Can 'permissive' hypercapnia modulate the severity of sepsis-induced ALI/ARDS?

Engineered Extracellular Vesicles: Emerging Therapeutic Strategies for Translational Applications

Extracellular vesicles (EVs) are small, membrane-bound vesicles used by cells to deliver biological cargo such as proteins, mRNA, and other biomolecules from one cell to another, thus inducing a specific response in the target cell and are a powerful method of cell to cell and organ to organ communication, especially during the pathogenesis of human disease. Thus, EVs may be utilized as prognostic and diagnostic biomarkers, but they also hold therapeutic potential just as mesenchymal stem cells have been used in therapeutics. However, unmodified EVs exhibit poor targeting efficacy, leading to the necessity of engineered EVS. To highlight the advantages and therapeutic promises of engineered EVs, in this review, we summarized the research progress on engineered EVs in the past ten years, especially in the past five years, and highlighted their potential applications in therapeutic development for human diseases. Compared to the existing stem cell-derived EV-based therapeutic strategies, engineered EVs show greater promise in clinical applications: First, engineered EVs mediate good targeting efficacy by exhibiting a targeting peptide that allows them to specifically target a specific organ or even cell type, thus avoiding accumulation in undesired locations and increasing the potency of the treatment. Second, engineered EVs can be artificially pre-loaded with any necessary biomolecular cargo or even therapeutic drugs to treat a variety of human diseases such as cancers, neurological diseases, and cardiovascular ailments. Further research is necessary to improve logistical challenges in large-scale engineered EV manufacturing, but current developments in engineered EVs prove promising to greatly improve therapeutic treatment for traditionally difficult to treat diseases.

An Exploratory Analysis of the Association between Hypercapnia and Hospital Mortality in Critically Ill Patients with Sepsis

Rationale: Hypercapnia may affect the outcome of sepsis. Very few clinical studies conducted in noncritically ill patients have investigated the effects of hypercapnia and hypercapnic acidemia in the context of sepsis. The effect of hypercapnia in critically ill patients with sepsis remains inadequately studied. Objectives: To investigate the association of hypercapnia with hospital mortality in critically ill patients with sepsis. Methods: This is a retrospective study conducted in three tertiary public hospitals. Critically ill patients with sepsis from three intensive care units between January 2011 and May 2019 were included. Five cohorts (exposure of at least 24, 48, 72, 120, and 168 hours) were created to account for immortal time bias and informative censoring. The association between hypercapnia exposure and hospital mortality was assessed with multivariable models. Subgroup analyses compared ventilated versus nonventilated and pulmonary versus nonpulmonary sepsis patients. Results: We analyzed 84,819 arterial carbon dioxide pressure measurements in 3,153 patients (57.6% male; median age was 62.5 years). After adjustment for key confounders, both in mechanically ventilated and nonventilated patients and in patients with pulmonary or nonpulmonary sepsis, there was no independent association of hypercapnia with hospital mortality. In contrast, in ventilated patients, the presence of prolonged exposure to both hypercapnia and acidemia was associated with increased mortality (highest odds ratio of 16.5 for ⩾120 hours of potential exposure; P = 0.007). Conclusions: After adjustment, isolated hypercapnia was not associated with increased mortality in patients with sepsis, whereas prolonged hypercapnic acidemia was associated with increased risk of mortality. These hypothesis-generating observations suggest that as hypercapnia is not an independent risk factor for mortality, trials of permissive hypercapnia avoiding or minimizing acidemia in sepsis may be safe.

lncRNA-SNHG14 Plays a Role in Acute Lung Injury Induced by Lipopolysaccharide through Regulating Autophagy via miR-223-3p/Foxo3a

lncRNAs play important roles in lipopolysaccharide- (LPS-) induced acute lung injury. But the mechanism still needs further research. In the present study, we investigate the functional role of the lncRNA-SNHG14/miR-223-3p/Foxo3a pathway in LPS-induced ALI and tried to confirm its regulatory effect on autophagy. Transcriptomic profile changes were identified by RNA-seq in LPS-treated alveolar type II epithelial cells. The expression changes of lncRNA-SNHG14/miR-223-3p/Foxo3a were confirmed using qRT-PCR and west blot. The binding relationship of lncRNA-SNHG14/miR-223-3p/and miR-223-3p/Foxo3a was verified using dual-luciferase reporter, RNA immunoprecipitation, and RNA pull-down assays. Using gain-of-function or loss-of-function approaches, the effect of lncRNA-SNHG14/miR-223-3p/Foxo3a was investigated in LPS-induced acute lung injury mice model and in vitro. Increasing of lncRNA-SNHG14 and Foxo3a with reducing miR-223-3p was found in LPS-treated A549 cells and lung tissue collected from the LPS-induced ALI model. lncRNA-SNHG14 inhibited miR-223-3p but promoted Foxo3a expression as a ceRNA. Artificially changes of lncRNA-SNHG14/miR-223-3p/Foxo3a pathway promoted or protected cell injury from LPS in vivo and in vitro. Autophagy activity could be influenced by lncRNA-SNHG14/miR-223-3p/Foxo3a pathway in cells with or without LPS treatment. In conclusion, aberrant expression changes of lncRNA-SNHG14 participated alveolar type II epithelial cell injury and acute lung injury induced by LPS through regulating autophagy. One underlying mechanism is that lncRNA-SNHG14 regulated autophagy by controlling miR-223-3p/Foxo3a as a ceRNA. It suggested that lncRNA-SNHG14 may serve as a potential therapeutic target for patients with sepsis-induced ALI.

Effect of acute isooxic hypercapnia on oxidative activity of systemic neutrophils in endotoxemic rabbits

Introduction

Whether carbon dioxide (CO₂) affects systemic oxidative phenomena under conditions of endotoxemia is not sufficiently clarified. The study aimed to assess the impact of moderate acute hypercapnia on the respiratory burst of circulating neutrophils in mechanically ventilated endotoxemic rabbits.

Material and methods

Twenty-four endotoxemic rabbits were mechanically ventilated with standard or CO₂-enriched gas mixture in order to obtain isooxic hypercapnia. At a baseline point and following 180 min of hypercapnic ventilation, luminol-dependent chemiluminescence (CL) of circulating neutrophils and serum 2-thiobarbituric acid reactive substance (TBARS) concentrations were measured. Throughout the study, leukocyte and neutrophil counts, pH status, circulatory parameters and body temperature were also assessed.

Results

Following 180 min of hypercapnic ventilation, opsonized zymosan (OZ)-stimulated neutrophils showed lower CL vs. the control group (p = 0.004). Other parameters studied were not affected.

Conclusions

Short-term isooxic hypercapnia in endotoxemic rabbits preserves circulating neutrophil count pattern and reactive oxygen species (ROS) generation, but it may reduce phagocytosis.

Airway pressure release ventilation versus low tidal volume ventilation for patients with acute respiratory distress syndrome/acute lung injury: a meta-analysis of randomized clinical trials

Background

It is uncertain whether airway pressure release ventilation (APRV) is better than low tidal volume ventilation (LTVV) for patients with acute respiratory distress syndrome (ARDS). The purpose of this meta-analysis was to compare APRV and LTVV on patients with ARDS.

Methods

Randomized controlled trials (RCTs) comparing outcomes in ARDS ventilator therapy with APRV or LTVV were identified using Medical Literature Analysis and Retrieval System Online (MEDLINE), Excerpta Medica Database (EMBASE), Cumulative Index to Nursing and Allied Health Literature (CINAHL), Web of Science, the Cochrane Library, and The Chinese Biomedicine Literature Database (SinoMed) from inception to March 2019.

Results

A total of 7 RCTs with a 405 patients were eligible for our meta-analysis. The results revealed that APRV was associated with lower hospital mortality [405 patients; odds ratio (OR), 0.57; 95% confidence interval (CI), 0.37-0.88; P=0.01], a shorter time of ventilator therapy [373 patients; mean difference (MD), 5.36; 95% CI, 1.99-8.73; P=0.002], and intensive care unit (ICU) stay (315 patients; MD, -4.50; 95% CI, -6.56 to -2.44; P<0.0001), better respiratory system compliance on day 3 (202 patients; MD, 8.19; 95% CI, 0.84-15.54; P=0.03), arterial partial pressure of oxygen/fraction of inspired oxygen (PaO2/FiO2) on day 3 (294 patients; MD, 44.40; 95% CI, 16.05-72.76; P=0.002), and higher mean arterial pressure (MAP) on day 3 (285 patients; MD, 4.18; 95% CI, 3.10-5.25; P<0.00001). There was no statistical difference in the incidence of pneumothorax (170 patients; OR, 0.40; 95% CI, 0.12-1.34; P=0.14).

Conclusions

The meta-analysis showed that APRV could reduce hospital mortality, duration of ventilation and ICU stay, improve lung compliance, oxygenation index, and MAP compared with LTVV for patients with ARDS. We found APRV to be a safe and effective ventilation mode for patients with ARDS.

Intravenous Immunoglobulin Attenuates Cecum Ligation and Puncture-Induced Acute Lung Injury by Inhibiting Apoptosis of Alveolar Epithelial Cells

PURPOSE

Intravenous immunoglobulin (IVIG) therapy has been used to treat sepsis, but its mechanisms of action remain unclear. Sepsis causes multiple organ failure, such as acute lung injury (ALI), which involves apoptosis of alveolar epithelial cells. In this study, we hypothesized that IVIG suppresses apoptosis in alveolar epithelial cells and evaluated mortality, cytokine levels, histological changes in the lung, and alveolar epithelial cell apoptosis after IVIG administration, in mice with experimentally induced sepsis.

METHODS

Mice received an injection of vehicle (saline) or immunoglobulin (100 mg/kg or 400 mg/kg) into the tail vein, after which they underwent cecal ligation and puncture. A sham-operated group was used as the normal control. Survival was assessed in all groups after 72 hours. Plasma levels of TNF-α and IL-6, histopathological changes and wet-to-dry ratio in lung, and alveolar epithelial cell apoptosis were evaluated in all groups at 4 hours after surgery.

RESULTS

In the vehicle group, histopathological injury of the lung was severe, and apoptosis of alveolar epithelial cells was significant. Survival and plasma cytokine levels were better in the IVIG treatment groups than in the vehicle group. IVIG 400 mg/kg suppressed apoptosis of alveolar epithelial cells and reduced ALI.

CONCLUSION

IVIG suppressed inflammatory cytokine levels and improved survival. Lung histopathology and alveolar epithelial cell apoptosis were improved by IVIG treatment, in a dose-dependent manner. Suppressing apoptosis in alveolar epithelial cells appears to be a mechanism by which IVIG improves survival.

Adipose-derived mesenchymal stem cells ameliorate the inflammatory reaction in CLP-induced septic acute lung injury rats via sTNFR1

We hypothesized that the adipose-derived mesenchymal stem cells (ADMSCs), which secrete high amounts of soluble molecules, such as soluble tumor necrosis factor receptor 1 (sTNFR1), may ameliorate sepsis-induced acute lung injury (ALI). A total of 120 male adult Sprague-Dawley rats were separated into four groups: the sham control (SC), sepsis induced by cecal ligation and puncture (CLP), CLP-ADMSCs, and CLP-sTNFR1 small interfering RNA (siRNA) groups; CLP groups underwent CLP and then received 1 × 106 ADMSCs with or without knockdown of sTNFR1 intravenously at 1 hr after surgery. Rats were killed at 3, 6, 24, and 48 hr after the SC or CLP procedures. 5-Ethynyl-2'-deoxyuridine-labeled ADMSCs extensively colonized the lungs at 6, 24, and 72 hr after injection. The lung wet/dry (W/D) weight ratios in the CLP group were higher than those in SC group; however, ADMSCs ameliorated the W/D weight ratios following CLP, and this effect was abolished by sTNFR1 siRNA treatment. The levels of serum sTNFR1 and interleukin-10 (IL-10) were higher in the CLP-ADMSCs group and lower in the SC group than in other groups; interestingly, these levels were higher in CLP and CLP-sTNFR1 siRNA groups than in SC group. Tumor necrosis factor-α and IL-6 levels increased significantly after CLP, and ADMSCs could alleviate these changes, but the effect was weakened by sTNFR1 siRNA treatment. The lung cell apoptosis and edema levels were consistent with IL-6 levels among all groups. Therapeutically administered ADMSCs secrete sTNFR1, which most likely protects against ALI in septic rats by ameliorating inflammation and lung edema.

Extrinsic acidosis suppresses glycolysis and migration while increasing network formation in pulmonary microvascular endothelial cells

Acidosis is common among critically ill patients, but current approaches to correct pH do not improve disease outcomes. During systemic acidosis, cells are either passively exposed to extracellular acidosis that other cells have generated (extrinsic acidosis) or they are exposed to acid that they generate and export into the extracellular space (intrinsic acidosis). Although endothelial repair following intrinsic acidosis has been studied, the impact of extrinsic acidosis on migration and angiogenesis is unclear. We hypothesized that extrinsic acidosis inhibits metabolism and migration but promotes capillary-like network formation in pulmonary microvascular endothelial cells (PMVECs). Extrinsic acidosis was modeled by titrating media pH. Two types of intrinsic acidosis were compared, including increasing cellular metabolism by chemically inhibiting carbonic anhydrases (CAs) IX and XII (SLC-0111) and with hypoxia. PMVECs maintained baseline intracellular pH for 24 h with both extrinsic and intrinsic acidosis. Whole cell CA IX protein expression was decreased by extrinsic acidosis but not affected by hypoxia. When extracellular pH was equally acidic, extrinsic acidosis suppressed glycolysis, whereas intrinsic acidosis did not. Extrinsic acidosis suppressed migration, but increased Matrigel network master junction and total segment length. CRISPR-Cas9 CA IX knockout PMVECs revealed an independent role of CA IX in promoting glycolysis, as loss of CA IX alone was accompanied by decreased hexokinase I and pyruvate dehydrogenase E1α expression and decreasing migration. 2-deoxy-d-glucose had no effect on migration but profoundly inhibited network formation and increased N-cadherin expression. Thus, we report that while extrinsic acidosis suppresses endothelial glycolysis and migration, it promotes network formation.

Pulmonary contusion

Lung contusion resulting from chest trauma may be present various clinical pictures. It quite often remains unrecognized and is only suspected later when severe complications have developed. Lung contusion may present in association with chest trauma but may also occur alone. It has to be emphasized, that lung contusion as a clinical identity does not necessarily require a blunt or penetrating chest to be in the background. Nowadays, as a result of traffic accidents, following high energy deceleration, lung contusion may present without an actual tissue damage in the chest wall as a condition initiating an independent, life-threatening generalised process. Although lung contusion shows similarities to blast injury of the lung with respect to clinical consequences, other factors play a role in its aetiology and pathology. Its description and recognition as an independent pathology is not simple. Several approaches exist: thoracic trauma, pulmonary contusion, pulmonary laceration, lung contusion; although these may show similar clinical signs, manifest in different pathologies. Pathologies with similar meaning and possibly similar clinical course cannot, actually, be differentiated; they may accompany other injuries to the trunk, skull or extremities, which, alone, are associated with high morbidity and mortality. Generally, it can be declared that besides high energy, blunt injuries affecting the trunk, lung contusion, has been an often neglected additional radiological finding attached to the main report, despite the fact, that its late consequences crucially determine the prospects of the injured.

Low-flow CO2 removal in combination with renal replacement therapy effectively reduces ventilation requirements in hypercapnic patients: a pilot study

Background

Lung-protective strategies are the cornerstone of mechanical ventilation in critically ill patients with both ARDS and other disorders. Extracorporeal CO₂ removal (ECCO₂R) may enhance lung protection by allowing even further reductions in tidal volumes and is effective in low-flow settings commonly used for renal replacement therapy. In this study, we describe for the first time the effects of a labeled and certified system combining ECCO₂R and renal replacement therapy on pulmonary stress and strain in hypercapnic patients with renal failure.

Methods

Twenty patients were treated with the combined system which incorporates a membrane lung (0.32 m²) in a conventional renal replacement circuit. After changes in blood gases under ECCO₂R were recorded, baseline hypercapnia was reestablished and the impact on ventilation parameters such as tidal volume and driving pressure was recorded.

Results

The system delivered ECCO₂R at rate of 43.4 ± 14.1 ml/min, PaCO₂ decreased from 68.3 ± 11.8 to 61.8 ± 11.5 mmHg (p < 0.05) and pH increased from 7.18 ± 0.09 to 7.22 ± 0.08 (p < 0.05). There was a significant reduction in ventilation requirements with a decrease in tidal volume from 6.2 ± 0.9 to 5.4 ± 1.1 ml/kg PBW (p < 0.05) corresponding to a decrease in plateau pressure from 30.6 ± 4.6 to 27.7 ± 4.1 cmH₂O (p < 0.05) and a decrease in driving pressure from 18.3 ± 4.3 to 15.6 ± 3.9 cmH₂O (p < 0.05), indicating reduced pulmonary stress and strain. No complications related to the procedure were observed.

Conclusions

The investigated low-flow ECCO₂R and renal replacement system can ameliorate respiratory acidosis and decrease ventilation requirements in hypercapnic patients with concomitant renal failure.

Trial registration NCT02590575, registered 10/23/2015.

Hypercapnia and hypercapnic acidosis in sepsis: harmful, beneficial or unclear?

Mortality related to sepsis among critically ill patients remains high. Recent literature suggests that hypercapnia may affect the pathophysiology of sepsis. The effects of hypercapnia on sepsis are largely related to the direct effect of hypercapnic acidosis on immune function and, as a consequence, of increased cardiac output that subsequently leads to improved tissue oxygenation. Appropriate management of hypercapnia may aid in improving the outcomes of sepsis. Our aim was to review the effects of compensated hypercapnia and hypercapnic acidosis on sepsis, with a specific focus on critically ill patients. Hypercapnic acidosis has been extensively studied in various in vivo animal models of sepsis and ex vivo studies. Published data from animal experimental studies suggest that the effects of hypercapnic acidosis are variable, with benefit shown in some settings of sepsis and harm in others. The effects may also vary at different time points during the course of sepsis. There are very few clinical studies investigating the effects of hypercapnia in prevention of sepsis and in established sepsis. It appears from these very limited clinical data that hypercapnia may be associated with adverse outcomes. There are no clinical studies investigating clinical outcomes of hypercapnic acidosis or compensated hypercapnia in sepsis and septic shock in critical care settings, thus extrapolation of the experimental results to guide critical care practice is difficult. Clinical studies are needed, especially in critically ill patients, to define the effects of compensated hypercapnia and hypercapnic acidosis that may aid clinicians to improve the outcomes in sepsis.

Necrotizing fasciitis: case series and review of the literature on clinical and medico-legal diagnostic challenges

Necrotizing fasciitis (NF) is a life-threatening infection of soft tissues spreading along the fasciae to the surrounding musculature, subcutaneous fat and overlying skin areas that can rapidly lead to septic shock and death. Due to the pandemic increase of medical malpractice lawsuits, above all in Western countries, the forensic pathologist is frequently asked to investigate post-mortem cases of NF in order to determine the cause of death and to identify any related negligence and/or medical error. Herein, we review the medical literature dealing with cases of NF in a post-mortem setting, present a case series of seven NF fatalities and discuss the main ante-mortem and post-mortem diagnostic challenges of both clinical and forensic interests. In particular, we address the following issues: (1) origin of soft tissue infections, (2) micro-organisms involved, (3) time of progression of the infection to NF, (4) clinical and histological staging of NF and (5) pros and cons of clinical and laboratory scores, specific forensic issues related to the reconstruction of the ideal medical conduct and the evaluation of the causal value/link of any eventual medical error.

Re-examining Permissive Hypercapnia in ARDS: A Narrative Review

Lung-protective ventilation (LPV) has become the cornerstone of management in patients with ARDS. A subset of patients is unable to tolerate LPV without significant CO₂ elevation. In these patients, permissive hypercapnia is used. Although thought to be benign, it is becoming increasingly evident that elevated CO₂ levels have significant physiological effects. In this narrative review, we highlight clinically relevant end-organ effects in both animal models and clinical studies. We also explore the association between elevated CO₂, acute cor pulmonale, and ICU mortality. We conclude with a brief review of alternative therapies for CO₂ management currently under investigation in patients with moderate to severe ARDS.

Senegenin Ameliorate Acute Lung Injury Through Reduction of Oxidative Stress and Inhibition of Inflammation in Cecal Ligation and Puncture-Induced Sepsis Rats

The purpose of this study was to assess the protective effect of senegenin on acute lung injury (ALI) in rats induced by sepsis. Rat ALI model was reproduced by cecal ligation and puncture (CLP). All rats were randomly divided into five groups: group 1 (control), group 2 (CLP), group 3 (CLP + senegenin 15 mg/kg), group 4 (CLP + senegenin 30 mg/kg), and group 5 (CLP + senegenin 60 mg/kg). CLP + senegenin groups received senegenin by gavage daily for consecutive 5 days, respectively, while the mice in control and CLP groups were given an equivalent volume of saline. We detected the lung wet/dry weight ratios and the histopathology of the lung. The levels of lung tissue myeloperoxidase (MPO), malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione (GSH) were determined. Meanwhile, the nuclear factor-kappa B (NF-κB) activation, tumor necrosis factor-alpha (TNF-α), and interleukin-1β (IL-1β) levels were studied. The results demonstrated that senegenin treatment significantly attenuated CLP-induced lung injury, including reduction of lung wet/dry weight ratio, protein leak, infiltration of leukocytes, and MPO activity. In addition, senegenin markedly decreased MDA content and increased SOD activity and GSH level. Serum levels of TNF-α and IL-1β were also decreased by senegenin administration. Furthermore, senegenin administration inhibited the nuclear translocation of NF-κB in the lungs. These findings indicate that senegenin exerts protective effects on CLP-induced septic rats. Senegenin may be a potential therapeutic agent against sepsis.

Acute respiratory distress syndrome

Acute respiratory distress syndrome presents as hypoxia and bilateral pulmonary infiltrates on chest imaging in the absence of heart failure sufficient to account for this clinical state. Management is largely supportive, and is focused on protective mechanical ventilation and the avoidance of fluid overload. Patients with severe hypoxaemia can be managed with early short-term use of neuromuscular blockade, prone position ventilation, or extracorporeal membrane oxygenation. The use of inhaled nitric oxide is rarely indicated and both β2 agonists and late corticosteroids should be avoided. Mortality remains at approximately 30%.

Lung protective ventilation in patients undergoing major surgery: a systematic review incorporating a Bayesian approach

OBJECTIVE

Protective ventilation (PV) has been validated in patients with acute respiratory distress syndrome. However, the effect of PV in patients undergoing major surgery is controversial. The study aimed to explore the beneficial effect of PV on patients undergoing a major operation by systematic review and meta-analysis.

SETTING

Various levels of medical centres.

PARTICIPANTS

Patients undergoing general anaesthesia.

INTERVENTIONS

PV with low tidal volume.

PRIMARY AND SECONDARY OUTCOME MEASURES

Study end points included acute lung injury (ALI), pneumonia, atelectasis, mortality, length of stay (LOS) in intensive care unit (ICU) and hospital.

METHODS

Databases including PubMed, Scopus, EBSCO and EMBASE were searched from inception to May 2015. Search strategies consisted of terms related to PV and anaesthesia. We reported OR for binary outcomes including ALI, mortality, pneumonia, atelectasis and other adverse outcomes. Weighted mean difference was reported for continuous outcomes such as LOS in the ICU and hospital, pH value, partial pressure of carbon dioxide, oxygenation and duration of mechanical ventilation (MV).

MAIN RESULTS

A total of 22 citations were included in the systematic review and meta-analysis. PV had protective effect against the development of ALI as compared with the control group, with an OR of 0.41 (95% CI 0.19 to 0.87). PV tended to be beneficial with regard to the development of pneumonia (OR 0.46, 95% CI 0.16 to 1.28) and atelectasis (OR 0.68, 95% CI 0.46 to 1.01), but statistical significance was not reached. Other adverse outcomes such as new onset arrhythmia were significantly reduced with the use of PV (OR 0.47, 95% CI 0.48 to 0.93).

CONCLUSIONS

The study demonstrates that PV can reduce the risk of ALI in patients undergoing major surgery. However, there is insufficient evidence that such a beneficial effect can be translated to more clinically relevant outcomes such as mortality or duration of MV.

TRIAL REGISTRATION NUMBER

The study was registered in PROSPERO (http://www.crd.york.ac.uk/PROSPERO/) under registration number CRD42013006416.

Hypercapnia attenuates ventilator-induced lung injury via a disintegrin and metalloprotease-17

Hypercapnic acidosis, common in mechanically ventilated patients, has been reported to exert both beneficial and harmful effects in models of lung injury. Understanding its effects at the molecular level may provide insight into mechanisms of injury and protection. The aim of this study was to establish the effects of hypercapnic acidosis on mitogen‐activated protein kinase (MAPK) activation, and determine the relevant signalling pathways. p44/42 MAPK activation in a murine model of ventilator‐induced lung injury (VILI) correlated with injury and was reduced in hypercapnia. When cultured rat alveolar epithelial cells were subjected to cyclic stretch, activation of p44/42 MAPK was dependent on epidermal growth factor receptor (EGFR) activity and on shedding of EGFR ligands; exposure to 12% CO2 without additional buffering blocked ligand shedding, as well as EGFR and p44/42 MAPK activation. The EGFR ligands are known substrates of the matrix metalloprotease ADAM17, suggesting stretch activates and hypercapnic acidosis blocks stretch‐mediated activation of ADAM17. This was corroborated in the isolated perfused mouse lung, where elevated CO2 also inhibited stretch‐activated shedding of the ADAM17 substrate TNFR1 from airway epithelial cells. Finally, in vivo confirmation was obtained in a two‐hit murine model of VILI where pharmacological inhibition of ADAM17 reduced both injury and p44/42 MAPK activation. Thus, ADAM17 is an important proximal mediator of VILI; its inhibition is one mechanism of hypercapnic protection and may be a target for clinical therapy.

Proteomic analysis of lung tissue in a rat acute lung injury model: identification of PRDX1 as a promoter of inflammation

Acute respiratory distress syndrome (ARDS) remains a high morbidity and mortality disease entity in critically ill patients, despite decades of numerous investigations into its pathogenesis. To obtain global protein expression changes in acute lung injury (ALI) lung tissues, we employed a high-throughput proteomics method to identify key components which may be involved in the pathogenesis of ALI. In the present study, we analyzed lung tissue proteomes of Pseudomonas aeruginosa-induced ALI rats and identified eighteen proteins whose expression levels changed more than twofold as compared to normal controls. In particular, we found that PRDX1 expression in culture medium was elevated by a lipopolysaccharide (LPS) challenge in airway epithelial cells in vitro. Furthermore, overexpression of PRDX1 increased the expression of proinflammatory cytokines interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α), whereas knockdown of PRDX1 led to downregulated expression of cytokines induced by LPS. In conclusion, our findings provide a global alteration in the proteome of lung tissues in the ALI rat model and indicate that PRDX1 may play a critical role in the pathogenesis of ARDS by promoting inflammation and represent a novel strategy for the development of new therapies against ALI.

The effects of salbutamol on epithelial ion channels depend on the etiology of acute respiratory distress syndrome but not the route of administration

Introduction

We investigated the effects of intravenous and intratracheal administration of salbutamol on lung morphology and function, expression of ion channels, aquaporin, and markers of inflammation, apoptosis, and alveolar epithelial/endothelial cell damage in experimental pulmonary (p) and extrapulmonary (exp) mild acute respiratory distress syndrome (ARDS).

Methods

In this prospective randomized controlled experimental study, 56 male Wistar rats were randomly assigned to mild ARDS induced by either intratracheal (n = 28, ARDSp) or intraperitoneal (n = 28, ARDSexp) administration of E. coli lipopolysaccharide. Four animals with no lung injury served as controls (NI). After 24 hours, animals were anesthetized, mechanically ventilated in pressure-controlled mode with low tidal volume (6 mL/kg), and randomly assigned to receive salbutamol (SALB) or saline 0.9% (CTRL), intravenously (i.v., 10 μg/kg/h) or intratracheally (bolus, 25 μg). Salbutamol doses were targeted at an increase of ≈ 20% in heart rate. Hemodynamics, lung mechanics, and arterial blood gases were measured before and after (at 30 and 60 min) salbutamol administration. At the end of the experiment, lungs were extracted for analysis of lung histology and molecular biology analysis. Values are expressed as mean ± standard deviation, and fold changes relative to NI, CTRL vs. SALB.

Results

The gene expression of ion channels and aquaporin was increased in mild ARDSp, but not ARDSexp. In ARDSp, intravenous salbutamol resulted in higher gene expression of alveolar epithelial sodium channel (0.20 ± 0.07 vs. 0.68 ± 0.24, p < 0.001), aquaporin-1 (0.44 ± 0.09 vs. 0.96 ± 0.12, p < 0.001) aquaporin-3 (0.31 ± 0.12 vs. 0.93 ± 0.20, p < 0.001), and Na-K-ATPase-α (0.39 ± 0.08 vs. 0.92 ± 0.12, p < 0.001), whereas intratracheal salbutamol increased the gene expression of aquaporin-1 (0.46 ± 0.11 vs. 0.92 ± 0.06, p < 0.001) and Na-K-ATPase-α (0.32 ± 0.07 vs. 0.58 ± 0.15, p < 0.001). In ARDSexp, the gene expression of ion channels and aquaporin was not influenced by salbutamol. Morphological and functional variables and edema formation were not affected by salbutamol in any of the ARDS groups, regardless of the route of administration.

Conclusion

Salbutamol administration increased the expression of alveolar epithelial ion channels and aquaporin in mild ARDSp, but not ARDSexp, with no effects on lung morphology and function or edema formation. These results may contribute to explain the negative effects of β2-agonists on clinical outcome in ARDS.

Ventilation strategies in burn intensive care: A retrospective observational study

Consensus regarding optimal burns intensive care (BICU) patient management is lacking. This study aimed to assess whether ventilation strategies, cardiovascular support and sedation in BICU patients have changed over time, and whether this affects outcome. A retrospective observational study comparing two 12-patient BICU cohorts (2005/06 and 2010/11) was undertaken. Demographic and admission characteristics, ventilation parameters, sedation, fluid resuscitation, cardiovascular support and outcome (length of stay, mortality) data were collected from patient notes. Data was analysed using T-tests, Fisher's exact and Mann-Whitney U tests. In our study cohort groups were equivalent in demographic and admission parameters. There were equal ventilator-free days in the two cohorts 10 ± 12.7 vs. 13.3 ± 12.2 ventilator free days; P = 0.447). The 2005/06 cohort were mechanically ventilated more often than in 2010/11 cohort (568 ventilator days/1000 patient BICU days vs. 206 ventilator days/1000 patient BICU days; P = 0.001). The 2005/06 cohort were ventilated less commonly in tracheostomy group/endotracheal tube spontaneous (17.8% vs. 26%; P = 0.001) and volume-controlled modes (34.4% vs. 40.8%; P = 0.001). Patients in 2010/11 cohort were more heavily sedated (P = 0.001) with more long-acting sedative drug use (P = 0.001) than the 2005/06 cohort, fluid administration was equivalent. Patient outcome did not vary. Inhalational injury patients were ventilated in volume-controlled (44.5% vs. 28.1%; P = 0.001) and pressure-controlled modes (18.2% vs. 9.5%; P = 0.001) more frequently than those without. Outcome did not vary. This study showed there has been shift away from mechanical ventilation, with increased use of tracheostomy/tracheal tube airway spontaneous ventilation. Inhalation injury patients require more ventilatory support though patient outcomes do not differ. Prospective trials are required to establish which strategies confer benefit.

Hypercapnia: is it protective in lung injury?

Hypercapnic acidosis has been regarded as a tolerated side effect of protective lung ventilation strategies. Various in vivo and ex vivo animal studies have shown beneficial effects in acute lung injury setting, but some recent work raised concerns about its anti-inflammatory properties. This mini-review article aims to expand the potential clinical spectrum of hypercapnic acidosis in critically ill patients with lung injury. Despite the proven benefits of hypercapnic acidosis, further safety studies including dose-effect, level-and-onset of anti-inflammatory effect, and safe applicability period need to be performed in various models of lung injury in animals and humans to further elucidate its protective role.

Ventilator settings and monitoring parameter targets for initiation of continuous mandatory ventilation: a questionnaire study

PURPOSE

To inform development of educational tools, we sought to identify initial ventilator settings and monitoring targets for 3 scenarios.

METHOD

A survey was e-mailed to Canadian Society of Respiratory Therapists members with 2 reminders in March/April 2011.

RESULTS

Total evaluable surveys were 363. More participants selected pressure as opposed to volume ventilation for acute respiratory distress syndrome (ARDS; 77%) than for chronic obstructive pulmonary disease (COPD; 50%) and postoperative ventilation (32%; P < .001). Mean tidal volume was lower for ARDS than for COPD and postoperative ventilation (5.7, 6.9, and 7.2 mL/kg, respectively; P < .001). Maximum acceptable plateau pressures were highest for ARDS (30 cm H2O vs 29 cm H2O [COPD] and 27 cm H2O [postoperative], P < .001). Initial positive expiratory end pressure (12 cm H2O vs 7 cm H2O vs 5 cm H2O) and fraction of inspired oxygen (Fio2; 1.0 vs 0.5 vs 0.3) were also higher for ARDS (both P < .001); however, only 8% selected a positive expiratory end pressure/Fio2 combination as recommended by ARDSnet. Values of oxygen saturation as measured by pulse oximetry of 97% (ARDS) and 94% (COPD and postoperative) were considered appropriate for Fio2 reduction. The lowest pH was 7.28 vs 7.23 vs 7.26; the highest pH was 7.46 vs 7.44 vs 7.46 (P < .001). Partial pressure of carbon dioxide (arterial) of 51 mm Hg (postoperative) to 65 mm Hg (ARDS) was considered acceptable.

CONCLUSION

Lung protective ventilation was favored, yet distinct differences in ventilator settings were evident. Monitoring targets suggested relatively conservative practices for Fio2 reduction but an understanding of permissive hypercapnia.

The effect of curcumin on sepsis-induced acute lung injury in a rat model through the inhibition of the TGF-β1/SMAD3 pathway

Curcumin has the potential to treat inflammatory diseases. This study investigated its effect on sepsis-induced acute lung injury (ALI) in a rat model. 125 healthy rats were randomly divided into five groups, including normal group, sham-operated group, sepsis group, dimethyl sulfoxide group, and curcumin-treated group (25 rats in each subgroup). Sepsis-induced acute lung injury was affected by cecal ligation and puncture surgery. At 0, 6, 12, 24, and 48 h after treatment, the lungs were harvested for histological and protein expression examinations. 24h after the initial treatment, real-time PCR and Western blot analysis showed that the expression of TGF-β1 and SMAD3-dependent signaling pathway was significantly decreased in the curcumin-treated group than other control groups (P<0.05). Therefore, curcumin played a protective role in sepsis-induced ALI, possibly through the inhibition of the expression of TGF-β1/SMAD3 pathway which may provide a new strategy for the treatment of sepsis-induced ALI.

Hypercapnic respiratory acidosis: a protective or harmful strategy for critically ill newborn foals?

This paper reviews both the beneficial and adverse effects of permissive hypercapnic respiratory acidosis in critically ill newborn foals. It has been shown that partial carbon dioxide pressure (PCO2) above the traditional safe range (hypercapnia), has beneficial effects on the physiology of the respiratory, cardiovascular, and nervous system in neonates. In human neonatal critical care medicine permissive hypercapnic acidosis is generally well-tolerated by patients and is more beneficial to their wellbeing than normal carbon dioxide (CO2) pressure or normocapnia. Even though adverse effects of hypercapnia have been reported, especially in patients with central nervous system pathology and/or chronic infection, critical care clinicians often artificially increase PCO2 to take advantage of its positive effects on compromised neonate tissues. This is referred to as therapeutic hypercapnia. Hypercapnic respiratory acidosis is common in critically ill newborn foals and has traditionally been considered as not beneficial. A search of online scientific databases was conducted to survey the literature on the effects of hypercapnia in neonates, with emphasis on newborn foals. The dynamic status of safety levels of PCO2 and data on the effectiveness of different carbon dioxide levels are not available for newborn foals and should be scientifically determined. Presently, permissive hypercapnia should be implemented or tolerated cautiously in compromised newborn foals and its use should be based on relevant data from adult horses and other species.

Critical care in the ED: potentially fatal asthma and acute lung injury syndrome

Emergency department clinicians are frequently called upon to assess, diagnose, and stabilize patients who present with acute respiratory failure. This review describes a rapid initial approach to acute respiratory failure in adults, illustrated by two common examples: (1) an airway disease - acute potentially fatal asthma, and (2) a pulmonary parenchymal disease - acute lung injury/acute respiratory distress syndrome. As such patients are usually admitted to hospital, discussion will be focused on those initial management aspects most relevant to the emergency department clinician.