Acute respiratory distress syndrome: underrecognition by clinicians and diagnostic accuracy of three clinical definitions

A pretrain-finetune approach for improving model generalizability in outcome prediction of acute respiratory distress syndrome patients

BACKGROUND

Early prediction of acute respiratory distress syndrome (ARDS) of critically ill patients in intensive care units (ICUs) has been intensively studied in the past years. Yet a prediction model trained on data from one hospital might not be well generalized to other hospitals. It is therefore essential to develop an accurate and generalizable ARDS prediction model adaptive to different hospital or medical centers.

METHODS

We analyzed electronic medical records of 200,859 and 50,920 hospitalized patients within 24 h after being diagnosed with ARDS from the Philips eICU Institute (eICU-CRD) and the Medical Information Mart for Intensive Care (MIMIC-IV) dataset, respectively. Patients were sorted into three groups, including rapid death, long stay, and recovery, based on their condition or outcome between 24 and 72 h after ARDS diagnosis. To improve prediction performance and generalizability, a "pretrain-finetune" approach was applied, where we pretrained models on the eICU-CRD dataset and performed model finetuning using only a part (35%) of the MIMIC-IV dataset, and then tested the finetuned models on the remaining data from the MIMIC-IV dataset. Well-known machine-learning algorithms, including logistic regression, random forest, extreme gradient boosting, and multilayer perceptron neural networks, were employed to predict ARDS outcomes. Prediction performance was evaluated using the area under the receiver-operating characteristic curve (AUC).

RESULTS

Results show that, in general, multilayer perceptron neural networks outperformed the other models. The use of pretrain-finetune yielded improved performance in predicting ARDS outcomes achieving a micro-AUC of 0.870 for the MIMIC-IV dataset, an improvement of 0.046 over the pretrain model.

CONCLUSIONS

The proposed pretrain-finetune approach can effectively improve model generalizability from one to another dataset in ARDS prediction.

Acute Respiratory Distress Syndrome: Definition, Diagnosis, and Routine Management

Acute respiratory distress syndrome (ARDS) is an acute inflammatory lung injury characterized by severe hypoxemic respiratory failure, bilateral opacities on chest imaging, and low lung compliance. ARDS is a heterogeneous syndrome that is the common end point of a wide variety of predisposing conditions, with complex pathophysiology and underlying mechanisms. Routine management of ARDS is centered on lung-protective ventilation strategies such as low tidal volume ventilation and targeting low airway pressures to avoid exacerbation of lung injury, as well as a conservative fluid management strategy.

Protocol and statistical analysis plan for the identification and treatment of hypoxemic respiratory failure and acute respiratory distress syndrome with protection, paralysis, and proning: A type-1 hybrid stepped-wedge cluster randomised effectiveness-implementation study

Objective

To describe a study protocol and statistical analysis plan (SAP) for the identification and treatment of hypoxemic respiratory failure (HRF) and acute respiratory distress syndrome (ARDS) with protection, paralysis, and proning (TheraPPP) study prior to completion of recruitment, electronic data retrieval, and analysis of any data.

Design

TheraPPP is a stepped-wedge cluster randomised study evaluating a care pathway for HRF and ARDS patients. This is a type-1 hybrid effectiveness-implementation study design evaluating both intervention effectiveness and implementation; however primarily powered for the effectiveness outcome.

Setting

Seventeen adult intensive care units (ICUs) across Alberta, Canada.

Participants

We estimate a sample size of 18816 mechanically ventilated patients, with 11424 patients preimplementation and 7392 patients postimplementation. We estimate 2688 sustained ARDS patients within our study cohort.

Intervention

An evidence-based, stakeholder-informed, multidisciplinary care pathway called Venting Wisely that standardises diagnosis and treatment of HRF and ARDS patients.

Main outcome measures

The primary outcome is 28-day ventilator-free days (VFDs). The primary analysis will compare the mean 28-day VFDs preimplementation and postimplementation using a mixed-effects linear regression model. Prespecified subgroups include sex, age, HRF, ARDS, COVID-19, cardiac surgery, body mass index, height, illness acuity, and ICU volume.

Results

This protocol and SAP are reported using the Standard Protocol Items: Recommendations for Interventional Trials guidance and the Guidelines for the Content of Statistical Analysis Plans in Clinical Trials. The study received ethics approval and was registered (ClinicalTrials.gov-NCT04744298) prior to patient enrolment.

Conclusions

TheraPPP will evaluate the effectiveness and implementation of an HRF and ARDS care pathway.

Evaluating construct validity of computable acute respiratory distress syndrome definitions in adults hospitalized with COVID-19: an electronic health records based approach

BACKGROUND

Evolving ARDS epidemiology and management during COVID-19 have prompted calls to reexamine the construct validity of Berlin criteria, which have been rarely evaluated in real-world data. We developed a Berlin ARDS definition (EHR-Berlin) computable in electronic health records (EHR) to (1) assess its construct validity, and (2) assess how expanding its criteria affected validity.

METHODS

We performed a retrospective cohort study at two tertiary care hospitals with one EHR, among adults hospitalized with COVID-19 February 2020-March 2021. We assessed five candidate definitions for ARDS: the EHR-Berlin definition modeled on Berlin criteria, and four alternatives informed by recent proposals to expand criteria and include patients on high-flow oxygen (EHR-Alternative 1), relax imaging criteria (EHR-Alternatives 2-3), and extend timing windows (EHR-Alternative 4). We evaluated two aspects of construct validity for the EHR-Berlin definition: (1) criterion validity: agreement with manual ARDS classification by experts, available in 175 patients; (2) predictive validity: relationships with hospital mortality, assessed by Pearson r and by area under the receiver operating curve (AUROC). We assessed predictive validity and timing of identification of EHR-Berlin definition compared to alternative definitions.

RESULTS

Among 765 patients, mean (SD) age was 57 (18) years and 471 (62%) were male. The EHR-Berlin definition classified 171 (22%) patients as ARDS, which had high agreement with manual classification (kappa 0.85), and was associated with mortality (Pearson r = 0.39; AUROC 0.72, 95% CI 0.68, 0.77). In comparison, EHR-Alternative 1 classified 219 (29%) patients as ARDS, maintained similar relationships to mortality (r = 0.40; AUROC 0.74, 95% CI 0.70, 0.79, Delong test P = 0.14), and identified patients earlier in their hospitalization (median 13 vs. 15 h from admission, Wilcoxon signed-rank test P < 0.001). EHR-Alternative 3, which removed imaging criteria, had similar correlation (r = 0.41) but better discrimination for mortality (AUROC 0.76, 95% CI 0.72, 0.80; P = 0.036), and identified patients median 2 h (P < 0.001) from admission.

CONCLUSIONS

The EHR-Berlin definition can enable ARDS identification with high criterion validity, supporting large-scale study and surveillance. There are opportunities to expand the Berlin criteria that preserve predictive validity and facilitate earlier identification.

Insights Regarding the Berlin Definition of ARDS from Prospective Observational Studies

The definition of acute respiratory distress syndrome (ARDS), has evolved since it was first described in 1967 by Ashbaugh and Petty to the current "Berlin" definition of ARDS developed in 2012 by an expert panel, that provided clarification on the definition of "acute," and on the cardiac failure criteria. It expanded the definition to include patients receiving non-invasive ventilation, and removed the term "acute lung injury" and added a requirement of patients to be receiving a minimum 5 cmH₂O expiratory pressure.Since 2012, a series of observational cohort studies have generated insights into the utility and robustness of this definition. This review will examine novel insights into the epidemiology of ARDS, failures in ARDS diagnosis, the role of lung imaging in ARDS, the novel ARDS cohort that is not invasively ventilated, lung compliance profiles in patients with ARDS, sex differences that exist in ARDS management and outcomes, the progression of ARDS following initial diagnosis, and the clinical profile and outcomes of confirmed versus resolved ARDS. Furthermore, we will discuss studies that challenge the utility of distinguishing ARDS from other causes of acute hypoxemic respiratory failure (AHRF) and identify issues that may need to be addressed in a revised definition.

Serum cytokine changes induced by direct hemoperfusion with polymyxin B-immobilized fiber in patients with acute respiratory failure

BACKGROUND

Polymyxin B-immobilized Fiber therapy (PMX-DHP) may improve the prognosis of patients with rapidly progressive interstitial lung diseases (ILDs). However, the mechanisms by which PMX-DHP ameliorates oxygenation are unclear. The present study aimed to clarify the changes in serum cytokine concentrations during PMX-DHP with steroid pulse therapy.

METHODS

Patients with acute respiratory failure (ARF) and rapidly progressive ILDs, acute exacerbation of idiopathic pulmonary fibrosis (IPF), or acute respiratory distress syndrome (ARDS), and treated with PMX-DHP were assessed, including patients with IPF. The serum concentrations of 38 cytokines were compared between the ARF and IPF groups before treatment. In the ARF group, cytokine levels were compared before, immediately after PMX-DHP, and the day after termination of steroid pulse therapy.

RESULTS

Fourteen ARF and eight IPF patients were enrolled. A comparison of the cytokine levels before treatment initiation revealed that EGF, GRO, IL-10, MDC, IL-12p70, IL-15, sCD40L, IL-7, IP-10, MCP-1, and MIP-1β were significantly different between the two groups. In the ARF group treated with PMX-DHP, the concentrations of MDC, IP-10, and TNF-α continuously decreased during treatment (P < 0.01). Further, the cytokine levels of GRO, IL-10, IL-1Ra, IL-5, IL-6, and MCP-1 decreased after the entire treatment period, with no change observed during the steroid-only period (P < 0.01, except GRO and MCP-1). Although PMX-DHP significantly reduced eotaxin and GM-CSF serum levels (P < 0.01 and P < 0.05), these levels did not change after treatment.

CONCLUSIONS

PMX-DHP combined with steroid pulse therapy might reduce GRO, IL-10, IL-1Ra, IL-5, IL-6, and MCP-1 levels in ARF, contributing to better oxygenation in the disorder.

Protectin D1 protects against lipopolysaccharide-induced acute lung injury through inhibition of neutrophil infiltration and the formation of neutrophil extracellular traps in lung tissue

Protectin D1 (PD1), a DHA-derived lipid mediator, has recently been shown to possess anti-inflammatory and pro-resolving properties. To date, little is known about the effect of PD1 on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice. The aim of the present study was to investigate the therapeutic effects of PD1 on LPS-induced ALI and its potential mechanisms of action. ALI was induced via an intraperitoneal injection of LPS, where PD1 (2 ng/mouse) was administered intravenously 30 min after LPS challenge. Mice were sacrificed 24 h after modeling. Lung histopathological changes were assessed using hematoxylin and eosin staining and myeloperoxidase (MPO) activity was tested using immunohistochemistry. Tumor necrosis-α and interleukin-6 levels in the bronchoalveolar lavage fluid (BALF) and serum were measured using ELISA. To detect neutrophil extracellular traps produced by infiltrated neutrophils in the lung tissue, immunofluorescence staining was performed using anti-MPO and anti-histone H3 antibodies. The results indicated that PD1 significantly attenuated histological damage and neutrophil infiltration in lung tissue, reduced the lung wet/dry weight ratio, protein concentration and proinflammatory cytokine levels in BALF and decreased proinflammatory cytokine levels in serum. Moreover, neutrophil citrullinated histone H3 (CitH3) expression was also reduced after PD1 administration. In conclusion, PD1 attenuated LPS-induced ALI in mice via inhibition of neutrophil extracellular trap formation in lung tissue. Therefore, PD1 administration may serve to be a new strategy for treating ALI.

The Controversy About the Effects of Different Doses of Corticosteroid Treatment on Clinical Outcomes for Acute Respiratory Distress Syndrome Patients: An Observational Study

Background: Corticosteroid usage in acute respiratory distress syndrome (ARDS) remains controversial. We aim to explore the correlation between the different doses of corticosteroid administration and the prognosis of ARDS.

Methods: All patients were diagnosed with ARDS on initial hospital admission and received systemic corticosteroid treatment for ARDS. The main outcomes were the effects of corticosteroid treatment on clinical parameters and the mortality of ARDS patients. Secondary outcomes were factors associated with the mortality of ARDS patients.

Results: 105 ARDS patients were included in this study. Corticosteroid treatment markedly decreased serum interleukin-18 (IL-18) level (424.0 ± 32.19 vs. 290.2 ± 17.14; p = 0.0003) and improved arterial partial pressure of oxygen/fraction of inspired oxygen (PaO₂/FiO₂) (174.10 ± 65.28 vs. 255.42 ± 92.49; p < 0.0001). The acute physiology and chronic health evaluation (APACHE II) score (16.15 ± 4.41 vs. 14.88 ± 4.57, p = 0.042) decreased significantly on the seventh day after systemic corticosteroid treatment. Interestingly, the serum IL-18 decreased significantly (304.52 ± 286.00 vs. 85.85 ± 97.22, p < 0.0001), whereas the improvement of PaO₂/FiO₂ (24.78 ± 35.03 vs. 97.17 ± 44.82, p < 0.001) was inconspicuous after systemic corticosteroid treatment for non-survival patients, compared with survival patients. Furthermore, the receiver operating characteristic (ROC) model revealed, when equivalent methylprednisolone usage was 146.5 mg/d, it had the best sensitivity and specificity to predict the death of ARDS. Survival analysis by Kaplan–Meier curves presented the higher 45-day mortality in high-dose corticosteroid treatment group (logrank test p < 0.0001). Multivariate Cox regression analyses demonstrated that serum IL-18 level, APACHE II score, D-dimer, and high-dose corticosteroid treatment were associated with the death of ARDS.

Conclusion: Appropriate dose of corticosteroids may be beneficial for ARDS patients through improving the oxygenation and moderately inhibiting inflammatory response. The benefits and risks should be carefully weighed when using high-dose corticosteroid for ARDS.

Trial registration: This work was registered in ClinicalTrials.gov. Name of the registry: Corticosteroid Treatment for Acute Respiratory Distress Syndrome. Trial registration number: NCT02819453. URL of trial registry record: https://register.clinicaltrials.gov.

Impact of Clinician Recognition of Acute Respiratory Distress Syndrome on Evidenced-Based Interventions in the Medical ICU

Acute respiratory distress syndrome is underrecognized in the ICU, but it remains uncertain if acute respiratory distress syndrome recognition affects evidence-based acute respiratory distress syndrome care in the modern era. We sought to determine the rate of clinician-recognized acute respiratory distress syndrome in an academic medical ICU and understand how clinician-recognized-acute respiratory distress syndrome affects clinical care and patient-centered outcomes.

DESIGN

Observational cohort study.

SETTING

Single medical ICU at an academic tertiary-care hospital.

PATIENTS

Nine hundred seventy-seven critically ill adults (381 with expert-adjudicated acute respiratory distress syndrome) enrolled from 2006 to 2015.

INTERVENTIONS

Clinician-recognized-acute respiratory distress syndrome was identified using an electronic keyword search of clinical notes in the electronic health record. We assessed the classification performance of clinician-recognized acute respiratory distress syndrome for identifying expert-adjudicated acute respiratory distress syndrome. We also compared differences in ventilator settings, diuretic prescriptions, and cumulative fluid balance between clinician-recognized acute respiratory distress syndrome and unrecognized acute respiratory distress syndrome.

MEASUREMENTS AND MAIN RESULTS

Overall, clinician-recognized-acute respiratory distress syndrome had a sensitivity of 47.5%, specificity 91.1%, positive predictive value 77.4%, and negative predictive value 73.1% for expert-adjudicated acute respiratory distress syndrome. Among the 381 expert-adjudicated acute respiratory distress syndrome cases, we did not observe any differences in ventilator tidal volumes between clinician-recognized-acute respiratory distress syndrome and unrecognized acute respiratory distress syndrome, but clinician-recognized-acute respiratory distress syndrome patients had a more negative cumulative fluid balance (mean difference, -781 mL; 95% CI, [-1,846 to +283]) and were more likely to receive diuretics (49.3% vs 35.7%, p = 0.02). There were no differences in mortality, ICU length of stay, or ventilator-free days.

CONCLUSIONS

Acute respiratory distress syndrome recognition was low in this single-center study. Although acute respiratory distress syndrome recognition was not associated with lower ventilator volumes, it was associated with differences in behaviors related to fluid management. These findings have implications for the design of future studies promoting evidence-based acute respiratory distress syndrome interventions in the ICU.

A survey on the practices and capabilities in the management of respiratory failure in South East England

Introduction

The variability of acute respiratory distress syndrome management may affect the referral practice to severe respiratory failure centres. We described the management of acute respiratory distress syndrome in our catchment area.

Methods

An electronic survey was administered to 42 intensive care units in South-East England.

Results

Response rate was 71.4%. High-flow nasal oxygen and non-invasive ventilation were used 'often' in moderate-acute respiratory distress syndrome by 46.7% and 60%. During invasive ventilation, 90% preferred pressure control, targeting tidal volumes of 6-8 ml/kg (53.3%) or 4-6 ml/kg (46.7%). Positive end-expiratory pressure was selected by positive end-expiratory pressure/inspiratory fraction of oxygen tables (50%) or decremental positive end-expiratory pressure trials (20%). Neuro-muscular blockers were widely used, although routinely by only 3.3%. High-frequency oscillatory ventilation (10%) and inhaled nitric oxide (13.3%) were rarely used. None used oesophageal manometry. Recruitment manoeuvres were used 'often' by 26.7%. Equipment (90%) and protocols (80%) for prone position were common, with sessions mostly lasting 12-18 h.

Conclusions

Although variable, practice well reflected the available evidence. Proning was widely practiced with good availability of educational resources and protocolised care.

Clinician Recognition of the Acute Respiratory Distress Syndrome: Risk Factors for Under-Recognition and Trends Over Time

OBJECTIVES

The acute respiratory distress syndrome is common in critically ill patients. Recognition is crucial because acute respiratory distress syndrome is associated with a high mortality rate, and low tidal volume ventilation improves mortality. However, acute respiratory distress syndrome often goes unrecognized. Risk factors for under-recognition and trends over time have not been fully described.

DESIGN

Retrospective chart review of patients with acute respiratory distress syndrome from a prospective cohort study of critically ill patients. For each patient's ICU stay, we searched the chart for terms that indicated that acute respiratory distress syndrome was diagnosed, in the differential diagnosis, or treated with low tidal volume ventilation.

SETTING

ICUs at a tertiary hospital at the University of California, San Francisco between 2008 and 2016.

PATIENTS

Critically ill patients with acute respiratory distress syndrome.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Acute respiratory distress syndrome was recognized in 70% of patients, and recognition increased from 60% in 2008-2009 to 92% in 2016 (p = 0.004). Use of tidal volumes less than 6.5 mL/kg also increased (p < 0.001) from 20% to 92%. Increased acute respiratory distress syndrome severity (p = 0.01) and vasopressor use (p = 0.04) were associated with greater recognition. Clinician diagnosis of acute respiratory distress syndrome and inclusion of acute respiratory distress syndrome in the differential diagnosis were associated with tidal volumes less than 6.5 mL/kg (51% use of tidal volume ≤ 6.5 mL/kg if acute respiratory distress syndrome recognized vs 15% if not recognized; p = 0.002). Diagnosing acute respiratory distress syndrome was associated with lower tidal volume in multivariate analysis.

CONCLUSIONS

Although acute respiratory distress syndrome recognition and low tidal volume ventilation use have increased over time, they remain less than universal. Clinician recognition of acute respiratory distress syndrome is associated with both systemic and respiratory severity of illness and is also associated with use of low tidal volume ventilation.

Development and Content Validation of a Multidisciplinary Standardized Management Pathway for Hypoxemic Respiratory Failure and Acute Respiratory Distress Syndrome

Supplemental Digital Content is available in the text.

Objectives:

Treatment of hypoxemic respiratory failure and acute respiratory distress syndrome is complex. Evidence-based therapies that can improve survival and guidelines advocating their use exist; however, implementation is inconsistent. Our objective was to develop and validate an evidence-based, stakeholder-informed standardized management pathway for hypoxemic respiratory failure and acute respiratory distress syndrome to improve adherence to best practice.

Design:

A standardized management pathway was developed using a modified Delphi consensus process with a multidisciplinary group of ICU clinicians. The proposed pathway was externally validated with a survey involving multidisciplinary stakeholders and clinicians.

Setting:

In-person meeting and web-based surveys of ICU clinicians from 17 adult ICUs in the province of Alberta, Canada.

Intervention:

Not applicable.

Measurements and Main Results:

The consensus panel was comprised of 30 ICU clinicians (4 nurses, 10 respiratory therapists, 15 intensivists, 1 nurse practitioner; median years of practice 17 [interquartile range, 13–21]). Ninety-one components were serially rated and revised over two rounds of online and one in-person review. The final pathway included 46 elements. For the validation survey, 692 responses (including 59% nurses, 33% respiratory therapists, 7% intensivists and 1% nurse practitioners) were received. Agreement of greater than 75% was achieved on 43 of 46 pathway elements.

Conclusions:

A 46-element evidence-informed hypoxemic respiratory failure and acute respiratory distress syndrome standardized management pathway was developed and demonstrated to have content validity.

Anti-inflammatory Effects of Sweroside on LPS-Induced ALI in Mice Via Activating SIRT1

Sweroside, as one of the main components of Swertia L. in Gentianaceae, has the effect of clearing heat and detoxifying. In previous studies, sweroside has been reported to have anti-inflammatory effect on LPS-induced inflammation by alleviating NF-κB signaling pathway. In this paper, we investigate the anti-inflammatory effects of sweroside by establishing LPS-induced acute lung injury (ALI) model in mice. Experimental results showed that sweroside could reduce the wet-to-dry ratio of the lung and inhibit MPO activity. In addition, it turned out that sweroside reduced pathological changes in lung tissue and the numbers of inflammatory cells. Moreover, sweroside significantly reduced the levels of inflammatory cytokines and down-regulated the NF-κB signaling pathway. And the results demonstrated that sweroside could increase the expression of SIRT1, and the protective effects of sweroside on LPS-induced ALI were reversed by SIRT1 inhibitor EX-527. In conclusion, sweroside can protect LPS-induced ALI mice through inhibiting inflammation.

The NLRP3-Inflammasome-Caspase-1 Pathway Is Upregulated in Idiopathic Pulmonary Fibrosis and Acute Exacerbations and Is Inducible by Apoptotic A549 Cells

Idiopathic pulmonary fibrosis (IPF) is a relentlessly progressive disease harboring significant morbidity and mortality despite recent advances in therapy. Regardless of disease severity acute exacerbations (IPF-AEs) may occur leading to considerable loss of function and are the leading cause of death in IPF. Histologic features of IPF-AE are very similar to acute respiratory distress syndrome (ARDS), but the underlying mechanisms are incompletely understood. We investigated the role of the NLRP3 inflammasome in IPF and IPF-AE. Bronchoalveolar lavage (BAL) cells were sampled from patients with IPF (n = 32), IPF-AE (n = 10), ARDS (n = 7) and healthy volunteers (HV, n = 37) and the NLRP3-inflammasome was stimulated in-vitro. We found the NLRP3 inflammasome to be hyper-inducible in IPF compared to HV with increased IL-1ß and pro-IL-1ß levels on ELISA upon stimulation as well as increased caspase-1 activity measured by caspase-1p20 immunoblotting. In IPF-AE, IL-1ß was massively elevated to an extent similar to ARDS. To evaluate potential mechanisms, we co-cultured BAL cells with radiated A549 cells (a model to simulate apoptotic alveolar epithelial cells), which led to increased NLRP3 mRNA expression and increased caspase-1 dependent IL-1ß production. In the presence of a reactive oxygen species (ROS) inhibitor (diphenyleneiodonium) and a cathepsin B inhibitor (E64D), NLRP3 expression was suppressed indicating that induction of NLRP3 activation following efferocytosis of apoptotic A549 cells is mediated via ROS and cathepsin-B. In summary, we present evidence of involvement of the NLRP3 inflammasome-caspase pathway in the pathogenesis of IPF-AE, similarly to ARDS, which may be mediated by efferocytosis of apoptotic alveolar epithelial cells in IPF.

Manipulation of ACE2 expression in COVID-19

SARS-CoV-2 is the virus responsible for the ongoing COVID-19 outbreak. The virus uses ACE2 receptor for viral entry. ACE2 is part of the counter-regulatory renin-angiotensin-aldosterone system and is also expressed in the lower respiratory tract along the alveolar epithelium. There is, however, significant controversy regarding the role of ACE2 expression in COVID-19 pathogenesis. Some have argued that decreasing ACE2 expression would result in decreased susceptibility to the virus by decreasing available binding sites for SARS-CoV-2 and restricting viral entry into the cells. Others have argued that, like the pathogenesis of other viral pneumonias, including those stemming from previous severe acute respiratory syndrome (SARS) viruses, once SARS-CoV-2 binds to ACE2, it downregulates ACE2 expression. Lack of the favourable effects of ACE2 might exaggerate lung injury by a variety of mechanisms. In order to help address this controversy, we conducted a literature search and review of relevant preclinical and clinical publications pertaining to SARS-CoV-2, COVID-19, ACE2, viral pneumonia, SARS, acute respiratory distress syndrome and lung injury. Our review suggests, although controversial, that patients at increased susceptibility to COVID-19 complications may have reduced baseline ACE2, and by modulating ACE2 expression one can possibly improve COVID-19 outcomes. Herein, we elucidate why and how this potential mechanism might work.

Epidemiology and Outcomes of Acute Respiratory Distress Syndrome Following Isolated Severe Traumatic Brain Injury

Patients with traumatic brain injury (TBI) are at risk for extra-cranial complications, such as the acute respiratory distress syndrome (ARDS). We conducted an analysis of risk factors, mortality, and healthcare utilization associated with ARDS following isolated severe TBI. The National Trauma Data Bank (NTDB) dataset files from 2007-2014 were used to identify adult patients who suffered isolated [other body region-specific Abbreviated Injury Scale (AIS) < 3] severe TBI [admission total Glasgow Coma Scale (GCS) from 3 to 8 and head region-specific AIS >3]. In-hospital mortality was compared between patients who developed ARDS and those who did not. Utilization of healthcare resources (ICU length of stay, hospital length of stay, duration of mechanical ventilation, and frequency of tracheostomy and gastrostomy tube placement) was also examined. This retrospective cohort study included 38,213 patients with an overall ARDS occurrence of 7.5%. Younger age, admission tachycardia, pre-existing vascular and respiratory diseases, and pneumonia were associated with the development of ARDS. Compared to patients without ARDS, patients that developed ARDS experienced increased in-hospital mortality (OR 1.13, 95% CI 1.01-1.26), length of stay (p = <0.001), duration of mechanical ventilation (p = < 0.001), and placement of tracheostomy (OR 2.70, 95% CI 2.34-3.13) and gastrostomy (OR 2.42, 95% CI 2.06-2.84). After isolated severe TBI, ARDS is associated with increased mortality and healthcare utilization. Future studies should focus on both prevention and management strategies specific to TBI-associated ARDS.

Purified β-glucans from the Shiitake mushroom ameliorates antibiotic-resistant Klebsiella pneumoniae-induced pulmonary sepsis

Bacterial infection remains the main cause of acute respiratory distress syndrome and is a leading cause of death and disability in critically ill patients. Here we report on the use of purified β-glucan (lentinan) extracts from Lentinus edodes (Shiitake) mushroom that can reduce infection by a multidrug-resistant clinical isolate of Klebsiella pneumoniae in a rodent pneumonia model, likely through immunomodulation. Adult male Sprague-Dawley rats were subjected to intra-tracheal administration of K. pneumoniae to induce pulmonary sepsis and randomized to three groups; vehicle control (Vehicle, n = 12), commercial lentinan (CL, n = 8) or in-house extracted lentinan (IHL, n = 8) were administered intravenously 1 h postinfection. Physiological parameters and blood gas analysis were measured, bacterial counts from bronchoalveolar-lavage (BAL) were determined, along with differential staining of white cells and measurement of protein concentration in BAL 48 h after pneumonia induction. Use of IHL extract significantly decreased BAL CFU counts. Both CL and IHL extractions reduced protein concentration in BAL. Use of IHL resulted in an improvement in physiological parameters compared to controls and CL. In conclusion, administration of lentinan to treat sepsis-induced lung injury appears safe and effective and may exert its effects in an immunomodulatory manner.

Pharmacological management of adult patients with acute respiratory distress syndrome

INTRODUCTION

There is still no definite drug for acute respiratory distress syndrome (ARDS) that is capable of reducing either short-term or long-term mortality. Therefore, great efforts are being made to identify a pharmacological approach that can be really effective.

AREAS COVERED

This review focuses on current challenges and future directions in the pharmacological management of ARDS, regardless of anti-infective treatments. The authors have excluded small randomized controlled trials (RCTs) with less than 60 patients because those studies do not have statistical power for outcome data, and also anecdotal trials but have considered the last meta-analysis on any drug.

EXPERT OPINION

There has been substantial progress in our knowledge of ARDS over the past two decades and many drugs have been used in its treatment. Nevertheless, effective targeted pharmacological treatments for ARDS are still lacking. The likely reason why a pharmacological approach is beneficial for some patients, but harmful for others is that ARDS is an extremely heterogeneous syndrome. To overcome this issue, a precision approach for ARDS, whereby therapies are specifically targeted to patients most likely to benefit, has been proposed. At present, however, the application of this approach seems to be a difficult task.

Can Serum Fibrinogen Predict ARDS?

Acute respiratory distress syndrome (ARDS) has a worldwide mortality of 10% to 30% with severe pneumonia being the primary cause. Diagnosis relies on clinical criteria which may lead to under-recognition and delayed evidence-based interventions. In previous studies, plasma fibrinogen was associated with progression to ARDS among patients with severe pneumonia. This is a prospective cohort study wherein we hypothesized that levels of plasma fibrinogen and change in levels of fibrinogen can predict development of ARDS among a cohort of patients with severe pneumonia based on the Infectious Diseases Society of America (IDSA) and the American Thoracic Society (ATS) consensus criteria. After acquiring consent, plasma fibrinogen levels were extracted upon enrollment and after 48 hours. These extraction times were arbitrarily chosen to determine whether levels rise or decline in relation to the course of disease. A total of 47 patients were prospectively followed within 7 days of enrollment, then divided into 2 groups, which included those who developed ARDS (n = 12, 25%) and those who did not (n = 35, 75%). Fibrinogen levels at baseline had sensitivity and specificity of 41.7% and 57.1%, respectively (P = .932) with an area under the curve (AUC) of 0.492; levels after 48 hours had sensitivity and specificity of 55.6% and 65.6%, respectively (P = .729) with an AUC of 0.538; and delta fibrinogen levels had sensitivity and specificity of 55.6% and 62.5%, respectively (P = 0.581) with an AUC of 0.561. Based on this study, plasma fibrinogen is an unreliable biomarker for predicting ARDS development in patients with severe pneumonia. In setting up this study, we experienced limitations which we had to accept but realizations of these led to the discovery of potential research areas. To our knowledge, this is the first Philippine study attempting to discover a biomarker for ARDS progression. It is recommended that further investigation on local incidence and other biomarkers for ARDS should be done.

Diagnostic accuracy of portable chest radiograph in mechanically ventilated patients when compared with autopsy findings

PURPOSE

Evaluate diagnostic accuracy of portable chest radiograph in mechanically ventilated patients taking autopsy findings as the gold standard and the interobserver agreement among intensivists and radiologists.

MATERIALS AND METHODS

Retrospective study of 422 patients over 22 years who died in the ICU, underwent an autopsy, and had at least one portable chest radiograph 72 h prior to death. Two intensivists and two radiologists independently read each chest radiograph. Sensitivity, specificity, positive and negative likelihood ratios were evaluated. Overall performance metrics accuracy between intensivists and radiologists were compared using a generalized estimating equation. Cohen's kappa coefficient was used to evaluate the interobserver agreement with the following values: <0.20:poor, 0.21-0.40:fair, 0.41-0.60:moderate, 0.61-0.80:good, 0.81-1.00:excellent.

RESULTS

Overall sensitivity and specificity for pneumonia was 24% and 91% respectively. Overall sensitivity and specificity for ARDS was 68% and 74% respectively. Sensitivity for pneumonia was higher among radiologists (p < 0,05). Specificity for ADRS was higher among radiologists (p < 0,05). Good interobserver agreement among radiologists and poor correlation between intensivists was found.

CONCLUSIONS

Chest radiographs has a moderate specificity for ARDS and a high specificity for pneumonia, with limited sensitivity in both entities. Interobserver agreement of portable chest radiograph in the mechanically ventilated patients is higher between radiologists than intensivists.

Global and Regional Diagnostic Accuracy of Lung Ultrasound Compared to CT in Patients With Acute Respiratory Distress Syndrome

OBJECTIVES

Lung CT is the reference imaging technique for acute respiratory distress syndrome, but requires transportation outside the intensive care and x-ray exposure. Lung ultrasound is a promising, inexpensive, radiation-free, tool for bedside imaging. Aim of the present study was to compare the global and regional diagnostic accuracy of lung ultrasound and CT scan.

DESIGN

A prospective, observational study.

SETTING

Intensive care and radiology departments of a University hospital.

PATIENTS

Thirty-two sedated, paralyzed acute respiratory distress syndrome patients (age 65 ± 14 yr, body mass index 25.9 ± 6.5 kg/m, and PaO2/FIO2 139 ± 47).

INTERVENTIONS

Lung CT scan and lung ultrasound were performed at positive end-expiratory pressure 5 cm H2O. A standardized assessment of six regions per hemithorax was used; each region was classified for the presence of normal aeration, alveolar-interstitial syndrome, consolidation, and pleural effusion. Agreement between the two techniques was calculated, and diagnostic variables were assessed for lung ultrasound using lung CT as a reference.

MEASUREMENTS AND MAIN RESULTS

Global agreement between lung ultrasound and CT ranged from 0.640 (0.391-0.889) to 0.934 (0.605-1.000) and was on average 0.775 (0.577-0.973). The overall sensitivity and specificity of lung ultrasound ranged from 82.7% to 92.3% and from 90.2% to 98.6%, respectively. Similar results were found with regional analysis. The diagnostic accuracy of lung ultrasound was significantly higher when those patterns not reaching the pleural surface were excluded (area under the receiver operating characteristic curve: alveolar-interstitial syndrome 0.854 [0.821-0.887] vs 0.903 [0.852-0.954]; p = 0.049 and consolidation 0.851 [0.818-0.884] vs 0.896 [0.862-0.929]; p = 0.044).

CONCLUSIONS

Lung ultrasound is a reproducible, sensitive, and specific tool, which allows for bedside detections of the morphologic patterns in acute respiratory distress syndrome. The presence of deep lung alterations may impact the diagnostic performance of this technique.

Aetiology and Short-Term Outcome of Acute Respiratory Distress Syndrome: A Real-World Experience from a Medical Intensive Care Unit in Southern India

Background

Acute respiratory distress syndrome (ARDS) is a highly fatal syndrome especially in resource constrained settings. In this study we prospectively studied the aetiology of ARDS and its short-term outcome.

Methods

Consecutive adults with suspected ARDS were screened. ARDS was diagnosed by the Berlin criteria. Aetiology was determined clinically, and by imaging and microbiological investigations. Patients presenting with fever, prominent cough and expectoration had a throat swab tested for influenza H1N1 virus. Outcome was discharge from hospital or death.

Results

A total of 42 patients, mean age 42.6 years, were studied. All received mechanical ventilation. Thirteen (31%) had pulmonary ARDS: H1N1 virus infection (n = 5), pneumonia (n = 7) and tuberculosis (n = 1). Twenty nine (69%) had extrapulmonary ARDS: sepsis (n = 16) and scrub typhus (n = 8). Thirty three (79%) died, of the nine survivors scrub typhus was diagnosed in seven patients.

Conclusion

The aetiology of ARDS in tropical medical setting is infection related. ARDS due to scrub typhus appeared to be mild with good outcome.

An NMR based panorama of the heterogeneous biology of acute respiratory distress syndrome (ARDS) from the standpoint of metabolic biomarkers

Acute respiratory distress syndrome (ARDS), manifested by intricate etiology and pathophysiology, demands careful clinical surveillance due to its high mortality and imminent life support measures. NMR based metabolomics provides an approach for ARDS which culminates from a wide spectrum of illness thereby confounding early manifestation and prognosis predictors. ¹ H NMR with its manifold applications in critical disease settings can unravel the biomarker of ARDS thus holding potent implications by providing surrogate endpoints of clinical utility. NMR metabolomics which is the current apogee platform of omics trilogy is contributing towards the possible panacea of ARDS by subsequent validation of biomarker credential on larger datasets. In the present review, the physiological derangements that jeopardize the whole metabolic functioning in ARDS are exploited and the biomarkers involved in progression are addressed and substantiated. The following sections of the review also outline the clinical spectrum of ARDS from the standpoint of NMR based metabolomics which is an emerging element of systems biology. ARDS is the main premise of intensivists textbook, which has been thoroughly reviewed along with its incidence, progressive stages of severity, new proposed diagnostic definition, and the preventive measures and the current pitfalls of clinical management. The advent of new therapies, the need for biomarkers, the methodology and the contemporary promising approaches needed to improve survival and address heterogeneity have also been evaluated. The review has been stepwise illustrated with potent biometrics employed to selectively pool out differential metabolites as diagnostic markers and outcome predictors. The following sections have been drafted with an objective to better understand ARDS mechanisms with predictive and precise biomarkers detected so far on the basis of underlying physiological parameters having close proximity to diseased phenotype. The aim of this review is to stimulate interest in conducting more studies to help resolve the complex heterogeneity of ARDS with biomarkers of clinical utility and relevance.

Imaging the Injured Lung: Mechanisms of Action and Clinical Use

Acute respiratory distress syndrome (ARDS) consists of acute hypoxemic respiratory failure characterized by massive and heterogeneously distributed loss of lung aeration caused by diffuse inflammation and edema present in interstitial and alveolar spaces. It is defined by consensus criteria, which include diffuse infiltrates on chest imaging-either plain radiography or computed tomography. This review will summarize how imaging sciences can inform modern respiratory management of ARDS and continue to increase the understanding of the acutely injured lung. This review also describes newer imaging methodologies that are likely to inform future clinical decision-making and potentially improve outcome. For each imaging modality, this review systematically describes the underlying principles, technology involved, measurements obtained, insights gained by the technique, emerging approaches, limitations, and future developments. Finally, integrated approaches are considered whereby multimodal imaging may impact management of ARDS.

Risk factors, characteristics, and outcomes of acute respiratory distress syndrome in dogs and cats: 54 cases

OBJECTIVE

To characterize the clinical features of the acute respiratory distress syndrome (ARDS), risk factors, and outcome in dogs and cats. The study also aimed to evaluate the current veterinary criteria for the diagnosis of ARDS by comparison of clinical diagnostic criteria with necropsy findings.

DESIGN

Retrospective study.

ANIMALS

Fifty-four client-owned animals, 46 dogs and 8 cats.

INTERVENTIONS

Medical records were reviewed for patients with the diagnosis of ARDS based on previously published clinical criteria or necropsy diagnosis. Signalment, clinical findings, and outcome were recorded.

MEASUREMENTS AND MAIN RESULTS

Animals were grouped according to a clinical or necropsy diagnosis: 43/54 (80%) were diagnosed with ARDS based on clinical criteria (group 1) and 11/54 (20%) were diagnosed with ARDS based on necropsy only (group 2). In group 1, 22/43 (51%) had a necropsy, which confirmed ARDS in 12/22 (54%). Direct (pulmonary) causes of ARDS were more common than indirect causes in dogs, while cats had a similar occurrence of direct and indirect causes. The most common risk factors identified in dogs were aspiration pneumonia (42%), systemic inflammatory response syndrome (SIRS) (29%), and shock (29%). All cats diagnosed clinically with ARDS had SIRS with or without sepsis. Of the animals with a clinical diagnosis of ARDS, 49% received mechanical ventilation and 58% received treatment (with or without mechanical ventilation) for 24 hours or longer. The overall case fatality rate was 84% in dogs and 100% in cats.

CONCLUSIONS AND CLINICAL RELEVANCE

As described in human literature, pneumonia was the most common risk factor in dogs with ARDS, whereas it was SIRS for the cat population. The high mortality rate and discrepancy between the clinical diagnosis and necropsy findings may highlight limitations in the clinical criteria for the diagnosis of ARDS and treatment in dogs and cats.

Network Pharmacology-Based Investigation of Protective Mechanism of Aster tataricus on Lipopolysaccharide-Induced Acute Lung Injury

Acute lung injury (ALI) is a common clinical condition that badly influences people's health. Recent studies indicated that Aster tataricus (RA) had potential effects on ALI, but the effective components and their mechanism is not clear. In this study, we found that the Fraction-75 eluted from RA extract could significantly protect the lipopolysaccharide (LPS)-induced ALI in mice, including alleviating the severity of lung pathology, attenuating the pulmonary edema, and reducing the release of inflammatory cells. Further ingredient analyses demonstrated that there were mainly 16 components in it, among which 10 components were collected according to their relative peak area and oral bioavailability. Next, the components-disease targets network suggested that the candidate components had extensive associations with 49 known therapeutic targets of ALI, among which 31 targets could be regulated by more than one component. Herein, GO functional and pathway analysis revealed that the common targets were associated with four biological processes, including the inflammatory response to stimulus, cellular process, chemokine biosynthetic process and immune system process. Furthermore, the ELISA validation indicated that the candidate components in RA extract may protect the LPS-induced ALI mainly through inhibiting the release of inflammatory cytokines and promoting the repair of vascular endothelial.

Practice of diagnosis and management of acute respiratory distress syndrome in mainland China: a cross-sectional study

Background

Although acute respiratory distress syndrome (ARDS) has been recognized for more than 50 years, limited information exists about the incidence and management of ARDS in mainland China. To evaluate the potential for improvement in management of patients with ARDS, this study was designed to describe the incidence and management of ARDS in mainland China.

Methods

, 2012) of all patients who fulfilled the Berlin or American European Consensus Conference (AECC) definition of ARDS in 20 intensive care units, with data collection related to the management of ARDS, patient characteristics and outcomes.

Results

was 90%. A recruitment maneuver was performed in 35.5% of the patients, and 8.7% of patients with severe ARDS received prone position. Overall hospital mortality was 34.0%. Hospital mortality was 21.8% for mild, 31.1% for moderate, and 60.0% for patients with severe ARDS (P=0.004).

Conclusions

Despite general acceptance of low Vt and limited Pplat, high driving pressure, low PEEP and low use of adjunctive measures may still be a concern in mainland China, especially in patients with severe ARDS.

Trial Registration

2012.

Simulation Training for Residents Focused on Mechanical Ventilation: A Randomized Trial Using Mannequin-Based Versus Computer-Based Simulation

Supplemental digital content is available in the text.

Introduction

Advances in knowledge regarding mechanical ventilation (MV), in particular lung-protective ventilation strategies, have been shown to reduce mortality. However, the translation of these advances in knowledge into better therapeutic performance in real-life clinical settings continues to lag. High-fidelity simulation with a mannequin allows students to interact in lifelike situations; this may be a valuable addition to traditional didactic teaching. The purpose of this study is to compare computer-based and mannequin-based approaches for training residents on MV.

Methods

This prospective randomized single-blind trial involved 50 residents. All participants attended the same didactic lecture on respiratory pathophysiology and were subsequently randomized into two groups: the mannequin group (n = 25) and the computer screen–based simulator group (n = 25). One week later, each underwent a training assessment using five different scenarios of acute respiratory failure of different etiologies. Later, both groups underwent further testing of patient management, using in situ high-fidelity simulation of a patient with acute respiratory distress syndrome.

Results

Baseline knowledge was not significantly different between the two groups (P = 0.72). Regarding the training assessment, no significant differences were detected between the groups. In the final assessment, the scores of only the mannequin group significantly improved between the training and final session in terms of either global rating score [3.0 (2.5–4.0) vs. 2.0 (2.0–3.0), P = 0.005] or percentage of key score (82% vs. 71%, P = 0.001).

Conclusions

Mannequin-based simulation has the potential to improve skills in managing MV.

Ginsenoside Rg3 Attenuates Lipopolysaccharide-Induced Acute Lung Injury via MerTK-Dependent Activation of the PI3K/AKT/mTOR Pathway

Acute lung injury (ALI) is a common clinical disease with high morbidity in both humans and animals. Ginsenoside Rg3, a type of traditional Chinese medicine extracted from ginseng, is widely used to cure many inflammation-related diseases. However, the specific molecular mechanism of the effects of ginsenoside Rg3 on inflammation has rarely been reported. Thus, we established a mouse model of lipopolysaccharide (LPS)-induced ALI to investigate the immune protective effects of ginsenoside Rg3 and explore its molecular mechanism. In wild type (WT) mice, we found that ginsenoside Rg3 treatment significantly mitigated pathological damages and reduced myeloperoxidase (MPO) activity as well as the production of pro-inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6); furthermore, the production of anti-inflammatory mediators interleukin-10 (IL-10) and transforming growth factor-β (TGF-β), polarization of M2 macrophages and expression levels of the phosphorylation of phosphatidylinositol 3-hydroxy kinase (PI3K), protein kinase B (PKB, also known as AKT), mammalian target of rapamycin (mTOR) and Mer receptor tyrosine kinase (MerTK) were promoted. However, there were no significant differences with regards to the pathological damage, MPO levels, inflammatory cytokine levels, and protein expression levels of the phosphorylation of PI3K, AKT and mTOR between the LPS treatment group and ginsenoside Rg3 group in MerTK^-/- mice. Taken together, the present study demonstrated that ginsenoside Rg3 could attenuate LPS-induced ALI by decreasing the levels of pro-inflammatory mediators and increasing the production of anti-inflammatory cytokines. These processes were mediated through MerTK-dependent activation of its downstream the PI3K/AKT/mTOR pathway. These findings identified a new site of the specific anti-inflammatory mechanism of ginsenoside Rg3.

Translating evidence into practice in acute respiratory distress syndrome: teamwork, clinical decision support, and behavioral economic interventions

PURPOSE OF REVIEW

Although the treatment of the acute respiratory distress syndrome (ARDS) with low tidal volume (LTV) mechanical ventilation improves mortality, it is not consistently administered in clinical practice. This review examines strategies to improve LTV and other evidence-based therapies for patients with ARDS.

RECENT FINDINGS

Despite the well established role of LTV in the treatment of ARDS, a recent multinational study suggests it is under-utilized in clinical practice. Strategies to improve LTV include audit and feedback, provider education, protocol development, interventions to improve ICU teamwork, computer decision support, and behavioral economic interventions such as making LTV the default-ventilator setting. These strategies typically target all patients receiving invasive mechanical ventilation, effectively avoiding the problem of poor ARDS recognition in clinical practice. To more effectively administer advanced ARDS therapies, such as prone positioning, better approaches for ARDS recognition will also be required.

SUMMARY

Multiple strategies can be utilized to improve adherence to LTV ventilation in ARDS patients.

Extravascular lung water measurements in acute respiratory distress syndrome: why, how, and when?

PURPOSE OF REVIEW

Increase in pulmonary vascular permeability accompanied with accumulation of excess extravascular lung water (EVLW) is the hallmark of acute respiratory distress syndrome (ARDS). Currently, EVLW and pulmonary vascular permeability index (PVPI) can be quantitatively measured using the transpulmonary thermodilution (TPTD) technique. We will clarify why, how, and when EVLW and PVPI measurements should be performed.

RECENT FINDINGS

Although the Berlin criteria of ARDS are simple and widely used, several criticisms of them have been published. The last 2 decades have witnessed the introduction and evolution of the TPTD technique for measuring EVLW and PVPI. Several publications have recommended to evaluate EVLW and the PVPI during the treatment of critically ill patients. Accurate and objective diagnoses can be made for ARDS patients using EVLW and PVPI. EVLW more than 10 ml/kg is a reasonable criterion for pulmonary edema, and EVLW more than 15 ml/kg for a severe condition. In addition to EVLW more than 10 mL/kg, PVPI more than three suggests increased vascular permeability (i.e., ARDS), and PVPI less than 2 represent normal vascular permeability (i.e., cardiogenic pulmonary edema).

SUMMARY

EVLW and PVPI measurement will open the door to future ARDS clinical practice and research, and have potential to be included in the future ARDS definition.

Mild to Moderate to Severe: What Drives the Severity of ARDS in Trauma Patients?

Acute respiratory distress syndrome (ARDS) is a complex inflammatory process with multifactorial etiologies. Risk factors for its development have been extensively studied, but factors associated with worsening severity of disease, as defined by the Berlin criteria, are poorly understood. A retrospective chart and trauma registry review identified trauma patients in our surgical intensive care unit who developed ARDS, defined according to the Berlin definition, between 2010 and 2015. The primary outcome was development of mild, moderate, or severe ARDS. A logistic regression model identified risk factors associated with developing ARDS and with worsening severity of disease. Of 2704 total patients, 432 (16%) developed ARDS. Of those, 100 (23%) were categorized as mild, 176 (41%) as moderate, and 156 (36%) as severe. Two thousand two hundred and seventy-two patients who did not develop ARDS served as controls. Male gender, blunt trauma, severe head and chest injuries, and red blood cell as well as total blood product transfusions are independent risk factors associated with ARDS. Worsening severity of disease is associated with severe chest trauma and volume of plasma transfusion. Novel findings in our study include the association between plasma transfusions and specifically severe chest trauma with worsening severity of ARDS in trauma patients.

Six-Month Outcome of Immunocompromised Patients with Severe Acute Respiratory Distress Syndrome Rescued by Extracorporeal Membrane Oxygenation. An International Multicenter Retrospective Study

Rationale: Because encouraging rates for hospital and long-term survival of immunocompromised patients in ICUs have been described, these patients are more likely to receive invasive therapies, like extracorporeal membrane oxygenation (ECMO).Objectives: To report outcomes of immunocompromised patients treated with ECMO for severe acute respiratory distress syndrome (ARDS) and to identify their pre-ECMO predictors of 6-month mortality and main ECMO-related complications.Methods: Retrospective multicenter study in 10 international ICUs with high volumes of ECMO cases. Immunocompromised patients, defined as having hematological malignancies, active solid tumor, solid-organ transplant, acquired immunodeficiency syndrome, or long-term or high-dose corticosteroid or immunosuppressant use, and severe ECMO-treated ARDS, from 2008 to 2015 were included.Measurements and Main Results: We collected demographics, clinical data, ECMO-related complications, and ICU- and 6 month-outcome data for 203 patients (median Acute Physiology and Chronic Health Evaluation II score, 28 [25th-75th percentile, 20-33]; age, 51 [38-59] yr; Pa_O2/Fi_O2, 60 [50-82] mm Hg before ECMO) who fulfilled our inclusion criteria. Six-month survival was only 30%, with a respective median ECMO duration and ICU stay of 8 (5-14) and 25 (16-50) days. Patients with hematological malignancies had significantly poorer outcomes than others (log-rank P = 0.02). ECMO-related major bleeding, cannula infection, and ventilator-associated pneumonia were frequent (36%, 10%, and 50%, respectively). Multivariate analyses retained fewer than 30 days between immunodeficiency diagnosis and ECMO cannulation as being associated with lower 6-month mortality (odds ratio, 0.32 [95% confidence interval, 0.16-0.66]; P = 0.002), and lower platelet count, higher Pco₂, age, and driving pressure as independent pre-ECMO predictors of 6-month mortality.Conclusions: Recently diagnosed immunodeficiency is associated with a much better prognosis in ECMO-treated severe ARDS. However, low 6-month survival of our large cohort of immunocompromised patients supports restricting ECMO to patients with realistic oncological/therapeutic prognoses, acceptable functional status, and few pre-ECMO mortality-risk factors.

Continued under-recognition of acute respiratory distress syndrome after the Berlin definition: what is the solution?

PURPOSE OF REVIEW

Timely recognition of acute respiratory distress syndrome (ARDS) may allow for more prompt management and less exacerbation of lung injury. However, the absence of a diagnostic test for ARDS means that the diagnosis of ARDS requires clinician recognition in what is usually a complicated and evolving illness. We review data concerning the extent of recognition of ARDS in the era of the Berlin definition of ARDS.

RECENT FINDINGS

ARDS continues to be under-recognized - even in the era of the more recent 'Berlin' definition, and significant delay in its recognition is common. Factors contributing to under-recognition may include the complexity of ARDS biology, low specificity of the consensus (diagnostic) criteria, and concerns about reliable interpretation of the chest radiograph. Understandably, 'external' factors are also at play: ICU occupancy and higher patient to clinician ratio impair recognition of ARDS. Timely recognition of ARDS appears important, as it is associated with the use of higher PEEP, prone positioning and neuromuscular blockade which can lower mortality. Computer-aided decision tools seem diagnostically useful, and together with the integration of reliable biomarkers, may further enhance and speed recognition of this syndrome.

SUMMARY

Significant numbers of patients with ARDS are still unrecognized by clinicians in the era of the Berlin definition of ARDS, with potentially important consequences for patient management and outcome.

Acute respiratory distress syndrome mimics: the role of lung biopsy

PURPOSE OF REVIEW

Acute respiratory distress syndrome (ARDS) mimics is a condition looking like ARDS but that does not fulfill every criterion according to the recent Berlin definition. The purpose of this review is to better delineate ARDS mimics, to discuss why the complete diagnosis of ARDS is important, and to make a brief overview on the role of open lung biopsy in this setting.

RECENT FINDINGS

Recent autopsy and lung biopsy data from ARDS patients compared lung histologic findings with the new Berlin definition of ARDS. Among them, there are some limited data about two niches, namely open lung biopsy and ARDS mimics suggesting that lung histology is important for making the diagnosis and offering the accurate management. This includes specific new treatments or stopping some medications toxic to the lung. Finally, ARDS with diffuse alveolar damage could be a specific subphenotype of ARDS with poor prognosis.

SUMMARY

An ARDS mimic enhances the need of making ARDS diagnosis as comprehensive as possible. In some limited cases, open lung biopsy in skilled hands may have implications for management.

X-Ray Dark-field Imaging to Depict Acute Lung Inflammation in Mice

The aim of this study was to evaluate the feasibility of early stage imaging of acute lung inflammation in mice using grating-based X-ray dark-field imaging in vivo. Acute lung inflammation was induced in mice by orotracheal instillation of porcine pancreatic elastase. Control mice received orotracheal instillation of PBS. Mice were imaged immediately before and 1 day after the application of elastase or PBS to assess acute changes in pulmonary structure due to lung inflammation. Subsequently, 6 mice from each group were sacrificed and their lungs were lavaged and explanted for histological analysis. A further 7, 14 and 21 days later the remaining mice were imaged again. All images were acquired with a prototype grating-based small-animal scanner to generate dark-field and transmission radiographs. Lavage confirmed that mice in the experimental group had developed acute lung inflammation one day after administration of elastase. Acute lung inflammation was visible as a striking decrease in signal intensity of the pulmonary parenchyma on dark-field images at day 1. Quantitative analysis confirmed that dark-field signal intensity at day 1 was significantly lower than signal intensities measured at the remaining timepoints, confirming that acute lung inflammation can be depicted in vivo with dark-field radiography.

Clinical Characteristics Based on the New Criteria of Acute Exacerbation in Patients with Idiopathic Pulmonary Fibrosis

Objective

Idiopathic pulmonary fibrosis (IPF) is the most common parenchymal lung disease. Patients with IPF sometimes develop acute exacerbation (AE), which predicts a poor prognosis. To evaluate the predictors of 90-day mortality of AE in patients with IPF based on the new 2016 criteria.

Materials and Methods

Sixty-five patients with AE were studied retrospectively between January 2001 and December 2016 at Okinawa Chubu Hospital.

Results

The mean age of the patients was 74 years, with 40 (61.5%) men and 25 (38.5%) women. Among our cohort, 37 were current or ex-smokers, with a mean exposure of 32.4 pack-years. The mean grade of the modified Medical Research Council breathlessness scale was 2.8, and the mean duration of dyspnea prior to admission was 6.5 days. Clubbed fingernails were present in 29% of patients. Triggered AE occurred in 12 (18%) of patients. Patients with triggered AE had more extensive ground-glass opacity and higher consolidation scores than the idiopathic AE group (7.3 vs. 4.2, p=0.01). The triggered group had shorter survival than the idiopathic group (1.4 vs. 11.4 months, p=0.094). Serum lactate dehydrogenase (LDH), ΔLDH, and the ratio of partial pressure of oxygen to the fraction of inspiratory oxygen ratio were strong predictors of 90-day mortality. Hazard ratios were 1.003 (p=0.004), 1.004 (p=0.02), and 0.994 (p=0.010), respectively.

Conclusion

Compared with idiopathic AE, triggered AE in patients with IPF had more extensive infiltration and tended toward shorter survival. Serial trends of serum LDH >2 weeks can help predict prognosis of AE in patients with IPF.

Effects of S-Nitroso-N-Acetyl-Penicillamine (SNAP) on Inflammation, Lung Tissue Apoptosis and iNOS Activity in a Rabbit Model of Acute Lung Injury

Acute lung injury is characterized by lung edema, surfactant dysfunction, and inflammation. The main goal of our study was to evaluate effects of S-nitroso-N-acetyl-penicillamine (SNAP) on migration of cells into the lung and their activation, inducible NO synthase (iNOS) activity, and apoptosis in experimental acute lung injury (ALI) in rabbits. ALI was induced by repetitive lung lavage with saline. The animals were divided into the following groups: (1) ALI without therapy, (2) lung injury treated with SNAP (ALI + SNAP), and (3) healthy animals (Control). After 5 h of ventilation, total and differential counts of cells in the bronchoalveolar lavage fluid (BALF) were assessed. Concentrations of interleukins (IL)-1ß, IL-6, and IL-8, endogenous secretory receptor for advanced glycation endproducts (esRAGE), sphingosine-1-phosphate receptor (S1PR)3, caspase-3, and mRNA expression of inducible NO synthase (iNOS) in lung tissue and nitrite/nitrate in plasma were analyzed. In the right lung, apoptotic cells were evaluated by TUNEL assay. In the animals with ALI, higher counts of cells, mainly neutrophils, in BALF and increased production of pro-inflammatory substances were observed compared with controls. SNAP therapy reduced a leak of cells into the lung and decreased concentrations of pro-inflammatory and apoptotic markers, reduced mRNA expression of iNOS, and decreased apoptotic index in the lung.

Metabolomics based predictive biomarker model of ARDS: A systemic measure of clinical hypoxemia

Despite advancements in ventilator technologies, lung supportive and rescue therapies, the outcome and prognostication in acute respiratory distress syndrome (ARDS) remains incremental and ambiguous. Metabolomics is a potential insightful measure to the diagnostic approaches practiced in critical disease settings. In our study patients diagnosed with mild and moderate/severe ARDS clinically governed by hypoxemic P/F ratio between 100-300 but with indistinct molecular phenotype were discriminated employing nuclear magnetic resonance (NMR) based metabolomics of mini bronchoalveolar lavage fluid (mBALF). Resulting biomarker prototype comprising six metabolites was substantiated highlighting ARDS susceptibility/recovery. Both the groups (mild and moderate/severe ARDS) showed distinct biochemical profile based on 83.3% classification by discriminant function analysis and cross validated accuracy of 91% using partial least squares discriminant analysis as major classifier. The predictive performance of narrowed down six metabolites were found analogous with chemometrics. The proposed biomarker model consisting of six metabolites proline, lysine/arginine, taurine, threonine and glutamate were found characteristic of ARDS sub-stages with aberrant metabolism observed mainly in arginine, proline metabolism, lysine synthesis and so forth correlating to diseased metabotype. Thus NMR based metabolomics has provided new insight into ARDS sub-stages and conclusively a precise biomarker model proposed, reflecting underlying metabolic dysfunction aiding prior clinical decision making.

Acute Exacerbation in Interstitial Lung Disease

Acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF) has been defined as an acute, clinically significant deterioration that develops within less than 1 month without obvious clinical cause like fluid overload, left heart failure, or pulmonary embolism. Pathophysiologically, damage of the alveoli is the predominant feature of AE-IPF which manifests histopathologically as diffuse alveolar damage and radiologically as diffuse, bilateral ground-glass opacification on high-resolution computed tomography. A growing body of literature now focuses on acute exacerbations of interstitial lung disease (AE-ILD) other than idiopathic pulmonary fibrosis. Based on a shared pathophysiology it is generally accepted that AE-ILD can affect all patients with interstitial lung disease (ILD) but apparently occurs more frequently in patients with an underlying usual interstitial pneumonia pattern. The etiology of AE-ILD is not fully understood, but there are distinct risk factors and triggers like infection, mechanical stress, and microaspiration. In general, AE-ILD has a poor prognosis and is associated with a high mortality within 6–12 months. Although there is a lack of evidence based data, in clinical practice, AE-ILD is often treated with a high dose corticosteroid therapy and antibiotics. This article aims to provide a summary of the clinical features, diagnosis, management, and prognosis of AE-ILD as well as an update on the current developments in the field.

How to approach the acute respiratory distress syndrome: Prevention, plan, and prudence

The acute respiratory distress syndrome (ARDS) is typically manifested by refractory hypoxemia with high mortality. A correct diagnosis is the first step to achieve better outcomes. An early intervention to manage modifiable risk factors of ARDS development and the avoidance of aggravating factors that increase disease severity and progression should be carefully addressed. A management plan is necessary at an early stage of ARDS to determine the level of intensive care. It should be carefully decided which therapeutic measures should be performed depending on the patient׳s underlying clinical condition. The clinician׳s considerate prudence is required in decisions of when to apply intensive measures for an ARDS treatment. Mechanical ventilator support should be carefully used depending on the patient׳s severity and pathological phase. Decreasing inappropriate alveolar strain through a low tidal volume under optimal positive end-expiratory pressure is key for ventilator support in ARDS. The extracorporeal membrane oxygenation applied in the experienced centers seems to improve the survival of patients with severe ARDS. A constellation of physical and psychological problems can develop or persist for up to 5 years in patients with ARDS. Therefore, an early mobilization with rehabilitation, even during an intensive care unit stay, should be seriously considered whenever feasible. Lastly, prevention of aspiration, stress ulcers, deep vein thrombosis, catheter-related infection, overhydration, and heavy sedation is essential to achieve better outcomes in ARDS.

Preventative effect of OMZ-SPT on lipopolysaccharide-induced acute lung injury and inflammation via nuclear factor-kappa B signaling in mice

Acute lung injury (ALI) is an early pathophysiologic change in acute respiratory distress syndrome and its management can be challenging. Omalizumab (Xolair™) is a recombinant DNA-derived, humanized antibody. OMZ-SPT is a polypeptide on the heavy chain of omalizumab monoclonal antibody. Here, we found that intramuscular administration of OMZ-SPT significantly improved survival and attenuated lung inflammation in female C57BL/6 mice suffering from lipopolysaccharide (LPS)-induced ALI. We also demonstrated that OMZ-SPT can inhibit expression of the inflammatory cytokines tumor necrosis factor-α, interleukin-1β and interleukin-6 by ELISA in mice suffering from LPS-induced ALI and a mouse macrophage line (RAW264.7 cells). In addition, we showed that OMZ-SPT inhibited LPS-induced activation of nuclear factor-kappa B (NF-κB) signaling and total expression of NF-κB by western blotting. These data suggest that OMZ-SPT could be a novel therapeutic choice for ALI.

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%.