepwise alveolar recruitment identified the optimal positive end-expiratory pressure to improve lung mechanics and oxygenation with minimal hemodynamic changes, without liver graft congestion/dysfunction, and was associated with significant reduction in postoperative pulmonary complications.

Optimal positive end-expiratory pressure to prevent anaesthesia-induced atelectasis in infants: A prospective, randomised, double-blind trial.

Paediatric patients have a particularly high incidence of anaesthesia-induced atelectasis. Applying positive end-expiratory pressure (PEEP) with an alveolar recruitment manoeuvre has been substantially studied and adopted in adults; however, few studies have been conducted in children. We compared the effects of three levels of PEEP (3, 6 and 9 cmH2O) on anaesthesia-induced atelectasis measured by ultrasound in infants between 6 and 12 months of age who were undergoing general anaesthesia. A prospective, randomised, double-blind trial. Department of Anaesthesia, single centre, South Korea, from May 2019 to March 2020. Children who were 6 to 12 months of age, whose American Society of Anesthesiologists (ASA) physical status was 1 or 2, whose height and weight were within two standard deviations of those of their peers, and who were scheduled for elective urological or general surgery were included in the study. The primary outcome was the lung ultrasound score at the end of the procedure. The secondary outcomes included dynamic compliance, peak inspiratory pressure, driving pressure, cardiac index, mean arterial pressure and heart rate before and after applying PEEP. The mean lung ultrasound score at the end of operation was 12.8 at PEEP 6 cmH2O and 12.1 at PEEP 9 cmH2O. Both were significantly lower than 18.4 at PEEP 3 cmH2O (P = 0.0002 and 0.00003, respectively). However, there was no significant difference between the scores of PEEP 6 cmH2O and PEEP 9 cmH2O. The Δ cardiac index (the cardiac index after PEEP - the cardiac index at 3 cmH2O of PEEP) was comparable among the three groups. To reduce anaesthesia-induced atelectasis measured by ultrasound in healthy infants undergoing low abdominal, genitourinary or superficial regional operations, 6 cmH2O of PEEP was more effective than 3 cmH2O. PEEP of 9 cmH2O was comparable with 6 cmH2O. ClinicalTrials.gov identifier NCT03969173.