Plasma angiopoietin-2 predicts the onset of acute lung injury in critically ill patients

Transpulmonary LOX-1 Levels Are Predictive of Acute Respiratory Distress Syndrome After Cardiac Surgery: A Proof-of-Concept Study

Background/Objectives: Acute respiratory distress syndrome (ARDS) is a life-threatening condition that frequently complicates high-risk cardiac surgery. We evaluated the circulating levels and transpulmonary gradient of intracellular proteins in patients at risk of developing ARDS after cardiac surgery using large scale-proteomics. Methods: We enrolled sixteen patients undergoing high-risk cardiac surgery, followed by planned ICU admission. Circulating levels of intracellular proteins were measured at the onset of the surgical procedure, at ICU admission (H0), and 24 h (H24) after surgery in blood samples simultaneously drawn from both the pulmonary artery and the left atrium. The primary endpoint was the occurrence of ARDS between ICU admission and the subsequent 48 h. Results: Among the studied proteins, the levels of intracellular lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) were higher at H24 in the pulmonary artery in patients who developed ARDS (6.96; 95% CI [6.83-7.23]) compared to patients who did not (6.48; 95% CI [6.27-6.66]), p-value = 0.016. The transpulmonary gradient of intracellular LOX-1 levels was not significantly different between ARDS and non-ARDS patients at H0 but it was more negative at H24 in ARDS (-0.23; 95% CI [-0.27, -0.14]) than in non-ARDS patients (0.03; 95% CI [-0.14, 0.32]; p-value= 0.031), with a hazard ratio HR = 0.39 (95% CI [0.18-0.86]); p-value= 0.035. The area under the ROC curve of H24 LOX-1 transpulmonary gradient to predict ARDS occurrence was 0.83 (95% CI [0.62-1.00]). Conclusions: The transpulmonary gradient of intracellular LOX-1 levels was negatively associated with the occurrence of ARDS within the first 48 h after high-risk cardiac surgery, suggesting that lung trapping of LOX-1 may be linked to postoperative ARDS.

Plasma microRNA biomarkers for multi-organ injury prediction in trauma patients

Trauma remains a leading cause of morbidity and mortality in part due to secondary multi-organ injury. However, our ability to predict the downstream pathophysiology and adverse outcomes of trauma is limited. Here, we select a panel of microRNAs (miRNAs) biomarker candidates based on plasma RNA-Seq analysis of trauma patients and the unique pro-inflammatory nucleotide motif structures identified via a machine learning-guided computer exhaustive search algorithm. We test the panel of plasma miRNAs for their association with various trauma pathophysiological markers and their ability to predict organ injury and immune responses to trauma. We find a marked elevation of these plasma miRNAs as well as multiple inflammatory and organ injury factors at time of admission in a cohort of 48 blunt trauma patients. The plasma levels of these miRNA biomarkers are highly associated with multiple pathophysiological markers known for organ injury, coagulopathy, endothelial activation, and innate inflammation. AUROC analyses indicate that these miRNA biomarkers possess strong abilities to distinguish trauma severity, brain and liver injuries, metabolic acidosis, coagulopathy, and innate inflammation. These observations offer insights into potential values of the selected plasma miRNAs in prediction of trauma pathophysiological risk and clinical outcomes.

Correlations between primary tumour location, biomarkers of inflammation and lung injury, and postoperative pulmonary complications in patients underwent laparoscopic colorectomy: a propensity score matched analysis of 300 patients

Introduction

The impact of distinct primary colorectal cancer (CRC) sites on lung injury and complications remains largely unexplored, despite the palpable differences in surgical positions, procedures, and the resulting mechanically induced respiratory pressures at each site.

Materials and methods

This study employed a forwards-looking approach utilising the propensity score matching (PSM) method; 300 patients with pathological CRC after laparoscopic surgery from April 2019 to May 2023 were enrolled. Two categories were bifurcated based on their surgical locations: the rectosigmoid colon (RSC) group and the descending/ascending colon (DAC) group, with a 2:1 ratio. The occurrence of postoperative pulmonary complications (PPCs) within a 30-day postoperative period was meticulously evaluated. Additionally, assessments have been performed for plasma biomarkers of immune response dynamics and lung injury (plasma soluble advanced glycation end-product receptor [sRAGE], angiopoietin-2 [ANG-2], interleukin-1β/6 [IL-1β/IL-6]) and other parameters.

Results

Although the increase in postoperative lung epithelial damage, as indicated by the plasma sRAGE levels, was significant in the RSC group (DAC vs. RSC; 1029.6 [576.8-1365.2] vs. 1271.6 [896.3-1587.6]; odds ratio=0.999; 95% CI: 0.998 to 1.000; P=0.007), a significantly increased percentage of PPCs was observed in the DAC group (DAC vs. RSC; hazard ratio=1.669; 95% CI, 1.141 to 2.439; P=0.008). A univariate Cox proportional hazards model revealed that sRAGE, ANG-2, IL-1β, and IL-6 levels were not correlated with the incidence of time-to-PPCs across the two cohorts (P>0.05). Propensity score-weighted Cox regression and causal mediation analysis further demonstrated that the DAC site directly affected the incidence of PPCs, regardless of the other baseline confounders and clinical covariates related to the tumour site and PPCs.

Conclusion

The primary site of CRC is an independent predictor of the development of PPCs. Despite the steep Trendelenburg position of the RSC group inciting more pulmonary stress, inflammation and lung epithelial injury, as indicated by higher sRAGE, it demonstrated a lower PPCs occurrence relative to its DAC counterpart, with a slightly inclined or reversed Trendelenburg position. None of the plasma biomarkers of inflammation or lung injury indicated sufficient prognostic value for PPCs.

Biomarkers of Acute Respiratory Distress Syndrome: Current State and Future Prospects

Biomarkers are an important tool aiding researchers in the study of acute respiratory distress syndrome (ARDS). Mechanisms involving injury to the alveolar-capillary membrane, endothelium and epithelium resulting in lung inflammation and alterations in coagulation pathways have been validated in human trials and have been used to discover promising phenotypes that share similar characteristics and differential treatment responses. The emergence of powerful point-of-care technologies will enable the prospective study of biomarkers for future enrichment trials with the goal of transforming biomarkers into the clinical realm to inform delivery of personalized medicine at the bedside.

Exploring Angiopoietin-2: Clinical Insights and Experimental Perspectives in Kidney Diseases

Angiopoietin-2, an important contributor to angiogenesis and vascular remodeling, is increasingly recognized in kidney research. This review explores clinical insights and experimental perspectives on angiopoietin-2 in kidney diseases. Traditionally seen as an antagonist of the Tie-2, which is a receptor tyrosine kinase of endothelial cells and some hematopoietic stem cells, angiopoietin-2 exerts both proangiogenic and antiangiogenic effects, making it a versatile and context-dependent player in kidney pathophysiology. Elevated circulating angiopoietin-2 levels in clinical scenarios are associated with sepsis and acute kidney injury (AKI), emphasizing its role as a biomarker of disease severity. In diabetic kidney disease, circulating angiopoietin-2 correlates with albuminuria, a crucial indicator of disease progression, and may serve as a treatment target in protecting the endothelium. Angiopoietin-2 is implicated in chronic kidney diseases (CKDs), where its elevated circulating levels correlate with kidney outcomes and cardiovascular complications, suggesting its potential impact on kidney function and overall health. In experimental settings, angiopoietin-2 plays a pivotal role in angiogenesis and lymphangiogenesis, influencing vascular stability and endothelial integrity. The context-dependent agonist and antagonist role of angiopoietin-2 is regulated by a Tie-2 phosphatase, vascular endothelial protein tyrosine phosphatase (VEPTP), further underscoring its complexity. Angiopoietin-2 is also involved in regulating cellular integrity, inflammation, and endothelial permeability, making it a promising therapeutic target for conditions characterized by disrupted endothelial junctions and vascular dysfunction. This review provides a comprehensive overview of the diverse roles of angiopoietin-2 in kidney research, offering insights into potential therapeutic targets and advancements in managing kidney diseases.

Angiopoietin II in Critically Ill Septic Patients: A Post Hoc Analysis of the DRAK Study

INTRODUCTION

Angiopoietin II (Ang-II) plays a pivotal role in the development of microcirculatory dysfunction as it provokes endothelial barrier disruption in patients with sepsis or septic shock. In particular, those with acute kidney injury show high Ang-II concentrations. So far, it is unclear which covariates influence Ang-II concentration in the early phase of sepsis, especially if extracorporeal therapies also do.

METHODS

Ang-II concentrations were measured in 171 patients with sepsis after the first day of antibiotic treatment between 03/2013 and 01/2015. Ang-II was correlated with potential influencing factors (Spearman correlation). A multivariate model was established including the significant correlating parameters. The Mann-Whitney U test and the Kruskal-Wallis test were used to detect significant differences in Ang-II concentration.

RESULTS

The median Ang-II concentration was 8015 pg/mL (interquartile range (IQR): 5024-14,185). A total of forty patients were treated with kidney replacement therapy (KRT) and 20 were supported by venovenous extracorporeal membrane oxygenation (vv-ECMO). Sequential organ failure assessment (SOFA) score (r = 0.541), creatinine clearance (r = -0.467), urinary output (r = -0.289), interleukin (IL)-6 (r = 0.529), C-reactive protein (CRP) (r = 0.241), platelet count (r = -0.419), bilirubin (r = 0.565), lactate (r = 0.322), KRT (r = 0.451), and fluid balance (r = 0.373) significantly correlated with Ang-II concentration and were included in the multivariate model. There, creatinine clearance (p < 0.01, b = -26.3, 95% confidence interval (CI) -41.8--10.8), fluid balance (p = 0.002, b = 0.92, 95% CI 0.33-1.51), and CRP (p = 0.004, b = 127.6, 95% CI 41.6-213.7) were associated with Ang-II concentration. Furthermore, patients with KRT (median: 15,219 pg/mL, IQR: 10,548-20,270) had significantly (p < 0.01) higher Ang-II concentrations than those with vv-ECMO support (median: 6412 pg/mL, IQR: 5246-10,257) or those without extracorporeal therapy (median: 7156 pg/mL, IQR: 4409-12,741).

CONCLUSION

Increased CRP, positive fluid balance, and impaired kidney function were associated with higher Ang-II concentrations in critically ill patients in the early stage of sepsis in this post hoc analysis. In particular, patients with KRT had very high Ang-II concentrations, whereas the use of vv-ECMO was not related to higher Ang-II concentrations. The significance for clinical practice should be clarified by a prospective study with standardized measurements.

Inter- and Intra-donor variability in bone marrow-derived mesenchymal stromal cells: implications for clinical applications

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) are attractive as a therapeutic modality in multiple disease conditions characterized by inflammation and vascular compromise. Logistically they are advantageous because they can be isolated from adult tissue sources, such as bone marrow (BM). The phase 2a START clinical trial determined BM-MSCs to be safe in patients with moderate-to-severe acute respiratory distress syndrome (ARDS). Herein, we examine a subset of the clinical doses of MSCs generated for the phase 2a START trial from three unique donors (1-3), where one of the donors' donated BM on two separate occasions (donor 3 and 3W).

METHODS

The main objective of this study was to correlate properties of the cells from the four lots with plasma biomarkers from treated patients and relevant to ARDS outcomes. To do this we evaluated MSC donor lots for (i) post-thaw viability, (ii) growth kinetics, (iii) metabolism, (iv) surface marker expression, (v) protein expression, (vi) immunomodulatory ability and (vii) their functional effects on regulating endothelial cell permeability.

RESULTS

MSC-specific marker expression and protection of thrombin-challenged endothelial barrier permeability was similar among all four donor lots. Inter and intra-donor variability was observed in all the other in vitro assays. Furthermore, patient plasma ANG-2 and protein C levels at 6 hours post-transfusion were correlated to cell viability in an inter- and intra-donor dependent manner.

CONCLUSIONS

These findings highlight the potential of donor dependent (inter-) and collection dependent (intra-) effects in patient biomarker expression.

[Mechanism of Extracellular Histone-Induced Endothelial Dysfunction Leading to Sepsis-Induced Acute Respiratory Distress Syndrome]

Objective

Sepsis-induced acute respiratory distress syndrome (ARDS) is an independent risk factor for mortality in critically ill septic patients. However, effective therapeutic targets are still unavailable due to the lack of understanding of its unclear pathogenesis. With increasing understanding in the roles of circulating histones and endothelial dysfunction in sepsis, we aimed to investigate the mechanism of histone-induced endothelial dysfunction leading to sepsis-induced ARDS and to provide experimental support for histone-targeted treatment of sepsis-induced ARDS.

Methods

First of all, in vitro experiments were conducted. Human umbilical vein endothelial cells (HUVEC) were stimulated with gradient concentrations of histones to explore for the optimal stimulation concentration in vitro. Then, HUVEC were exposed to histones at an optimal concentration with or without resatorvid (TAK-242), a selective inhibitor of Toll-like receptor 4 (TLR4), for 24 hours for modeling. The cells were divided into 4 groups: 1) the blank control group, 2) the blank control+TAK-242 intervention group, 3) the histone stimulation group, and 4) the histone+TAK-242 intervention group. HUVEC apoptosis was determined by flow cytometry, VE-Cadherin expression in endothelial cells was determined by Western blot, and the integrity of adhesion connections between endothelial cells was evaluated with confocal fluorescence microscopic images. Male C57BL/6 mice aged 6-8 weeks and weighing 22-25 g were used for the in vivo experiment. Then, the mice were given cecal ligation and puncture (CLP) as well as histone injection at 50 mg/kg via the tail vein for sepsis modeling. The experimental animals were divided into 6 groups: 1) the blank control group, 2) the blank control+TAK-242 intervention group, 3) the CLP model group, 4) the CLP+TAK-242 intervention group, 5) the histone model group, and 6) the histone+TAK-242 intervention group. After 24 h, the concentrations of serum interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were determined using ELISA kits. Western blot was performed to determine the expression of vascular endothelial (VE)-cadherin in the lung tissue. Hematoxylin and eosin (HE) staining was performed to observe the pathological changes in the lung tissue of the mice. Evans Blue was injected via the tail vein 30 min before the mice were sacrificed. Lung tissue was collected after the mice were sacrificed. Then, the concentrations of Evans blue dye per unit mass in the lung tissue from mice of different groups were evaluated, the rates of pulmonary endothelial leakage were calculated, and the integrity of the pulmonary endothelial barrier was evaluated.

Results

The results of the in vitro experiment showed that, compared with those of the control group, HUVEC apoptosis was significantly increased under histone stimulation (P<0.05), the expression of VE-cadherin was decreased (P<0.05), and the integrity of adherens junctions between endothelial cells was damaged. TAK-242 can significantly inhibit histone-induced HUVEC apoptosis and VE-cadherin expression reduction and maintain the integrity of adherens junctions between endothelial cells. According to the findings from the in vivo experiments, in mice with CLP-induced and histone-induced sepsis, TAK-242 effectively alleviated the increase in serum concentrations of IL-6 and TNF-α, reduced the downregulation of VE-cadherin expression in the lung tissue (P<0.05), decreased endothelial permeability of the lung vessels, and improved pathological injury in the lung tissue.

Conclusion

By binding to TLR-4, histone decreases VE-cadherin expression on the surface of vascular endothelial cells, disrupts the integrity of intercellular adherens junctions, and triggers pathological damage to lung tissue. Using TLR-4 inhibitors can prevent sepsis-induced ARDS in histone-induced sepsis.

MiR-145-5p reduced ANG II-induced ACE2 shedding and the inflammatory response in alveolar epithelial cells by targeting ADAM17 and inhibiting the AT1R/ADAM17 pathway

The excessive elevation of angiotensin II (ANG II) is closely associated with the occurrence and development of aortic dissection (AD)-related acute lung injury (ALI), through its binding to angiotensin II receptor type I (AT1R). MiR-145-5p is a noncoding RNA that can be involved in a variety of cellular physiopathological processes. Transfection with miR-145-5p was found to downregulated the expression of A disintegrin and metalloprotease 17 (ADAM17) and reduced the levels of angiotensin-converting enzyme 2 (ACE2) in lung tissue, while concurrently increasing plasma ACE2 levels in the AD combined with ALI mice. ADAM17 was proved to be a target of miR-145-5p. Transfection with miR-145-5p decreased the shedding of ACE2 and alleviated the inflammatory response induced by ANG II through targeting ADAM17 and inhibiting the AT1R/ADAM17 pathway in A549 cells. In conclusion, our present study demonstrates the role and mechanism of miR-145-5p in alleviating ANG II-induced acute lung injury, providing a new insight into miRNA therapy for reducing lung injury in patients with aortic dissection.

Respiratory drive heterogeneity associated with systemic inflammation and vascular permeability in acute respiratory distress syndrome

BACKGROUND

In acute respiratory distress syndrome (ARDS), respiratory drive often differs among patients with similar clinical characteristics. Readily observable factors like acid-base state, oxygenation, mechanics, and sedation depth do not fully explain drive heterogeneity. This study evaluated the relationship of systemic inflammation and vascular permeability markers with respiratory drive and clinical outcomes in ARDS.

METHODS

ARDS patients enrolled in the multicenter EPVent-2 trial with requisite data and plasma biomarkers were included. Neuromuscular blockade recipients were excluded. Respiratory drive was measured as PES0.1, the change in esophageal pressure during the first 0.1 s of inspiratory effort. Plasma angiopoietin-2, interleukin-6, and interleukin-8 were measured concomitantly, and 60-day clinical outcomes evaluated.

RESULTS

54.8% of 124 included patients had detectable respiratory drive (PES0.1 range of 0-5.1 cm H2O). Angiopoietin-2 and interleukin-8, but not interleukin-6, were associated with respiratory drive independently of acid-base, oxygenation, respiratory mechanics, and sedation depth. Sedation depth was not significantly associated with PES0.1 in an unadjusted model, or after adjusting for mechanics and chemoreceptor input. However, upon adding angiopoietin-2, interleukin-6, or interleukin-8 to models, lighter sedation was significantly associated with higher PES0.1. Risk of death was less with moderate drive (PES0.1 of 0.5-2.9 cm H2O) compared to either lower drive (hazard ratio 1.58, 95% CI 0.82-3.05) or higher drive (2.63, 95% CI 1.21-5.70) (p = 0.049).

CONCLUSIONS

Among patients with ARDS, systemic inflammatory and vascular permeability markers were independently associated with higher respiratory drive. The heterogeneous response of respiratory drive to varying sedation depth may be explained in part by differences in inflammation and vascular permeability.

Rapidly improving ARDS differs clinically and biologically from persistent ARDS

BACKGROUND

Rapidly improving acute respiratory distress syndrome (RIARDS) is an increasingly appreciated subgroup of ARDS in which hypoxemia improves within 24 h after initiation of mechanical ventilation. Detailed clinical and biological features of RIARDS have not been clearly defined, and it is unknown whether RIARDS is associated with the hypoinflammatory or hyperinflammatory phenotype of ARDS. The purpose of this study was to define the clinical and biological features of RIARDS and its association with inflammatory subphenotypes.

METHODS

We analyzed data from 215 patients who met Berlin criteria for ARDS (endotracheally intubated) and were enrolled in a prospective observational cohort conducted at two sites, one tertiary care center and one urban safety net hospital. RIARDS was defined according to previous studies as improvement of hypoxemia defined as (i) PaO2:FiO2 > 300 or (ii) SpO2: FiO2 > 315 on the day following diagnosis of ARDS (day 2) or (iii) unassisted breathing by day 2 and for the next 48 h (defined as absence of endotracheal intubation on day 2 through day 4). Plasma biomarkers were measured on samples collected on the day of study enrollment, and ARDS phenotypes were allocated as previously described.

RESULTS

RIARDS accounted for 21% of all ARDS participants. Patients with RIARDS had better clinical outcomes compared to those with persistent ARDS, with lower hospital mortality (13% vs. 57%; p value < 0.001) and more ICU-free days (median 24 vs. 0; p value < 0.001). Plasma levels of interleukin-6, interleukin-8, and plasminogen activator inhibitor-1 were significantly lower among patients with RIARDS. The hypoinflammatory phenotype of ARDS was more common among patients with RIARDS (78% vs. 51% in persistent ARDS; p value = 0.001).

CONCLUSIONS

This study identifies a high prevalence of RIARDS in a multicenter observational cohort and confirms the more benign clinical course of these patients. We report the novel finding that RIARDS is characterized by lower concentrations of plasma biomarkers of inflammation compared to persistent ARDS, and that hypoinflammatory ARDS is more prevalent among patients with RIARDS. Identification and exclusion of RIARDS could potentially improve prognostic and predictive enrichment in clinical trials.

Trauma diagnostic-related target proteins and their detection techniques

Trauma is a significant health issue that not only leads to immediate death in many cases but also causes severe complications, such as sepsis, thrombosis, haemorrhage, acute respiratory distress syndrome and traumatic brain injury, among trauma patients. Target protein identification technology is a vital technique in the field of biomedical research, enabling the study of biomolecular interactions, drug discovery and disease treatment. It plays a crucial role in identifying key protein targets associated with specific diseases or biological processes, facilitating further research, drug design and the development of treatment strategies. The application of target protein technology in biomarker detection enables the timely identification of newly emerging infections and complications in trauma patients, facilitating expeditious medical interventions and leading to reduced post-trauma mortality rates and improved patient prognoses. This review provides an overview of the current applications of target protein identification technology in trauma-related complications and provides a brief overview of the current target protein identification technology, with the aim of reducing post-trauma mortality, improving diagnostic efficiency and prognostic outcomes for patients.

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

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

Glucocorticoid use in acute respiratory failure from pulmonary causes and association with early changes in the systemic host immune response

BACKGROUND

Glucocorticoids are commonly used in patients with or at-risk for acute respiratory distress syndrome (ARDS), but optimal use remains unclear despite well-conducted clinical trials. We performed a secondary analysis in patients previously enrolled in the Acute Lung Injury and Biospecimen Repository at the University of Pittsburgh. The primary aim of our study was to investigate early changes in host response biomarkers in response to real-world use of glucocorticoids in patients with acute respiratory failure due to ARDS or at-risk due to a pulmonary insult. Participants had baseline plasma samples obtained on study enrollment and on follow-up 3 to 5 days later to measure markers of innate immunity (IL-6, IL-8, IL-10, TNFr1, ST2, fractalkine), epithelial injury (sRAGE), endothelial injury (angiopoietin-2), and host response to bacterial infections (procalcitonin, pentraxin-3). In our primary analyses, we investigated the effect of receiving glucocorticoids between baseline and follow-up samples on host response biomarkers measured at follow-up by doubly robust inverse probability weighting analysis. In exploratory analyses, we examined associations between glucocorticoid use and previously characterized host response subphenotypes (hyperinflammatory and hypoinflammatory).

RESULTS

67 of 148 participants (45%) received glucocorticoids between baseline and follow-up samples. Dose and type of glucocorticoids varied. Regimens that used hydrocortisone alone were most common (37%), and median daily dose was equivalent to 40 mg methylprednisolone (interquartile range: 21, 67). Participants who received glucocorticoids were more likely to be female, to be on immunosuppressive therapy at baseline, and to have higher baseline levels of ST-2, fractalkine, IL-10, pentraxin-3, sRAGE, and TNFr1. Glucocorticoid use was associated with decreases in IL-6 and increases in fractalkine. In exploratory analyses, glucocorticoid use was more frequent in participants in the hyperinflammatory subphenotype (58% vs 40%, p = 0.05), and was not associated with subphenotype classification at the follow-up time point (p = 0.16).

CONCLUSIONS

Glucocorticoid use varied in a cohort of patients with or at-risk for ARDS and was associated with early changes in the systemic host immune response.

Attributable mortality of ARDS among critically ill patients with sepsis: a multicenter, retrospective cohort study

BACKGROUND

Both sepsis and acute respiratory distress syndrome (ARDS) are common severe diseases in the intensive care unit (ICU). There is no large-scale multicenter study to clarify the attributable mortality of ARDS among septic patients. This study aimed to evaluate the excess mortality of ARDS in critically ill patients with sepsis.

METHODS

The data were obtained from a multicenter, prospective cohort study in 18 Chinese ICUs between January 2014 and August 2015. The study population was septic patients after ICU admission. The patients were categorized into two groups: those who developed ARDS (ARDS group) within seven days following a sepsis diagnosis and those who did not develop ARDS (non-ARDS group). Applying propensity score matching (PSM), patients were matched 1:1 as ARDS and non-ARDS groups. Mortality attributed to ARDS was calculated. Subsequently, we conducted a survival analysis to estimate the impact of ARDS on mortality. The primary endpoint was 30-day mortality after sepsis diagnosis.

RESULTS

2323 septic patients were eligible, 67.8% developed ARDS. After PSM, 737 patients with ARDS were matched 1:1 with 737 non-ARDS patients. ARDS's overall 30-day attributable mortality was 11.9% (95% CI 7.5-16.3%, p < 0.001). Subgroup analysis showed that the 30-day attributable mortality of mild, moderate, and severe ARDS was 10.5% (95% CI 4.0-16.8%, p < 0.001), 11.6% (95% CI 4.7-18.4%, p < 0.001) and 18.1% (95% CI 4.5-30.9%, p = 0.006), respectively. ARDS was an independent risk factor for 30-day mortality, with adjusted hazard ratios of 1.30 (95% CI 1.03-1.64, p = 0.027), 1.49 (95% CI 1.20-1.85, p < 0.001), and 1.95 (95% CI 1.51-2.52, p < 0.001) for mild, moderate, and severe ARDS, respectively.

CONCLUSIONS

The overall 30-day attributable mortality of ARDS among critically ill patients with sepsis was 11.9%. Compared with mild and moderate ARDS, severe ARDS contributed more to death. ARDS was significantly associated with an increase in the 30-day mortality.

Acute respiratory distress syndrome heterogeneity and the septic ARDS subgroup

Acute respiratory distress syndrome (ARDS) is an acute diffuse inflammatory lung injury characterized by the damage of alveolar epithelial cells and pulmonary capillary endothelial cells. It is mainly manifested by non-cardiogenic pulmonary edema, resulting from intrapulmonary and extrapulmonary risk factors. ARDS is often accompanied by immune system disturbance, both locally in the lungs and systemically. As a common heterogeneous disease in critical care medicine, researchers are often faced with the failure of clinical trials. Latent class analysis had been used to compensate for poor outcomes and found that targeted treatment after subgrouping contribute to ARDS therapy. The subphenotype of ARDS caused by sepsis has garnered attention due to its refractory nature and detrimental consequences. Sepsis stands as the most predominant extrapulmonary cause of ARDS, accounting for approximately 32% of ARDS cases. Studies indicate that sepsis-induced ARDS tends to be more severe than ARDS caused by other factors, leading to poorer prognosis and higher mortality rate. This comprehensive review delves into the immunological mechanisms of sepsis-ARDS, the heterogeneity of ARDS and existing research on targeted treatments, aiming to providing mechanism understanding and exploring ideas for accurate treatment of ARDS or sepsis-ARDS.

Serum Angiopoietin-2 level increase differs between polytraumatized patients with and without central nervous system injuries

Since endothelial cells rapidly release Angiopoietin-2 (Ang-2) in response to vascular injury and inflammatory stimuli, we aimed to investigate if its serum levels increase in polytraumatized patients. Our cohort study evaluated 28 blunt polytrauma survivors (mean age, 38.4 years; median ISS, 34) who were directly admitted to our level I trauma center in 2018. We assessed the serum Ang-2 level at admission and on days 1, 3, 5, 7, and 10 during hospitalization. Ang-2 was released into the circulation immediately after polytrauma. At admission (day 0), it amounted to 8286 ± 5068 pg/mL, three-and-a-half times the reference value of 2337 ± 650 pg/mL assessed in a healthy control group. Subgroup analysis provided a higher mean Ang-2 level in the CNSI group combining all patients suffering a brain or spinal cord injury compared to the non-CNSI group solely on day 0 [11083 ± 5408 pg/mL versus 3963 ± 2062 pg/mL; p < 0.001]. Whereas the mean Ang-2 level increased only in the non-CNSI group from day 0 to day 3 (p = 0.009), the respective curves showed similar continuous decreases starting with day 3. Multivariate logistic regression analysis revealed an association between the Ang-2 day 0 level and the presence of a CNSI (OR = 1.885; p = 0.048). ROC analysis provided a cutoff level of 5352 pg/mL. In our study group, serum Ang-2 levels assessed at admission differed between polytraumatized patients with and without brain or spinal cord injuries. Based on our findings, we consider serum Ang-2 levels an effective biomarker candidate for indicating CNSI in these patients at admission, worthy of further evaluation in large multicenter studies.

Subphenotypes in patients with acute respiratory distress syndrome treated with high-flow oxygen

BACKGROUND

Acute respiratory distress syndrome (ARDS) subphenotypes differ in outcomes and treatment responses. Subphenotypes in high-flow nasal oxygen (HFNO)-treated ARDS patients have not been investigated.

OBJECTIVES

To identify biological subphenotypes in HFNO-treated ARDS patients.

METHODS

Secondary analysis of a prospective multicenter observational study including ARDS patients supported with HFNO. Plasma inflammation markers (interleukin [IL]-6, IL-8, and IL-33 and soluble suppression of tumorigenicity-2 [sST2]) and lung epithelial (receptor for advanced glycation end products [RAGE] and surfactant protein D [SP-D]) and endothelial (angiopoietin-2 [Ang-2]) injury were measured. These biomarkers and bicarbonate were used in K-means cluster analysis to identify subphenotypes. Logistic regression was performed on biomarker combinations to predict clustering. We chose the model with the best AUROC and the lowest number of variables. This model was used to describe the HAIS (High-flow ARDS Inflammatory Subphenotype) score.

RESULTS

Among 41 HFNO patients, two subphenotypes were identified. Hyperinflammatory subphenotype (n = 17) showed higher biomarker levels than hypoinflammatory (n = 24). Despite similar baseline characteristics, the hyperinflammatory subphenotype had higher 60-day mortality (47 vs 8.3% p = 0.014) and longer ICU length of stay (22.0 days [18.0-30.0] vs 39.5 [25.5-60.0], p = 0.034). The HAIS score, based on IL-8 and sST2, accurately distinguished subphenotypes (AUROC 0.96 [95%CI: 0.90-1.00]). A HAIS score ≥ 7.45 was predictor of hyperinflammatory subphenotype.

CONCLUSION

ARDS patients treated with HFNO exhibit two biological subphenotypes that have similar clinical characteristics, but hyperinflammatory patients have worse outcomes. The HAIS score may identify patients with hyperinflammatory subphenotype and might be used for enrichment strategies in future clinical trials.

Three subtypes of postoperative ARDS that showing different outcomes and responses to mechanical ventilation and fluid management: A machine learning and latent profile analysis

BACKGROUND

ARDS is a heterogeneous clinical syndrome, and operation and trauma are common indirect etiologies. The identification of postoperative ARDS subtypes may optimize individualized clinical management.

OBJECTIVES

To identify the subtypes of postoperative ARDS and explore the impact of therapy on outcomes.

METHODS

This retrospective study used data obtained from a database. Patients diagnosed with ARDS who underwent surgical procedures within 7 days were included in the study. Laboratory and clinical variables were used for latent profile analysis (LPA). XGBoost and multivariable logistic regression models were used to explore the association between therapy and outcomes.

RESULTS

A total of 1065 patients were included. The LPA identified three subtypes of postoperative ARDS: Patients in profile 1 were mainly accepted neurosurgery, while those in profile 2 and 3 were treated with orthopedic and vascular or thoracic surgery, respectively. The XGBoost model effectively predicted mortality with an AUC of 0.935, which was higher than SOFA (0.622), APACHE 2 (0.629), SLIP (0.579), and SLIP-2 (0.550).

CONCLUSIONS

This study identified three subtypes of postoperative ARDS with different clinical characteristics, mechanical support, and fluid resuscitation responses.

MicroRNA-1 protects the endothelium in acute lung injury

Acute lung injury (ALI) and its most severe form, acute respiratory distress syndrome (ARDS), cause severe endothelial dysfunction in the lung, and vascular endothelial growth factor (VEGF) is elevated in ARDS. We found that the levels of a VEGF-regulated microRNA, microRNA-1 (miR-1), were reduced in the lung endothelium after acute injury. Pulmonary endothelial cell-specific (EC-specific) overexpression of miR-1 protected the lung against cell death and barrier dysfunction in both murine and human models and increased the survival of mice after pneumonia-induced ALI. miR-1 had an intrinsic protective effect in pulmonary and other types of ECs; it inhibited apoptosis and necroptosis pathways and decreased capillary leak by protecting adherens and tight junctions. Comparative gene expression analysis and RISC recruitment assays identified miR-1 targets in the context of injury, including phosphodiesterase 5A (PDE5A), angiopoietin-2 (ANGPT2), CNKSR family member 3 (CNKSR3), and TNF-α-induced protein 2 (TNFAIP2). We validated miR-1-mediated regulation of ANGPT2 in both mouse and human ECs and found that in a 119-patient pneumonia cohort, miR-1 correlated inversely with ANGPT2. These findings illustrate a previously unknown role of miR-1 as a cytoprotective orchestrator of endothelial responses to acute injury with prognostic and therapeutic potential.

Early plasma proteomic biomarkers and prediction model of acute respiratory distress syndrome after cardiopulmonary bypass: a prospective nested cohort study

BACKGROUND

Early recognition of the risk of acute respiratory distress syndrome (ARDS) after cardiopulmonary bypass (CPB) may improve clinical outcomes. The main objective of this study was to identify proteomic biomarkers and develop an early prediction model for CPB-ARDS.

METHODS

The authors conducted three prospective nested cohort studies of all consecutive patients undergoing cardiac surgery with CPB at Union Hospital of Tongji Medical College Hospital. Plasma proteomic profiling was performed in ARDS patients and matched controls (Cohort 1, April 2021-July 2021) at multiple timepoints: before CPB (T1), at the end of CPB (T2), and 24 h after CPB (T3). Then, for Cohort 2 (August 2021-July 2022), biomarker expression was measured and verified in the plasma. Furthermore, lung ischemia/reperfusion injury (LIRI) models and sham-operation were established in 50 rats to explore the tissue-level expression of biomarkers identified in the aforementioned clinical cohort. Subsequently, a machine learning-based prediction model incorporating protein and clinical predictors from Cohort 2 for CPB-ARDS was developed and internally validated. Model performance was externally validated on Cohort 3 (January 2023-March 2023).

RESULTS

A total of 709 proteins were identified, with 9, 29, and 35 altered proteins between ARDS cases and controls at T1, T2, and T3, respectively, in Cohort 1. Following quantitative verification of several predictive proteins in Cohort 2, higher levels of thioredoxin domain containing 5 (TXNDC5), cathepsin L (CTSL), and NPC intracellular cholesterol transporter 2 (NPC2) at T2 were observed in CPB-ARDS patients. A dynamic online predictive nomogram was developed based on three proteins (TXNDC5, CTSL, and NPC2) and two clinical risk factors (CPB time and massive blood transfusion), with excellent performance (precision: 83.33%, sensitivity: 93.33%, specificity: 61.16%, and F1 score: 85.05%). The mean area under the receiver operating characteristics curve (AUC) of the model after 10-fold cross-validation was 0.839 (95% CI: 0.824-0.855). Model discrimination and calibration were maintained during external validation dataset testing, with an AUC of 0.820 (95% CI: 0.685-0.955) and a Brier Score of 0.177 (95% CI: 0.147-0.206). Moreover, the considerably overexpressed TXNDC5 and CTSL proteins identified in the plasma of patients with CPB-ARDS, exhibited a significant upregulation in the lung tissue of LIRI rats.

CONCLUSIONS

This study identified several novel predictive biomarkers, developed and validated a practical prediction tool using biomarker and clinical factor combinations for individual prediction of CPB-ARDS risk. Assessing the plasma TXNDC5, CTSL, and NPC2 levels might identify patients who warrant closer follow-up and intensified therapy for ARDS prevention following major surgery.

Precision Medicine Using Simultaneous Monitoring and Assessment with Imaging and Biomarkers to Manage Mechanical Ventilation in ARDS

Acute respiratory distress syndrome (ARDS) has a ~ 40% mortality rate with an increasing prevalence exacerbated by the COVID-19 pandemic. Mechanical ventilation is the primary means for life-saving support to buy time for lung healing in ARDS patients, however, it can also lead to ventilator-induced lung injury (VILI). Effective strategies to reduce or prevent VILI are necessary but are not currently delivered. Therefore, we aim at evaluating the current imaging technologies to visualize where pressure and volume being delivered to the lung during mechanical ventilation; and combining plasma biomarkers to guide management of mechanical ventilation. We searched PubMed and Medline using keywords and analyzed the literature, including both animal models and human studies, to examine the independent use of computed tomography (CT) to evaluate lung mechanics, electrical impedance tomography (EIT) to guide ventilation, ultrasound to monitor lung injury, and plasma biomarkers to indicate status of lung pathophysiology. This investigation has led to our proposal of the combination of imaging and biomarkers to precisely deliver mechanical ventilation to improve patient outcomes in ARDS.

A Focused Review of the Initial Management of Patients with Acute Respiratory Distress Syndrome

At present, the management of patients with acute respiratory distress syndrome (ARDS) largely focuses on ventilator settings to limit intrathoracic pressures by using low tidal volumes and on FiO₂/PEEP relationships to maintain optimal gas exchange. Acute respiratory distress syndrome is a complex medical disorder that can develop in several primary acute disorders, has a rapid time course, and has several classifications that can reflect either the degree of hypoxemia, the extent of radiographic involvement, or the underlying pathogenesis. The identification of subtypes of patients with ARDS would potentially make precision medicine possible in these patients. This is a very difficult challenge given the heterogeneity in the clinical presentation, pathogenesis, and treatment responses in these patients. The analysis of large databases of patients with acute respiratory failure using statistical methods such as cluster analysis could identify phenotypes that have different outcomes or treatment strategies. However, clinical information available on presentation is unlikely to separate patients into groups that allow for secure treatment decisions or outcome predictions. In some patients, non-invasive positive pressure ventilation provides adequate support through episodes of acute respiratory failure, and the development of specialized units to manage patients with this support might lead to the better use of hospital resources. Patients with ARDS have capillary leak, which results in interstitial and alveolar edema. Early attention to fluid balance in these patients might improve gas exchange and alter the pathophysiology underlying the development of severe ARDS. Finally, more attention to the interaction of patients with ventilators through complex monitoring systems has the potential to identify ventilator dyssynchrony, leading to ventilator adjustments and potentially better outcomes. Recent studies with COVID-19 patients provide tentative answers to some of these questions. In addition, expert clinical investigators have analyzed the promise and difficulties associated with the development of precision medicine in patients with ARDS.

Diagnostic and prognostic value of Ang-2 in ARDS: a systemic review and meta-analysis

BACKGROUND

To investigate the diagnostic and prognostic value of angiopoietin-2 (Ang-2) for acute respiratory distress syndrome (ARDS).

METHODS

Seven databases (4 English and 3 Chinese databases) were searched, the quality was evaluated by QUADAS-2 and GRADE profile. The bivariate model was employed to combine area under the curve (AUC), pooled sensitivity (pSEN) and pooled specificity (pSPE), the Fagan's nomogram was employed for evaluating clinical utility. This study was registered in PROSPERO (NO.CRD42022371488).

RESULTS

18 eligible studies comprising 27 datasets (12 diagnostic and 15 prognostic datasets) were included for meta-analysis. For diagnostic analysis, Ang-2 yielded an AUC of 0.82, with a pSEN of 0.78 and a pSPE of 0.74; in clinical utility analysis, a pretest probability of 50% regulated the post probability positive (PPP) of 75% and the post probability negative (PPN) of 23%. In prognostic analysis, Ang-2 yielded an AUC of 0.83, with a pSEN of 0.69, a pSPE of 0.81, and good clinical utility (a pretest probability of 50% regulated the PPP of 79% and the PPN of 28%). Heterogeneity existed in both diagnostic and prognostic analysis.

CONCLUSIONS

Ang-2 demonstrates promising diagnostic and prognostic capabilities as a noninvasive circulating biomarker for ARDS, especially in the Chinese population. It is advisable to dynamically monitor Ang-2 in critically ill patients both suspected and with confirmed ARDS.

Early plasma angiopoietin-2 is prognostic for ARDS and mortality among critically ill patients with sepsis

Angiopoietin-2 (Ang-2) is associated with vascular endothelial injury and permeability in the acute respiratory distress syndrome (ARDS) and sepsis. Elevated circulating Ang-2 levels may identify critically ill patients with distinct pathobiology amenable to targeted therapy. We hypothesized that plasma Ang-2 measured shortly after hospitalization among patients with sepsis would be associated with the development of ARDS and poor clinical outcomes. To test this hypothesis, we measured plasma Ang-2 in a cohort of 757 patients with sepsis, including 267 with ARDS, enrolled in the emergency department or early in their ICU course before the COVID-19 pandemic. Multivariable models were used to test the association of Ang-2 with the development of ARDS and 30-day morality. We found that early plasma Ang-2 in sepsis was associated with higher baseline severity of illness, the development of ARDS, and mortality risk. The association between Ang-2 and mortality was strongest among patients with ARDS and sepsis as compared to those with sepsis alone (OR 1.81 vs. 1.52 per log Ang-2 increase). These findings might inform models testing patient risk prediction and strengthen the evidence for Ang-2 as an appealing biomarker for patient selection for novel therapeutic agents to target vascular injury in sepsis and ARDS.

Increased Alveolar Epithelial Damage Markers and Inflammasome-Regulated Cytokines Are Associated with Pulmonary Superinfection in ARDS

Acute respiratory distress syndrome (ARDS) is a life-threatening form of respiratory failure defined by dysregulated immune homeostasis and alveolar epithelial and endothelial damage. Up to 40% of ARDS patients develop pulmonary superinfections, contributing to poor prognosis and increasing mortality. Understanding what renders ARDS patients highly susceptible to pulmonary superinfections is therefore essential. We hypothesized that ARDS patients who develop pulmonary superinfections display a distinct pulmonary injury and pro-inflammatory response pattern. Serum and BALF samples from 52 patients were collected simultaneously within 24 h of ARDS onset. The incidence of pulmonary superinfections was determined retrospectively, and the patients were classified accordingly. Serum concentrations of the epithelial markers soluble receptor for advanced glycation end-products (sRAGE) and surfactant protein D (SP-D) and the endothelial markers vascular endothelial growth factor (VEGF) and angiopoetin-2 (Ang-2) as well as bronchoalveolar lavage fluid concentrations of the pro-inflammatory cytokines interleukin 1ß (IL-1ß), interleukin 18 (IL-18), interleukin 6 (IL-6), and tumor necrosis factor-alpha (TNF-a) were analyzed via multiplex immunoassay. Inflammasome-regulated cytokine IL-18 and the epithelial damage markers SP-D and sRAGE were significantly increased in ARDS patients who developed pulmonary superinfections. In contrast, endothelial markers and inflammasome-independent cytokines did not differ between the groups. The current findings reveal a distinct biomarker pattern that indicates inflammasome activation and alveolar epithelial injury. This pattern may potentially be used in future studies to identify high-risk patients, enabling targeted preventive strategies and personalized treatment approaches.

Plasma metabolic profiling implicates dysregulated lipid metabolism and glycolytic shift in hyperinflammatory ARDS

Using latent class analysis (LCA) of clinical and protein biomarkers, researchers have identified two phenotypes of the acute respiratory distress syndrome (ARDS) with divergent clinical trajectories and treatment responses. We investigated whether plasma metabolites differed among patients with LCA-derived hyperinflammatory and hypoinflammatory ARDS, and we tested the prognostic utility of adding metabolic clusters to LCA phenotypes. We analyzed data from 93 patients with ARDS and sepsis enrolled in a multicenter prospective cohort of critically ill patients, comparing 970 metabolites between the two LCA-derived phenotypes. In all, 188 metabolites were differentially abundant between the two LCA-derived phenotypes. After adjusting for age, sex, confounding medications, and comorbid liver and kidney disease, 82 metabolites remained significantly different. Patients with hyperinflammatory ARDS had reduced circulating lipids but high levels of pyruvate, lactate, and malate. Metabolic cluster and LCA-derived phenotypes were each significantly and independently associated with survival. Patients with hyperinflammatory ARDS may be experiencing a glycolytic shift leading to dysregulated lipid metabolism. Metabolic profiling offers prognostic information beyond what is captured by LCA phenotypes alone. Deeper biological profiling may identify key differences in pathogenesis among patients with ARDS and may lead to novel targeted therapies.

Advancing Precision Medicine for the Diagnosis and Treatment of Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a common and life-threatening cause of respiratory failure. Despite decades of research, there are no effective pharmacologic therapies to treat this disease process and mortality remains high. The shortcomings of prior translational research efforts have been increasingly attributed to the heterogeneity of this complex syndrome, which has led to an increased focus on elucidating the mechanisms underlying the interpersonal heterogeneity of ARDS. This shift in focus aims to move the field towards personalized medicine by defining subgroups of ARDS patients with distinct biology, termed endotypes, to quickly identify patients that are most likely to benefit from mechanism targeted treatments. In this review, we first provide a historical perspective and review the key clinical trials that have advanced ARDS treatment. We then review the key challenges that exist with regards to the identification of treatable traits and the implementation of personalized medicine approaches in ARDS. Lastly, we discuss potential strategies and recommendations for future research that we believe will aid in both understanding the molecular pathogenesis of ARDS and the development of personalized treatment approaches.

Association of the C-terminal 42-peptide fragment of alpha-1 antitrypsin with the severity of ARDS: A pilot study

BACKGROUND

Acute respiratory distress syndrome is a life-threatening condition with a hospital mortality rate of up to 40%. Biomarkers related to the pathophysiology of ARDS may not only identify patients at risk but may also serve as potential therapeutic targets. This study examined the association between the proteolytic C-terminal 42-peptide fragment of alpha-1 antitrypsin and ARDS severity.

METHODS

The 42-peptide fragment and interleukin-6 levels were measured in 21 patients with mild-to-moderate ARDS and 47 patients with moderate-to-severe ARDS on days 1, 3, and 5 after diagnosis/admission to the intensive care unit. To elucidate the association between both biomarkers and the PaO₂/FiO₂ ratio, the concentrations of both biomarkers were compared between the two groups, and a multivariate regression analysis was performed.

RESULTS

The concentrations of both biomarkers were higher in patients with moderate-to-severe ARDS. While the PaO₂/FiO₂ ratio increased from day 1 to day 3, the concentrations of both biomarkers decreased. Multivariate regression analysis revealed negative associations between the PaO₂/FiO₂ ratio and both the C-terminal 42-peptide of alpha-1 antitrypsin and interleukin-6 on day 1 (beta: -0.138, p = 0.052; beta: -0.096, p = 0.004) and on day 3 (beta: -0.157, p = 0.045; beta: -0.106, p = 0.043).

INTERPRETATION

The C-terminal 42-peptide of alpha-1 antitrypsin is a new biomarker associated with ARDS severity. Its predictive value in identifying patients at risk of developing moderate-to-severe ARDS must be investigated in additional, independent prospective studies.

Targeting SELPLG/P-selectin glycoprotein ligand 1 in preclinical ARDS: Genetic and epigenetic regulation of the SELPLG promoter

We previously identified a missense single nucleotide polymorphism rs2228315 (G>A, Met62Ile) in the selectin-P-ligand gene (SELPLG), encoding P-selectin glycoprotein ligand 1 (PSGL-1), to be associated with increased susceptibility to acute respiratory distress syndrome (ARDS). These earlier studies demonstrated that SELPLG lung tissue expression was increased in mice exposed to lipopolysaccharide (LPS)- and ventilator-induced lung injury (VILI) suggesting that inflammatory and epigenetic factors regulate SELPLG promoter activity and transcription. In this report, we used a novel recombinant tandem PSGL1 immunoglobulin fusion molecule (TSGL-Ig), a competitive inhibitor of PSGL1/P-selectin interactions, to demonstrate significant TSGL-Ig-mediated decreases in SELPLG lung tissue expression as well as highly significant protection from LPS- and VILI-induced lung injury. In vitro studies examined the effects of key ARDS stimuli (LPS, 18% cyclic stretch to simulate VILI) on SELPLG promoter activity and showed LPS-mediated increases in SELPLG promoter activity and identified putative promoter regions associated with increased SELPLG expression. SELPLG promoter activity was strongly regulated by the key hypoxia-inducible transcription factors, HIF-1α, and HIF-2α as well as NRF2. Finally, the transcriptional regulation of SELPLG promoter by ARDS stimuli and the effect of DNA methylation on SELPLG expression in endothelial cell was confirmed. These findings indicate SELPLG transcriptional regulation by clinically-relevant inflammatory factors with the significant TSGL-Ig-mediated attenuation of LPS and VILI highly consistent with PSGL1/P-selectin as therapeutic targets in ARDS.

Inflammatory biomarkers and pendelluft magnitude in ards patients transitioning from controlled to partial support ventilation

The transition from controlled to partial support ventilation is a challenge in acute respiratory distress syndrome (ARDS) patients due to the risks of patient-self-inflicted lung injury. The magnitude of tidal volume (V_T) and intrapulmonary dyssynchrony (pendelluft) are suggested mechanisms of lung injury. We conducted a prospective, observational, physiological study in a tertiary academic intensive care unit. ARDS patients transitioning from controlled to partial support ventilation were included. On these, we evaluated the association between changes in inflammatory biomarkers and esophageal pressure swing (ΔP_es), transpulmonary driving pressure (ΔP_L), V_T, and pendelluft. Pendelluft was defined as the percentage of the tidal volume that moves from the non-dependent to the dependent lung region during inspiration, and its frequency at different thresholds (- 15, - 20 and - 25%) was also registered. Blood concentrations of inflammatory biomarkers (IL-6, IL-8, TNF-α, ANGPT2, RAGE, IL-18, Caspase-1) were measured before (T₀) and after 4-h (T₄) of partial support ventilation. Pendelluft, ΔP_es, ΔP_L and V_T were recorded. Nine out of twenty-four patients (37.5%) showed a pendelluft mean ≥ 10%. The mean values of ΔP_es, ΔP_L, and V_T were - 8.4 [- 6.7; - 10.2] cmH₂O, 15.2 [12.3-16.5] cmH₂O and 8.1 [7.3-8.9] m/kg PBW, respectively. Significant associations were observed between the frequency of high-magnitude pendelluft and IL-8, IL-18, and Caspase-1 changes (T₀/T₄ ratio). These results suggest that the frequency of high magnitude pendelluft may be a potential determinant of inflammatory response related to inspiratory efforts in ARDS patients transitioning to partial support ventilation. Future studies are needed to confirm these results.

Advanced development and mechanism of sepsis-related acute respiratory distress syndrome

The introduction of the Sepsis 3.0 guidelines in 2016 improved our understanding of sepsis diagnosis and therapy. Personalized treatment strategies and nursing methods for sepsis patients are recommended in the "Save Sepsis Campaign" in 2021. However, mortality in sepsis patients remains high. Patients with sepsis-related acute respiratory distress syndrome account for around 30% of them, with fatality rates ranging from 30 to 40%. Pathological specimens from individuals with sepsis-related ARDS frequently demonstrate widespread alveolar damage, and investigations have revealed that pulmonary epithelial and pulmonary endothelial injury is the underlying cause. As a result, the purpose of this work is to evaluate the mechanism and research progress of pulmonary epithelial and pulmonary endothelial damage in sepsis-related ARDS, which may provide new directions for future research, diagnosis, and therapy.

Integrated host-microbe plasma metagenomics for sepsis diagnosis in a prospective cohort of critically ill adults

We carried out integrated host and pathogen metagenomic RNA and DNA next generation sequencing (mNGS) of whole blood (n = 221) and plasma (n = 138) from critically ill patients following hospital admission. We assigned patients into sepsis groups on the basis of clinical and microbiological criteria. From whole-blood gene expression data, we distinguished patients with sepsis from patients with non-infectious systemic inflammatory conditions using a trained bagged support vector machine (bSVM) classifier (area under the receiver operating characteristic curve (AUC) = 0.81 in the training set; AUC = 0.82 in a held-out validation set). Plasma RNA also yielded a transcriptional signature of sepsis with several genes previously reported as sepsis biomarkers, and a bSVM sepsis diagnostic classifier (AUC = 0.97 training set; AUC = 0.77 validation set). Pathogen detection performance of plasma mNGS varied on the basis of pathogen and site of infection. To improve detection of virus, we developed a secondary transcriptomic classifier (AUC = 0.94 training set; AUC = 0.96 validation set). We combined host and microbial features to develop an integrated sepsis diagnostic model that identified 99% of microbiologically confirmed sepsis cases, and predicted sepsis in 74% of suspected and 89% of indeterminate sepsis cases. In summary, we suggest that integrating host transcriptional profiling and broad-range metagenomic pathogen detection from nucleic acid is a promising tool for sepsis diagnosis.

Serial Measurements of Protein Biomarkers in Sepsis-Induced Acute Respiratory Distress Syndrome

The role of early, serial measurements of protein biomarkers in sepsis-induced acute respiratory distress syndrome (ARDS) is not clear.

OBJECTIVES

To determine the differences in soluble receptor for advanced glycation end-products (sRAGEs), angiopoietin-2, and surfactant protein-D (SP-D) levels and their changes over time between sepsis patients with and without ARDS.

DESIGN SETTING AND PARTICIPANTS

Prospective observational cohort study of adult patients admitted to the medical ICU at Grady Memorial Hospital within 72 hours of sepsis diagnosis.

MAIN OUTCOMES AND MEASURES

Plasma sRAGE, angiopoietin-2, and SP-D levels were measured for 3 consecutive days after enrollment. The primary outcome was ARDS development, and the secondary outcome of 28-day mortality. The biomarker levels and their changes over time were compared between ARDS and non-ARDS patients and between nonsurvivors and survivors.

RESULTS

We enrolled 111 patients, and 21 patients (18.9%) developed ARDS. The three biomarker levels were not significantly different between ARDS and non-ARDS patients on all 3 days of measurement. Nonsurvivors had higher levels of all three biomarkers than did survivors on multiple days. The changes of the biomarker levels over time were not different between the outcome groups. Logistic regression analyses showed association between day 1 SP-D level and mortality (odds ratio, 1.52; 95% CI, 1.03-2.24; p = 0.03), and generalized estimating equation analyses showed association between angiopoietin-2 levels and mortality (estimate 0.0002; se 0.0001; p = 0.04).

CONCLUSIONS AND RELEVANCE

Among critically ill patients with sepsis, sRAGE, angiopoietin-2, and SP-D levels were not significantly different between ARDS and non-ARDS patients but were higher in nonsurvivors compared with survivors. The trend toward higher levels of sRAGE and SP-D, but not of angiopoietin-2, in ARDS patients may indicate the importance of epithelial injury in sepsis-induced ARDS. Changes of the biomarker levels over time were not different between the outcome groups.

New Insights into Clinical and Mechanistic Heterogeneity of the Acute Respiratory Distress Syndrome: Summary of the Aspen Lung Conference 2021

Clinical and molecular heterogeneity are common features of human disease. Understanding the basis for heterogeneity has led to major advances in therapy for many cancers and pulmonary diseases such as cystic fibrosis and asthma. Although heterogeneity of risk factors, disease severity, and outcomes in survivors are common features of the acute respiratory distress syndrome (ARDS), many challenges exist in understanding the clinical and molecular basis for disease heterogeneity and using heterogeneity to tailor therapy for individual patients. This report summarizes the proceedings of the 2021 Aspen Lung Conference, which was organized to review key issues related to understanding clinical and molecular heterogeneity in ARDS. The goals were to review new information about ARDS phenotypes, to explore multicellular and multisystem mechanisms responsible for heterogeneity, and to review how best to account for clinical and molecular heterogeneity in clinical trial design and assessment of outcomes. The report concludes with recommendations for future research to understand the clinical and basic mechanisms underlying heterogeneity in ARDS to advance the development of new treatments for this life-threatening critical illness.

Characterization of Platelet Biologic Markers in the Early Pathogenesis of Postoperative Acute Respiratory Distress Syndrome

Animal models and limited human studies have suggested a plausible role for platelets in the pathogenesis and resolution of acute respiratory distress syndrome (ARDS). However, there are little data regarding the role of platelets in ARDS development.

OBJECTIVES

The objective of this study was to characterize the role of platelets in a postoperative ARDS model through an analysis of two platelet-specific biologic markers: thromboxane A₂ (TxA₂) and soluble CD-40-ligand (sCD40L).

DESIGN SETTING AND PARTICIPANTS

This was a nested case-control study of ARDS cases matched to non-ARDS controls. Blood samples were collected from a cohort of 500 patients undergoing thoracic, aortic vascular, or cardiac surgery that placed them at high-risk of developing postoperative ARDS.

MAIN OUTCOMES AND MEASURES

TxA₂ and sCD40L were analyzed at baseline (prior to surgical incision) as well as 2 hours and 6 hours after the key intraoperative events believed to be associated with increased risk of postoperative ARDS.

RESULTS

Of 500 patients enrolled, 20 ARDS cases were matched 1:2 to non-ARDS controls based on age, sex, surgical procedure, and surgical lung injury prediction score. Those who developed ARDS had longer surgeries, greater fluid administration, and higher peak inspiratory pressures. There were no significant differences in levels of TxA₂ or sCD40L at baseline, at 2 hours, or at 6 hours. There was also no difference in the change in biomarker concentration between baseline and 2 hours or baseline and 6 hours.

CONCLUSIONS

Two novel platelet-associated biologic markers (TxA₂ and sCD40L) were not elevated in patients who developed ARDS in a postoperative ARDS model. Although limited by the relatively small study size, these results do not support a clear role for platelets in the early pathogenesis of postoperative ARDS.

Angiopoietin 2 Is Associated with Vascular Necroptosis Induction in Coronavirus Disease 2019 Acute Respiratory Distress Syndrome

Vascular injury is a well-established, disease-modifying factor in acute respiratory distress syndrome (ARDS) pathogenesis. Recently, coronavirus disease 2019 (COVID-19)-induced injury to the vascular compartment has been linked to complement activation, microvascular thrombosis, and dysregulated immune responses. This study sought to assess whether aberrant vascular activation in this prothrombotic context was associated with the induction of necroptotic vascular cell death. To achieve this, proteomic analysis was performed on blood samples from COVID-19 subjects at distinct time points during ARDS pathogenesis (hospitalized at risk, N = 59; ARDS, N = 31; and recovery, N = 12). Assessment of circulating vascular markers in the at-risk cohort revealed a signature of low vascular protein abundance that tracked with low platelet levels and increased mortality. This signature was replicated in the ARDS cohort and correlated with increased plasma angiopoietin 2 levels. COVID-19 ARDS lung autopsy immunostaining confirmed a link between vascular injury (angiopoietin 2) and platelet-rich microthrombi (CD61) and induction of necrotic cell death [phosphorylated mixed lineage kinase domain-like (pMLKL)]. Among recovery subjects, the vascular signature identified patients with poor functional outcomes. Taken together, this vascular injury signature was associated with low platelet levels and increased mortality and can be used to identify ARDS patients most likely to benefit from vascular targeted therapies.

Glycocalyx heparan sulfate cleavage promotes endothelial cell angiopoietin-2 expression by impairing shear stress-related AMPK/FoxO1 signaling

Angiopoietin-2 (Ang-2) is a key mediator of vascular disease during sepsis, and elevated plasma levels of Ang-2 are associated with organ injury scores and poor clinical outcomes. We have previously observed that biomarkers of endothelial glycocalyx (EG) damage correlate with plasma Ang-2 levels, suggesting a potential mechanistic linkage between EG injury and Ang-2 expression during states of systemic inflammation. However, the cell signaling mechanisms regulating Ang-2 expression following EG damage are unknown. In the current study, we determined the temporal associations between plasma heparan sulfate (HS) levels as a marker of EG erosion and plasma Ang-2 levels in children with sepsis and in mouse models of sepsis. Secondly, we evaluated the role of shear stress-mediated 5'-adenosine monophosphate-activated protein kinase (AMPK) signaling in Ang-2 expression following enzymatic HS cleavage from the surface of human primary lung microvascular endothelial cells (HLMVEC). We found that plasma HS levels peak prior to plasma Ang-2 levels in children and mice with sepsis. Further, we discovered that impaired AMPK signaling contributes to increased Ang-2 expression following HS cleavage from flow conditioned HLMVECs, establishing a novel paradigm by which Ang-2 may be upregulated during sepsis.

Safety, efficacy and biomarkers analysis of mesenchymal stromal cells therapy in ARDS: a systematic review and meta-analysis based on phase I and II RCTs

Background

Mesenchymal stromal cells (MSCs) therapy for acute respiratory distress syndrome (ARDS) is an emerging treatment, but most of the current trials of MSCs stay in the animal experimental stage, and the safety and efficacy of MSCs in clinical application are not clear. We aimed to analyze the safety, efficacy and biomarkers of mesenchymal stromal cells in the treatment of ARDS.

Methods

For this systematic review and meta-analysis, we searched PubMed, Embase, Cochrane Central Register of Controlled Trials, Web of science, CNKI, VIP and Wan Fang data, studies published between database inception and Mar 17, 2022. All randomized controlled trials (RCT) of stem cell interventions for ARDS were included, without language or date restrictions. We did separate meta-analyses for mortality, subjects with adverse events (AEs) and subjects with serious adverse events (SAEs). Since the trials data are dichotomous outcomes, the odds ratio (OR) is adopted for meta-analysis. The quality of the evidence was assessed with the Cochrane risk of bias tool.

Findings

In total, 5 trials involving 171 patients with ARDS were included in this meta-analysis. A total of 99 individuals were randomly assigned to receive MSCs treatment, and 72 were randomly assigned to receive placebo treatment. Treatment with MSCs appeared to increase the occurrence of adverse events, but this result was not statistically significant (OR, 1.58; 95%CI, 0.64–3.91; P = 0.32). The occurrence of serious adverse events was lower in the MSCs group than in the placebo group (OR, 0.57; 95%CI, 0.14–2.32; P = 0.43); there seems to be no significant difference between the two groups in terms of 28 days mortality (OR, 0.93; 95%CI, 0.45–1.89); oxygenation index and biomarkers showed a tendency to improve in treatment, but there was a lack of more statistically significant clinical evidence to support them.

Interpretation

Based on the current clinical trials, MSCs intervention has some safety for ARDS patients, but its effectiveness and predictive value of airspace biomarkers need to be determined by more large-scale, standard randomized controlled trials.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02956-3.

Circulating eNAMPT as a biomarker in the critically ill: acute pancreatitis, sepsis, trauma, and acute respiratory distress syndrome

Background

Nicotinamide phosphoribosyltransferase (NAMPT) exhibits dual functionality – as an intracellular enzyme regulating nicotinamide adenine dinucleotide metabolism and as an extracellular secreted protein (eNAMPT) to function as a cytokine regulator of innate immunity via binding to Toll-Like receptor 4 and NF-κB activation. In limited preclinical and clinical studies, eNAMPT was implicated in the pathobiology of acute respiratory distress syndrome (ARDS) suggesting that eNAMPT could potentially serve as a diagnostic and prognostic biomarker. We investigated the feasibility of circulating eNAMPT levels to serve as a biomarker in an expanded cohort of patients with ARDS and ARDS-predisposing conditions that included acute pancreatitis, sepsis, and trauma with comparisons to controls.

Methods

A total of 671 patients and 179 healthy controls were included in two independent cohorts. Plasma and serum eNAMPT levels were quantified using one of two complementary Enzyme-linked Immunosorbent Assays. After log base 2 variance stabilizing transformation of plasma/serum eNAMPT measurements, differences between healthy controls and each disease cohort were compared using linear regression or a generalized estimating equation (GEE) model where applicable. Complementary analyses included sensitivity, specificity, positive predictive values, negative predictive values, and the area under the receiver operating curve.

Results

Compared to controls, circulating eNAMPT levels were significantly elevated in subjects with acute pancreatitis, sepsis, trauma, and ARDS (all p < 0.01). In the acute pancreatitis cohort, circulating eNAMPT levels positively correlated with disease severity (p < 0.01).

Conclusions

Circulating eNAMPT levels are novel biomarker in the critically ill with acute pancreatitis, sepsis, trauma, and/or ARDS with the potential to reflect disease severity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-022-01718-1.

Functional Transcriptomic Studies of Immune Responses and Endotoxin Tolerance in Early Human Sepsis

BACKGROUND

Limited studies have functionally evaluated the heterogeneity in early ex vivo immune responses during sepsis. Our aim was to characterize early sepsis ex vivo functional immune response heterogeneity by studying whole blood endotoxin responses and derive a transcriptional metric of ex vivo endotoxin response.

METHODS

Blood collected within 24 h of hospital presentation from 40 septic patients was divided into two fractions and incubated with media (unstimulated) or endotoxin. Supernatants and cells were isolated, and responses measured using: supernatant cytokines, lung endothelial permeability after supernatant exposure, and RNA expression. A transcriptomic signature was derived in unstimulated cells to predict the ex vivo endotoxin response. The signature was tested in a separate cohort of 191 septic patients to evaluate for association with clinical outcome. Plasma biomarkers were quantified to measure in vivo host inflammation.

RESULTS

Ex vivo response to endotoxin varied and was unrelated to immunosuppression, white blood cell count, or the causative pathogen. Thirty-five percent of patients demonstrated a minimal response to endotoxin, suggesting early immunosuppression. High ex vivo cytokine production by stimulated blood cells correlated with increased in vitro pulmonary endothelial cell permeability and was associated with attenuated in vivo host inflammation. A four-gene signature of endotoxin response detectable without the need for a functional assay was identified. When tested in a separate cohort of septic patients, its expression was inversely associated with hospital mortality.

CONCLUSIONS

An attenuated ex vivo endotoxin response in early sepsis is associated with greater host in vivo inflammation and a worse clinical outcome.

Proinflammatory Endothelial Phenotype in Very Preterm Infants: A Pilot Study

Very preterm infants are exposed to prenatal inflammatory processes and early postnatal hemodynamic and respiratory complications, but limited data are available about the endothelial effect of these conditions. The present pilot study investigates the perinatal endothelial phenotype in very preterm infants (VPIs) and explores its predictive value on neonatal mortality and hemodynamic and respiratory complications. Angiopoietin 1 (Ang-1), Ang-2, E-selectin, vascular adhesion molecule 1 (VCAM-1), tissue factor (TF), and endothelin 1 (ET-1) concentrations were tested in first (T1), 3rd (T2), and 7–10th (T3) day of life in 20 VPIs using Luminex technology and compared with 14 healthy full-term infants (FTIs). Compared to FTIs, VPIs had lower Ang-1 at T1 and T2; higher Ang-2 at T1, T2, and T3; higher Ang-2/Ang-1 ratio at T1, T2, and T3; lower E-selectin at T1, T2, and T3; higher VCAM-1 at T1; higher TF at T2. No differences in concentrations were found in neonatal deaths. VPIs with hemodynamic or respiratory complications had higher Ang-2 at T3. Perinatal low Ang-1 and high Ang-2 associated with high VCAM-1 and TF in VPIs suggest a proinflammatory endothelial phenotype, resulting from the synergy of a pathological prenatal inheritance and a premature extrauterine transition.

Towards a biological definition of ARDS: are treatable traits the solution?

The pathophysiology of acute respiratory distress syndrome (ARDS) includes the accumulation of protein-rich pulmonary edema in the air spaces and interstitial areas of the lung, variable degrees of epithelial injury, variable degrees of endothelial barrier disruption, transmigration of leukocytes, alongside impaired fluid and ion clearance. These pathophysiological features are different between patients contributing to substantial biological heterogeneity. In this context, it is perhaps unsurprising that a wide range of pharmacological interventions targeting these pathophysiological processes have failed to improve patient outcomes. In this manuscript, our goal is to provide a narrative summary of the potential methods to capture the underlying biological heterogeneity of ARDS and discuss how this information could inform future ARDS redefinitions. We discuss what biological tests are available to identify patients with any of the following predominant biological patterns: (1) epithelial and/or endothelial injury, (2) protein rich pulmonary edema and (3) systemic or within lung inflammatory responses.

Differentiating children with sepsis with and without acute respiratory distress syndrome using proteomics

Both sepsis and acute respiratory distress syndrome (ARDS) rely on imprecise clinical definitions leading to heterogeneity, which has contributed to negative trials. Because circulating protein/DNA complexes have been implicated in sepsis and ARDS, we aimed to develop a proteomic signature of DNA-bound proteins to discriminate between children with sepsis with and without ARDS. We performed a prospective case-control study in 12 children with sepsis with ARDS matched to 12 children with sepsis without ARDS on age, severity of illness score, and source of infection. We performed co-immunoprecipitation and downstream proteomics in plasma collected ≤ 24 h of intensive care unit admission. Expression profiles were generated, and a random forest classifier was used on differentially expressed proteins to develop a signature which discriminated ARDS. The classifier was tested in six independent blinded samples. Neutrophil and nucleosome proteins were over-represented in ARDS, including two S100A proteins, superoxide dismutase (SOD), and three histones. Random forest produced a 10-protein signature that accurately discriminated between children with sepsis with and without ARDS. This classifier perfectly assigned six independent blinded samples as having ARDS or not. We validated higher expression of the most informative discriminating protein, galectin-3-binding protein, in children with ARDS. Our methodology has applicability to isolation of DNA-bound proteins from plasma. Our results support the premise of a molecular definition of ARDS, and give preliminary insight into why some children with sepsis, but not others, develop ARDS.

Phenotyping in acute respiratory distress syndrome: state of the art and clinical implications

PURPOSE OF REVIEW

Decades of research in acute respiratory distress syndrome (ARDS) have led to few interventions that impact clinical outcomes. The pandemic of patients with ARDS due to the novel SARS-CoV-2 infection has stressed the need for more effective therapies in ARDS. Phenotyping may enable successful trials and precision therapeutics in this patient population.

RECENT FINDINGS

Clinical phenotypes that group patients by shared cause, time-course or radiographic presentation are of prognostic value, but their use is limited by misclassification. Physiological phenotypes, including the P/F ratio, ventilatory ratio and dead space fraction, predict poor outcomes but can rapidly change, making them unstable over time. Biologic phenotypes have prognostic value with composite clinical and biomarker sub-phenotypes additionally impacting treatment response but are yet to be prospectively validated.

SUMMARY

Although much progress has been made in ARDS phenotyping, implementation of precision medicine practices will depend on conducting phenotype-aware trials using rapid point of care assays or machine learning algorithms. Omics studies will enhance our understanding of biologic determinants of clinical outcomes in ARDS sub-phenotypes. Whether biologic ARDS sub-phenotypes are specific to this syndrome or rather more broadly identify endotypes of critical illness remains to be determined.

Latent class analysis-derived subphenotypes are generalisable to observational cohorts of acute respiratory distress syndrome: a prospective study

RATIONALE

Using latent class analysis (LCA), two subphenotypes of acute respiratory distress syndrome (ARDS) have consistently been identified in five randomised controlled trials (RCTs), with distinct biological characteristics, divergent outcomes and differential treatment responses to randomised interventions. Their existence in unselected populations of ARDS remains unknown. We sought to identify subphenotypes in observational cohorts of ARDS using LCA.

METHODS

LCA was independently applied to patients with ARDS from two prospective observational cohorts of patients admitted to the intensive care unit, derived from the Validating Acute Lung Injury markers for Diagnosis (VALID) (n=624) and Early Assessment of Renal and Lung Injury (EARLI) (n=335) studies. Clinical and biological data were used as class-defining variables. To test for concordance with prior ARDS subphenotypes, the performance metrics of parsimonious classifier models (interleukin 8, bicarbonate, protein C and vasopressor-use), previously developed in RCTs, were evaluated in EARLI and VALID with LCA-derived subphenotypes as the gold-standard.

RESULTS

A 2-class model best fit the population in VALID (p=0.0010) and in EARLI (p<0.0001). Class 2 comprised 27% and 37% of the populations in VALID and EARLI, respectively. Consistent with the previously described 'hyperinflammatory' subphenotype, Class 2 was characterised by higher proinflammatory biomarkers, acidosis and increased shock and worse clinical outcomes. The similarities between these and prior RCT-derived subphenotypes were further substantiated by the performance of the parsimonious classifier models in both cohorts (area under the curves 0.92-0.94). The hyperinflammatory subphenotype was associated with increased prevalence of chronic liver disease and neutropenia and reduced incidence of chronic obstructive pulmonary disease. Measurement of novel biomarkers showed significantly higher levels of matrix metalloproteinase-8 and markers of endothelial injury in the hyperinflammatory subphenotype, whereas, matrix metalloproteinase-9 was significantly lower.

CONCLUSION

Previously described subphenotypes are generalisable to unselected populations of non-trauma ARDS.

Association between inflammatory biomarkers and acute respiratory distress syndrome or acute lung injury risk : A systematic review and meta-analysis

Background

The relationship between acute respiratory distress syndrome (ARDS)/acute lung injury (ALI) and levels of certain inflammatory factors remains controversial. The purpose of this meta-analysis was to summarize the available studies evaluating the association between levels of inflammatory factors and ARDS/ALI incidence.

Methods

We searched the PubMed, EmBase, and Cochrane databases for studies published up to July 2017. For each inflammatory factor, a random effects model was employed to pool results from different studies.

Results

We identified 63 studies that included 6243 patients in our meta-analysis. Overall, the results indicated that the levels of angiopoietin (ANG)-2 (standard mean difference, SMD: 1.34; P < 0.001), interleukin (IL)-1β (SMD: 0.92; P = 0.012), IL‑6 (SMD: 0.66; P = 0.005), and tumor necrosis factor (TNF)-α (SMD: 0.98; P = 0.001) were significantly higher in patients with ARDS/ALI than in unaffected individuals. No significant differences were observed between patients with ARDS/ALI and unaffected individuals in terms of the levels of IL‑8 (SMD: 0.61; P = 0.159), IL-10 (SMD: 1.10; P = 0.231), and plasminogen activator inhibitor (PAI)-1 (SMD: 0.70; P = 0.060).

Conclusions

ARDS/ALI is associated with a significantly elevated levels of ANG‑2, IL-1β, IL‑6, and TNF‑α, but not with IL‑8, IL-10, and PAI‑1 levels.

Supplementary Information

The online version of this article (10.1007/s00508-021-01971-3) contains supplementary material, which is available to authorized users.