Fifty Years of Research in ARDS. Is Acute Respiratory Distress Syndrome a Preventable Disease?

Extracorporeal membrane oxygenation as rescue therapy for severe hypoxemic respiratory failure

Extracorporeal membrane oxygenation (ECMO) has been used for more than 50 years as salvage therapy for patients with severe cardiopulmonary failure refractory to conventional treatment. ECMO was first used in the 1960s to treat hypoxemic respiratory failure in newborns. On the basis of its success in that population, ECMO began to be used in the early 1970s to treat adult hypoxemic respiratory failure. However, outcomes for adults were, somewhat perplexingly, quite poor. By the 1980s, use of ECMO for severe hypoxemia was rare outside of the pediatric population. ECMO technology, however, continued to evolve and improve. Multiple case reports and small series describing ECMO use as rescue for adults with severe hypoxemia from various lung pathologies have appeared in the literature over the past three decades. Adult respiratory distress syndrome (ARDS) is often the final common pathway of various pathologies affecting adults and causing hypoxemic respiratory failure. It is prevalent in intensive care units throughout the world and has, since it was first described in 1967, carried a high mortality. No specific therapy for ARDS has been found, and current care is supportive, primarily by mechanical ventilation. Results from recent randomized controlled trials, however, suggest that ECMO may have a place in the treatment of these patients. This article reviews these studies and recommends adding severe ARDS to the list of established indications for ECMO in patients with hypoxemic respiratory failure.

Alleviation of Inflammatory Response of Pulmonary Fibrosis in Acute Respiratory Distress Syndrome by Puerarin via Transforming Growth Factor (TGF-β1)

BACKGROUND Acute respiratory distress syndrome (ARDS) in infants is acute and progressive hypoxic respiratory failure caused by various extrapulmonary pathogenic factors besides cardiogenic factors. Diffuse alveolar injury and progression to pulmonary fibrosis are pathological features of ARDS. The present study sought to determine how puerarin influences the inflammatory response caused by pulmonary fibrosis in ARDS in infants. MATERIAL AND METHODS The human lung fibroblasts cell line HLF1 was treated with different concentrations of puerarin in different groups for various times. TGF-ß1 was overexpressed by TGF-ß1 (2 ng/mL) in routine experiments, and the treated cells and culture supernatant were collected for analysis in each step. Cell apoptosis was measured by flow cytometry, TUNEL assay, and detection of caspase 3 and Bcl-2. Cell proliferation was assessed by CCK-8 assay. Real-time PCR and Western blot assay were used to assess mRNA and protein levels of TGF-ß1 and Smad3, respectively. The related cytokines were assessed by ELISA. RESULTS Results showed that puerarin promoted the apoptosis and inhibited the proliferation of HLF1 cells. Caspase 3 was upregulated, whereas Bcl-2, TGF-ß1, and Smad3 were downregulated by puerarin. IL-1, IL-2, and IL-4, secreted by HLF1 cells, were reduced, but IL-10 showed the opposite trend. When TGF-ß1 was overexpressed, Smad3 was promoted, and IL-1, IL-2, and IL-4 was increased in HLF1 cells. Finally, overexpression of TGF-ß1 reversed the effect of puerarin in HLF1 cells. CONCLUSIONS Puerarin regulated the proliferation and apoptosis of pulmonary fibrosis cells, and affected the secretion of inflammatory cytokines. Thus, puerarin alleviated the inflammatory response resulting from pulmonary fibrosis by regulating the TGF-ß1/Smad3 pathway in infants with ARDS.

Diagnostic and prognostic values of serum activin-a levels in patients with acute respiratory distress syndrome

Background

We aimed to evaluate whether serum activin-A levels are elevated and have any value in predicting severity and prognosis in acute respiratory distress syndrome (ARDS).

Methods

Retrospective cohort study was performed with patients who were admitted to MICU with diagnosis of ARDS and have serum samples stored within 48 h of Intensive care unit (ICU) admission between March 2013 and December 2016 at a single tertiary referral hospital. Serum activin-A levels were measured with ELISA kit, and were compared with those of normal healthy control and non-ARDS sepsis patients.

Results

Total 97 ARDS patients were included for the study. Levels of Activin-A were elevated in ARDS patients compared to those of healthy controls (Log-transformed activin-A levels 2.89 ± 0.36 vs. 2.34 ± 0.11, p < 0.001, absolute activin-A levels 1525.6 ± 1060.98 vs. 225.9 ± 30.1, p = 0.016) and non-ARDS sepsis patients (Log-transformed activin-A levels 2.89 ± 0.36 vs. 2.73 ± 0.34, p = 0.002, Absolute activin-A levels 1525.6 ± 1060.98 vs. 754.8 ± 123.5 pg/mL, p = 0.036). When excluding five outliers with extremely high activin-A levels, activin-A showed statistically significant correlation with in-hospital mortalities (In-hospital survivors 676.2 ± 407 vs. non-survivors 897.9 ± 561.9 pg/mL, p = 0.047). In predicting in-hospital mortality, serum activin-A concentrations showed superior area under curve compared to that of Acute physiologic and chronic health evaluation II scores (0.653; 95% CI [0541, 0.765] vs. 0.591, 95% CI [0.471, 0.710]). With cut-off level of 708 pg/mL, those with high serum activin-A levels had more than twofold increased risk of in-hospital mortalities. However, those relations were missing when outliers were in.

Conclusions

Serum activin-A levels in ARDS patients are elevated. However, its levels are weakly associated with ARDS outcomes.

Electronic supplementary material

The online version of this article (10.1186/s12890-019-0879-6) contains supplementary material, which is available to authorized users.

Machine learning for patient risk stratification for acute respiratory distress syndrome

BACKGROUND

Existing prediction models for acute respiratory distress syndrome (ARDS) require manual chart abstraction and have only fair performance-limiting their suitability for driving clinical interventions. We sought to develop a machine learning approach for the prediction of ARDS that (a) leverages electronic health record (EHR) data, (b) is fully automated, and (c) can be applied at clinically relevant time points throughout a patient's stay.

METHODS AND FINDINGS

We trained a risk stratification model for ARDS using a cohort of 1,621 patients with moderate hypoxia from a single center in 2016, of which 51 patients developed ARDS. We tested the model in a temporally distinct cohort of 1,122 patients from 2017, of which 27 patients developed ARDS. Gold standard diagnosis of ARDS was made by intensive care trained physicians during retrospective chart review. We considered both linear and non-linear approaches to learning the model. The best model used L2-logistic regression with 984 features extracted from the EHR. For patients observed in the hospital at least six hours who then developed moderate hypoxia, the model achieved an area under the receiver operating characteristics curve (AUROC) of 0.81 (95% CI: 0.73-0.88). Selecting a threshold based on the 85th percentile of risk, the model had a sensitivity of 56% (95% CI: 35%, 74%), specificity of 86% (95% CI: 85%, 87%) and positive predictive value of 9% (95% CI: 5%, 14%), identifying a population at four times higher risk for ARDS than other patients with moderate hypoxia and 17 times the risk of hospitalized adults.

CONCLUSIONS

We developed an ARDS prediction model based on EHR data with good discriminative performance. Our results demonstrate the feasibility of a machine learning approach to risk stratifying patients for ARDS solely from data extracted automatically from the EHR.

Rationale and design of a prospective, multicentre, randomised, conventional treatment-controlled, parallel-group trial to evaluate the efficacy and safety of ulinastatin in preventing acute respiratory distress syndrome in high-risk patients

INTRODUCTION

Acute respiratory distress syndrome (ARDS) is challenging in the intensive care unit (ICU). Although pharmacotherapy for ARDS has gained increasing attention, most trials have yielded negative results. Patients with ARDS have usually been recruited as subjects; the inflammatory reaction has already expanded into a cascade at this point, and its severity is sufficient to damage the lung parenchyma. This raises the question of whether early treatment can prevent ARDS and the associated lung injury. We hypothesise that ARDS is preventable in high-risk patients by administration of ulinastatin as an anti-inflammatory drug before ARDS onset, and we are performing a study to test ulinastatin, a protease inhibitor, versus treatment-as-usual in a group of patients at increased risk for ARDS.

METHODS AND ANALYSIS

This report presents the protocol for a multicentre, randomised, conventional treatment-controlled, parallel group study to prevent the development of ARDS using ulinastatin in high-risk patients. The study population will comprise patients at risk of ARDS in the ICU (≥18 years of age and Lung Injury Prediction Score of >4); patients with confirmed ARDS and some other conditions (immunodeficiency, use of some drugs, etc.) will be excluded. The enrolled patients will be randomly allocated to an ulinastatin group (ulinastatin will be intravenously administered every 8 hours for a total of 600 000 U/day for five consecutive days) or control group. The efficacy of ulinastatin in preventing ARDS development will be evaluated by the incidence rate of ARDS as the primary outcome; the secondary outcomes include the severity of ARDS, clinical outcome, extrapulmonary organ function and adverse events incurred by ulinastatin. Based on the results of preliminary studies and presuming the incidence of ARDS will decrease by 9% in high-risk patients, 880 patients are needed to obtain statistical power of 80%.

ETHICS AND DISSEMINATION

This study has been approved by the Peking University Third Hospital Medical Science Research Ethics Committee. The findings will be published in peer-reviewed journals and presented at national and international conferences.

TRIAL REGISTRATION NUMBER

NCT03089957; Pre-results.

Outcomes of Patients Presenting with Mild Acute Respiratory Distress Syndrome

Editor’s Perspective

What We Already Know about This Topic

What This Article Tells Us That Is New

Background

Patients with initial mild acute respiratory distress syndrome are often underrecognized and mistakenly considered to have low disease severity and favorable outcomes. They represent a relatively poorly characterized population that was only classified as having acute respiratory distress syndrome in the most recent definition. Our primary objective was to describe the natural course and the factors associated with worsening and mortality in this population.

Methods

This study analyzed patients from the international prospective Large Observational Study to Understand the Global Impact of Severe Acute Respiratory Failure (LUNG SAFE) who had initial mild acute respiratory distress syndrome in the first day of inclusion. This study defined three groups based on the evolution of severity in the first week: “worsening” if moderate or severe acute respiratory distress syndrome criteria were met, “persisting” if mild acute respiratory distress syndrome criteria were the most severe category, and “improving” if patients did not fulfill acute respiratory distress syndrome criteria any more from day 2.

Results

Among 580 patients with initial mild acute respiratory distress syndrome, 18% (103 of 580) continuously improved, 36% (210 of 580) had persisting mild acute respiratory distress syndrome, and 46% (267 of 580) worsened in the first week after acute respiratory distress syndrome onset. Global in-hospital mortality was 30% (172 of 576; specifically 10% [10 of 101], 30% [63 of 210], and 37% [99 of 265] for patients with improving, persisting, and worsening acute respiratory distress syndrome, respectively), and the median (interquartile range) duration of mechanical ventilation was 7 (4, 14) days (specifically 3 [2, 5], 7 [4, 14], and 11 [6, 18] days for patients with improving, persisting, and worsening acute respiratory distress syndrome, respectively). Admissions for trauma or pneumonia, higher nonpulmonary sequential organ failure assessment score, lower partial pressure of alveolar oxygen/fraction of inspired oxygen, and higher peak inspiratory pressure were independently associated with worsening.

Conclusions

Most patients with initial mild acute respiratory distress syndrome continue to fulfill acute respiratory distress syndrome criteria in the first week, and nearly half worsen in severity. Their mortality is high, particularly in patients with worsening acute respiratory distress syndrome, emphasizing the need for close attention to this patient population.

Biomarkers for Acute Respiratory Distress syndrome and prospects for personalised medicine

Acute lung injury (ALI) affects over 10% of patients hospitalised in critical care, with acute respiratory distress syndrome (ARDS) being the most severe form of ALI and having a mortality rate in the region of 40%. There has been slow but incremental progress in identification of biomarkers that contribute to the pathophysiology of ARDS, have utility in diagnosis and monitoring, and that are potential therapeutic targets (Calfee CS, Delucchi K, Parsons PE, Thompson BT, Ware LB, Matthay MA, Thompson T, Ware LB, Matthay MA, Lancet Respir Med 2014, 2:611–-620). However, a major issue is that ARDS is such a heterogeneous, multi-factorial, end-stage condition that the strategies for “lumping and splitting” are critical (Prescott HC, Calfee CS, Thompson BT, Angus DC, Liu VX, Am J Respir Crit Care Med 2016, 194:147–-155). Nevertheless, sequencing of the human genome, the availability of improved methods for analysis of transcription to mRNA (gene expression), and development of sensitive immunoassays has allowed the application of network biology to ARDS, with these biomarkers offering potential for personalised or precision medicine (Sweeney TE, Khatri P, Toward precision medicine Crit Care Med; 2017 45:934-939).

Biomarker panels have potential applications in molecular phenotyping for identifying patients at risk of developing ARDS, diagnosis of ARDS, risk stratification and monitoring. Two subphenotypes of ARDS have been identified on the basis of blood biomarkers: hypo-inflammatory and hyper-inflammatory. The hyper-inflammatory subphenotype is associated with shock, metabolic acidosis and worst clinical outcomes. Biomarkers of particular interest have included interleukins (IL-6 and IL-8), interferon gamma (IFN-γ), surfactant proteins (SPD and SPB), von Willebrand factor antigen, angiopoietin 1/2 and plasminogen activator inhibitor-1 (PAI-1). In terms of gene expression (mRNA) in blood there have been found to be increases in neutrophil-related genes in sepsis-induced and influenza-induced ARDS, but whole blood expression does not give a robust diagnostic test for ARDS.

Despite improvements in management of ARDS on the critical care unit, this complex disease continues to be a major life-threatening event. Clinical trials of β₂-agonists, statins, surfactants and keratinocyte growth factor (KGF) have been disappointing. In addition, monoclonal antibodies (anti-TNF) and TNFR fusion protein have also been unconvincing. However, there have been major advances in methods of mechanical ventilation, a neuromuscular blocker (cisatracurium besilate) has shown some benefit, and stem cell therapy is being developed. In the future, by understanding the role of biomarkers in the pathophysiology of ARDS and lung injury, it is hoped that this will provide rational therapeutic targets and ultimately improve clinical care (Seymour CW, Gomez H, Chang CH, Clermont G, Kellum JA, Kennedy J, Yende S, Angus DC, Crit Care 2017, 21:257).

Rapamycin ameliorates lipopolysaccharide-induced acute lung injury by inhibiting IL-1β and IL-18 production

Interleukin (IL)-1β and IL-18 play central and detrimental roles in the development of acute lung injury (ALI), and mammalian target of rapamycin (mTOR) is involved in regulating IL-1β and IL-18 production. However, it is not clear whether the mTOR specific inhibitor rapamycin can attenuate lipopolysaccharide (LPS)-induced ALI by modulating IL-1β and IL-18 production. In this study, we found that rapamycin ameliorated LPS-induced ALI by inhibiting NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome-mediated IL-1β and IL-18 secretion. Mechanistically, elevated autophagy and decreased nuclear factor (NF)-κB activation were associated with downregulated IL-1β and IL-18. Moreover, rapamycin reduced leukocyte infiltration in the lung tissue and bronchoalveolar lavage fluid (BALF), and contributed to the alleviation of LPS-induced ALI. Consistently, rapamycin also significantly inhibited IL-1β and IL-18 production by RAW264.7 cells via increased autophagy and decreased NF-κB signaling in vitro. Our results demonstrated that rapamycin protects mice against LPS-induced ALI partly by inhibiting the production and secretion of IL-1β and IL-18. mTOR and rapamycin might represent an appropriate therapeutic target and strategy for preventing ALI induced by LPS.

Respiratory failure in the hematopoietic stem cell transplant recipient

The number of patients receiving hematopoietic stem cell transplantation (HSCT) is rapidly rising worldwide. Despite substantial improvements in peri-transplant care, pulmonary complications resulting in respiratory failure remain a major contributor to morbidity and mortality in the post-transplant period, and represent a major barrier to the overall success of HSCT. Infectious complications include pneumonia due to bacteria, viruses, and fungi, and most commonly occur during neutropenia in the early post-transplant period. Non-infectious complications include idiopathic pneumonia syndrome, peri-engraftment respiratory distress syndrome, diffuse alveolar hemorrhage, pulmonary veno-occlusive disease, delayed pulmonary toxicity syndrome, cryptogenic organizing pneumonia, bronchiolitis obliterans syndrome, and post-transplant lymphoproliferative disorder. These complications have distinct clinical features and risk factors, occur at differing times following transplant, and contribute to morbidity and mortality.

Approaches and techniques to avoid development or progression of acute respiratory distress syndrome

PURPOSE OF REVIEW

Despite major improvement in ventilation strategies, hospital mortality and morbidity of the acute respiratory distress syndrome (ARDS) remain high. A lot of therapies have been shown to be ineffective for established ARDS. There is a growing interest in strategies aiming at avoiding development and progression of ARDS.

RECENT FINDINGS

Recent advances in this field have explored identification of patients at high-risk, nonspecific measures to limit the risks of inflammation, infection and fluid overload, prevention strategies of ventilator-induced lung injury and patient self-inflicted lung injury, and pharmacological treatments.

SUMMARY

There is potential for improvement in the management of patients admitted to intensive care unit to reduce ARDS incidence. Apart from nonspecific measures, prevention of ventilator-induced lung injury and patient self-inflicted lung injury are of major importance.

RAB26-dependent autophagy protects adherens junctional integrity in acute lung injury

Microvascular barrier dysfunction is the central pathophysiological feature of acute lung injury (ALI). RAB26 is a newly identified small GTPase involved in the regulation of endothelial cell (EC) permeability. However, the mechanism behind this protection has not been clearly elucidated. Here we found that RAB26 promoted the integrity of adherens junctions (AJs) in a macroautophagy/autophagy-dependent manner in ALI. RAB26 is frequently downregulated in mouse lungs after LPS treatment. Mice lacking Rab26 exhibited phosphorylated SRC expression and increased CDH5/VE-cadherin phosphorylation, leading to AJ destruction. rab26-null mice showed further aggravation of the effects of endotoxin insult on lung vascular permeability and water content. Depletion of RAB26 resulted in upregulation of phosphorylated SRC, enhancement of CDH5 phosphorylation, and aggravation of CDH5 internalization, thereby weakening AJ integrity and endothelial barrier function in human pulmonary microvascular endothelial cells (HPMECs). RAB26 overexpression caused active interaction between SRC and the autophagy marker LC3-II and promoted degradation of phosphorylated SRC. Furthermore, RAB26 was involved in a direct and activation-dependent manner in autophagy induction through interaction with ATG16L1 in its GTP-bound form. These findings demonstrate that RAB26 exerts a protective effect on endothelial cell (EC) permeability, which is in part dependent on autophagic targeting of active SRC, and the resultant CDH5 dephosphorylation maintains AJ stabilization. Thus, RAB26-mediated autophagic targeting of phosphorylated SRC can maintain barrier integrity when flux through the RAB26-SRC pathway is protected. These findings suggest that activation of RAB26-SRC signaling provides a new therapeutic opportunity to prevent vascular leakage in ALI.

ABBREVIATIONS

AJs: adherens junctions; ALI: acute lung injury; ARDS: acute respiratory distress syndrome; ATG5: autophagy related 5; ATG12: autophagy related 12; ATG 16L1: autophagy related 16 like; 1 BALF: bronchoalveolar lavage fluidCQ: chloroquine; Ctrl: control; EC: endothelial cell; GFP: green fluorescent protein; HA-tagged; RAB26^WT: HA-tagged wild-type; RAB26  HA-tagged; RAB26^QL: HA-tagged; RAB26^Q123LHA-tagged; RAB26^NI: HA-tagged; RAB26^N177IHPMECs: human pulmonary microvascular endothelial cells; H&E: hematoxylin & eosin; IgG: immunoglobulin; GIF: immunofluorescence; IP: immunoprecipitationi;. p.: intraperitoneal; LPS: lipopolysaccharide; PBS: phosphate-buffered salinesi; RNA: small interfering;RNASQSTM1/p62, sequestosome; 1TBS: Tris-buffered saline; VEGF: vascular endothelial growth factor; WB: western blot; WT: wild-type.

Amicus or Adversary Revisited: Platelets in Acute Lung Injury and Acute Respiratory Distress Syndrome

Platelets are essential cellular effectors of hemostasis and contribute to disease as circulating effectors of pathologic thrombosis. These are their most widely known biologic activities. Nevertheless, recent observations demonstrate that platelets have a much more intricate repertoire beyond these traditional functions and that they are specialized for contributions to vascular barrier integrity, organ repair, antimicrobial host defense, inflammation, and activities across the immune continuum. Paradoxically, on the basis of clinical investigations and animal models of disease, some of these newly discovered activities of platelets appear to contribute to tissue injury. Studies in the last decade indicate unique interactions of platelets and their precursor, the megakaryocyte, in the lung and implicate platelets as essential effectors in experimental acute lung injury and clinical acute respiratory distress syndrome. Additional discoveries derived from evolving work will be required to precisely define the contributions of platelets to complex subphenotypes of acute lung injury and to determine if these remarkable and versatile blood cells are therapeutic targets in acute respiratory distress syndrome.

Low endocan levels are predictive of Acute Respiratory Distress Syndrome in severe sepsis and septic shock

PURPOSE

Endocan is a circulating proteoglycan measured at high blood levels during severe sepsis, with a likely lung anti-inflammatory function. The aim of this study was to assess whether paradoxically low endocan levels at Intensive Care Unit (ICU) admission could predict Acute Respiratory Distress Syndrome (ARDS) within 72 h in severe septic patients.

MATERIALS AND METHODS

Patients admitted for severe sepsis in the ICU of a French University Hospital were included in a prospective single-center observational study between October 2014 and March 2016.

RESULTS

72 patients admitted in ICU for severe sepsis were included. Endocan blood values at inclusion were significantly lower in patients who developed an ARDS at 72 h (p < 0.001). For endocan blood values > 5.36 ng/mL, the adjusted OR for development of ARDS at 72 h was of 0.001 (95% CI 0-0.215; p = 0.011). In our cohort, an endocan value < 2.54 ng/mL predicted ARDS at 72 h with a positive predictive value of 1 (Sp = 1 (95% CI 0.94-1)).

CONCLUSIONS

In a cohort of severe septic patients, we observed that low blood levels of endocan at ICU admission were predictive of ARDS at 72 h.

Early Intravascular Events Are Associated with Development of Acute Respiratory Distress Syndrome. A Substudy of the LIPS-A Clinical Trial

RATIONALE

Acute respiratory distress syndrome (ARDS) is a devastating illness with limited therapeutic options. A better understanding of early biochemical and immunological events in ARDS could inform the development of new preventive and treatment strategies.

OBJECTIVES

To determine select peripheral blood lipid mediator and leukocyte responses in patients at risk for ARDS.

METHODS

Patients at risk for ARDS were randomized as part of a multicenter, double-blind clinical trial of aspirin versus placebo (the LIPS-A [Lung Injury Prevention Study with Aspirin] trial; NCT01504867). Plasma thromboxane B2 (TXB2), aspirin-triggered lipoxin A4 (15-epi-LXA4, ATL), and peripheral blood leukocyte number and activation were determined on enrollment and after treatment with either aspirin or placebo.

MEASUREMENTS AND MAIN RESULTS

Thirty-three of 367 subjects (9.0%) developed ARDS after randomization. Baseline ATL levels, total monocyte counts, intermediate monocyte counts, and monocyte-platelet aggregates were associated with the development of ARDS. Peripheral blood neutrophil count and monocyte-platelet aggregates significantly decreased over time. Of note, nine subjects developed ARDS after randomization yet before study drug initiation, including seven subjects assigned to aspirin treatment. Subjects without ARDS at the time of first dose demonstrated a lower incidence of ARDS with aspirin treatment. Compared with placebo, aspirin significantly decreased TXB2 and increased the ATL/TXB2 ratio.

CONCLUSIONS

Biomarkers of intravascular monocyte activation in at-risk patients were associated with development of ARDS. The potential clinical benefit of early aspirin for prevention of ARDS remains uncertain. Together, results of the biochemical and immunological analyses provide a window into the early pathogenesis of human ARDS and represent potential vascular biomarkers of ARDS risk. Clinical trial registered with www.clinicaltrials.gov (NCT01504867).

Nrf2 activation protects against intratracheal LPS induced mouse/murine acute respiratory distress syndrome by regulating macrophage polarization

The transcription factor nuclear factor E2-related factor 2 (Nrf2) is known to control the expression of antioxidant response elements and cytoprotective genes and modulate inflammatory response, helping to ameliorate damage in many diseases. Exactly how Nrf2 regulates innate inflammatory homeostasis remains unclear. In this study, we provide in vitro and in vivo evidence that Nrf2 plays a crucial role in macrophage polarization and acute respiratory distress syndrome (ARDS). We conducted in vitro experiments using a mouse alveolar macrophage cell line as well as primary cultures of macrophages in which cells were exposed to lipopolysaccharide (LPS) or interferon-γ in order to mimic ARDS, in the presence or absence of the Nrf2 activator tert-butylhydroquinone (tBHQ). Using siRNA-mediated Nrf2 knockdown, we showed that Nrf2 inhibited the inflammatory response by promoting M2 macrophage polarization and inhibiting M1 macrophage polarization. At the same time, tBHQ activated Nrf2-mediated inhibition of the p65 nuclear factor-κB pathway and activation of peroxisome proliferator-activated receptor-γ, which play important roles in regulating macrophage polarization. We also conducted in vivo experiments in which mice were given tBHQ with or without intratracheal LPS, then their survival was monitored, lung injury was assessed using histology, and levels of pro- and anti-inflammatory cytokines were assayed in the lungs and serum. Activation of Nrf2 with tBHQ dramatically reduced LPS-induced mortality and lung injury, down-regulated pro-inflammatory mediators and up-regulated anti-inflammatory mediators. These results suggest that Nrf2 can help prevent ARDS progression by promoting M2 polarization of macrophages. Interfering with Nrf2 may be an effective strategy for reprogramming macrophage polarization in order to treat ARDS.

High-frequency power of heart rate variability can predict the outcome of thoracic surgical patients with acute respiratory distress syndrome on admission to the intensive care unit: a prospective, single-centric, case-controlled study

BACKGROUND

The morbidity and mortality of acute respiratory distress syndrome (ARDS) remains high, and the strategic focus of ARDS research has shifted toward identifying patients at high risk of mortality early in the course of illness. This study intended to identify the heart rate variability (HRV) measure that can predict the outcome of patients with ARDS on admission to the surgical intensive care unit (SICU).

METHODS

Patients who had lung or esophageal cancer surgery were included either in the ARDS group (n = 21) if they developed ARDS after surgery or in the control group (n = 11) if they did not. The ARDS patients were further stratified into survivors and non-survivors subgroups according to their outcomes. HRV measures of the patients were used for statistical analysis.

RESULTS

The mean RR interval (mRRI), high-frequency power (HFP) and product of low-/high-frequency power ratio tidal volume and tidal volume (LHR*VT) were significantly lower (p < 0.05), while the normalized HFP to VT ratio (nHFP/VT) was significantly higher in the ARDS patients (p = 0.011). The total power (TP), low-frequency power (LFP), HFP and HFP/VT were all significantly higher in the non-survived ARDS patients, whereas Richmond Agitation-Sedation Scale (RASS) was significantly lower in the non-survived ARDS patients. After adjustment for RASS, age and gender, firth logistic regression analysis identified the HFP, TP as the significant independent predictors of mortality for ARDS patients.

CONCLUSIONS

The vagal modulation of thoracic surgical patients with ARDS was enhanced as compared to that of non-ARDS patients, and the non-survived ARDS patients had higher vagal activity than those of survived ARDS patients. The vagal modulation-related parameters such as TP and HFP were independent predictors of mortality in patients with ARDS on admission to the SICU, and the HFP was found to be the best predictor of mortality for those ARDS patients. Increased vagal modulation might be an indicator for poor prognosis in critically ill patients following thoracic surgery.

Receptor for advanced glycation end-products and ARDS prediction: a multicentre observational study

Acute respiratory distress syndrome (ARDS) prediction remains challenging despite available clinical scores. To assess soluble receptor for advanced glycation end-products (sRAGE), a marker of lung epithelial injury, as a predictor of ARDS in a high-risk population, adult patients with at least one ARDS risk factor upon admission to participating intensive care units (ICUs) were enrolled in a multicentre, prospective study between June 2014 and January 2015. Plasma sRAGE and endogenous secretory RAGE (esRAGE) were measured at baseline (ICU admission) and 24 hours later (day one). Four AGER candidate single nucleotide polymorphisms (SNPs) were also assayed because of previous reports of functionality (rs1800625, rs1800624, rs3134940, and rs2070600). The primary outcome was ARDS development within seven days. Of 500 patients enrolled, 464 patients were analysed, and 59 developed ARDS by day seven. Higher baseline and day one plasma sRAGE, but not esRAGE, were independently associated with increased ARDS risk. AGER SNP rs2070600 (Ser/Ser) was associated with increased ARDS risk and higher plasma sRAGE in this cohort, although confirmatory studies are needed to assess the role of AGER SNPs in ARDS prediction. These findings suggest that among at-risk ICU patients, higher plasma sRAGE may identify those who are more likely to develop ARDS.

Acute Respiratory Distress Syndrome Cases Volume and ICU Mortality in Medical Patients

OBJECTIVES

To determine whether ICUs caring for higher volumes of acute respiratory distress syndrome patients would be associated with lower ICU mortality.

DESIGN

A 9-year multicenter retrospective cohort study of prospectively collected data.

SETTING

French medical ICUs.

PATIENTS

From 2004 to 2012, acute respiratory distress syndrome cases were identified from a coding system through a regional database (Collège des Utilisateurs de Données en Réanimation).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Volume was calculated as the cumulative annual mean number of acute respiratory distress syndrome cases. Severity (Simplified Acute Physiology Score 2) and ICU mortality between categories (low, medium, and high) of acute respiratory distress syndrome cases volume were analyzed. Multivariable analysis using mixed effects models was performed to adjust for severity of illness and confounding factors. Over the study period, 8,383 acute respiratory distress syndrome patients among 31 ICUs met the study inclusion criteria. Overall, Simplified Acute Physiology Score 2 (median [interquartile]) was 58 (43-74), whereas ICU mortality was 53.7%. Severity as assessed by Simplified Acute Physiology Score 2 (median [interquartile]) was significantly higher in high-volume ICUs (> 65 acute respiratory distress syndrome per year) as compared to low (≤ 29 acute respiratory distress syndrome per year) and medium-volume ICUs (> 29-65 acute respiratory distress syndrome per year): 61 (46-77) versus 55 (41-72) and 55.0 (40-72), respectively (p < 0.01). ICU mortality was similar across the acute respiratory distress syndrome volume categories (53.6%, 54.1%, and 53.3% in low-, medium-, and high-volume categories ICUs, respectively). After adjustment for confounders, acute respiratory distress syndrome case volume was independently associated with ICU mortality (odds ratio for log-transformed volume: 0.77 [95% CI, 0.62-0.96]; p = 0.02).

CONCLUSIONS

ICUs caring for higher volumes of acute respiratory distress syndrome cases were associated with lower ICU mortality.

Pharmacological modulation of C-X-C motif chemokine receptor 4 influences development of acute respiratory distress syndrome after lung ischaemia-reperfusion injury

Activation of C-X-C motif chemokine receptor 4 (CXCR4) has been reported to result in lung protective effects in various experimental models. The effects of pharmacological CXCR4 modulation on the development of acute respiratory distress syndrome (ARDS) after lung injury, however, are unknown. Thus, we studied whether blockade and activation of CXCR4 influences development of ARDS in a unilateral lung ischaemia-reperfusion injury rat model. Anaesthetized, mechanically ventilated animals underwent right lung ischaemia (series 1, 30 minutes; series 2, 60 minutes) followed by reperfusion for 300 minutes. In series 1, animals were treated with vehicle or 0.7 μmol/kg of AMD3100 (CXCR4 antagonist) and in series 2 with vehicle, 0.7 or 3.5 μmol/kg ubiquitin (non-cognate CXCR4 agonist) within 5 minutes of reperfusion. AMD3100 significantly reduced PaO₂ /FiO₂ ratios, converted mild ARDS with vehicle treatment into moderate ARDS (PaO₂ /FiO₂ ratio<200) and increased histological lung injury. Ubiquitin dose-dependently increased PaO₂ /FiO₂ ratios, converted moderate-to-severe into mild-to-moderate ARDS and reduced protein content of bronchoalveolar lavage fluid (BALF). Measurements of cytokine levels (TNFα, IL-6, IL-10) in lung homogenates and BALF showed that AMD3100 reduced IL-10 levels in homogenates from post-ischaemic lungs, whereas ubiquitin dose-dependently increased IL-10 levels in BALF from post-ischaemic lungs. Our findings establish a cause-effect relationship for the effects of pharmacological CXCR4 modulation on the development of ARDS after lung ischaemia-reperfusion injury. These data further suggest CXCR4 as a new drug target to reduce the incidence and attenuate the severity of ARDS after lung injury.

Inhalation therapies in acute respiratory distress syndrome

The defining features of acute respiratory distress syndrome (ARDS) are an excessive inflammatory respiratory response associated with high morbidity and mortality. Treatment consists mainly of measures to avoid worsening lung injury and cannot reverse the underlying pathophysiological process. New pharmacological agents have shown promising results in preclinical studies; however, they have not been successfully translated to patients with ARDS. The lack of effective therapeutic interventions has resulted in a recent interest in strategies to prevent ARDS with treatments delivering medications directly to the lungs by inhalation and nebulization, hopefully minimizing systemic adverse events. We analyzed the effect of different aerosolized drugs such as bronchodilators, corticosteroids, pulmonary vasodilators, anticoagulants, mucolytics and surfactant. New therapeutic strategies and ongoing trials using carbon monoxide (CO) and AP301 peptide are also briefly reviewed.

Reliability and Validity of the Checklist for Early Recognition and Treatment of Acute Illness and Injury as a Charting Tool in the Medical Intensive Care Unit

Background:

Resuscitation of critically ill patients is complex and potentially prone to diagnostic errors and therapeutic harm. The Checklist for early recognition and treatment of acute illness and injury (CERTAIN) is an electronic tool that aims to provide decision-support, charting, and prompting for standardization. This study sought to evaluate the validity and reliability of CERTAIN in a real-time Intensive Care Unit (ICU).

Materials and Methods:

This was a prospective pilot study in the medical ICU of a tertiary care medical center. A total of thirty patient encounters over 2 months period were charted independently by two CERTAIN investigators. The inter-observer recordings and comparison to the electronic medical records (EMR) were used to evaluate reliability and validity, respectively. The primary outcome was reliability and validity measured using Cohen's Kappa statistic. Secondary outcomes included time to completion, user satisfaction, and learning curve.

Results:

A total of 30 patients with a median age of 59 (42–78) years and median acute physiology and chronic health evaluation III score of 38 (23–50) were included in this study. Inter-observer agreement was very good (κ = 0.79) in this study and agreement between CERTAIN and the EMR was good (κ = 0.5). CERTAIN charting was completed in real-time that was 121 (92–150) min before completion of EMR charting. The subjective learning curve was 3.5 patients without differences in providers with different levels of training.

Conclusions:

CERTAIN provides a reliable and valid method to evaluate resuscitation events in real time. CERTAIN provided the ability to complete data in real-time.