Early identification of patients at risk of acute lung injury: evaluation of lung injury prediction score in a multicenter cohort study

Acute Respiratory Distress Syndrome Prediction Score: Derivation and Validation

BACKGROUND

Despite advances in treatment strategies, acute respiratory distress syndrome (ARDS) after cardiac surgery remains associated with high morbidity and mortality. A method of screening patients for risk of ARDS after cardiac surgery is needed.

OBJECTIVES

To develop and validate an ARDS prediction score designed to identify patients at high risk of ARDS after cardiac or aortic surgery.

METHODS

An ARDS prediction score was derived from a retrospective derivation cohort and validated in a prospective cohort. Discrimination and calibration of the score were assessed with area under the receiver operating characteristic curve and the Hosmer-Lemeshow goodness-of-fit test, respectively. A sensitivity analysis was conducted to assess model performance at different cutoff points.

RESULTS

The retrospective derivation cohort consisted of 201 patients with and 602 patients without ARDS who had undergone cardiac or aortic surgery. Nine routinely available clinical variables were included in the ARDS prediction score. In the derivation cohort, the score distinguished patients with versus without ARDS with area under the curve of 0.84 (95% CI, 0.81-0.88; Hosmer-Lemeshow P = .55). In the validation cohort, 46 of 1834 patients (2.5%) had ARDS develop within 7 days after cardiac or aortic surgery. Area under the curve was 0.78 (95% CI, 0.71-0.85), and the score was well calibrated (Hosmer-Lemeshow P = .53).

CONCLUSIONS

The ARDS prediction score can be used to identify high-risk patients from the first day after cardiac or aortic surgery. Patients with a score of 3 or greater should be closely monitored. The score requires external validation before clinical use.

Comparison of direct and indirect models of early induced acute lung injury

Background

The animal experimental counterpart of human acute respiratory distress syndrome (ARDS) is acute lung injury (ALI). Most models of ALI involve reproducing the clinical risk factors associated with human ARDS, such as sepsis or acid aspiration; however, none of these models fully replicates human ARDS.

Aim

To compare different experimental animal models of ALI, based on direct or indirect mechanisms of lung injury, to characterize a model which more closely could reproduce the acute phase of human ARDS.

Materials and methods

Adult male Sprague-Dawley rats were subjected to intratracheal instillations of (1) HCl to mimic aspiration of gastric contents; (2) lipopolysaccharide (LPS) to mimic bacterial infection; (3) HCl followed by LPS to mimic aspiration of gastric contents with bacterial superinfection; or (4) cecal ligation and puncture (CLP) to induce peritonitis and mimic sepsis. Rats were sacrificed 24 h after instillations or 24 h after CLP.

Results

At 24 h, rats instilled with LPS or HCl-LPS had increased lung permeability, alveolar neutrophilic recruitment and inflammatory markers (GRO/KC, TNF-α, MCP-1, IL-1β, IL-6). Rats receiving only HCl or subjected to CLP had no evidence of lung injury.

Conclusions

Rat models of ALI induced directly by LPS or HCl-LPS more closely reproduced the acute phase of human ARDS than the CLP model of indirectly induced ALI.

Obesity: A critical risk factor in the COVID-19 pandemic

Obesity is an emerging independent risk factor for susceptibility to and severity of coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Previous viral pandemics have shown that obesity, particularly severe obesity (BMI > 40 kg/m2 ), is associated with increased risk of hospitalization, critical care admission and fatalities. In this narrative review, we examine emerging evidence of the influence of obesity on COVID-19, the challenges to clinical management from pulmonary, endocrine and immune dysfunctions in individuals with obesity and identify potential areas for further research. We recommend that people with severe obesity be deemed a vulnerable group for COVID-19; clinical trials of pharmacotherapeutics, immunotherapies and vaccination should prioritize inclusion of people with obesity.

Lung protection in acute respiratory distress syndrome: what should we target?

PURPOSE OF REVIEW

Most clinical trials of lung-protective ventilation have tested one-size-fits-all strategies with mixed results. Data are lacking on how best to tailor mechanical ventilation to patient-specific risk of lung injury.

RECENT FINDINGS

Risk of ventilation-induced lung injury is determined by biological predisposition to biophysical lung injury and physical mechanical perturbations that concentrate stress and strain regionally within the lung. Recent investigations have identified molecular subphenotypes classified as hyperinflammatory and hypoinflammatory acute respiratory distress syndrome (ARDS), which may have dissimilar risk for ventilation-induced lung injury. Mechanically, gravity-dependent atelectasis has long been recognized to decrease total aerated lung volume available for tidal ventilation, a concept termed the 'ARDS baby lung'. Recent studies have demonstrated that the aerated baby lung also has nonuniform stress/strain distribution, with potentially injurious forces concentrated in zones of heterogeneity where aerated alveoli are adjacent to flooded or atelectatic alveoli. The preponderance of evidence also indicates that current standard-of-care tidal volume management is not universally protective in ARDS. When considering escalation of lung-protective interventions, potential benefits of the intervention should be weighed against tradeoffs of accompanying cointerventions required, for example, deeper sedation or neuromuscular blockade. A precision medicine approach to lung-protection would weigh.

SUMMARY

A precision medicine approach to lung-protective ventilation requires weighing four key factors in each patient: biological predisposition to biophysical lung injury, mechanical predisposition to biophysical injury accounting for spatial mechanical heterogeneity within the lung, anticipated benefits of escalating lung-protective interventions, and potential unintended adverse effects of mandatory cointerventions.

Machine Learning Methods to Predict Acute Respiratory Failure and Acute Respiratory Distress Syndrome

Acute respiratory failure (ARF) is a common problem in medicine that utilizes significant healthcare resources and is associated with high morbidity and mortality. Classification of acute respiratory failure is complicated, and it is often determined by the level of mechanical support that is required, or the discrepancy between oxygen supply and uptake. These phenotypes make acute respiratory failure a continuum of syndromes, rather than one homogenous disease process. Early recognition of the risk factors for new or worsening acute respiratory failure may prevent that process from occurring. Predictive analytical methods using machine learning leverage clinical data to provide an early warning for impending acute respiratory failure or its sequelae. The aims of this review are to summarize the current literature on ARF prediction, to describe accepted procedures and common machine learning tools for predictive tasks through the lens of ARF prediction, and to demonstrate the challenges and potential solutions for ARF prediction that can improve patient outcomes.

Body Mass Index and Risk for Intubation or Death in SARS-CoV-2 Infection : A Retrospective Cohort Study

BACKGROUND

Obesity is a risk factor for pneumonia and acute respiratory distress syndrome.

OBJECTIVE

To determine whether obesity is associated with intubation or death, inflammation, cardiac injury, or fibrinolysis in coronavirus disease 2019 (COVID-19).

DESIGN

Retrospective cohort study.

SETTING

A quaternary academic medical center and community hospital in New York City.

PARTICIPANTS

2466 adults hospitalized with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 infection over a 45-day period with at least 47 days of in-hospital observation.

MEASUREMENTS

Body mass index (BMI), admission biomarkers of inflammation (C-reactive protein [CRP] level and erythrocyte sedimentation rate [ESR]), cardiac injury (troponin level), and fibrinolysis (D-dimer level). The primary end point was a composite of intubation or death in time-to-event analysis.

RESULTS

Over a median hospital length of stay of 7 days (interquartile range, 3 to 14 days), 533 patients (22%) were intubated, 627 (25%) died, and 59 (2%) remained hospitalized. Compared with overweight patients, patients with obesity had higher risk for intubation or death, with the highest risk among those with class 3 obesity (hazard ratio, 1.6 [95% CI, 1.1 to 2.1]). This association was primarily observed among patients younger than 65 years and not in older patients (P for interaction by age = 0.042). Body mass index was not associated with admission levels of biomarkers of inflammation, cardiac injury, or fibrinolysis.

LIMITATIONS

Body mass index was missing for 28% of patients. The primary analyses were conducted with multiple imputation for missing BMI. Upper bounding factor analysis suggested that the results are robust to possible selection bias.

CONCLUSION

Obesity is associated with increased risk for intubation or death from COVID-19 in adults younger than 65 years, but not in adults aged 65 years or older.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Disease Mechanisms of Perioperative Organ Injury

Despite substantial advances in anesthesia safety within the past decades, perioperative mortality remains a prevalent problem and can be considered among the top causes of death worldwide. Acute organ failure is a major risk factor of morbidity and mortality in surgical patients and develops primarily as a consequence of a dysregulated inflammatory response and insufficient tissue perfusion. Neurological dysfunction, myocardial ischemia, acute kidney injury, respiratory failure, intestinal dysfunction, and hepatic impairment are among the most serious complications impacting patient outcome and recovery. Pre-, intra-, and postoperative arrangements, such as enhanced recovery after surgery programs, can contribute to lowering the occurrence of organ dysfunction, and mortality rates have improved with the advent of specialized intensive care units and advances in procedures relating to extracorporeal organ support. However, no specific pharmacological therapies have proven effective in the prevention or reversal of perioperative organ injury. Therefore, understanding the underlying mechanisms of organ dysfunction is essential to identify novel treatment strategies to improve perioperative care and outcomes for surgical patients. This review focuses on recent knowledge of pathophysiological and molecular pathways leading to perioperative organ injury. Additionally, we highlight potential therapeutic targets relevant to the network of events that occur in clinical settings with organ failure.

Acute hypoxaemic respiratory failure in a low-income country: a prospective observational study of hospital prevalence and mortality

INTRODUCTION

Limited data exist on the epidemiology of acute hypoxaemic respiratory failure (AHRF) in low-income countries (LICs). We sought to determine the prevalence of AHRF in critically ill adult patients admitted to a Ugandan tertiary referral hospital; determine clinical and treatment characteristics as well as assess factors associated with mortality.

MATERIALS AND METHODS

We conducted a prospective observational study at the Mulago National Referral and Teaching Hospital in Uganda. Critically ill adults who were hospitalised at the emergency department and met the criteria for AHRF (acute shortness of breath for less than a week) were enrolled and followed up for 90 days. Multivariable analyses were conducted to determine the risk factors for death.

RESULTS

A total of 7300 patients was screened. Of these, 327 (4.5%) presented with AHRF. The majority (60 %) was male and the median age was 38 years (IQR 27-52). The mean plethysmographic oxygen saturation (SpO₂) was 77.6% (SD 12.7); mean SpO₂/FiO₂ ratio 194 (SD 32) and the mean Lung Injury Prediction Score (LIPS) 6.7 (SD 0.8). Pneumonia (80%) was the most common diagnosis. Only 6% of the patients received mechanical ventilatory support. In-hospital mortality was 77% with an average length of hospital stay of 9.2 days (SD 7). At 90 days after enrolment, the mortality increased to 85%. Factors associated with mortality were severity of hypoxaemia (risk ratio (RR) 1.29 (95% CI 1.15 to 1.54), p=0.01); a high LIPS (RR 1.79 (95% CI 1.79 1.14 to 2.83), p=0.01); thrombocytopenia (RR 1.23 (95% CI 1.11 to 1.38), p=0.01); anaemia (RR 1.15 (95% CI 1.01 to 1.31), p=0.03) ; HIV co-infection (RR 0.84 (95% CI 0.72 to 0.97), p=0.019) and male gender (RR 1.15 (95% CI 1.01 to 1.31) p=0.04).

CONCLUSIONS

The prevalence of AHRF among emergency department patients in a tertiary hospital in an LIC was low but was associated with very high mortality. Pneumonia was the most common cause of AHRF. Mortality was associated with higher severity of hypoxaemia, high LIPS, anaemia, HIV co-infection, thrombocytopenia and being male.

A Longer Route to the PICU Can Lead to a Longer Stay in the PICU: A Single-Center Retrospective Cohort Study

INTRODUCTION

Admission to the pediatric ICU versus general pediatric floor for patients is a significant triage decision for emergency department physicians. Escalation of care within 24 hours of hospital admission is considered as a quality metric for pediatric E.R. There exists, however, a lack of data to show that such escalation leads to a poor outcome.

METHODS

A retrospective cohort study was conducted to compare outcomes of patients who required escalation of care within 24 hours of hospital admission to the pediatric ICU (cases) from 01/01 2015 to 02/28 2019 with those who were directly admitted from emergency department to the PICU (controls). A total of 327 cases were compared to 931 controls. Univariate and multivariable regression analysis was done to compare the length of stay and mortality data.

RESULTS

Patients who required escalation of care were significantly younger (median age 1.9 years compared to 4.6 years for controls) and had lower severity of illness score (PIM 3). Cases had a much higher proportion of respiratory diagnosis. ICU length of stay, hospital length of stay and the direct cost was significantly higher for cases compared to controls. This difference persisted for all age groups and respiratory diagnosis. The cost of care, however, was only different for 1-5 years and >5 years age groups. The difference in ICU length of stay (Δ11.1%) and hospital length of stay (Δ7.8%) persisted on multivariate regression analysis after controlling for age, sex, PIM3 score, and diagnostic variables. There was no difference in mortality on the univariate or multivariate analysis between the 2 groups.

CONCLUSIONS

Patients who required escalation of care within 24 hours of hospital admissions have more prolonged ICU and hospital stay and potentially increased cost of care. This measure should be considered while making patient disposition decisions in the emergency department.

High-fat diet-induced obesity affects alpha 7 nicotine acetylcholine receptor expressions in mouse lung myeloid cells

Ample evidence indicates that obesity causes dysfunctions in the lung. Previous studies also show that cholinergic anti-inflammatory pathways play crucial roles in obesity-induced chronic inflammation via α7 nicotinic acetylcholine receptor (α7nAChR) signaling. However, it remains unclear whether and how obesity affects the expressions of α7nAChR in myeloid cells in the lung. To address this question, we treated regular chow diet-fed mice or high-fat diet induced obese mice with lipopolysaccharide (LPS) or vehicle via endotracheal injections. By using a multicolor flow cytometry approach to analyze and characterize differential cell subpopulations and α7nAChR expressions, we find no detectable α7nAChR in granulocytes, monocytes and alveolar macrophages, and low expression levels of α7nAChR were detected in interstitial macrophages. Interestingly, we find that a challenge with LPS treatment significantly increased expression levels of α7nAChR in monocytes, alveolar and interstitial macrophages. Meanwhile, we observed that the expression levels of α7nAChR in alveolar and interstitial macrophages in high-fat diet induced obese mice were lower than regular chow diet-fed mice challenged by the LPS. Together, our findings indicate that obesity alters the expressions of α7nAChR in differential lung myeloid cells.

The Association between Prehospital Vulnerability, ARDS Development, and Mortality among At-Risk Adults. Results from the LIPS-A Clinical Trial

Rationale: No previous studies have examined the role of prehospital vulnerability in acute respiratory distress syndrome (ARDS) development and mortality in an acutely ill adult population.Objectives: To describe the association between prehospital vulnerability and 1) the development of ARDS, 2) 28-day mortality, and 3) 1-year mortality.Methods: This was a longitudinal prospective cohort study nested within the multicenter LIPS-A (Lung Injury Prevention Study-Aspirin) trial. We analyzed 301 participants who completed Vulnerable Elders Survey (VES) at baseline. Multivariable logistic regression and Cox regression analyses were used to describe the association between vulnerability and short-term outcomes (ARDS and 28-day mortality) and long-term outcomes (1-year mortality), respectively.Results: The VES score ranged from 0 to 10 (median [interquartile range], 2.0 [0-6]); 143 (47.5%) fit criteria for prehospital vulnerability (VES ≥ 3). Vulnerability was not significantly associated with ARDS development (10 [7.0%] vulnerable patients developed ARDS as per LIPS-A study criteria vs. 20 [12.7%] without vulnerability; P = 0.10; adjusted odds ratio [95% confidence interval (CI)], 0.54 [0.24-1.24]; P = 0.15). Nor was vulnerability associated with 28-day mortality (15 [10.5%] vulnerable patients were dead by Day 28 vs. 11 [7.0%] nonvulnerable patients; P = 0.28; adjusted odds ratio [95% CI], 0.95 [0.39-2.26]; P = 0.90). Vulnerability was significantly associated with 1-year mortality in hospital survivors (35 [26.9%] vs. 13 [9.3%]; adjusted hazard ratio [95% CI], 2.20 [1.10-4.37]; P = 0.02).Conclusions: In a population of adults recruited for their high risk of ARDS, prehospital vulnerability, measured by VES, was highly prevalent and strongly associated with 1-year mortality.

Machine Learning Models of Acute Kidney Injury Prediction in Acute Pancreatitis Patients

Background. Acute kidney injury (AKI) has long been recognized as a common and important complication of acute pancreatitis (AP). In the study, machine learning (ML) techniques were used to establish predictive models for AKI in AP patients during hospitalization. This is a retrospective review of prospectively collected data of AP patients admitted within one week after the onset of abdominal pain to our department from January 2014 to January 2019. Eighty patients developed AKI after admission (AKI group) and 254 patients did not (non-AKI group) in the hospital. With the provision of additional information such as demographic characteristics or laboratory data, support vector machine (SVM), random forest (RF), classification and regression tree (CART), and extreme gradient boosting (XGBoost) were used to build models of AKI prediction and compared to the predictive performance of the classic model using logistic regression (LR). XGBoost performed best in predicting AKI with an AUC of 91.93% among the machine learning models. The AUC of logistic regression analysis was 87.28%. Present findings suggest that compared to the classical logistic regression model, machine learning models using features that can be easily obtained at admission had a better performance in predicting AKI in the AP patients.

Δ9-Tetrahydrocannabinol Prevents Mortality from Acute Respiratory Distress Syndrome through the Induction of Apoptosis in Immune Cells, Leading to Cytokine Storm Suppression

Acute Respiratory Distress Syndrome (ARDS) causes up to 40% mortality in humans and is difficult to treat. ARDS is also one of the major triggers of mortality associated with coronavirus-induced disease (COVID-19). We used a mouse model of ARDS induced by Staphylococcal enterotoxin B (SEB), which triggers 100% mortality, to investigate the mechanisms through which Δ9-tetrahydrocannabinol (THC) attenuates ARDS. SEB was used to trigger ARDS in C3H mice. These mice were treated with THC and analyzed for survival, ARDS, cytokine storm, and metabolome. Additionally, cells isolated from the lungs were used to perform single-cell RNA sequencing and transcriptome analysis. A database analysis of human COVID-19 patients was also performed to compare the signaling pathways with SEB-mediated ARDS. The treatment of SEB-mediated ARDS mice with THC led to a 100% survival, decreased lung inflammation, and the suppression of cytokine storm. This was associated with immune cell apoptosis involving the mitochondrial pathway, as suggested by single-cell RNA sequencing. A transcriptomic analysis of immune cells from the lungs revealed an increase in mitochondrial respiratory chain enzymes following THC treatment. In addition, metabolomic analysis revealed elevated serum concentrations of amino acids, lysine, n-acetyl methionine, carnitine, and propionyl L-carnitine in THC-treated mice. THC caused the downregulation of miR-185, which correlated with an increase in the pro-apoptotic gene targets. Interestingly, the gene expression datasets from the bronchoalveolar lavage fluid (BALF) of human COVID-19 patients showed some similarities between cytokine and apoptotic genes with SEB-induced ARDS. Collectively, this study suggests that the activation of cannabinoid receptors may serve as a therapeutic modality to treat ARDS associated with COVID-19.

Machine Learning Predicts Prolonged Acute Hypoxemic Respiratory Failure in Pediatric Severe Influenza

Supplemental Digital Content is available in the text.

Influenza virus is a major cause of acute hypoxemic respiratory failure. Early identification of patients who will suffer severe complications can help stratify patients for clinical trials and plan for resource use in case of pandemic.

Increased Th17 and Th22 Cell Percentages Predict Acute Lung Injury in Patients with Sepsis

PURPOSE

This study was conducted to investigate the percentages of Th22 and Th17 cells in the peripheral blood of septic patients with and without acute lung injury (ALI) and their clinical significance.

METHODS

A total of 479 patients were divided into non-ALI and ALI groups. The percentages of Th22 and Th17 cells and the levels of interleukin 22 (IL-22), 6 (IL-6), and 17 (IL-17) were determined. Receiver operating characteristic curve analysis was performed to assess the diagnostic value of Th22 and Th17 cells to predict sepsis-induced ALI.

RESULTS

The lung injury prediction score (LIPS), IL-6, IL-17, and IL-22 levels and the percentages of Th17 and Th22 cells were significantly higher in the ALI group (P < 0.05). They were significant factors affecting sepsis-induced ALI (P < 0.05). Multivariate logistic regression analysis showed that the LIPS (OR = 1.130), IL-17 (OR = 1.982), IL-22 (OR = 2.612) and the percentages of Th17 (OR = 2.211) and Th22 (OR = 3.230) cells were independent risk factors for ALI. The area under the curve of Th22 cells was 0.844 to predict ALI with a cutoff value of 6.81%. The sensitivity and specificity for early diagnosis of sepsis-induced ALI by the Th22 cell percentage were 78.72% and 89.13%, respectively.

CONCLUSIONS

Th22 and Th17 cells in peripheral blood are significantly increased in septic patients with ALI and they may be used as biomarkers for early diagnosis of sepsis-induced ALI.

Supervised machine learning for the early prediction of acute respiratory distress syndrome (ARDS)

PURPOSE

Acute respiratory distress syndrome (ARDS) is a serious respiratory condition with high mortality and associated morbidity. The objective of this study is to develop and evaluate a novel application of gradient boosted tree models trained on patient health record data for the early prediction of ARDS.

MATERIALS AND METHODS

9919 patient encounters were retrospectively analyzed from the Medical Information Mart for Intensive Care III (MIMIC-III) data base. XGBoost gradient boosted tree models for early ARDS prediction were created using routinely collected clinical variables and numerical representations of radiology reports as inputs. XGBoost models were iteratively trained and validated using 10-fold cross validation.

RESULTS

On a hold-out test set, algorithm classifiers attained area under the receiver operating characteristic curve (AUROC) values of 0.905 when tested for the detection of ARDS at onset and 0.827, 0.810, and 0.790 for the prediction of ARDS at 12-, 24-, and 48-h windows prior to onset, respectively.

CONCLUSION

Supervised machine learning predictions may help predict patients with ARDS up to 48 h prior to onset.

Descriptive Acute Respiratory Distress Syndrome (ARDS) in adults with imported severe Plasmodium falciparum malaria: A 10 year-study in a Portuguese tertiary care hospital

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a severe complication of malaria that remains largely unstudied. We aim to describe the development of ARDS associated with severe P. falciparum malaria, its management and impact on clinical outcome.

METHODS

Retrospective observational study of adult patients admitted with severe P. falciparum malaria in an Intensive Care Unit (ICU) of a tertiary care hospital from Portugal from 2008 to 2018. A multivariate logistic regression analysis was used to identify factors associated with the development of ARDS, defined according to Berlin Criteria. Prognosis was assessed by case-fatality ratio, nosocomial infection and length of stay.

RESULTS

98 patients were enrolled, of which 32 (33%) developed ARDS, a median of 2 days after starting antimalarial medication (IQR 0-4, range 0-6). Length of stay in ICU and in hospital were significantly longer in patients who developed ARDS: 13 days (IQR 10-18) vs 3 days (IQR 2-5) and 21 days (IQR 15-30.5) vs 7 days (IQR 6-10), respectively. Overall case-fatality ratio in ICU was 4.1% and did not differ between groups. The risk of ARDS development is difficult to establish.

CONCLUSION

ARDS is a hard to predict late complication of severe malaria. A low threshold for ICU admission and monitoring should be used. Ideally patients should be managed in a centre with experience and access to advanced techniques.

The ex vivo perfused human lung is resistant to injury by high-dose S. pneumoniae bacteremia

Few patients with bacteremia from a nonpulmonary source develop acute respiratory distress syndrome (ARDS). However, the mechanisms that protect the lung from injury in bacteremia have not been identified. We simulated bacteremia by adding Streptococcus pneumoniae to the perfusate of the ex vivo perfused human lung model. In contrast to a pneumonia model in which bacteria were instilled into the distal air spaces of one lobe, injection of high doses of S. pneumoniae into the perfusate was not associated with alveolar epithelial injury as demonstrated by low protein permeability of the alveolar epithelium, intact alveolar fluid clearance, and the absence of alveolar edema. Unexpectedly, the ex vivo human lung rapidly cleared large quantities of S. pneumoniae even though the perfusate had very few intravascular phagocytes and lacked immunoglobulins or complement. The bacteria were cleared in part by the small number of neutrophils in the perfusate, alveolar macrophages in the airspaces, and probably by interstitial pathways. Together, these findings identify one mechanism by which the lung and the alveolar epithelium are protected from injury in bacteremia.

Protective ventilation from ICU to operating room: state of art and new horizons

The prevention of ventilator-associated lung injury (VALI) and postoperative pulmonary complications (PPC) is of paramount importance for improving outcomes both in the operating room and in the intensive care unit (ICU). Protective respiratory support includes a wide spectrum of interventions to decrease pulmonary stress-strain injuries. The motto 'low tidal volume for all' should become routine, both during major surgery and in the ICU, while application of a high positive end-expiratory pressure (PEEP) strategy and of alveolar recruitment maneuvers requires a personalized approach and requires further investigation. Patient self-inflicted lung injury is an important type of VALI, which should be diagnosed and mitigated at the early stage, during restoration of spontaneous breathing. This narrative review highlights the strategies used for protective positive pressure ventilation. The emerging concepts of damaging energy and power, as well as pathways to personalization of the respiratory settings, are discussed in detail. In the future, individualized approaches to protective ventilation may involve multiple respiratory settings extending beyond low tidal volume and PEEP, implemented in parallel with quantifying the risk of VALI and PPC.

The acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a prevalent cause of acute respiratory failure with high rates of mortality, as well as short- and long-term complications, such as physical and cognitive impairment. Therefore, early recognition of this syndrome and application of well-demonstrated therapeutic interventions are essential to change the natural course of this entity and bring about positive clinical outcomes. In this article, we review updated concepts in ARDS. Specifically, we discuss the current definition of ARDS, its risk factors, and the evidence supporting ventilation management, adjunctive therapies, and interventions required in refractory hypoxemia.

Circulating miRNA 887 is differentially expressed in ARDS and modulates endothelial function

Circulating microRNAs (miRNAs) can be taken up by recipient cells and have been recently associated with the acute respiratory distress syndrome (ARDS). Their role in host predisposition to the syndrome is unknown. The objective of the study was to identify circulating miRNAs associated with the development of sepsis-related ARDS and examine their impact on endothelial cell gene expression and function. We determined miRNA levels in plasma collected from subjects during the first 24 h of admission to a tertiary intensive care unit for sepsis. A miRNA that was differentially expressed between subjects who did and did not develop ARDS was identified and was transfected into human pulmonary microvascular endothelial cells (HPMECs). RNA sequencing, in silico analysis, cytokine expression, and leukocyte migration assays were used to determine the impact of this miRNA on gene expression and cell function. In two cohorts, circulating miR-887-3p levels were elevated in septic patients who developed ARDS compared with those who did not. Transfection of miR-887-3p into HPMECs altered gene expression, including the upregulation of several genes previously associated with ARDS (e.g., CXCL10, CCL5, CX3CL1, VCAM1, CASP1, IL1B, IFNB, and TLR2), and activation of cellular pathways relevant to the response to infection. Functionally, miR-887-3p increased the endothelial release of chemokines and facilitated trans-endothelial leukocyte migration. Circulating miR-887-3p is associated with ARDS in critically ill patients with sepsis. In vitro, miR-887-3p regulates the expression of genes relevant to ARDS and neutrophil tracking. This miRNA may contribute to ARDS pathogenesis and could represent a novel therapeutic target.

Protective effects of aerosolized pulmonary surfactant powder in a model of ventilator-induced lung injury

Mechanical ventilation may contribute to the impairment of the pulmonary surfactant system, which is one of the mechanisms leading to the progression of acute lung injury. To investigate the potential protective effects of pulmonary surfactant in a rat model of ventilator-induced lung injury, the surfactant powder was aerosolized using an in-house made device designed to deliver the aerosolized powder to the inspiratory line of a rodent ventilator circuit. Rats were randomized to (i) administration of aerosolized recombinant surfactant protein C based pulmonary surfactant, (ii) intratracheally instillation of the same surfactant re-constituted in saline, and (iii) no treatment. Animals were monitored during 2 h of high-tidal volume mechanical ventilation, after which rats were sacrificed, and further analysis of lung mechanics and surfactant function were completed. Blood gas measurements during ventilation showed extended maintenance of oxygen levels above 400 mmHg in aerosol treated animals over non-treated and instilled groups, while total protein analysis showed reduced levels in the aerosol compared to non-treated groups. Dynamic captive bubble surface tension measurements showed the activity of surfactant recovered from aerosol treated animals is maintained below 1 mN/m. The prophylactic treatment of aerosolized surfactant powder reduced the severity of lung injury in this model.

Association of Intraoperative Ventilator Management With Postoperative Oxygenation, Pulmonary Complications, and Mortality

BACKGROUND

"Lung-protective ventilation" describes a ventilation strategy involving low tidal volumes (VTs) and/or low driving pressure/plateau pressure and has been associated with improved outcomes after mechanical ventilation. We evaluated the association between intraoperative ventilation parameters (including positive end-expiratory pressure [PEEP], driving pressure, and VT) and 3 postoperative outcomes: (1) PaO2/fractional inspired oxygen tension (FIO2), (2) postoperative pulmonary complications, and (3) 30-day mortality.

METHODS

We retrospectively analyzed adult patients who underwent major noncardiac surgery and remained intubated postoperatively from 2006 to 2015 at a single US center. Using multivariable regressions, we studied associations between intraoperative ventilator settings and lowest postoperative PaO2/FIO2 while intubated, pulmonary complications identified from discharge diagnoses, and in-hospital 30-day mortality.

RESULTS

Among a cohort of 2096 cases, the median PEEP was 5 cm H2O (interquartile range = 4-6), median delivered VT was 520 mL (interquartile range = 460-580), and median driving pressure was 15 cm H2O (13-19). After multivariable adjustment, intraoperative median PEEP (linear regression estimate [B] = -6.04; 95% CI, -8.22 to -3.87; P < .001), median FIO2 (B = -0.30; 95% CI, -0.50 to -0.10; P = .003), and hours with driving pressure >16 cm H2O (B = -5.40; 95% CI, -7.2 to -4.2; P < .001) were associated with decreased postoperative PaO2/FIO2. Higher postoperative PaO2/FIO2 ratios were associated with a decreased risk of pulmonary complications (adjusted odds ratio for each 100 mm Hg = 0.495; 95% CI, 0.331-0.740; P = .001, model C-statistic of 0.852) and mortality (adjusted odds ratio = 0.495; 95% CI, 0.366-0.606; P < .001, model C-statistic of 0.820). Intraoperative time with VT >500 mL was also associated with an increased likelihood of developing a postoperative pulmonary complication (adjusted odds ratio = 1.06/hour; 95% CI, 1.00-1.20; P = .042).

CONCLUSIONS

In patients requiring postoperative intubation after noncardiac surgery, increased median FIO2, increased median PEEP, and increased time duration with elevated driving pressure predict lower postoperative PaO2/FIO2. Intraoperative duration of VT >500 mL was independently associated with increased postoperative pulmonary complications. Lower postoperative PaO2/FIO2 ratios were independently associated with pulmonary complications and mortality. Our findings suggest that postoperative PaO2/FIO2 may be a potential target for future prospective trials investigating the impact of specific ventilation strategies for reducing ventilator-induced pulmonary injury.

Decreased Hospital Length of Stay With Early Administration of Oseltamivir in Patients Hospitalized With Influenza

Objective

To evaluate the effects of timely oseltamivir administration in patients hospitalized with seasonal influenza.

Patients and Methods

We performed a single-center retrospective cohort study for hospitalized patients who tested positive for influenza between December 1, 2010, and July 1, 2014. We compared outcomes for patients who received antivirals within 48 hours of symptoms to those of patients who either received oseltamivir after 48 hours or never received oseltamivir. Hospital length of stay (LOS) and 90-day mortality were compared using Cox regression models. Antiviral administration was analyzed as a time-varying covariate.

Results

During the study period, 433 patients were hospitalized with laboratory-confirmed influenza. Of these patients, 146 (33.7%) received oseltamivir within 48 hours of symptoms, 202 (46.7%) received oseltamivir after 48 hours of symptoms, and 85 (19.6%) did not receive antivirals. Baseline characteristics were similar among these patient groups. Receiving oseltamivir within 48 hours was associated with shorter hospital LOS (5.9 days vs 7.2 days; P=.03) but no significant difference in 90-day mortality (13.7% vs 11.5%; P=.51). In a Cox regression analysis, patients who received antivirals within 48 hours had a 50% higher chance of being discharged (hazard ratio, 1.50; 95% CI, 1.14-1.98) on any given day during hospital stay.

Conclusion

In patients hospitalized with laboratory-confirmed influenza, timely administration of oseltamivir was associated with shorter hospital LOS.

Acute respiratory distress syndrome in acute pancreatitis

Development of organ failure is one of the major determinants of mortality in patients with acute pancreatitis (AP). Acute respiratory distress syndrome (ARDS) is an important cause of respiratory failure in AP and is associated with high mortality. Pathogenesis of ARDS in AP is incompletely understood. Release of various cytokines plays an important role in development of ARDS in AP. Increased gut permeability due to various toxins, inflammatory mediators, and pancreatic enzymes potentiates lung injury by gut-lymph-lung axis leading on to increased translocation of bacterial endotoxins. Various scoring systems, serum levels of various cytokines and lung ultrasound have been evaluated for prediction of development of ARDS in AP with varying results. Various drugs have shown encouraging results in prevention of ARDS in animal models but these encouraging results in animal models are yet to be confirmed in clinical studies. There is no specific effective treatment for ARDS. Treatment of sepsis and local complications of AP should be done according to the standard management strategies. Lung protective ventilatory strategies are of paramount importance to improve outcome of patients of AP with ARDS and therefore effective coordination between gastroenterologists and intensivists is needed for effective management of these patients.

Emerging concepts in ventilation-induced lung injury

Ventilation-induced lung injury results from mechanical stress and strain that occur during tidal ventilation in the susceptible lung. Classical descriptions of ventilation-induced lung injury have focused on harm from positive pressure ventilation. However, injurious forces also can be generated by patient effort and patient–ventilator interactions. While the role of global mechanics has long been recognized, regional mechanical heterogeneity within the lungs also appears to be an important factor propagating clinically significant lung injury. The resulting clinical phenotype includes worsening lung injury and a systemic inflammatory response that drives extrapulmonary organ failures. Bedside recognition of ventilation-induced lung injury requires a high degree of clinical acuity given its indistinct presentation and lack of definitive diagnostics. Yet the clinical importance of ventilation-induced lung injury is clear. Preventing such biophysical injury remains the most effective management strategy to decrease morbidity and mortality in patients with acute respiratory distress syndrome and likely benefits others at risk.

Higher incidence of acute respiratory distress syndrome in cardiac surgical patients with elevated serum procalcitonin concentration: a prospective cohort study

BACKGROUND

Inflammatory response is activated during cardiopulmonary bypass (CPB), which may lead to acute respiratory distress syndrome (ARDS) and procalcitonin (PCT) increases during this inflammatory response. The objective of the study was to validate whether patients with higher serum PCT concentrations have a higher incidence of ARDS.

METHODS

The study was a prospective, single-center, observational cohort study. All patients who received cardiac surgery with CPB were screened for study eligibility. Patients were assigned to the PCT-elevated cohort or the control cohort according to serum PCT concentration on the first postoperative day with a cut-off value of 7.0 ng/mL. Patients were followed up until the 7th postoperative day. The primary endpoint was the incidence of ARDS, which was diagnosed according to the Berlin definition.

RESULTS

A total of 296 patients were enrolled, 64 patients were assigned to the PCT-elevated cohort and 232 patients were assigned to the control cohort. PCT concentration was 16.23 ± 5.9 ng/mL in the PCT-elevated cohort, and 2.70 ± 1.43 ng/mL in the control cohort (p < 0.001). The incidence of ARDS was significantly higher in the PCT-elevated cohort than in the control cohort (21.9% versus 5.6%, p < 0.001). The incidence of moderate-to-severe ARDS was also significantly higher in the PCT-elevated cohort than in the control cohort (10.9% versus 0.4%, p < 0.001). The hazard ratio of ARDS at 7 days in the PCT-elevated cohort, as compared with the control cohort, was 6.8 (95% confidence interval 2.7 to 17.4). The hazard ratio of moderate-to-severe ARDS in the PCT-elevated cohort was 57.3 (95% confidence interval 10.4 to 316.3). The positive predictive value of PCT for ARDS and moderate-to-severe ARDS were 0.242 and 0.121, respectively; the negative predictive value of PCT for ARDS and moderate-to-severe ARDS were 0.952 and 1.0, respectively.

CONCLUSION

Cardiac surgical patients with elevated PCT concentration have a higher incidence of ARDS. Elevated PCT may serve as a warning signal of postoperative ARDS in patients undergoing cardiac surgery with CPB. Study registration Chinese Clinical Trial Registry (ChiCTR-OCH-14005076).

Injury Characteristics and von Willebrand Factor for the Prediction of Acute Respiratory Distress Syndrome in Patients With Burn Injury: Development and Internal Validation

OBJECTIVE

To derive and validate a prediction model for the development of ARDS in burn-injured patients.

SUMMARY BACKGROUND DATA

Burn injury carries the highest incidence of acute respiratory distress syndrome (ARDS) among all predisposing conditions, but few studies exist on risk factors in these patients. Studies employing biomarkers and clinical risk factors for predicting ARDS mortality have recently been examined but none exist for onset of ARDS nor in patients with burn injury.

METHODS

This was a prospective multicenter study of 113 patients with isolated burn injury or inhalation injury. Clinical variables and plasma biomarkers representative of endothelial injury, epithelial injury, or inflammation were collected within 24 hours of admission. The most parsimonious model was chosen by considering discrimination, calibration, and model fit.

RESULTS

Among the biomarkers measured in patients with burn injuries, a one-standard deviation increase in log-transformed levels of the A2 domain of von Willebrand factor in the first 24 hours was most strongly associated with the development of ARDS (OR 7.72; 95% CI: 1.64-36.28, P = 0.03). Of candidate models, a 3-variable model with %TBSA, inhalation injury, and von Willebrand factor-A2 had comparable discrimination to more complex models (area under the curve: 0.90; 95% CI 0.85-0.96). The 3-variable model had good model fit by Hosmer-Lemeshow test (P = 0.74) and maintained similar discrimination after accounting for performance optimism (Bootstrapped area under the curve: 0.90; 95% CI: 0.84-0.95).

CONCLUSIONS

The 3-variable model with %TBSA, inhalation injury, and von Willebrand factor could be used to better identify at-risk patients for both the study and prevention of ARDS in patients with burn injury.

Towards Reliable ARDS Clinical Decision Support: ARDS Patient Analytics with Free-text and Structured EMR Data

In this work, we utilize a combination of free-text and structured data to build Acute Respiratory Distress Syndrome(ARDS) prediction models and ARDS phenotype clusters. We derived 'Patient Context Vectors' representing patientspecific contextual ARDS risk factors, utilizing deep-learning techniques on ICD and free-text clinical notes data. The Patient Context Vectors were combined with structured data from the first 24 hours of admission, such as vital signs and lab results, to build an ARDS patient prediction model and an ARDS patient mortality prediction model achieving AUC of 90.16 and 81.01 respectively. The ability of Patient Context Vectors to summarize patients' medical history and current conditions is also demonstrated by the automatic clustering of ARDS patients into clinically meaningful phenotypes based on comorbidities, patient history, and presenting conditions. To our knowledge, this is the first study to successfully combine free-text and structured data, without any manual patient risk factor curation, to build real-time ARDS prediction models.

Clinical Characteristics, Major Morbidity, and Mortality in Trauma-Related Pediatric Acute Respiratory Distress Syndrome

OBJECTIVES

To determine the presence, central characteristics, and impact on major morbidity and mortality of trauma-related pediatric acute respiratory distress syndrome.

DESIGN

Retrospective review of a prospective trauma database.

SETTING

American College of Surgeons verified level 1 trauma center in an urban setting.

PATIENTS

Trauma patients age 0 to 18 years old inclusive.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of the 7,382 patients presenting within the 10-year study period, 646 met study criteria for inclusion in the analysis. Trauma-related pediatric acute respiratory distress syndrome was present in 9% of the analyzed cohort. On univariate analysis and compared with those without, trauma-related pediatric acute respiratory distress syndrome occurred more commonly among those with traumatic brain injury (77.2% vs 45.5%; p < 0.001), non-accidental trauma (28.8% vs 10.2%; p < 0.001), and an injury severity score greater than 30 (27.1% vs 3.8%; p 0.001). New or progressive multiple organ dysfunction syndrome was significantly higher in trauma-related pediatric acute respiratory distress syndrome patients (86.7% vs 10.4%; p < 0.001) as was mortality (18.3% vs 3.1%; p < 0.001) than in those without. The presence of trauma-related pediatric acute respiratory distress syndrome (odds ratio, 6.98; 95% CI, 2.95-16.5; p < 0.001), younger age (odds ratio, 0.93; 95% CI, 0.87-0.99; p = 0.038), and worse injury severity (odds ratio, 1.19; 95% CI, 1.14-1.24; p < 0.001) were all independent statistical predictors of new or progressive multiple organ dysfunction syndrome in this retrospective cohort. Mortality in patients without trauma-related pediatric acute respiratory distress syndrome increased with increasing injury severity, whereas mortality in patients with trauma-related pediatric acute respiratory distress syndrome was the same regardless of injury severity. On multivariable regression analysis, while age and injury severity were independent statistical predictors of mortality, trauma-related pediatric acute respiratory distress syndrome was not (odds ratio, 2.35; 95% CI, 0.88-6.28; p = 0.087).

CONCLUSIONS

Pediatric acute respiratory distress syndrome is present in the pediatric trauma population. Trauma-related pediatric acute respiratory distress syndrome is associated with eight times the organ dysfunction and five times the mortality compared with patients without trauma-related pediatric acute respiratory distress syndrome, yet research in this area is lacking. Further prospective, mechanistic evaluations are essential to understand why these patients are at risk and how to effectively intervene to improve outcomes.

Patient-ventilator asynchrony in conventional ventilation modes during short-term mechanical ventilation after cardiac surgery: randomized clinical trial

INTRODUCTION AND AIM

Studies regarding asynchrony in patients in the cardiac postoperative period are still only a few. The main objective of our study was to compare asynchronies incidence and its index (AI) in 3 different modes of ventilation (volume-controlled ventilation [VCV], pressure-controlled ventilation [PCV] and pressure-support ventilation [PSV]) after ICU admission for postoperative care.

METHODS

A prospective parallel randomised trialin the setting of a non-profitable hospital in Brazil. The participants were patients scheduled for cardiac surgery. Patients were randomly allocated to VCV or PCV modes of ventilation and later both groups were transitioned to PSV mode.

RESULTS

All data were recorded for 5 minutes in each of the three different phases: T1) in assisted breath, T2) initial spontaneous breath and T3) final spontaneous breath, a marking point prior to extubation. Asynchronies were detected and counted by visual inspection method by two independent investigators. Reliability, inter-rater agreement of asynchronies, asynchronies incidence, total and specific asynchrony indexes (AIt and AIspecific) and odds of AI ≥10% weighted by total asynchrony were analysed. A total of 17 patients randomly allocated to the VCV (n=9) or PCV (n=8) group completed the study. High inter-rated agreement for AIt (ICC 0.978; IC95%, 0,963-0.987) and good reliability (r=0.945; p<0.001) were found. Eighty-two % of patients presented asynchronies, although only 7% of their total breathing cycles were asynchronous. Early cycling and double triggering had the highest rates of asynchrony with no difference between groups. The highest odds of AI ≥10% were observed in VCV regardless the phase: OR 2.79 (1.36-5.73) in T1 vs T2, p=0.005; OR 2.61 (1.27-5.37) in T1 vs T3, p=0.009 and OR 4.99 (2.37-10.37) in T2 vs T3, p<0.001.

CONCLUSIONS

There was a high incidence of breathing asynchrony in postoperative cardiac patients, especially when initially ventilated in VCV. VCV group had a higher chance of AI ≥10% and this chance remained high in the following PSV phases.

Risk modifiers of acute respiratory distress syndrome in patients with non-pulmonary sepsis: a retrospective analysis of the FORECAST study

Background

Predisposing conditions and risk modifiers instead of causes and risk factors have recently been used as alternatives to identify patients at a risk of acute respiratory distress syndrome (ARDS). However, data regarding risk modifiers among patients with non-pulmonary sepsis is rare.

Methods

We conducted a secondary analysis of the multicenter, prospective, Focused Outcomes Research in Emergency Care in Acute Respiratory Distress Syndrome, Sepsis and Trauma (FORECAST) cohort study that was conducted in 59 intensive care units (ICUs) in Japan during January 2016–March 2017. Adult patients with severe sepsis caused by non-pulmonary infection were included, and the primary outcome was having ARDS, defined as meeting the Berlin definition on the first or fourth day of screening. Multivariate logistic regression modeling was used to identify risk modifiers associated with ARDS, and odds ratios (ORs) and their 95% confidence intervals were reported. The following explanatory variables were then assessed: age, sex, admission source, body mass index, smoking status, congestive heart failure, chronic obstructive pulmonary disease, diabetes mellitus, steroid use, statin use, infection site, septic shock, and acute physiology and chronic health evaluation (APACHE) II score.

Results

After applying inclusion and exclusion criteria, 594 patients with non-pulmonary sepsis were enrolled, among whom 85 (14.3%) had ARDS. Septic shock was diagnosed in 80% of patients with ARDS and 66% of those without ARDS (p = 0.01). APACHE II scores were higher in patients with ARDS [26 (22–33)] than in those without ARDS [21 (16–28), p < 0.01]. In the multivariate logistic regression model, the following were independently associated with ARDS: ICU admission source [OR, 1.89 (1.06–3.40) for emergency department compared with hospital wards], smoking status [OR, 0.18 (0.06–0.59) for current smoking compared with never smoked], infection site [OR, 2.39 (1.04–5.40) for soft tissue infection compared with abdominal infection], and APACHE II score [OR, 1.08 (1.05–1.12) for higher compared with lower score].

Conclusions

Soft tissue infection, ICU admission from an emergency department, and a higher APACHE II score appear to be the risk modifiers of ARDS in patients with non-pulmonary sepsis.

Risk Factors and Etiologies of Pediatric Acute Respiratory Distress Syndrome

The risk factors for acute respiratory distress syndrome (ARDS) have been a focus for clinicians and researchers from the original description in 1967 to the most recent Pediatric Acute Lung Injury Consensus Conference (PALICC). Indeed, there are many comorbidities and risk factors that predispose a patient to develop pediatric ARDS (PARDS) including, but not limited to, immunodeficiency, weight extremes, genetics, and environmental factors. These are particularly important to investigators because accurate prediction of which patients are at greatest risk of PARDS – both the development of PARDS and worse clinical outcomes after PARDS has been established – is key to identifying the next generation of diagnostic techniques and preventative strategies. In addition to those risk factors, there are specific disease processes that lead to the development of PARDS, often divided into direct or pulmonary insults and indirect or extrapulmonary insults. Finally, beyond the clinically visible risk factors, researchers are attempting to identify novel biomarkers to uncover hidden phenotypes of PARDS and enrich the prognostication and prediction of patient outcomes. This chapter delves into each of these concepts.

What factors predispose patients to acute respiratory distress syndrome?

Sepsis, pneumonia, and shock are the most common conditions predisposing to acute respiratory distress syndrome (ARDS) and certain host genetic variants have been associated with the development of ARDS. Risk modifiers include abuse of alcohol and tobacco, malnutrition, and obesity. The Lung Injury Prediction Score (LIPS) and the simplified Early Acute Lung Injury Score predict ARDS based on clinical and investigational criteria. Hospital-acquired ARDS may result from a medley factors of which high tidal volume ventilation, high oxygen concentration, and plasma transfusion are most commonly implicated. The Checklist for Lung Injury Prevention (CLIP) has been developed to ensure compliance with evidence-based practice that may affect ARDS occurrence. To date, no pharmacologic intervention has been shown to prevent ARDS

Acute Respiratory Distress Syndrome Novel Therapies

Acute respiratory distress syndrome (ARDS) was first described in 1967. Since then, several landmark studies have been published that have greatly influenced the way we diagnose and treat patients with ARDS. Despite extensive research and advancements in ventilator strategies, moderate-severe ARDS has been associated with high mortality rates. Current treatment remains primarily supportive with lung-protective ventilation strategies. Pharmacological therapies that reduce the severity of lung injury in vivo and in vitro have not yet translated into effective clinical treatment options. Currently, the mortality rate of severe ARDS remains in the range of 30% to 40%. To review, the mainstay of ARDS management includes mechanical ventilation with low tidal volumes to decrease barotrauma, prone ventilation, conservative fluid management, and neuromuscular blockade. ARDS survivors tend to have long-term and potentially permanent neuromuscular, cognitive, and psychological symptoms, affecting patient's quality of life posthospitalization. These long-term effects are likely secondary to prolonged hospitalizations, prolonged mechanical ventilation, utilization of prone strategies, utilization of paralytic drugs, and occasionally steroids. Therefore, several novel therapies outside the realm of advanced ventilation and prone positioning methods are being studied. In this article, we discuss a few of these novel therapies including prophylactic aspirin, inhaled nitric oxide, mesenchymal stem cells, and intravenous β-agonists. Steroids and extracorporeal membrane oxygenation have been discussed in a previous article.

Acute Respiratory Distress Syndrome From an Infectious Disease Perspective

Acute respiratory distress syndrome (ARDS) is an inflammatory form of lung injury in response to various clinical entities or inciting events, quite frequently due to an underlying infection. Morbidity and mortality associated with ARDS are significant. Hence, early recognition and targeted treatment are crucial to improve clinical outcomes. This article encompasses the most common infectious etiologies of ARDS and their clinical presentations and management, along with commonly encountered infectious complications in such patients.

Risk factors for the development of acute respiratory distress syndrome in mechanically ventilated adults in Peru: a multicenter observational study

Background

Clinical and epidemiological differences between acute respiratory distress syndrome (ARDS) that presents at the initiation of mechanical ventilation [MV] (ARDS at MV onset) and that which develops during the course of MV (ARDS after MV onset) are not well understood. We conducted an observational study in five Peruvian ICUs to characterize differences between ARDS at MV onset and after MV onset and identify risk factors for the development of ARDS after MV onset.

Methods

We consecutively enrolled critically ill patients with acute respiratory failure requiring at least 24 h of mechanical ventilation and followed them prospectively during the first 28 days and compared baseline characteristics and clinical outcomes by ARDS status.

Results

We enrolled 1657 participants on MV (mean age 60.0 years, 55% males) of whom 334 (20.2%) had ARDS at MV onset and 180 (10.9%) developed ARDS after MV onset. Average tidal volume at the initiation of MV was 8.7 mL/kg of predicted body weight (PBW) for participants with ARDS at MV onset, 8.6 mL/kg PBW for those who developed ARDS after MV onset, and 8.5 mL/kg PBW for those who never developed ARDS (p = 0.23). Overall, 90-day mortality was 56% and 55% for ARDS after MV onset and ARDS at MV onset, respectively, as compared to 46% among those who never developed ARDS (p < 0.01). Adults with ARDS had a higher body mass index (BMI) than those without ARDS (27.3 vs 26.5 kg/m², p < 0.01). Higher peak pressure (adjusted interquartile OR = 1.51, 95% CI 1.21–1.88), higher mean airway pressure (adjusted interquartile OR = 1.41, 95% CI 1.13–1.76), and higher positive end-expiratory pressure (adjusted interquartile OR = 1.29, 95% CI 1.10–1.50) at MV onset were associated with a higher odds of developing ARDS after MV onset.

Conclusions

In this study of mechanically ventilated patients, 31% of study participants had ARDS at some point during their ICU stay. Optimal lung-protective ventilation was not used in a majority of patients. Patients with ARDS after MV onset had a similar 90-day mortality as those with ARDS at MV onset. Higher airway pressures at MV onset, higher PEEP, and higher BMI were associated with the development of ARDS after MV onset.

RNAi therapeutic strategies for acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS), replacing the clinical term acute lung injury, involves serious pathophysiological lung changes that arise from a variety of pulmonary and nonpulmonary injuries and currently has no pharmacological therapeutics. RNA interference (RNAi) has the potential to generate therapeutic effects that would increase patient survival rates from this condition. It is the purpose of this review to discuss potential targets in treating ARDS with RNAi strategies, as well as to outline the challenges of oligonucleotide delivery to the lung and tactics to circumvent these delivery barriers.

Use of pressure-regulated volume control in the first 48 hours of hospitalization of mechanically ventilated patients with sepsis or septic shock, with or without ARDS

Purpose

To evaluate the impact of pressure-regulated volume control (PRVC/VC+) use on delivered tidal volumes in patients with acute respiratory distress syndrome (ARDS) or at risk for ARDS.

Materials and methods

Retrospective study of mechanically ventilated adult patients with severe sepsis or septic shock.

Results

A total of 272 patients were divided into patients with recognized ARDS, patients without ARDS, and patients with unrecognized ARDS. Over 90% of patients were ventilated with PRVC on admission, resulting in delivered tidal volumes significantly higher than set tidal volumes among all groups at all time points, even after ARDS recognition (p < 0.001). Tidal volumes were lower for patients with pulmonary sepsis as compared to those with a nonpulmonary origin (p < 0.001).

Conclusions

Using PRVC promotes augmented delivered tidal volumes, often in excess of 6 mL/kg ideal body weight. Correct recognition of ARDS and having pulmonary sepsis improves compliance with low-stretch protocol ventilation.

Pertinent clinical outcomes in pediatric survivors of pediatric acute respiratory distress syndrome (PARDS): a narrative review

The objectives of this review are to describe the limitations of commonly used clinical outcomes [e.g., mortality, ventilation parameters, need for extracorporeal membrane oxygenation (ECMO), pediatric intensive care unit (PICU) and hospital length of stay (LOS)] in pediatric acute respiratory distress syndrome (PARDS) studies; and to explore other pertinent clinical outcomes that pediatric critical care practitioners should consider in future clinical practice and research studies. These include long-term pulmonary function, risk of pulmonary hypertension (PHT), nutrition status and growth, PICU-acquired weakness, neurological outcomes and neurocognitive development, functional status, health-related quality of life (HRQOL)], health-care costs, caregiver and family stress. PubMed was searched using the following keywords or medical subject headings (MESH): "acute lung injury (ALI)", "acute respiratory distress syndrome (ARDS)", "pediatric acute respiratory distress syndrome (PARDS)", "acute hypoxemia respiratory failure", "outcomes", "pediatric intensive care unit (PICU)", "lung function", "pulmonary hypertension", "growth", "nutrition', "steroid", "PICU-acquired weakness", "functional status scale", "neurocognitive", "psychology", "health-care expenditure", and "HRQOL". The concept of contemporary measure outcomes was adapted from adult ARDS long-term outcome studies. Articles were initially searched from existing PARDS articles pool. If the relevant measure outcomes were not found, where appropriate, we considered studies from non-ARDS patients within the PICU in whom these outcomes were studied. Long-term outcomes in survivors of PARDS were not follow-up in majority of pediatric studies regardless of whether the new or old definitions of ARDS in children were used. Relevant studies were scarce, and the number of participants was small. As such, available studies were not able to provide conclusive answers to most of our clinical queries. There remains a paucity of data on contemporary clinical outcomes in PARDS studies. In addition to the current commonly used outcomes, clinical researchers and investigators should consider examining these contemporary outcome measures in PARDS studies in the future.

Predictive model for acute respiratory distress syndrome events in ICU patients in China using machine learning algorithms: a secondary analysis of a cohort study

BACKGROUND

To develop a machine learning model for predicting acute respiratory distress syndrome (ARDS) events through commonly available parameters, including baseline characteristics and clinical and laboratory parameters.

METHODS

A secondary analysis of a multi-centre prospective observational cohort study from five hospitals in Beijing, China, was conducted from January 1, 2011, to August 31, 2014. A total of 296 patients at risk for developing ARDS admitted to medical intensive care units (ICUs) were included. We applied a random forest approach to identify the best set of predictors out of 42 variables measured on day 1 of admission.

RESULTS

All patients were randomly divided into training (80%) and testing (20%) sets. Additionally, these patients were followed daily and assessed according to the Berlin definition. The model obtained an average area under the receiver operating characteristic (ROC) curve (AUC) of 0.82 and yielded a predictive accuracy of 83%. For the first time, four new biomarkers were included in the model: decreased minimum haematocrit, glucose, and sodium and increased minimum white blood cell (WBC) count.

CONCLUSIONS

This newly established machine learning-based model shows good predictive ability in Chinese patients with ARDS. External validation studies are necessary to confirm the generalisability of our approach across populations and treatment practices.

Definition and global epidemiology of pediatric acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) has been known to occur in children since early descriptions of the disease, but pediatric specific diagnostic criteria were first established in 2015 with the Pediatric Acute Lung Injury Consensus Conference (PALICC) definition of pediatric ARDS (PARDS). There were substantial changes proposed with the PALICC definition, including simplification of radiographic criteria, use of pulse oximetry based metrics to define PARDS, specific criteria for non-invasive ventilation, and the use of oxygenation index (OI) instead of PaO2/FiO2 ratio for those on invasive ventilation. While these changes could potentially result in major changes in the reported incidence and outcome of PARDS, review of the recent literature since publication of the PALICC definitions highlight that major elements regarding the contemporary epidemiology of PARDS have remained stable over the past 20 years. This highlights that the PARDS definition is likely catching up to changes in clinical practice, and suggests that this new definition should be used moving forward as it is more reflective of current practice than historical definitions. However, it is also clear that PARDS severity alone (as measured by the PALICC) criteria insufficiently characterizes the risk for mortality or other important clinical outcomes amongst PARDS patients, although there appears to be some association between PARDS severity and outcome, particularly when hypoxemia is severe.

Chronic, Silent Microaspiration Masquerading as Interstitial Lung Disease

Chronic, silent microaspiration is a common but underrecognized pathologic process in pulmonary medicine. The clinical presentation is variable and diagnosis can be challenging. We present the case of a 55-year-old woman with known emphysema, who was referred to us for progressive respiratory failure that was unresponsive to therapy. The patient had 9 hospital admissions in the preceding 5 months and was treated with multiple courses of antibiotics and systemic steroid therapy for a diagnosis of cryptogenic organizing pneumonia. The steroid therapy was complicated by 51 pounds of weight gain. She had conversational as well as profound exertional shortness of breath. Physical examination revealed a woman in moderate distress and bilateral diffuse wheezing and rhonchi. Computed tomography of the chest revealed areas of bronchocentric consolidation and bronchial wall thickening in the bilateral lower lobes. She underwent surgical lung biopsy and the histopathology was consistent with chronic aspiration pneumonia.

How to optimize critical care resources in surgical patients: intensive care without physical borders

PURPOSE OF REVIEW

Timely identification of surgery patients at risk of postoperative complications is important to improve the care process, including critical care. This review discusses epidemiology and impact of postoperative complications; prediction scores used to identify surgical patients at risk of complications, and the role of critical care in the postoperative management. It also discusses how critical care may change, with respect to admission to the ICU.

RECENT FINDING

Optimization of postoperative outcome, next to preoperative and intraoperative optimization, consists of using risk scores to early identify patients at risk of developing complications. Critical care consultancy should be performed in the ward after surgery, if necessary. ICUs could work at different levels of intensity, but remain preferably multidisciplinary, combining care for surgical and medical patients. ICU admission should still be considered for those patients at very high risk of postoperative complications, and for those receiving complex or emergency interventions.

SUMMARY

To optimize critical care resources for surgery patients at high risk of postoperative complications, the care process should not only include critical care and monitoring in ICUs, but also strict monitoring in the ward. Prediction scores could help to timely identify patients at risk. More intense care (monitoring) outside the ICU could improve outcome. This concept of critical care without borders could be implemented in the near future to optimize the local resources and improve patient safety. Predict more, do less in ICUs, and more in the ward.

Rapid breath analysis for acute respiratory distress syndrome diagnostics using a portable two-dimensional gas chromatography device

Acute respiratory distress syndrome (ARDS) is the most severe form of acute lung injury, responsible for high mortality and long-term morbidity. As a dynamic syndrome with multiple etiologies, its timely diagnosis is difficult as is tracking the course of the syndrome. Therefore, there is a significant need for early, rapid detection and diagnosis as well as clinical trajectory monitoring of ARDS. Here, we report our work on using human breath to differentiate ARDS and non-ARDS causes of respiratory failure. A fully automated portable 2-dimensional gas chromatography device with high peak capacity (> 200 at the resolution of 1), high sensitivity (sub-ppb), and rapid analysis capability (~ 30 min) was designed and made in-house for on-site analysis of patients' breath. A total of 85 breath samples from 48 ARDS patients and controls were collected. Ninety-seven elution peaks were separated and detected in 13 min. An algorithm based on machine learning, principal component analysis (PCA), and linear discriminant analysis (LDA) was developed. As compared to the adjudications done by physicians based on the Berlin criteria, our device and algorithm achieved an overall accuracy of 87.1% with 94.1% positive predictive value and 82.4% negative predictive value. The high overall accuracy and high positive predicative value suggest that the breath analysis method can accurately diagnose ARDS. The ability to continuously and non-invasively monitor exhaled breath for early diagnosis, disease trajectory tracking, and outcome prediction monitoring of ARDS may have a significant impact on changing practice and improving patient outcomes. Graphical abstract.