Acute respiratory distress syndrome: shifting the emphasis from treatment to prevention

Establishment and validation of predictive model of ARDS in critically ill patients

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a prevalent complication among critically ill patients, constituting around 10% of intensive care unit (ICU) admissions and mortality rates ranging from 35 to 46%. Hence, early recognition and prediction of ARDS are crucial for the timely administration of targeted treatment. However, ARDS is frequently underdiagnosed or delayed, and its heterogeneity diminishes the clinical utility of ARDS biomarkers. This study aimed to observe the incidence of ARDS among high-risk patients and develop and validate an ARDS prediction model using machine learning (ML) techniques based on clinical parameters.

METHODS

This prospective cohort study in China was conducted on critically ill patients to derivate and validate the prediction model. The derivation cohort, consisting of 400 patients admitted to the ICU of the Peking University Third Hospital(PUTH) between December 2020 and August 2023, was separated for training and internal validation, and an external data set of 160 patients at the FU YANG People's Hospital from August 2022 to August 2023 was employed for external validation. Least absolute shrinkage and selection operator (LASSO) and multivariate logistic regression were used to screen predictor variables. Multiple ML classification models were integrated to analyze and identify the best models. Several evaluation indexes were used to compare the model performance, including the area under the receiver-operating-characteristic curve (AUC) and decision curve analysis (DCA). SHapley Additive ex Planations (SHAP) is used to interpret ML models.

RESULTS

400 critically ill patients were included in the analysis, with 117 developing ARDS during follow-up. The final model included gender, Lung Injury Prediction Score (LIPS), Hepatic Disease, Shock, and combined Lung Contusion. Based on the AUC and DCA in the validation group, the logistic model demonstrated excellent performance, achieving an AUC of 0.836 (95% CI: 0.762-0.910). For external validation, comprising 160 patients, 44 of whom developed ARDS, the AUC was 0.799 (95% CI: 0.723-0.875), significantly outperforming the LIPS score alone.

CONCLUSION

Combining the LIPS score with other clinical parameters in a logistic regression model provides a more accurate, clinically applicable, and user-friendly ARDS prediction tool than the LIPS score alone.

A Simple Nomogram for Predicting the Development of ARDS in Postoperative Patients with Gastrointestinal Perforation: A Single-Center Retrospective Study

Background

Acute respiratory distress syndrome (ARDS) is a severe form of organ dysfunction and a common postoperative complication. This study aims to develop a predictive model for ARDS in postoperative patients with gastrointestinal perforation to facilitate early detection and effective prevention.

Methods

In this single-center retrospective study, clinical data were collected from postoperative patients with gastrointestinal perforation admitted to the ICU in Hebei Provincial People's Hospital from October 2017 to May 2024. Univariate analysis and multifactorial logistic regression analysis were used to determine the independent risk factors for developing ARDS. Nomograms were developed to show predictive models, and the discrimination, calibration, and clinical usefulness of the models were assessed using the C-index, calibration plots, and decision curve analysis (DCA).

Results

Two hundred patients were ultimately included for analysis. In the development cohort, 38 (27.1%) of 140 patients developed ARDS, and in the internal validation cohort, 13 (21.7%) of 60 patients developed ARDS. The multivariate logistic regression analysis revealed the site of perforation (OR = 0.164, P = 0.006), the duration of surgery (OR = 0.986, P = 0.008), BMI (OR = 1.197, P = 0.015), SOFA (OR = 1.443, P = 0.001), lactate (OR = 1.500, P = 0.017), and albumin (OR = 0.889, P = 0.007) as the independent risk factors for ARDS development. The area under the curve (AUC) was 0.921 (95% CI: 0.869, 0.973) for the development cohort and 0.894 (95% CI: 0.809, 0.978) for the validation cohort. The calibration curve and decision curve analysis (DCA) demonstrate that the nomogram possesses good predictive value and clinical practicability.

Conclusion

Our research introduced a nomogram that integrates six independent risk factors, facilitating the precise prediction of ARDS risk in postoperative patients following gastrointestinal perforation.

A Systematic Review and Meta-Analysis of Independent Predictors for Acute Respiratory Distress Syndrome in Patients Presenting With Sepsis

The current meta-analysis was conducted to determine the predictors of acute respiratory distress syndrome (ARDS) in patients with sepsis. The present meta-analysis was conducted in accordance with the MOOSE (Meta-analysis of Observational Studies in Epidemiology) guidelines. We conducted a systematic search using the PubMed, Cochrane Library, and EMBASE databases for studies published between 1 January 2000 and 28 February 2023 that assessed the predictors of ARDS in patients with sepsis. We used key terms such as "predictors," "acute respiratory distress syndrome," and "sepsis" to search for relevant articles. Our search was limited to human studies published in English. A total of six studies were included in this meta-analysis. Of the six studies, four were retrospective and two were prospective. The pooled incidence of ARDS was 11.27%. We identified six factors with a consistent and statistically significant association with ARDS, including sequential organ failure assessment (SOFA) score, Acute Physiology and Chronic Health Evaluation (APACHE) II score, pulmonary sepsis, smoking, pancreatitis, and C-reactive protein. Age, diabetes, and chronic obstructive pulmonary disease (COPD) were not found to be significantly associated with ARDS in this patient population. It is important for healthcare providers to consider these predictors when assessing patients with sepsis and septic shock to identify those at high risk for developing ARDS and implement appropriate preventive measures.

CORRELATION BETWEEN RED BLOOD CELL DISTRIBUTION WIDTH-TO-PLATELET RATIO AND MORTALITY IN PATIENTS WITH ACUTE RESPIRATORY DISTRESS SYNDROME: A RETROSPECTIVE COHORT STUDY

ABSTRACT

Background: This study aims to assess the prognostic value of red blood cell distribution width-to-platelet ratio (RPR) in acute respiratory distress syndrome (ARDS) patients. Methods: The data collected from 540 ARDS patients from 2001 to 2012 were obtained from the Medical Information Mart for Intensive Care III Database. The 28-day all-cause mortality risk was considered as the primary outcome parameter, and the secondary outcomes were 60- and 90-day all-cause mortality. The association between RPR (≥0.19 vs. <0.19) and mortality was assessed by Cox proportional hazards models, and potential nonlinear associations were assessed by restricted cubic spline regression analysis. Results: The 28-day all-cause mortality was 22.4%. Among the 121 deaths, 92 (20.0%) presented with an RPR <0.19, and 29 patients had RPR ≥0.19 ( P < 0.001). The 60- and 90-day all-cause mortality was 27% and 28.7%, respectively. After adjusting for the relevant factors in the multivariate model, RPR ≥0.19 was independently correlated with the 28-day all-cause mortality (hazard ratio, 2.74; 95% confidence interval, 1.46-5.15; P = 0.002). There was no nonlinear relationship between RPR and the risk of 28-day all-cause mortality ( P for overall association <0.001, P for nonlinear = 0.635). Similar results were observed for both the pneumonia and nonpneumonia subgroups and sensitivity analyses. Conclusions: The data promote the use of RPR as a valuable prognostic indicator for ARDS patients.

Risk factors for acute respiratory distress syndrome in sepsis patients: a retrospective study from a tertiary hospital in China

Background

Less is known about the risk factors for acute respiratory distress syndrome (ARDS) in sepsis patients diagnosed according to sepsis 3.0 criteria. Moreover, the risk factors for ARDS severity remain unclear.

Methods

We retrospectively collected the characteristics of sepsis patients from the intensive care unit of the First Affiliated Hospital of China Medical University from January 2017 to September 2018. Logistic regression was used in determining the risk factors.

Results

529 patients with sepsis were enrolled and 179 developed ARDS. The most common infection sites were acute abdominal infection (n = 304) and pneumonia (n = 117). Multivariate analysis showed that patients with pancreatitis with local infection (odds ratio [OR], 3.601; 95% confidence interval [CI], 1.429–9.073, P = 0.007), pneumonia (OR 3.486; 95% CI 1.890–6.430, P < 0.001), septic shock (OR 2.163; 95% CI 1.429–3.275, P < 0.001), a higher sequential organ failure assessment (SOFA) score (OR 1.241; 95% CI 1.155–1.333, P < 0.001) and non-pulmonary SOFA score (OR 2.849; 95% CI 2.113–3.841, P < 0.001) were independent risk factors for ARDS. Moreover, pneumonia is associated with increased severity of ARDS (OR 2.512; 95% CI 1.039–6.067, P = 0.041).

Conclusions

We determined five risk factors for ARDS in sepsis patients. Moreover, pneumonia is significantly associated with an increased severity of ARDS.

Randomized, Placebo-controlled Trial of Inhaled Treprostinil for Patients at Risk for Acute Respiratory Distress Syndrome

Rationale: Inhaled treprostinil may improve oxygenation and have additional antiinflammatory effects in early acute hypoxemic respiratory failure, potentially preventing or reducing the severity of acute respiratory distress syndrome (ARDS).Objectives: To determine whether administration of inhaled treprostinil to patients at risk for ARDS is feasible, safe, and efficacious.Methods: We performed a double-blind, placebo-controlled, single-center randomized pilot trial at a quaternary care academic medical center. Patients with acute hypoxemia due to pneumonia or signs of low-pressure pulmonary edema with a unilateral or bilateral infiltrate on chest imaging and a 4 L/min supplemental oxygen requirement not requiring positive pressure ventilation were evaluated. Randomized patients received study drug or placebo (2:1 ratio). Treatment was initiated at 6 breaths every 4 hours and titrated up to 12 breaths. Subjects were maintained on treatment for 7 days and then tapered off over a period of 4 days. Study drug was stopped if positive pressure ventilation was required (invasive or noninvasive).Results: Fourteen patients were enrolled over a period of 31 months. Baseline characteristics were not significantly different between treatment groups with respect to age, sex, race, Acute Physiologic Assessment and Chronic Health Evaluation score, lung injury prediction score, or baseline mean oxygen saturation as measured by pulse oximetry (Sp_O2):fraction of inspired oxygen (Fi_O2) ratio. Trends in daily baseline and 30-minute postdose Sp_O2:Fi_O2 ratio for all treatment points were not significantly different between placebo and treprostinil. Four patients required positive pressure ventilation in the treprostinil group versus one in the placebo group.Conclusions: Inhaled treprostinil administration is feasible in patients at risk for ARDS but was not associated with improvement in the Sp_O2:Fi_O2 ratio relative to placebo. Drug-associated adverse events were not severe nor unexpected based on the known adverse effect profile of inhaled treprostinil. The clinical benefit of this intervention is unclear at this time in the absence of larger studies.Clinical trial registered with Clinicaltrials.gov (NCT02370095).

Nanotherapeutics in the treatment of acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a form of oxygenation failure primarily characterized by rapid inflammation resulting from a direct pulmonary or indirect systemic insult. ARDS has been a major cause of death in the recent COVID-19 outbreak wherein asymptomatic respiratory tract infection progresses to ARDS from pneumonia have emphasized the need for a reliable therapy for the disease. The disease has a high mortality rate of approximately 30-50%. Despite the high mortality rate, a dearth of effective pharmacotherapy exists that demands extensive research in this area. The complex ARDS pathophysiology which remains to be understood completely and the multifactorial etiology of the disease has led to the poor diagnosis, impeded drug-delivery to the deeper pulmonary tissues, and delayed treatment of the ARDS patients. Besides, critically ill patients are unable to tolerate the off-target side effects. The vast domain of nanobiotechnology presents several drug delivery systems offering numerous benefits such as targeted delivery, prolonged drug release, and uniform drug-distribution. The present review presents a brief insight into the ARDS pathophysiology and summarizes conventional pharmacotherapies available to date. Furthermore, the review provides an updated report of major developments in the nanomedicinal approaches for the treatment of ARDS. We also discuss different nano-formulations studied extensively in the ARDS preclinical models along with underlining the advantages as well as challenges that need to be addressed in the future.

Predictive Role of Lung Injury Prediction Score in the Development of Acute Respiratory Distress Syndrome in Korea

PURPOSE

Early recognition and therapeutic intervention are important in patients at high risk of acute respiratory distress syndrome (ARDS). The lung injury prediction score (LIPS) has been used to predict ARDS development; however, it was developed based on the previous definition of ARDS. We investigated the predictive role of LIPS in ARDS development according to its Berlin definition in the Korean population.

MATERIALS AND METHODS

This was a retrospective study that enrolled adult patients admitted to the intensive care unit (ICU) at a single university-affiliated hospital in Korea from September 1, 2018, to August 31, 2019. LIPS at the time of ICU admission and the development of ARDS were evaluated.

RESULTS

Of the 548 enrolled patients, 33 (6.0%) fulfilled the Berlin ARDS definition. The LIPS for non-ARDS and ARDS groups were 4.96±3.05 and 8.53±2.45, respectively (p<0.001); it was significantly associated with ARDS development (odds ratio 1.48, 95% confidence interval, 1.29-1.69; p<0.001). LIPS >6 predicted the development of ARDS with a sensitivity of 84.8% and a specificity of 67.2% [area under the curve (AUC)=0.82]. A modified LIPS model adjusted for age and severity at ICU admission predicted ICU mortality in patients with ARDS (AUC=0.80), but not in those without ARDS (AUC=0.54).

CONCLUSION

LIPS predicted the development of ARDS as diagnosed by the Berlin definition in the Korean population. LIPS provides useful information for managing patients with ARDS.

Association of Serum Mannose With Acute Respiratory Distress Syndrome Risk and Survival

IMPORTANCE

Acute respiratory distress syndrome (ARDS) confers high mortality risk among critically ill patients. Identification of biomarkers associated with ARDS risk may guide clinical diagnosis and prognosis.

OBJECTIVE

To systematically evaluate the association of blood metabolites with ARDS risk and survival.

DESIGN, SETTING, AND PARTICIPANTS

In this cohort study, data from the Molecular Epidemiology of ARDS (MEARDS) study, a prospective cohort of 403 patients with ARDS and 1227 non-ARDS controls, were analyzed. Patients were recruited in intensive care units (ICUs) at Massachusetts General Hospital and Beth Israel Deaconess Medical Center, both in Boston, Massachusetts, from January 1, 1998, to December 31, 2014. Data analysis was performed from December 9, 2018, to January 4, 2019.

MAIN OUTCOMES AND MEASURES

Participants were followed up daily for ARDS development defined by Berlin criteria, requiring fulfillment of chest radiograph and oxygenation criteria on the same calendar day during invasive ventilatory assistance. A 2-stage study design was used to explore novel metabolites associated with ARDS risk and survival.

RESULTS

Of the 1630 participants from MEARDS who were admitted to the ICU , 403 (24.7%) were diagnosed with ARDS (mean [SD] age, 63.0 [17.0] years; 251 [62.3%] male) and 1227 (75.3%) were at-risk but did not have ARDS (mean [SD] age, 62.3 [16.9] years; 753 [61.4%] male). Mendelian randomization suggested that genetically regulated serum mannose was associated with ARDS risk (odds ratio [OR], 0.64; 95% CI, 0.53-0.78; P = 7.46 × 10-6) in the discovery stage. In the functional validation stage incorporating 83 participants with ARDS and matched at-risk participants in the control group from the ICU, the protective association of mannose with ARDS risk was validated (OR, 0.67; 95% CI, 0.46-0.97; P = .03). Furthermore, serum mannose was associated with 28-day (OR, 0.25; 95% CI, 0.11-0.56; P = 6.95 × 10-4) and 60-day (OR, 0.36; 95% CI, 0.19-0.71; P = 3.12 × 10-3) mortality and 28-day (hazard ratio, 0.49; 95% CI, 0.32-0.74; P = 6.41 × 10-4) and 60-day (hazard ratio, 0.55; 95% CI, 0.37-0.80; P = 2.11 × 10-3) survival.

CONCLUSIONS AND RELEVANCE

In this study, genetically regulated serum mannose appeared to be associated with ARDS risk and outcome, and increased serum mannose at admission was associated with reduced ARDS risk and better survival. These findings could inform prevention and clinical intervention in ARDS cases, which have increased with the expansion of the coronavirus disease 2019 pandemic.

Genomics and the Acute Respiratory Distress Syndrome: Current and Future Directions

The excessive hospital mortality associated with acute respiratory distress syndrome (ARDS) in adults mandates an urgent need for developing new therapies and tools for the early risk assessment of these patients. ARDS is a heterogeneous syndrome with multiple different pathogenetic processes contributing differently in different patients depending on clinical as well as genetic factors. Identifying genetic-based biomarkers holds the promise for establishing effective predictive and prognostic stratification methods and for targeting new therapies to improve ARDS outcomes. Here we provide an updated review of the available evidence supporting the presence of genetic factors that are predictive of ARDS development and of fatal outcomes in adult critically ill patients and that have been identified by applying different genomic and genetic approaches. We also introduce other incipient genomics approximations, such as admixture mapping, metagenomics and genome sequencing, among others, that will allow to boost this knowledge and likely reveal new genetic predictors of ARDS susceptibility and prognosis among critically ill patients.

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 Children With Critical Bronchiolitis Meeting at Risk for Pediatric Acute Respiratory Distress Syndrome Criteria

OBJECTIVES

New definitions of pediatric acute respiratory distress syndrome include criteria to identify a subset of children "at risk for pediatric acute respiratory distress syndrome." We hypothesized that, among PICU patients with bronchiolitis not immediately requiring invasive mechanical ventilation, those meeting at risk for pediatric acute respiratory distress syndrome criteria would have worse clinical outcomes, including higher rates of pediatric acute respiratory distress syndrome development.

DESIGN

Single-center, retrospective chart review.

SETTING

Mixed medical-surgical PICU within a tertiary academic children's hospital.

PATIENTS

Children 24 months old or younger admitted to the PICU with a primary diagnosis of bronchiolitis from September 2013 to April 2014. Children intubated before PICU arrival were excluded.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Collected data included demographics, respiratory support, oxygen saturation, and chest radiograph interpretation by staff radiologist. Oxygen flow (calculated as FIO2 × flow rate [L/min]) was calculated when oxygen saturation was 88-97%. The median age of 115 subjects was 5 months (2-11 mo). Median PICU length of stay was 2.8 days (1.5-4.8 d), and median hospital length of stay was 5 days (3-10 d). The criteria for at risk for pediatric acute respiratory distress syndrome was met in 47 of 115 subjects (40.9%). Children who were at risk for pediatric acute respiratory distress syndrome were more likely to develop pediatric acute respiratory distress syndrome (15/47 [31.9%] vs 1/68 [1.5%]; p < 0.001), had longer PICU length of stay (4.6 d [2.8-10.2 d] vs 1.9 d [1.0-3.1 d]; p < 0.001) and hospital length of stay (8 d [5-16 d] vs 4 d [2-6 d]; p < 0.001), and increased need for invasive mechanical ventilation (16/47 [34.0%] vs 2/68 [2.9%]; p < 0.001), compared with those children who did not meet at risk for pediatric acute respiratory distress syndrome criteria.

CONCLUSIONS

Our data suggest that the recent definition of at risk for pediatric acute respiratory distress syndrome can successfully identify children with critical bronchiolitis who have relatively unfavorable clinical courses.

Red blood cell distribution width is an independent risk factor in the prediction of acute respiratory distress syndrome after severe burns

BACKGROUND

The occurrence of acute respiratory distress syndrome (ARDS) significantly increases the mortality and morbidity of major burns; there are few laboratory markers that predict the development of ARDS in severe burns. This study was to investigate the relationship between complete blood count (CBC) parameters and the incidence of ARDS in severe burn patients.

METHODS

An eight-year retrospective study was performed on 610 severe burn patients who were admitted to the First Affiliated Hospital of Anhui Medical University and Rui Jin Hospital of Shanghai Jiao Tong University from January 2008 to December 2015. The patients were divided into two groups based on the development of ARDS. A blood sample was taken at admission and CBC parameters were examined. Univariate logistic regression analysis was used to evaluate the risk factors for the development of ARDS.

RESULTS

Of these 610 patients, 143 developed ARDS giving a rate of 23.44%. The percentage of deep second degree and full thickness burn, inhalation injury and red blood cell distribution width (RDW) were independently associated with the development of ARDS in severe burn patients. Every 1% increase in RDW was associated with a 29% increase in the risk to develop ARDS.

CONCLUSIONS

The findings of this study suggest that an elevated RDW is associated with an increased risk of ARDS and RDW is an independent risk factor in the prediction of ARDS after severe burns.

A modified acute respiratory distress syndrome prediction score: a multicenter cohort study in China

Background

Early recognition of the risks of acute respiratory distress syndrome (ARDS) and prevention of the development of ARDS may be more effective in improving patient outcomes. We performed the present study to determine the ARDS risk factors in a Chinese population and validate a score to predict the development of ARDS.

Methods

This was an observational multicenter cohort study performed in 13 tertiary hospitals in China. Patients admitted into participating intensive care units (ICUs) from January 1 to January 31, 2012, and from January 1 to January 10, 2013, were enrolled in a retrospective derivation cohort and a prospective validation cohort, respectively. In the derivation cohort, the potential risk factors of ARDS were collected. The confirmed risk factors were determined with univariate and multivariate logistic regression analyses, and then the modified ARDS prediction score (MAPS) was established. We prospectively enrolled patients to verify the accuracy of MAPS.

Results

A total of 479 and 198 patients were enrolled into the retrospective derivation cohort and the prospective validation cohort, respectively. A total of 93 (19.4%) patients developed ARDS in the derivation cohort. Acute pancreatitis, pneumonia, hypoalbuminemia, acidosis, and high respiratory rate were the risk factors for ARDS. The MAPS discriminated patients who developed ARDS from those who did not, with an area under the curve (AUC) of 0.809 [95% confidence interval (CI), 0.758-0.859, P<0.001]. In the prospective validation cohort, performance of the MAPS was similar to the retrospective derivation cohort, with an AUC of 0.792 (95% CI, 0.717-0.867, P<0.001). The lung injury prediction score (LIPS) showed a predicted value of an AUC of 0.770 (95% CI, 0.728-0.812, P<0.001) in our patients, which was significantly lower than our score (P<0.046).

Conclusions

The MAPS based on risk factors could help the clinician to predict patients who will develop ARDS.

Trial registration

ClinicalTrials.gov NCT01666834.

Preemptive Mechanical Ventilation Based on Dynamic Physiology in the Alveolar Microenvironment: Novel Considerations of Time-Dependent Properties of the Respiratory System

The acute respiratory distress syndrome (ARDS) remains a serious clinical problem with the current treatment being supportive in the form of mechanical ventilation. However, mechanical ventilation can be a double-edged sword; if set properly, it can significantly reduce ARDS associated mortality but if set improperly it can have unintended consequences causing a secondary ventilator induced lung injury (VILI). The hallmark of ARDS pathology is a heterogeneous lung injury, which predisposes the lung to a secondary VILI. The current standard of care approach is to wait until ARDS is well established and then apply a low tidal volume (LVt) strategy to avoid over-distending the remaining normal lung. However, even with the use of LVt strategy, the mortality of ARDS remains unacceptably high at ~40%. In this review, we analyze the lung pathophysiology associated with ARDS that renders the lung highly vulnerable to a secondary VILI. The current standard of care LVt strategy is critiqued as well as new strategies used in combination with LVt to protect the lung. Using the current understanding of alveolar mechanics (i.e. the dynamic change in alveolar size and shape with tidal ventilation) we provide a rationale for why the current protective ventilation strategies have not further reduced ARDS mortality. New strategies of protective ventilation based on dynamic physiology in the micro-environment (i.e. alveoli and alveolar ducts) are discussed. Current evidence suggests that alveolar inflation and deflation is viscoelastic in nature, with a fast and slow phase in both alveolar recruitment and collapse. Using this knowledge, a ventilation strategy with a prolonged time at inspiration would recruit alveoli and a brief release time at expiration would prevent alveolar collapse, converting heterogeneous to homogeneous lung inflation significantly reducing ARDS incidence and mortality.

Personalizing mechanical ventilation according to physiologic parameters to stabilize alveoli and minimize ventilator induced lung injury (VILI)

It has been shown that mechanical ventilation in patients with, or at high-risk for, the development of acute respiratory distress syndrome (ARDS) can be a double-edged sword. If the mechanical breath is improperly set, it can amplify the lung injury associated with ARDS, causing a secondary ventilator-induced lung injury (VILI). Conversely, the mechanical breath can be adjusted to minimize VILI, which can reduce ARDS mortality. The current standard of care ventilation strategy to minimize VILI attempts to reduce alveolar over-distension and recruitment-derecruitment (R/D) by lowering tidal volume (Vt) to 6 cc/kg combined with adjusting positive-end expiratory pressure (PEEP) based on a sliding scale directed by changes in oxygenation. Thus, Vt is often but not always set as a "one-size-fits-all" approach and although PEEP is often set arbitrarily at 5 cmH2O, it may be personalized according to changes in a physiologic parameter, most often to oxygenation. However, there is evidence that oxygenation as a method to optimize PEEP is not congruent with the PEEP levels necessary to maintain an open and stable lung. Thus, optimal PEEP might not be personalized to the lung pathology of an individual patient using oxygenation as the physiologic feedback system. Multiple methods of personalizing PEEP have been tested and include dead space, lung compliance, lung stress and strain, ventilation patterns using computed tomography (CT) or electrical impedance tomography (EIT), inflection points on the pressure/volume curve (P/V), and the slope of the expiratory flow curve using airway pressure release ventilation (APRV). Although many studies have shown that personalizing PEEP is possible, there is no consensus as to the optimal technique. This review will assess various methods used to personalize PEEP, directed by physiologic parameters, necessary to adaptively adjust ventilator settings with progressive changes in lung pathophysiology.

Recent directions in personalised acute respiratory distress syndrome medicine

Acute respiratory distress syndrome (ARDS) is heterogeneous by definition and patient response varies depending on underlying biology and their severity of illness. Although ARDS subtypes have been identified with different prognoses in past studies, the concept of phenotypes or endotypes does not extend to the clinical definition of ARDS. This has possibly hampered the development of therapeutic interventions that target select biological mechanisms of ARDS. Recently, a major advance may have been achieved as it may now be possible to identify ARDS subtypes that may confer different responses to therapy. The aim of personalised medicine is to identify, select, and test therapies that are most likely to be associated with a favourable outcome in a specific patient. Several promising approaches to ARDS subtypes capable of predicting therapeutic response, and not just prognosis, are highlighted in this perspective paper. An overview is also provided of current and future directions regarding the provision of personalised ARDS medicine. The importance of delivering the right care, at the right time, to the right patient, is emphasised.

Whole blood microRNA markers are associated with acute respiratory distress syndrome

BACKGROUND

MicroRNAs (miRNAs) can play important roles in inflammation and infection, which are common manifestations of acute respiratory distress syndrome (ARDS). We assessed if whole blood miRNAs were potential diagnostic biomarkers for human ARDS.

METHODS

This nested case-control study (N = 530) examined a cohort of ARDS patients and critically ill at-risk controls. Whole blood miRNA profiles and logistic regression analyses identified miRNAs correlated with ARDS. Stratification analysis also assessed selected miRNA markers for their role in sepsis and pneumonia associated with ARDS. Receiver operating characteristic (ROC) analysis evaluated miRNA diagnostic performance, along with Lung Injury Prediction Score (LIPS).

RESULTS

Statistical analyses were performed on 294 miRNAs, selected from 754 miRNAs after quality control screening. Logistic regression identified 22 miRNAs from a 156-patient discovery cohort as potential risk or protective markers of ARDS. Three miRNAs-miR-181a, miR-92a, and miR-424-from the discovery cohort remained significantly associated with ARDS in a 373-patient independent validation cohort (FDR q < 0.05) and meta-analysis (p < 0.001). ROC analyses demonstrated a LIPS baseline area-under-the-curve (AUC) value of ARDS of 0.708 (95% CI 0.651-0.766). Addition of miR-181a, miR-92a, and miR-424 to LIPS increased baseline AUC to 0.723 (95% CI 0.667-0.778), with a relative integrated discrimination improvement of 2.40 (p = 0.005) and a category-free net reclassification index of 27.21% (p = 0.01).

CONCLUSIONS

miR-181a and miR-92a are risk biomarkers for ARDS, whereas miR-424 is a protective biomarker. Addition of these miRNAs to LIPS can improve the risk estimate for ARDS.

Preadmission Oral Corticosteroids Are Associated With Reduced Risk of Acute Respiratory Distress Syndrome in Critically Ill Adults With Sepsis

OBJECTIVES

To determine the association between preadmission oral corticosteroid receipt and the development of acute respiratory distress syndrome in critically ill patients with sepsis.

DESIGN

Retrospective observational study.

SETTING

Medical, surgical, trauma, and cardiovascular ICUs of an academic medical center.

PATIENTS

A total of 1,080 critically ill patients with sepsis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The unadjusted occurrence rate of acute respiratory distress syndrome within 96 hours of ICU admission was 35% among patients who had received oral corticosteroids compared with 42% among those who had not (p = 0.107). In a multivariable analysis controlling for prespecified confounders, preadmission oral corticosteroids were associated with a lower incidence of acute respiratory distress syndrome in the 96 hours after ICU admission (odds ratio, 0.53; 95% CI, 0.33-0.84; p = 0.008), a finding that persisted in multiple sensitivity analyses. The median daily dose of oral corticosteroids among the 165 patients receiving oral corticosteroids, in prednisone equivalents, was 10 mg (interquartile range, 5-30 mg). Higher doses of preadmission oral corticosteroids were associated with a lower incidence of acute respiratory distress syndrome (odds ratio for 30 mg of prednisone compared with 5 mg 0.53; 95% CI, 0.32-0.86). In multivariable analyses, preadmission oral corticosteroids were not associated with in-hospital mortality (odds ratio, 1.41; 95% CI, 0.87-2.28; p = 0.164), ICU length of stay (odds ratio, 0.90; 95% CI, 0.63-1.30; p = 0.585), or ventilator-free days (odds ratio, 1.06; 95% CI, 0.71-1.57; p = 0.783).

CONCLUSIONS

Among ICU patients with sepsis, preadmission oral corticosteroids were independently associated with a lower incidence of early acute respiratory distress syndrome.

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.

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

Despite significant advances in our understanding and management of patients with acute respiratory distress syndrome (ARDS), the morbidity and mortality from ARDS remains high. Given the limited number of effective treatments for established ARDS, the strategic focus of ARDS research has shifted toward identifying patients with or at high risk of ARDS early in the course of the underlying illness, when strategies to reduce the development and progression of ARDS and associated organ failures can be systematically evaluated. In this review, we summarize the rationale, current evidence, and future directions in ARDS prevention.

Preemptive hemodynamic intervention restricting the administration of fluids attenuates lung edema progression in oleic acid-induced lung injury

OBJECTIVE

A study is made of the influence of preemptive hemodynamic intervention restricting fluid administration upon the development of oleic acid-induced lung injury.

DESIGN

A randomized in vivo study in rabbits was carried out.

SETTING

University research laboratory.

SUBJECTS

Sixteen anesthetized, mechanically ventilated rabbits.

VARIABLES

Hemodynamic measurements obtained by transesophageal Doppler signal. Respiratory mechanics computed by a least square fitting method. Lung edema assessed by the ratio of wet weight to dry weight of the right lung. Histological examination of the left lung.

INTERVENTIONS

Animals were randomly assigned to either the early protective lung strategy (EPLS) (n=8) or the early protective hemodynamic strategy (EPHS) (n=8). In both groups, lung injury was induced by the intravenous infusion of oleic acid (OA) (0.133mlkg^-1h^-1 for 2h). At the same time, the EPLS group received 15mlkg^-1h^-1 of Ringer lactate solution, while the EPHS group received 30mlkg^-1h^-1. Measurements were obtained at baseline and 1 and 2h after starting OA infusion.

RESULTS

After 2h, the cardiac index decreased in the EPLS group (p<0.05), whereas in the EPHS group it remained unchanged. Lung compliance decreased significantly only in the EPHS group (p<0.05). Lung edema was greater in the EPHS group (p<0.05). Histological damage proved similar in both groups (p=0.4).

CONCLUSIONS

In this experimental model of early lung injury, lung edema progression was attenuated by preemptively restricting the administration of fluids.

Protective Ventilation Improves Gas Exchange, Reduces Incidence of Atelectases, and Affects Metabolic Response in Major Pancreatoduodenal Surgery

Background

Protective perioperative ventilation has been shown to improve outcomes and reduce the incidence of postoperative pulmonary complications. The goal of this study was to assess the effects of ventilation with low tidal volume (V_T) either alone or in a combination with moderate permissive hypercapnia in major pancreatoduodenal interventions.

Materials and methods

Sixty adult patients scheduled for elective pancreatoduodenal surgery with duration >2 h were enrolled into a prospective single-center study. All patients were randomized to three groups receiving high V_T [10 mL/kg of predicted body weight (PBW), the HVT group, n = 20], low V_T (6 mL/kg PBW, the LVT group, n = 20), and low V_T combined with a moderate hypercapnia and hypercapnic acidosis (6 mL/kg PBW, PaCO₂ 45–60 mm Hg, the LVT + HC group, n = 20). Cardiopulmonary parameters and the incidence of complications were registered during surgery and postoperatively.

Results and discussion

The values of V_T were 610 (563–712), 370 (321–400), and 340 (312–430) mL/kg for the HVT, the LVT, and the LVT + HC groups, respectively (p < 0.001). Compared to the HVT group, PaO₂/FiO₂ ratio was increased in the LVT group by 15%: 333 (301–381) vs. 382 (349–423) mm Hg at 24 h postoperatively (p < 0.05). The HVT group had significantly higher incidence of atelectases (n = 6), despite lower incidence of smoking compared with the LVT (n = 1) group (p = 0.017) and demonstrated longer length of hospital stay. The patients of the LVT + HC group had lower arterial lactate and bicarbonate excess values by the end of surgery.

Conclusion

In major pancreatoduodenal interventions, preventively protective V_T improves postoperative oxygenation, reduces the incidence of atelectases, and shortens length of hospital stay. The combination of low V_T and permissive hypercapnia results in hypercapnic acidosis decreasing the lactate concentration but adding no additional benefits and warrants further investigations.

Activation of Coagulation and Fibrinolysis in Acute Respiratory Distress Syndrome: A Prospective Pilot Study

INTRODUCTION

Coagulation and fibrinolysis remain sparsely addressed with regards to acute respiratory distress syndrome (ARDS). We hypothesized that ARDS development might be associated with changes in plasma coagulation and fibrinolysis. Our aim was to investigate the relationships between ARDS diagnosis and plasma concentrations of tissue factor (TF), tissue plasminogen activator (t-PA), and plasminogen activator inhibitor-1 (PAI-1) in mechanically ventilated patients at increased risk of developing ARDS.

MATERIALS AND METHODS

We performed an ethically approved prospective observational pilot study. Inclusion criteria were patients with PaO₂/FiO₂ < 300 mmHg admitted to the intensive care unit (ICU) for mechanical ventilation for 24 h, or more, because of one or more disease conditions associated with increased risk of developing ARDS. Exclusion criteria were age below 18 years; cardiac disease. We sampled plasma prospectively and compared patients who developed ARDS with those who did not using descriptive statistics and chi-square analysis of baseline demographical and clinical data. We also analyzed plasma concentrations of TF, t-PA, and PAI-1 at inclusion (T₀) and on third (T₃) and seventh day (T₇) of the ICU stay with non-parametric statistics inclusive their sensitivity and specificity associated with the development of ARDS using receiver operating characteristic curve analysis. Statistical significance: p < 0.05.

RESULTS

Of 24 patients at risk, 6 developed mild ARDS and 4 of each moderate or severe ARDS, respectively, 3 ± 2 (mean ± SD) days after inclusion. Median plasma concentrations of TF and PAI-1 were significantly higher at T₇ in patients with ARDS, as compared to non-ARDS. Simultaneously, we found moderate correlations between plasma concentrations of TF and PAI-1, TF and PaO₂/FiO₂, and positive end-expiratory pressure and TF. TF plasma concentration was associated with ARDS with 71% sensitivity and 100% specificity, a cut off level of 145 pg/ml and AUC 0.78, p = 0.02. PAI-1 displayed 64% sensitivity and 100% specificity with a cut off concentration of 117.5 pg/ml and AUC 0.77, p = 0.02. t-PA did not change significantly during the observation time.

CONCLUSION

This pilot study showed that increased plasma concentrations of TF and PAI-1 might support ARDS diagnoses in mechanically ventilated patients after 7 days in ICU.

Manipulating the air-filled zebrafish swim bladder as a neutrophilic inflammation model for acute lung injury

Acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS), are life-threatening diseases that are associated with high mortality rates due to treatment limitations. Neutrophils play key roles in the pathogenesis of ALI/ARDS by promoting the inflammation and injury of the alveolar microenvironment. To date, in vivo functional approaches have been limited by the inaccessibility to the alveolar sacs, which are located at the anatomical terminal of the respiratory duct in mammals. We are the first to characterize the swim bladder of the zebrafish larva, which is similar to the mammalian lung, as a real-time in vivo model for examining pulmonary neutrophil infiltration during ALI. We observed that the delivery of exogenous materials, including lipopolysaccharide (LPS), Poly IC and silica nanoparticles, by microinjection triggered significant time- and dose-dependent neutrophil recruitment into the swim bladder. Neutrophils infiltrated the LPS-injected swim bladder through the blood capillaries around the pneumatic duct or a site near the pronephric duct. An increase in the post-LPS inflammatory cytokine mRNA levels coincided with the in vivo neutrophil aggregation in the swim bladder. Microscopic examinations of the LPS-injected swim bladders further revealed in situ injuries, including epithelial distortion, endoplasmic reticulum swelling and mitochondrial injuries. Inhibitor screening assays with this model showed a reduction in neutrophil migration into the LPS-injected swim bladder in response to Shp2 inhibition. Moreover, the pharmacological suppression and targeted disruption of Shp2 in myeloid cells alleviated pulmonary inflammation in the LPS-induced ALI mouse model. Additionally, we used this model to assess pneumonia-induced neutrophil recruitment by microinjecting bronchoalveolar lavage fluid from patients into swim bladders; this injection enhanced neutrophil aggregation relative to the control. In conclusion, our findings highlight the swim bladder as a promising and powerful model for mechanistic and drug screening studies of alveolar injuries.

Clinical predictors of early acute respiratory distress syndrome in trauma patients

BACKGROUND

The objectives of this study were to examine the incidence and severity of early acute respiratory distress syndrome (ARDS) according to the Berlin Definition and to identify risk factors associated with the development of early post-traumatic ARDS.

METHODS

A 2.5-year retrospective database of adult trauma patients who required mechanical ventilation for greater than 48 hours at a level 1 trauma center was analyzed for variables predictive of early (<48 hours after injury), mild, moderate, and severe ARDS and in-hospital mortality.

RESULTS

Of 305 patients, 59 (19.3%) developed early ARDS: mild, 27 (45.8%); moderate, 26 (44.1%); and severe, 6 (10.1%). Performance of an emergent thoracotomy, blunt mechanism, and fresh frozen plasma administration were independently associated with the development of early ARDS. ARDS was not predictive of mortality.

CONCLUSIONS

Trauma patients with blunt mechanism, who receive fresh frozen plasma, or undergo thoracotomy, are at risk of developing early ARDS.