Positive End-expiratory Pressure Ventilation Research Articles

High PEEP with recruitment maneuvers versus Low PEEP During General Anesthesia for Surgery - a Bayesian individual patient data meta-analysis of three randomized clinical trials.

The influence of high positive end-expiratory pressure (PEEP) with recruitment maneuvers on the occurrence of postoperative pulmonary complications after surgery is still not definitively established. Bayesian analysis can help to gain further insights from the available data and provide a probabilistic framework that is easier to interpret. Our objective was to estimate the posterior probability that the use of high PEEP with recruitment maneuvers is associated with reduced postoperative pulmonary complications in patients with intermediate-to-high risk under neutral, pessimistic, and optimistic expectations regarding the treatment effect. Multilevel Bayesian logistic regression analysis on individual patient data from three randomized clinical trials carried out on surgical patients at Intermediate-to-High Risk for postoperative pulmonary complications. The main outcome was the occurrence of postoperative pulmonary complications in the early postoperative period. We studied the effect of high PEEP with recruitment maneuvers versus Low PEEP Ventilation. Priors were chosen to reflect neutral, pessimistic, and optimistic expectations of the treatment effect. Using a neutral, pessimistic, or optimistic prior, the posterior mean odds ratio (OR) for High PEEP with recruitment maneuvers compared to Low PEEP was 0.85 (95% Credible Interval [CrI] 0.71 to 1.02), 0.87 (0.72 to 1.04), and 0.86 (0.71 to 1.02), respectively. Regardless of prior beliefs, the posterior probability of experiencing a beneficial effect exceeded 90%. Subgroup analysis indicated a more pronounced effect in patients who underwent laparoscopy (OR: 0.67 [0.50 to 0.87]) and those at high risk for PPCs (OR: 0.80 [0.53 to 1.13]). Sensitivity analysis, considering severe postoperative pulmonary complications only or applying a different heterogeneity prior, yielded consistent results. High PEEP with recruitment maneuvers demonstrated a moderate reduction in the probability of PPC occurrence, with a high posterior probability of benefit observed consistently across various prior beliefs, particularly among patients who underwent laparoscopy.

Evaluation of the Effectiveness of Adjunctive N-Acetylcysteine Nebulizer in Critically Ill Patients with COVID-19: A Pre-post Study

Abstract Background: The uncontrolled inflammatory immune response associated with SARS-CoV-2 can lead to cytokine storm and acute respiratory distress syndrome. N-Acetylcysteine (NAC) nebulizer therapy is being considered as a potential treatment option in coronavirus disease 2019 (COVID-19) patients due to its mucolytic, antioxidant, anti-inflammatory, and antiviral properties. However, the use of NAC in critically ill COVID-19 patients has not been extensively studied. Therefore, a study was conducted to evaluate the effectiveness of adjunctive NAC on respiratory function in critically ill patients with COVID-19. Materials and Methods: A pre-post retrospective study included critically ill patients with COVID-19 admitted to the intensive care units and received NAC nebulizers between March 2020 and July 2021. The primary outcome was to assess the PaO2/FiO2 (P/F) ratio differences before and after NAC administration. Other outcomes were considered secondary, such as the positive end-expiratory pressure (PEEP), tidal volume, and invasive mechanical ventilation (MV) status. A paired t test or Wilcoxon signed-rank test was used based on the data distribution. A P value of <0.05 was considered statistically significant. Results: The results revealed that a total of 1081 critically ill patients with COVID-19 were screened during the study period, and only 44 were included. Most of the patients were male (75%) with a median age of 58 years (range = 48.5–76.5 years). Before NAC initiation, the median P/F ratio was 136.55 (with a range of 92.15–207.3), whereas 24 h post-initiation, it increased significantly to a median of 159.7 (with a range of 109.6–270.2; P = 0.02). In contrast, no statistically significant differences were observed in PEEP, tidal volume, and invasive MV status before and after NAC initiation. Conclusion: This study concludes that adjunctive NAC therapy in critically ill patients with COVID-19 was associated with improved P/F ratio 24 h:24-h post-initiation. This improvement occurred without significant differences observed in PEEP, tidal volume, and invasive MV status. However, it is essential to conduct randomized control trials to validate these findings and determine their clinical significance.

Exploring alveolar recruitability using positive end-expiratory pressure in mice overexpressing TGF-β1: a structure–function analysis

Pre-injured lungs are prone to injury progression in response to mechanical ventilation. Heterogeneous ventilation due to (micro)atelectases imparts injurious strains on open alveoli (known as volutrauma). Hence, recruitment of (micro)atelectases by positive end-expiratory pressure (PEEP) is necessary to interrupt this vicious circle of injury but needs to be balanced against acinar overdistension. In this study, the lung-protective potential of alveolar recruitment was investigated and balanced against overdistension in pre-injured lungs. Mice, treated with empty vector (AdCl) or adenoviral active TGF-β1 (AdTGF-β1) were subjected to lung mechanical measurements during descending PEEP ventilation from 12 to 0 cmH2O. At each PEEP level, recruitability tests consisting of two recruitment maneuvers followed by repetitive forced oscillation perturbations to determine tissue elastance (H) and damping (G) were performed. Finally, lungs were fixed by vascular perfusion at end-expiratory airway opening pressures (Pao) of 20, 10, 5 and 2 cmH2O after a recruitment maneuver, and processed for design-based stereology to quantify derecruitment and distension. H and G were significantly elevated in AdTGF-β1 compared to AdCl across PEEP levels. H was minimized at PEEP = 5–8 cmH2O and increased at lower and higher PEEP in both groups. These findings correlated with increasing septal wall folding (= derecruitment) and reduced density of alveolar number and surface area (= distension), respectively. In AdTGF-β1 exposed mice, 27% of alveoli remained derecruited at Pao = 20 cmH2O. A further decrease in Pao down to 2 cmH2O showed derecruitment of an additional 1.1 million alveoli (48%), which was linked with an increase in alveolar size heterogeneity at Pao = 2–5 cmH2O. In AdCl, decreased Pao resulted in septal folding with virtually no alveolar collapse. In essence, in healthy mice alveoli do not derecruit at low PEEP ventilation. The potential of alveolar recruitability in AdTGF-β1 exposed mice is high. H is optimized at PEEP 5–8 cmH2O. Lower PEEP folds and larger PEEP stretches septa which results in higher H and is more pronounced in AdTGF-β1 than in AdCl. The increased alveolar size heterogeneity at Pao = 5 cmH2O argues for the use of PEEP = 8 cmH2O for lung protective mechanical ventilation in this animal model.

Effects of driving pressure-guided ventilation on postoperative pulmonary complications in patients with COVID-19 undergoing abdominal surgery: A post-hoc propensity score-matched analysis

BackgroundApplication of individualized positive end-expiratory pressure (PEEP) based on minimum driving pressure facilitates to prevent from postoperative pulmonary complications (PPCs). Whether lung protective ventilation strategy can reduce the risk of PPCs in COVID-19 patients remains unclear. In this study, we compared the effects of driving pressure-guided ventilation with conventional mechanical ventilation on PPCs in patients with COVID-19. MethodsPatients infected COVID-19 within 30-day before surgery were retrospectively enrolled consecutively. Patients were divided into two group: driving pressure-guided lung protective ventilation strategy group (LPVS group) and conventional mechanical ventilation group (Control group). Propensity score matching for variables selected was used by logistic regression with the nearest-neighbor method. The outcomes were the incidence of PPCs and hypoxemia in post-anesthesia care unit. ResultsThere was no significant difference in the baseline data between both groups (P > 0.05). The incidence of PPCs (12.73 % vs 36.36 %, χ2 = 7.068, P = 0.008) and hypoxemia [18.18 % vs 38.18 %, χ2 = 4.492, P = 0.034], and lung ultrasound scores [4.68 ± 1.60 vs 8.39 ± 1.87, t = 8.383, P < 0.001] in LPVS group were lower than control group. The PEEP, airway pressure and plateau pressure in LPVS group were higher than control group, but driving pressure and tidal volume was lower than control group, the difference was statistically significant (P < 0.05). ConclusionIndividualized PEEP ventilation strategy guided by minimum driving pressure could improve oxygenation and reduce the incidence of PPCs in surgical patients with COVID-19.

Influence of Fractional Inspired Oxygen Tension on Lung Perfusion Distribution, Regional Ventilation, and Lung Volume during Mechanical Ventilation of Supine Healthy Swine.

Lower fractional inspired oxygen tension (Fio2) during general anesthesia can reduce lung atelectasis. The objectives are to evaluate the effect of two Fio2 (0.4 and 1) during low positive end-expiratory pressure (PEEP) ventilation over lung perfusion distribution, volume, and regional ventilation. These variables were evaluated at two PEEP levels and unilateral lung atelectasis. In this exploratory study, 10 healthy female piglets (32.3 ± 3.4 kg) underwent mechanical ventilation in two atelectasis models: (1) bilateral gravitational atelectasis (n = 6), induced by changes in PEEP and Fio2 in three combinations: high PEEP with low Fio2 (Fio2 = 0.4), zero PEEP (PEEP0) with low Fio2 (Fio2 = 0.4), and PEEP0 with high Fio2 (Fio2 = 1); and (2) unilateral atelectasis (n = 6), induced by left bronchial occlusion, with the left lung aerated (Fio2 = 0.21) and low aerated (Fio2 = 1; n = 5 for this step). Measurements were conducted after 10 min in each step, encompassing assessment of respiratory mechanics, oxygenation, and hemodynamics; lung ventilation and perfusion by electrical impedance tomography; and lung aeration and perfusion by computed tomography. During bilateral gravitational atelectasis, PEEP reduction increased atelectasis in dorsal regions, decreased respiratory compliance, and distributed lung ventilation to ventral regions with a parallel shift of perfusion to the same areas. With PEEP0, there were no differences between low and high Fio2 in respiratory compliance (23.9 ± 6.5 ml/cm H2O vs. 21.9 ± 5.0; P = 0.441), regional ventilation, and regional perfusion, despite higher lung collapse (18.6 ± 7.6% vs. 32.7 ± 14.5%; P = 0.045) with high Fio2. During unilateral lung atelectasis, the deaerated lung had a lower shunt (19.3 ± 3.6% vs. 25.3 ± 5.5%; P = 0.045) and lower computed tomography perfusion to the left lung (8.8 ± 1.8% vs. 23.8 ± 7.1%; P = 0.007). PEEP0 with low Fio2, compared with high Fio2, did not produce significant changes in respiratory system compliance, regional lung ventilation, and perfusion despite significantly lower lung collapse. After left bronchial occlusion, the shrinkage of the parenchyma with Fio2 = 1 enhanced hypoxic pulmonary vasoconstriction, reducing intrapulmonary shunt and perfusion of the nonventilated areas.

The Impact of Driving Pressure-Guided Positive End-Expiratory Pressure Ventilation on Cerebral Blood Flow and Pulmonary Function in Patients Undergoing Laparoscopic Radical Prostatectomy.

To examine the impact of driving pressure-guided positive end-expiratory pressure ventilation on cerebral blood flow and pulmonary function in patients undergoing laparoscopic radical prostatectomy. A retrospective analysis was conducted on clinical data from patients who underwent laparoscopic radical prostatectomy at our hospital between June 2022 and June 2023. The patients were divided into two groups, namely the conventional ventilation group and the driving pressure-guided positive end-expiratory pressure ventilation group. Measurements and analyses were performed on cerebral blood flow, neurological status, and pulmonary function parameters. A total of 105 patients were included in this single-centre retrospective study, with 51 patients in the conventional ventilation group and 54 patients in the driving pressure-guided positive end-expiratory pressure ventilation group. The driving pressure-guided positive end-expiratory pressure ventilation group demonstrated significantly higher cerebral blood flow, cerebral autoregulation index, cerebrovascular resistance, and cerebral oxygen saturation compared to the conventional ventilation group (p < 0.05). Additionally, patients in the driving pressure-guided positive end-expiratory pressure ventilation group exhibited improved neurological outcomes, a higher partial pressure of oxygen/fraction of inspired oxygen ratio, increased lung compliance, decreased peak expiratory flow, elevated respiratory rate, and a lower lung injury score compared to the conventional ventilation group (p < 0.05). The findings suggest that driving pressure-guided positive end-expiratory pressure ventilation might positively influence cerebral blood flow and pulmonary function parameters in patients undergoing laparoscopic radical prostatectomy.

Safety and Feasibility of Intraoperative High PEEP Titrated to the Lowest Driving Pressure (ΔP)-Interim Analysis of DESIGNATION.

Uncertainty remains about the best level of intraoperative positive end-expiratory pressure (PEEP). An ongoing RCT ('DESIGNATION') compares an 'individualized high PEEP' strategy ('iPEEP')-titrated to the lowest driving pressure (ΔP) with recruitment maneuvers (RM), with a 'standard low PEEP' strategy ('low PEEP')-using 5 cm H2O without RMs with respect to the incidence of postoperative pulmonary complications. This report is an interim analysis of safety and feasibility. From September 2018 to July 2022, we enrolled 743 patients. Data of 698 patients were available for this analysis. Hypotension occurred more often in 'iPEEP' vs. 'low PEEP' (54.7 vs. 44.1%; RR, 1.24 (95% CI 1.07 to 1.44); p < 0.01). Investigators were compliant with the study protocol 285/344 patients (82.8%) in 'iPEEP', and 345/354 patients (97.5%) in 'low PEEP' (p < 0.01). Most frequent protocol violation was missing the final RM at the end of anesthesia before extubation; PEEP titration was performed in 99.4 vs. 0%; PEEP was set correctly in 89.8 vs. 98.9%. Compared to 'low PEEP', the 'iPEEP' group was ventilated with higher PEEP (10.0 (8.0-12.0) vs. 5.0 (5.0-5.0) cm H2O; p < 0.01). Thus, in patients undergoing general anesthesia for open abdominal surgery, an individualized high PEEP ventilation strategy is associated with hypotension. The protocol is feasible and results in clear contrast in PEEP. DESIGNATION is expected to finish in late 2023.

High positive end-expiratory pressure ventilation mitigates the progression from unilateral pulmonary contusion to ARDS: An animal study.

Pulmonary contusion (PC) is common in severely traumatized patients and can lead to respiratory failure requiring mechanical ventilation (MV). Ventilator-induced lung injury (VILI) might aggravate lung damage. Despite underrepresentation of trauma patients in trials on lung-protective MV, results are extrapolated to these patients, potentially disregarding important pathophysiological differences. Three MV protocols with different positive end-expiratory pressure (PEEP) levels: ARDSnetwork lower PEEP (ARDSnet-low), ARDSnetwork higher PEEP (ARDSnet-high), and open lung concept (OLC) were applied in swine for 24 hours following PC. Gas exchange, lung mechanics, quantitative computed tomography, and diffuse alveolar damage (DAD) score were analyzed. Results are given as median (interquartile range) at 24 hours. Statistical testing was performed using general linear models (group effect) over all measurement points and pairwise Mann-Whitney U tests for DAD. There were significant differences between groups: PEEP ( p < 0.0001) ARDSnet-low (8 [8-10] cmH 2 O), ARDSnet-high (12 [12-12] cmH 2 O), OLC (21 [20-22] cmH 2 O). The fraction of arterial partial pressure of oxygen and inspired oxygen fraction ( p = 0.0016) was lowest in ARDSnet-low (78 (73-111) mm Hg) compared with ARDSnet-high (375 (365-423) mm Hg) and OLC (499 (430-523) mm Hg). The end-expiratory lung volume (EELV) differed significantly ( p < 0.0001), with highest values in OLC (64% [60-70%]) and lowest in ARDSnet-low (34% [24-37%]). Costa's surrogate for mechanical power differed significantly ( p < 0.0001), with lowest values for ARDSnet-high (73 [58-76]) compared with OLC (105 [108-116]). Diffuse alveolar damage was lower in ARDSnet-high compared with ARDSnet-low (0.0007). Progression to ARDS, 24 hours after PC, was mitigated by OLC and ARDSnet-high. Both concepts restored EELV. ARDSnet-high had the lowest mechanical power surrogate and DAD. Our data suggest, that ARDSnet-high restored oxygenation and functional lung volume and reduced physiological and histological surrogates for VILI. ARDSnet-low generated unfavorable outcomes, such as loss of EELV, increased mechanical power and DAD after PC in swine. The high respiratory rate in the OLC may blunt favorable effects of lung recruitment.

Lung Ultrasound to Determine the Effect of Lower vs. Higher PEEP on Lung Aeration in Patients without ARDS—A Substudy of a Randomized Clinical Trial

Background: Ventilation with lower positive end–expiratory pressure (PEEP) may cause loss of lung aeration in critically ill invasively ventilated patients. This study investigated whether a systematic lung ultrasound (LUS) scoring system can detect such changes in lung aeration in a study comparing lower versus higher PEEP in invasively ventilated patients without acute respiratory distress syndrome (ARDS). Methods: Single center substudy of a national, multicenter, randomized clinical trial comparing lower versus higher PEEP ventilation strategy. Fifty–seven patients underwent a systematic 12–region LUS examination within 12 h and between 24 to 48 h after start of invasive ventilation, according to randomization. The primary endpoint was a change in the global LUS aeration score, where a higher value indicates a greater impairment in lung aeration. Results: Thirty–three and twenty–four patients received ventilation with lower PEEP (median PEEP 1 (0–5) cm H2O) or higher PEEP (median PEEP 8 (8–8) cm H2O), respectively. Median global LUS aeration scores within 12 h and between 24 and 48 h were 8 (4 to 14) and 9 (4 to 12) (difference 1 (–2 to 3)) in the lower PEEP group, and 7 (2–11) and 6 (1–12) (difference 0 (–2 to 3)) in the higher PEEP group. Neither differences in changes over time nor differences in absolute scores reached statistical significance. Conclusions: In this substudy of a randomized clinical trial comparing lower PEEP versus higher PEEP in patients without ARDS, LUS was unable to detect changes in lung aeration.

Positive End-Expiratory Pressure Levels in Adult Patients With Acute Lung Injury and Acute Respiratory Distress Syndrome

Positive End-Expiratory Pressure Levels in Adult Patients With Acute Lung Injury and Acute Respiratory Distress Syndrome

Individualized dynamic PEEP (dynPEEP) vs. positive pressure ventilation in delivery room management: A retrospective cohort study.

Although nasal continuous positive airway pressure (nCPAP) is recommended in delivery room (DR) management for preterm infants, the effect of delivering nCPAP at 6-8 cmH2O is not satisfactory. Therefore, we conducted this retrospective cohort study to compare the effects of individualized dynamic positive end-expiratory pressure (dynPEEP) vs. positive pressure ventilation (PPV) in the DR on clinical outcomes. Preterm infants with a gestational age (GA) less than 30 weeks who received PPV (peak inspiratory pressure, PIP/PEEP 15-25/6-8 cmH2O) from August 2018 to July 2020 were included as Cohort 1 (PPV group, n = 55), and those who received dynPEEP (nCPAP 8-15 cmH2O) from June 2020 to April 2022 were included as Cohort 2 (dynPEEP group, n = 62). Primary outcomes included the DR intubation rate and the bronchopulmonary dysplasia (BPD) rate. The secondary outcomes included DR stabilization, transfer, admission, respiratory function, and other outcomes. The percentage of singleton infants was higher in the PPV group (63.6%) than in the dynPEEP group (22.6%, p = 0.000). The DR intubation and chest compression rates were higher in the PPV group (80.0% and 18.2%, respectively) than in the dynPEEP group (45.2%, p = 0.000; 3.0%, p = 0.008, respectively). The percentage of patients with 5-min Apgar scores < 5 was higher in the PPV group (9.1%) than in the dynPEEP group (0%, p = 0.016). The partial pressure of carbon dioxide was lower in the PPV group (49.77 ± 11.28) than in the dynPEEP group (56.44 ± 13.17, p = 0.004), and lactate levels were higher in the PPV group (3.60 (2.10, 5.90)) than in the dynPEEP group (2.25 (1.38, 3.33), p = 0.002). No significant differences in the BPD rate or other secondary outcomes were noted. In this retrospective cohort study, the dynPEEP strategy reduced the need for DR intubation compared with PPV. The dynPEEP strategy is feasible and potentially represents an alternative respiratory strategy to PPV. Nevertheless, a randomized control trial is needed to evaluate the dynPEEP strategy.

Effects of Electrical Impedance Tomography-Guided Positive End-Expiratory Pressure on Postoperative Cardiopulmonary Exercise Capacity in Elderly Patients: Study Protocol for a Randomized Controlled Trial.

BACKGROUND Mechanical ventilation can lead to cardiopulmonary complications in elderly patients undergoing abdominal surgery plus general anesthesia. The cardiopulmonary exercise test (CPET) is a dynamic and noninvasive evaluation method for assessing the cardiopulmonary system function under rest and stress. Positive end-expiratory pressure (PEEP) titration guided by electrical impedance tomography (EIT) can individualize lung protection strategies and may be beneficial in postoperative cardiopulmonary exercise capacity for these patients. MATERIAL AND METHODS This study is a prospective, single-center, randomized, and controlled trail that will include 80 elderly patients scheduled for major abdominal surgery. The patients will be divided into 2 groups: (1) intervention group: using individualized PEEP ventilation; and (2) control group: using fixed PEEP ventilation (3-5 cmH₂O). RESULTS The primary outcome is the change of postoperative cardiopulmonary exercise capacity. CONCLUSIONS In this study, we will evaluate if EIT-guided PEEP titration can improve postoperative cardiopulmonary exercise capacity and reduce postoperative complications in elderly patients undergoing open abdominal surgery plus general anesthesia. If the result is in accordance with the hypothesis, it would provide evidence to aid the perioperative management for these patients.

Effect of positive end-expiratory pressure on pulmonary compliance and pulmonary complications in patients undergoing robot-assisted laparoscopic radical prostatectomy: a randomized control trial

BackgroundTo observe the effects of different positive end-expiratory pressure (PEEP) ventilation strategies on pulmonary compliance and complications in patients undergoing robotic-assisted laparoscopic prostate surgery.MethodsA total of 120 patients with the American Society of Anesthesiologists Physical Status Class I or II who underwent elective robotic-assisted laparoscopic prostatectomy were enrolled. We randomized the patients divided into divided into three groups of 40 patients each: PEEP0, PEEP5, or PEEP10. Master Anesthetist used volume control ventilation intraoperatively with an intraoperative deep muscle relaxation strategy. Respiratory mechanics indexes were recorded at six time-points: 10 mimuts after anaesthesia induction, immediately after pneumoperitoneum establishment, 30 min, 60 min, 90 min, and at the end of pneumoperitoneum. Arterial blood gas analysis and oxygenation index calculation were performed 10 mimuts after anaesthesia induction, 60 mimuts after pneumoperitoneum, and after tracheal extubation. Postoperative pulmonary complications were also recorded.ResultsAfter pneumoperitoneum, peak inspiratory pressure (Ppeak), plateau pressure (Pplat), mean pressure (Pmean), driving pressure (ΔP), and airway resistance (Raw) increased significantly, and pulmonary compliance (Crs) decreased, persisting during pneumoperitoneum in all groups. Between immediately after pneumoperitoneum establishment, 30 min, 60 min, and 90 min, pulmonary compliance in the 10cmH2OPEEP group was higher than in the 5cmH2OPEEP (P < 0.05) and 0cmH2OPEEP groups(P < 0.05). The driving pressure (ΔP) immediately after pneumoperitoneum establishment, at 30 min, 60 min, and 90 min in the 10cmH2OPEEP group was lower than in the 5cmH2OPEEP (P < 0.05) and 0cmH2OPEEP groups (P < 0.05). Sixty min after pneumoperitoneum and tracheal extubation, the PaCO2 did not differ significantly among the three groups (P > 0.05). The oxygenation index (PaO2/FiO2) was higher in the PEEP5 group than in the PEEP0 and PEEP10 groups 60 min after pneumoperitoneum and after tracheal extubation, with a statistically significant difference (P < 0.05). In postoperative pulmonary complications, the incidence of atelectasis was higher in the PEEP0 group than in the PEEP5 and PEEP10 groups, with a statistically significant difference (p < 0.05).ConclusionThe use of PEEP at 5cmH2O during RARP increases lung compliance, improves intraoperative oxygenation index and reduces postoperative atelectasis.Trial registrationThis study was registered in the China Clinical Trials Registry on May 30, 2020 (Registration No. ChiCTR2000033380).

Effect of positive end-expiratory pressure on cardiac function in patients with early left ventricular diastolic dysfunction: a prospective cohort study

To evaluate the effect of positive end-expiratory pressure (PEEP) ventilation on cardiac function in patients with early left ventricular (LV) diastolic dysfunction undergoing laparoscopic radical gastrectomy. Patients who underwent laparoscopic radical gastrectomy under elective general anesthesia from July 2021 to February 2022 at the Subei People's Hospital were enrolled [age 60-75 years old, American Society of Anesthesiologists (ASA) grade I-II, and left ventricular ejection fraction (LVEF) > 0.50]. Transthoracic echocardiography (TTE) was performed before operation, and the peak early diastolic velocity (E peak) and peak late diastolic velocity (A peak) at the mitral ostium were recorded and the E/A and E peak deceleration time (DT) were calculated. Then isovolumic relaxation time (IVRT) and early peak mitral annular diastolic velocity (e') were recorded and left ventricular E/e' (LVE/e') was calculated. According to the E/A, mitral e', LVE/e', DT, and IVRT, the patients were divided into early LV diastolic dysfunction group (E/A < 1, mitral e' < 7 cm/s, LVE/e' > 14, DT > 200 ms, and IVRT > 100 ms) and normal cardiac function group (1 < E/A < 2, 160 ms < DT < 240 ms, and 70 ms < IVRT < 90 ms), with 35 patients in each group. Both groups were received fixed 5 cmH2O (1 cmH2O ≈ 0.098 kPa) PEEP 5 minutes after the beginning of the pneumoperitoneum until the end of the procedure. A volume controlled ventilation was used with a tidal volume (VT) of 7 mL/kg, an inspired oxygen concentration of 0.60, and an inspiratory to expiratory ratio of 1:2. Left and right myocardial systolic and diastolic function related parameters, including LVEF, LV global longitudinal strain (LVGLS), tricuspid annulus plane systolic migration (TAPSE), the peak early diastolic velocity (E peak) at the mitral and tricuspid valve ostia and the peak early diastolic velocity (e') at the corresponding annulus were measured by transesophageal echocardiography (TEE) before tracheal intubation (T0), 5 minutes after the pneumoperitoneum (T1), 5 minutes after PEEP ventilation (T2), 30 minutes after PEEP ventilation (T3), and 5 minutes after the end of pneumoperitoneum (T4), respectively. The left and right ventricular myocardial performance index (LVMPI/RVMPI) was calculated. Finally, 60 patients were included in the analysis, including 28 patients in the early LV diastolic dysfunction group and 32 patients in the normal cardiac function group. Compared with those at T0, mean arterial pressure (MAP), LVEF, mitral e', LVGLS, tricuspid e' and TAPSE were significantly lower in the normal cardiac function group at T1, and the early LV diastolic dysfunction group at T1, T2, and T3, and LVMPI, LVE/e', RVE/e', and RVMPI were significantly higher. At T4, the LVE/e' and the RVE/e' were significantly higher in the early LV diastolic dysfunction group than those at T0 (LVE/e': 16.52±1.26 vs. 14.32±1.09, and RVE/e': 18.71±1.74 vs. 16.51±1.93, respectively, both P < 0.05), Mitral e' and tricuspid e' were significantly lower than those at T0 [mitral e' (m/s): 0.07±0.01 vs. 0.09±0.01, tricuspid e' (m/s): 0.06±0.01 vs. 0.08±0.01, both P < 0.05]. Compared with the normal cardiac function group, MAP, LVEF, mitral e', LVGLS, tricuspid e', and TAPSE at T1, T2, and T3 were significantly lower in the early LV diastolic dysfunction group, while LVMPI, LVE/e', RVE/e', and RVMPI were significantly higher. At T4, the LVE/e' and the RVE/e' were significantly higher in the early LV diastolic dysfunction group than those in the normal cardiac function group (LVE/e': 16.52±1.26 vs. 9.87±1.25, RVE/e': 18.71±1.74 vs. 10.97±1.70, both P < 0.05). Mitral e' and tricuspid e' were significantly lower in the normal cardiac function group [mitral e' (m/s): 0.07±0.01 vs. 0.11±0.02, tricuspid e' (m/s): 0.06±0.01 vs. 0.10±0.02, both P < 0.05]. In early LV diastolic dysfunction patients, compared with patients with normal cardiac function, 5 cmH2O PEEP can further exacerbate left and right myocardial systolic and diastolic function in patients during pneumoperitoneum; when the pneumoperitoneum was ended, 5 cmH2O PEEP only worsen left and right myocardial diastolic function in patients, and did not affect left and right myocardial systolic function.

Efficacy of Higher Positive End-Expiratory Pressure Ventilation Strategy in Patients With Acute Respiratory Distress Syndrome: A Systematic Review and Meta-Analysis.

Previous systematic reviews and meta-analyses assessing the pooled effects of higher positive end-expiratory pressure (PEEP) failed to show significantly reduced mortality in patients with acute respiratory distress syndrome (ARDS). Some new randomized controlled trials (RCTs) have been reported and an updated systematic review is needed to evaluate the use of higher PEEP in patients with ARDS.We searched MEDLINE, Cochrane Central Register of Controlled Trials (CENTRAL), EMBASE, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Igaku-Chuo-Zasshi, ICTRP, the National Institute of Health Clinical Trials Register, and the reference list of recent guidelines. We included RCTs to compare the higher PEEP ventilation strategy with the lower strategy in patients with ARDS. Two authors independently assessed the eligibility of the studies and extracted the data. The primary outcomes were 28-day mortality. The GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) methodology was used to evaluate the certainty of the evidence.Among the 6530 screened records, 16 randomized trials involving 4150 patients were included in our meta-analysis. When comparing higher PEEP versus lower PEEP, the pooled risk ratio (RR) for 28-day mortality was 0.85 (15 studies, n=4108, 95% CI 0.72 to 1.00, I2=58%, low certainty of evidence). Subgroup analysis by study participants with a low tidal volume (LTV) strategy showed an interaction (P for interaction, 0.001).Our study showed that in patients with ARDS, the use of higher PEEP did not significantly reduce 28-day mortality compared to the use of lower PEEP.

Spatiotemporal distribution of cellular injury and leukocytes during the progression of ventilator-induced lung injury.

Supportive mechanical ventilation is a necessary lifesaving treatment for acute respiratory distress syndrome (ARDS). This intervention often leads to injury exacerbation by ventilator-induced lung injury (VILI). Patterns of injury in ARDS and VILI are recognized to be heterogeneous; however, quantification of these injury distributions remains incomplete. Developing a more detailed understanding of injury heterogeneity, particularly how it varies in space and time, can help elucidate the mechanisms of VILI pathogenesis. Ultimately, this knowledge can be used to develop protective ventilation strategies that slow disease progression. To expand existing knowledge of VILI heterogeneity, we document the spatial evolution of cellular injury distribution and leukocyte infiltration, on the micro- and macroscales, during protective and injurious mechanical ventilation. We ventilated naïve mice using either high inspiratory pressure and zero positive end-expiratory pressure ventilation or low tidal volume with positive end-expiratory pressure. Distributions of cellular injury, identified with propidium iodide staining, were microscopically analyzed at three levels of injury severity. Cellular injury initiated in diffuse, quasi-random patterns, and progressed through expansion of high-density regions of injured cells termed "injury clusters." The density profile of the expanding injury regions suggests that stress shielding occurs, protecting the already injured regions from further damage. Spatial distribution of leukocytes did not correlate with that of cellular injury or ventilation-induced changes in lung function. These results suggest that protective ventilation protocols should protect the interface between healthy and injured regions to stymie injury propagation.

Influence of positive end-expiratory pressure on arterial blood pressure in mechanically ventilated trauma patients in the field: a retrospective cohort study.

Ventilation with positive end-expiratory pressure (PEEP) may result in decreased venous return to the heart and therefore decrease cardiac output. We evaluated the influence of PEEP ventilation on arterial blood pressure in the field in 296 posttraumatic intubated patients being treated by a helicopter emergency medical service in a retrospective cohort study. Initial systolic blood pressure on the scene, upon hospital admission and their mean difference were compared between patients being ventilated with no/low PEEP (0–0.3 kPa) and moderate PEEP (0.3–1 kPa). In a subgroup analysis of initially hemodynamic unstable patients (systolic blood pressure < 80 mmHg), systolic blood pressure was compared between patients being ventilated with no/low or moderate PEEP Further, the mean difference between initial systolic blood pressure and upon hospital admission was correlated with the chosen PEEP. Systolic arterial blood pressure of patients being ventilated with no/low PEEP improved from 105 ± 36 mmHg to 112 ± 38 mmHg, and that of patients being ventilated with moderate PEEP improved from 105 ± 38 mmHg to 119 ± 27 mmHg. In initially unstable patients being ventilated with no/low PEEP systolic blood pressure improved from initially 55 ± 36 mmHg to 78 ± 30 mmHg upon hospital admission, and in those being ventilated with moderate PEEP, the systolic blood pressure improved from 43 ± 38 mmHg to 91 ± 27 mmHg. There was no significant correlation between the chosen PEEP and the mean difference of systolic blood pressure (Pearson’s correlation, r = 0.07, P = 0.17). Ventilation with moderate PEEP has no adverse effect on arterial systolic blood pressure in this cohort of trauma patients requiring mechanical ventilation. Initially unstable patients being ventilated with moderate PEEP tend to be hemodynamically more stable.

Hemodynamic, renal and hormonal effects of lung protective ventilation during robot-assisted radical prostatectomy, analysis of secondary outcomes from a randomized controlled trial

BackgroundLung protective ventilation with low tidal volume (TV) and increased positive end-expiratory pressure (PEEP) can have unfavorable effects on the cardiovascular system. We aimed to investigate whether lung protective ventilation has adverse impact on hemodynamic, renal and hormonal variables.MethodsIn this randomized, single-blinded, placebo-controlled study, 24 patients scheduled for robot-assisted radical prostatectomy were included. Patients were equally randomized to receive either ventilation with a TV of 6 ml/IBW and PEEP of 10 cm H2O (LTV-h.PEEP) or ventilation with a TV of 10 ml/IBW and PEEP of 4 cm H2O (HTV-l.PEEP). Before, during and after surgery, hemodynamic variables were measured, and blood and urine samples were collected. Blood samples were analyzed for plasma concentrations of electrolytes and vasoactive hormones. Urine samples were analyzed for excretions of electrolytes and markers of nephrotoxicity.ResultsComparable variables were found among the two groups, except for significantly higher postoperative levels of plasma brain natriuretic peptide (p = 0.033), albumin excretion (p = 0.012) and excretion of epithelial sodium channel (p = 0.045) in the LTV-h.PEEP ventilation group compared to the HTV-l.PEEP ventilation group. In the combined cohort, we found a significant decrease in creatinine clearance (112.0 [83.4;126.7] ml/min at baseline vs. 45.1 [25.4;84.3] ml/min during surgery) and a significant increase in plasma concentrations of renin, angiotensin II, and aldosterone.ConclusionLung protective ventilation was associated with minor adverse hemodynamic and renal effects postoperatively. All patients showed a substantial but transient reduction in renal function accompanied by activation of the renin-angiotensin-aldosterone system.Trial registrationClinicalTrials, NCT02551341. Registered 13 September 2015.

Effect of mechanical ventilation during cardiopulmonary bypass on oxidative stress: a randomized clinical trial

BackgroundCardiopulmonary bypass (CPB) causes systemic oxidative stress response and endothelial damage in systemic organs. We investigated the effects of positive end-expiratory pressure (PEEP) and mechanical ventilation (MV) applications on oxidative stress in CPB. MethodsSeventy-one patients were recruited and 60 completed the study. Randomized groups: MV off (Group 1); MV on, tidal volume (TV) at 3–4 mL.kg-1 (Group 2); MV on, TV at 3–4 mL.kg-1, PEEP at 5 cmH2O (Group 3), n = 20 in each group. As oxidative stress markers, we used glutathione peroxidase (GPx), total antioxidant status (TAS), total oxidant status (TOS), total and native thiol (TT, NT), malondialdehyde (MDA), and catalase. We also investigated the correlation between oxidative stress and postoperative intubation time. ResultsThe postoperative GPx levels in Group 2 were higher than Group 3 (p = 0.017). In groups 2 and 3, TAS levels were higher postoperatively than intraoperatively (p = 0.001, p = 0.019, respectively). In Group 2, the TT levels were higher postoperatively than preoperatively and intraoperatively (p = 0.008). In Group 3, the postoperative MDA levels were higher than preoperatively (p = 0.001) and were higher than both postoperative levels of Group 1 and 2 (p = 0.043, p = 0.003). As the preoperative TAS (Group 2) decreased and the postoperative NT (Group 2) and catalase (Group 3) increased, the postoperative intubation time lengthened. ConclusionMV ( 3–4 mL.kg-1) alone seems to be the most advantageous strategy. Prolonged postoperative intubation time was associated with both increased NT and catalase levels.

Effect of different levels of PEEP on mortality in ICU patients without acute respiratory distress syndrome: systematic review and meta-analysis with trial sequential analysis.

ObjectiveTo determine whether higher positive end- expiratory pressure (PEEP) could provide a survival advantage for patients without acute respiratory distress syndrome (ARDS) compared with lower PEEP.MethodsEligible studies were identified through searches of Embase, Cochrane Library, Web of Science, Medline, and Wanfang database from inception up to 1 June 2021. Trial sequential analysis (TSA) was used in this meta-analysis.Data synthesisTwenty-seven randomized controlled trials (RCTs) were identified for further evaluation. Higher and lower PEEP arms included 1330 patients and 1650 patients, respectively. A mean level of 9.6±3.4 cmH2O was applied in the higher PEEP groups and 1.9±2.6 cmH2O was used in the lower PEEP groups. Higher PEEP, compared with lower PEEP, was not associated with reduction of all-cause mortality (RR 1.03; 95% CI 0.91–1.18; P =0.627), and 28-day mortality (RR 1.07 ; 95% CI 0.92–1.24; P =0.365). In terms of risk of ARDS (RR 0.43; 95% CI 0.24–0.78; P =0.005), duration of intensive care unit (MD -1.04; 95%CI-1.36 to −0.73; P < 0.00001), and oxygenation (MD 40.30; 95%CI 0.94 to 79.65; P = 0.045), higher PEEP was superior to lower PEEP. Besides, the pooled analysis showed no significant differences between groups both in the duration of mechanical ventilation (MD 0.00; 95%CI-0.13 to 0.13; P = 0.996) and hospital stay (MD -0.66; 95%CI-1.94 to 0.61; P = 0.309). More importantly, lower PEEP did not increase the risk of pneumonia, atelectasis, barotrauma, hypoxemia, or hypotension among patients compared with higher PEEP. The TSA analysis showed that the results of all-cause mortality and 28-day mortality might be false-negative results.ConclusionsOur results suggest that a lower PEEP ventilation strategy was non-inferior to a higher PEEP ventilation strategy in ICU patients without ARDS, with no increased risk of all-cause mortality and 28-day mortality. Further high-quality RCTs should be performed to confirm these findings.