Acute respiratory distress in adults

Modified Xiao-Qing-Long-decoction prevents inflammation and promotes Nur77 expression in mice with acute respiratory distress syndrome by inhibiting HDAC7 expression

CONTEXT

Modified Xiao-Qing-Long-decoction (MXQLD) is believed to have the potential to alleviate lung diseases.

OBJECTIVE

We explored the effects and mechanisms of MXQLD in acute respiratory distress syndrome (ARDS).

MATERIALS AND METHODS

Thirty male C57BL/6 mice were randomized into sham (distilled water), model (distilled water), MXQLD (1 g/kg MXQLD), DEX (distilled water + 0.7 mg/kg dexamethasone), MXQLD + oe-HDAC7 (HDAC7 over-expression + 1 g/kg MXQLD) groups. Except for HDAC7 over-expression on day 0 and dexamethasone injection on day 12, all treatments were administered every two days from day 0 to day 10. On day 12, except for the sham group, all mice underwent cecal ligation and puncture surgery to establish ARDS models. After surgery, pulmonary functions, protein concentration of bronchoalveolar lavage fluid (BALF) and lung tissue morphology in mice were detected. Furthermore, pro-inflammatory cytokine concentrations (IL-6, IL-1β, and TNF-α) in BALF supernatant and serum were quantified. Additionally, HDAC7, Nur77, ZO-1, occludin, and claudin protein expressions were detected.

RESULTS

MXQLD treatment improved pulmonary functions and alleviated lung injury for ARDS mice. Furthermore, MXQLD treatment decreased protein concentration in BALF, and inhibited pro-inflammatory cytokine release in BALF supernatant and serum for ARDS mice. Additionally, MXQLD treatment down-regulated HDAC7 expression, but up-regulated Nur77, ZO-1, occludin, and claudin expressions for ARDS mice. Importantly, the preventive effects of MXQLD in ARDS mice were reversed by HDAC7 over-expression.

DISCUSSION AND CONCLUSION

MXQLD may prevent inflammation and promote Nur77 expression in ARDS by inhibiting HDAC7 expression, indicating that MXQLD may be a promising drug for preventing ARDS.

Thrombospondin-1 modulation by Bifidobacterium spp. mitigates lung damage in an acute lung injury mouse model

Our study shows that Bifidobacterium spp. supplementation reduces lung damage in acute lung injury by enhancing immune cell activity and restoring thrombospondin-1 levels, offering a promising therapeutic approach for the treatment of ALI/ARDS.

BACKGROUND

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are critical conditions characterized by severe lung inflammation and damage, often exacerbated by mechanical ventilation. Probiotics, particularly those containing Bifidobacterium spp. (Bifidus) have shown promise in modulating immune responses and reducing inflammation.

METHODS

In this study, we investigated the effects of Bifidus supplementation in a mouse model of lipopolysaccharide induced ALI and ventilator-induced lung injury.

RESULTS

Our results demonstrate that Bifidus significantly ameliorates lung injury by enhancing efferocytosis and reducing pro-inflammatory cytokine levels. Single-cell RNA sequencing revealed significant changes in lung immune cell populations, particularly macrophages and monocytes, which showed increased efferocytosis activity and modulation of key signaling pathways such as TNF, MAPK and TLR. Notably, Bifidus feeding restored thrombospondin-1 levels in lung tissue, facilitating clearance of apoptotic cells and promoting resolution of inflammation.

CONCLUSIONS

Overall, our study highlights the potential of Bifidus as a therapeutic strategy to mitigate lung injury in ALI/ARDS.

Driving pressure in acute respiratory distress syndrome for developing a protective lung strategy: A systematic review

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a critical condition characterized by acute hypoxemia, non-cardiogenic pulmonary edema, and decreased lung compliance. The Berlin definition, updated in 2012, classifies ARDS severity based on the partial pressure of arterial oxygen/fractional inspired oxygen fraction ratio. Despite various treatment strategies, ARDS remains a significant public health concern with high mortality rates.

AIM

To evaluate the implications of driving pressure (DP) in ARDS management and its potential as a protective lung strategy.

METHODS

We conducted a systematic review using databases including EbscoHost, MEDLINE, CINAHL, PubMed, and Google Scholar. The search was limited to articles published between January 2015 and September 2024. Twenty-three peer-reviewed articles were selected based on inclusion criteria focusing on adult ARDS patients undergoing mechanical ventilation and DP strategies. The literature review was conducted and reported according to PRISMA 2020 guidelines.

RESULTS

DP, the difference between plateau pressure and positive end-expiratory pressure, is crucial in ARDS management. Studies indicate that lower DP levels are significantly associated with improved survival rates in ARDS patients. DP is a better predictor of mortality than tidal volume or positive end-expiratory pressure alone. Adjusting DP by optimizing lung compliance and minimizing overdistension and collapse can reduce ventilator-induced lung injury.

CONCLUSION

DP is a valuable parameter in ARDS management, offering a more precise measure of lung stress and strain than traditional metrics. Implementing DP as a threshold for safety can enhance protective ventilation strategies, potentially reducing mortality in ARDS patients. Further research is needed to refine DP measurement techniques and validate its clinical application in diverse patient populations.

Tracheostomy Tube Change Versus PEEP Titration on Tracheostomy-Dependent Infants With Airway Malacia and Ventilator Instability

OBJECTIVE

To investigate the impact of positive end-expiratory pressure (PEEP) titrations or tracheostomy size change (trach change) on ventilation stability in infants with tracheobronchomalacia.

STUDY DESIGN

A retrospective chart review.

SETTING

Tertiary care children's hospital from 2015 to 2023.

METHODS

A retrospective chart review on ventilator and tracheostomy-dependent patients <1 year of age. Demographics, bronchoscopic findings, and ventilator outcomes within 14 days were recorded. Analysis was performed with chi-square, Fisher's exact, binomial regression analysis, and two-tailed t tests.

RESULTS

Of 71 patients (66% male, median 6.1 months old [interquartile range, IQR, 4.6-7.3]) who underwent 74 initial bronchoscopies, the PEEP titration cohort (n = 37) experienced an improvement (narrower) in 24-hour mean ventilatory ranges (peak inspiratory pressure [PIP] 5.6 pre vs 2.9 post, P = .01; fraction of inspired oxygen [FiO2] range 5% vs 3%, P = .04), whereas the trach change cohort did not (PEEP 5.9 vs 5.6, P = .8; FiO2 10% vs 5%, P = .07). In patients with airway malacia, the PEEP titration cohort had improved PIP ranges postintervention (5.5 vs 3.0, P = .02), whereas the trach change cohort did not (4.4 vs 6.6, P = .13). In patients without airway malacia, trach change correlated with improved PIP (8.4 vs 3.8, P = .04). Repeat bronchoscopy after initial intervention was significantly more common after trach change compared to PEEP titration (22% vs 3%, P = .01).

CONCLUSION

PEEP titration was associated with improved PIP and FiO2 ventilatory outcomes with a lower rate of repeat bronchoscopy compared to trach change, suggesting trach change alone may have little impact with greater subsequent interventional needs compared to PEEP titration.

Defining and subphenotyping ARDS: insights from an international Delphi expert panel

Although the definition of acute respiratory distress syndrome (ARDS) has undergone numerous revisions aimed at enhancing its diagnostic accuracy and clinical practicality, the usefulness and precision of these definitions remain matters of ongoing discussion. In this Position Paper, we report on a Delphi study to reach a consensus on the conceptual model of ARDS, specifically identifying its defining components within clinical, research, and educational contexts as well as exploring the potential role of subphenotyping. We did a four-round Delphi study, involving experts in ARDS research and management from a diverse range of geoeconomic regions and professional backgrounds. Consensus was achieved for the conceptual model of ARDS; key components to be included for an ARDS definition in the context of research, education, and patient management; and the need for further research in subphenotyping ARDS. Additionally, we highlight knowledge gaps and research priorities that could guide future investigations in this area. Our study builds on previous non-Delphi-based consensus processes (eg, the new global definition of ARDS and recent society-based guidelines) by using a rigorous Delphi method that ensured panellist anonymity and used clear quantitative criteria to mitigate potential peer pressure and group conformity. The findings underscore the need to refine the ARDS definition to better account for the heterogeneity of clinical presentations and underlying pathophysiology, and to improve diagnostic precision, including the use of subphenotyping where appropriate.

The impact of the inflammatory pulmonary microenvironment on the behavior and function of mesenchymal stromal cells

INTRODUCTION

Acute respiratory distress syndrome is characterized by the dysregulation and activation of several inflammatory pathways which lead to widespread inflammation in the lungs. Presently, direct therapy is unavailable and the use of mesenchymal stromal cells as a direct therapy has been proposed, as early-phase studies have shown promise.

AREAS COVERED

MSCs exert various therapeutic effects on the inflammatory microenvironment, such as anti-microbial effects, restoration of the alveolar-capillary barrier, and exuding various anti-inflammatory effects. However, to exert these effects MSCs need to be submitted to specific external stimuli which can affect their immunomodulation, survival, migration and metabolic state. This review references several articles found through targeted searches in PubMed [Accessed between November 2024 and March 2025], for key terms such as 'mesenchymal stromal cells', 'inflammatory microenvironment', anti-inflammatory', 'metabolism', and 'immunomodulation'.

EXPERT OPINION

The advancement of MSCs therapy in the treatment of ARDS has not progressed as effectively as one might have anticipated. Several clinical findings have established patient subgroups based on inflammatory cytokine profiles and severity of ARDS. This variation in patients may influence the clinical efficacy of MSCs and instead of concluding that MSCs therapy is not worth pursuing, more research is needed to develop an appropriate therapy.

Reflections on the introduction of surfactant therapy for neonates with respiratory distress

When pulmonary surfactant was first detected in the 1950s by Pattle and Clements, many thousands of infants perished each year due to a respiratory illness termed hyaline membrane disease. Hyaline membranes are formed by plasma leaking through damaged endothelial barriers into the terminal bronchiolar: alveolar spaces. Since the leaking plasma lacks erythrocytes, these clots are opaque. Insightful research by Avery and Mead soon led to the suggestion that the neonatal respiratory distress syndrome (RDS) did not arise because of the presence of hyaline membranes, but rather was related to the lack of sufficient pulmonary surfactant, mainly as a result of immaturity. Unfortunately, initial attempts at treating RDS with aerosolized dipalmitoyl-phosphatidylcholine, the major single molecular component, proved unsuccessful. Almost 20 years later, it was demonstrated by Enhorning and Robertson that treating prematurely delivered rabbit pups with natural surfactant prevents respiratory failure. Initially, it appeared unlikely that animal surfactants could be used for therapy with human infants. However, in 1980, Fujiwara demonstrated that a modified bovine surfactant extract promoted gaseous exchange with infants suffering from RDS. Soon a number of bovine and porcine-modified surfactants and two wholly synthetic formulations were shown to alleviate RDS. The present review relates some of the key scientific findings and significant clinical contributions responsible for reducing the neonatal morbidity and mortality associated with RDS. It further describes some of the more recent findings on the biological, biophysical, and physiological significance of pulmonary surfactant in health and disease.

Characteristics, triggers, treatments, and experimental models of neonatal acute respiratory distress syndrome

Neonatal acute respiratory distress syndrome (NARDS) is a severe and potentially life-threatening form of lung injury recently defined by the International Neonatal ARDS Consensus. It is marked by extensive lung inflammation and damage to the alveolar epithelium and vascular endothelium. NARDS can be triggered by direct inflammatory exposures, such as pneumonia and aspiration, and indirect exposures, including sepsis, necrotizing enterocolitis, and chorioamnionitis. This review provides clinicians and researchers with the latest insights on NARDS. We adopt a cross-disciplinary approach to discuss the diagnostic criteria, pathobiology, triggers, epidemiology, and treatments of NARDS. In addition, we summarize existing clinical studies and advanced preclinical models that help address current knowledge gaps. Future research should focus on standardizing the Montreux consensus definition of NARDS in preclinical and clinical studies, identifying biomarkers, developing prediction models, and exploring novel therapies for affected infants.

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.

Gut bacterial lactate stimulates lung epithelial mitochondria and exacerbates acute lung injury

Acute respiratory distress syndrome (ARDS) is an often fatal critical illness where lung epithelial injury leads to intrapulmonary fluid accumulation. ARDS became widespread during the COVID-19 pandemic, motivating a renewed effort to understand the complex etiology of this disease. Rigorous prior work has implicated lung endothelial and epithelial injury in response to an insult such as bacterial infection; however, the impact of microorganisms found in other organs on ARDS remains unclear. Here, we use a combination of gnotobiotic mice, cell culture experiments, and re-analyses of a large metabolomics dataset from ARDS patients to reveal that gut bacteria impact lung cellular respiration by releasing metabolites that alter mitochondrial activity in lung epithelium. Colonization of germ-free mice with a complex gut microbiota stimulated lung mitochondrial gene expression. A single human gut bacterial species, Bifidobacterium adolescentis, was sufficient to replicate this effect, leading to a significant increase in mitochondrial membrane potential in lung epithelial cells. We then used genome sequencing and mass spectrometry to confirm that B. adolescentis produces L -lactate, which was sufficient to increase mitochondrial activity in lung epithelial cells. Finally, we found that serum lactate was significantly associated with disease severity in patients with ARDS from the Early Assessment of Renal and Lung Injury (EARLI) cohort. Together, these results emphasize the importance of more broadly characterizing the microbial etiology of ARDS and other lung diseases given the ability of gut bacterial metabolites to remotely control lung cellular respiration. Our discovery of a single bacteria-metabolite pair provides a proof-of-concept for systematically testing other microbial metabolites and a mechanistic biomarker that could be pursued in future clinical studies. Furthermore, our work adds to the growing literature linking the microbiome to mitochondrial function, raising intriguing questions as to the bidirectional communication between our endo- and ecto-symbionts.

N-Acetylcysteine in the Treatment of Acute Lung Injury: Perspectives and Limitations

N-acetylcysteine (NAC) can take part in the treatment of chronic respiratory diseases because of the potent mucolytic, antioxidant, and anti-inflammatory effects of NAC. However, less is known about its use in the treatment of acute lung injury. Nowadays, an increasing number of studies indicates that early administration of NAC may reduce markers of oxidative stress and alleviate inflammation in animal models of acute lung injury (ALI) and in patients suffering from distinct forms of acute respiratory distress syndrome (ARDS) or pulmonary infections including community-acquired pneumonia or Coronavirus Disease (COVID)-19. Besides low costs, easy accessibility, low toxicity, and rare side effects, NAC can also be combined with other drugs. This article provides a review of knowledge on the mechanisms of inflammation and oxidative stress in various forms of ALI/ARDS and critically discusses experience with the use of NAC in these disorders. For preparing the review, articles published in the English language from the PubMed database were used.

Individualized PEEP can improve both pulmonary hemodynamics and lung function in acute lung injury

RATIONALE

There are several approaches to select the optimal positive end-expiratory pressure (PEEP), resulting in different PEEP levels. The impact of different PEEP settings may extend beyond respiratory mechanics, affecting pulmonary hemodynamics.

OBJECTIVES

To compare PEEP levels obtained with three titration strategies-(i) highest respiratory system compliance (CRS), (ii) electrical impedance tomography (EIT) crossing point; (iii) positive end-expiratory transpulmonary pressure (PL)-in terms of regional respiratory mechanics and pulmonary hemodynamics.

METHODS

Experimental studies in two porcine models of acute lung injury: (I) bilateral injury induced in both lungs, generating a highly recruitable model (n = 37); (II) asymmetrical injury, generating a poorly recruitable model (n = 13). In all experiments, a decremental PEEP titration was performed monitoring PL, EIT (collapse, overdistention, and regional ventilation), respiratory mechanics, and pulmonary and systemic hemodynamics.

MEASUREMENTS AND MAIN RESULTS

PEEP titration methods resulted in different levels of median optimal PEEP in bilateral lung injury: 14(12-14) cmH2O for CRS, 11(10-12) cmH2O for EIT, and 8(8-10) cmH2O for PL, p < 0.001. Differences were less pronounced in asymmetrical lung injury. PEEP had a quadratic U-shape relationship with pulmonary artery pressure (R2 = 0.94, p < 0.001), right-ventricular systolic transmural pressure, and pulmonary vascular resistance. Minimum values of pulmonary vascular resistance were found around individualized PEEP, when ventilation distribution and pulmonary circulation were simultaneously optimized.

CONCLUSIONS

In porcine models of acute lung injury with variable lung recruitability, both low and high levels of PEEP can impair pulmonary hemodynamics. Optimized ventilation and hemodynamics can be obtained simultaneously at PEEP levels individualized based on respiratory mechanics, especially by EIT and esophageal pressure.

Advances in acute respiratory distress syndrome: focusing on heterogeneity, pathophysiology, and therapeutic strategies

In recent years, the incidence of acute respiratory distress syndrome (ARDS) has been gradually increasing. Despite advances in supportive care, ARDS remains a significant cause of morbidity and mortality in critically ill patients. ARDS is characterized by acute hypoxaemic respiratory failure with diffuse pulmonary inflammation and bilateral edema due to excessive alveolocapillary permeability in patients with non-cardiogenic pulmonary diseases. Over the past seven decades, our understanding of the pathology and clinical characteristics of ARDS has evolved significantly, yet it remains an area of active research and discovery. ARDS is highly heterogeneous, including diverse pathological causes, clinical presentations, and treatment responses, presenting a significant challenge for clinicians and researchers. In this review, we comprehensively discuss the latest advancements in ARDS research, focusing on its heterogeneity, pathophysiological mechanisms, and emerging therapeutic approaches, such as cellular therapy, immunotherapy, and targeted therapy. Moreover, we also examine the pathological characteristics of COVID-19-related ARDS and discuss the corresponding therapeutic approaches. In the face of challenges posed by ARDS heterogeneity, recent advancements offer hope for improved patient outcomes. Further research is essential to translate these findings into effective clinical interventions and personalized treatment approaches for ARDS, ultimately leading to better outcomes for patients suffering from ARDS.

Battlefield mechanical ventilation and extracorporeal membrane oxygenation: A scoping review

BACKGROUND

Casualties of military conflicts suffer a multitude of injuries, and recent research has documented a significant number develop acute respiratory distress syndrome (ARDS). The present study undertakes a scoping review of research on the treatment of ARDS in combat casualties near the battlefield.

METHODS

We review the extent of the current ARDS care, from intubation and mechanical ventilation (MV) to the use of extracorporeal membrane oxygenation (ECMO), and how the respective echelons of care across the Military Health System (MHS) are involved in the care of these patients. Online databases were used to identify article published 1988-2022, from which we selected 112 publications from various countries including the USA, UK, Germany, Italy, and India that used military relevant keywords (i.e., battlefield, combat, deployed, military trauma), in the titles or abstract in conjunction with the MeSH descriptors for battlefield respiratory failure, and MV or ECMO.

RESULTS

Mechanical ventilation and ECMO have clearly moved forward with progressions in technologies and now are routinely used and are well documented in the prehospital setting and during aeromedical transport. Overview of the MHS and descriptive analysis of battlefield casualties are well represented in the literature. There are multiple publications on airway management on the battlefield and innumerable regarding the somewhat comparable civilian prehospital trauma airway management.

CONCLUSION

While there is an abundance of publications on MV in the prehospital and combat environments, there are few case examples of the use of ECMO on the battlefield. Although MV may be required for many combat casualties, airway management failure remains the second leading cause of preventable death on the battlefield.

A narrative review on the future of ARDS: evolving definitions, pathophysiology, and tailored management

Acute respiratory distress syndrome (ARDS) is a severe complication of critical illness, characterized by bilateral lung infiltrates and hypoxemia. Its clinical and pathophysiological heterogeneity poses challenges for both diagnosis and treatment. This review outlines the evolution of ARDS definitions, discusses the underlying pathophysiology of ARDS, and examines the clinical implications of its heterogeneity. Traditional ARDS definitions required invasive mechanical ventilation and relied on arterial blood gas measurements to calculate the PaO2/FiO2 ratio. Recent updates have expanded these criteria to include patients receiving noninvasive respiratory support, such as high-flow nasal oxygen, and the adoption of the SpO2/FiO2 ratio as an alternative to the PaO2/FiO2 ratio. While these changes broaden the diagnostic criteria, they also introduce additional complexity. ARDS heterogeneity-driven by varying etiologies, clinical subphenotypes, and underlying biological mechanisms-highlights the limitations of a uniform management approach. Emerging evidence highlights the presence of distinct ARDS subphenotypes, each defined by unique molecular and clinical characteristics, offering a pathway to more precise therapeutic targeting. Advances in omics technologies-encompassing genomics, proteomics, and metabolomics-are paving the way for precision-medicine approaches with the potential to revolutionize ARDS management by tailoring interventions to individual patient profiles. This paradigm shift from broad diagnostic categories to precise, subphenotype-driven care holds promise for redefining the landscape of treatment for ARDS and, ultimately, improving outcomes in this complex, multifaceted syndrome.

Macrophage pyroptosis and its crucial role in ALI/ARDS

Acute lung injury(ALI)/acute respiratory distress syndrome(ARDS) is a severe clinical syndrome characterized by high morbidity and mortality, primarily due to lung injury. However, the pathogenesis of ALI/ARDS remains a complex issue. In recent years, the role of macrophage pyroptosis in lung injury has garnered extensive attention worldwide. This paper reviews the mechanism of macrophage pyroptosis, discusses its role in ALI/ARDS, and introduces several drugs and intervening measures that can regulate macrophage pyroptosis to influence the progression of ALI/ARDS. By doing so, we aim to enhance the understanding of the mechanism of macrophage pyroptosis in ALI/ARDS and provide novel insights for its treatment.

Pathophysiological mechanisms of ARDS: a narrative review from molecular to organ-level perspectives

BACKGROUND

Acute respiratory distress syndrome (ARDS) remains a life-threatening pulmonary condition with persistently high mortality rates despite significant advancements in supportive care. Its complex pathophysiology involves an intricate interplay of molecular and cellular processes, including cytokine storms, oxidative stress, programmed cell death, and disruption of the alveolar-capillary barrier. These mechanisms drive localized lung injury and contribute to systemic inflammatory response syndrome and multiple organ dysfunction syndrome. Unlike prior reviews that primarily focus on isolated mechanisms, this narrative review synthesizes the key pathophysiological processes of ARDS across molecular, cellular, tissue, and organ levels.

MAIN BODY

By integrating classical theories with recent research advancements, we provide a comprehensive analysis of how inflammatory mediators, metabolic reprogramming, oxidative stress, and immune dysregulation synergistically drive ARDS onset and progression. Furthermore, we critically evaluate current evidence-based therapeutic strategies, such as lung-protective ventilation and prone positioning, while exploring innovative therapies, including stem cell therapy, gene therapy, and immunotherapy. We emphasize the significance of ARDS subtypes and their inherent heterogeneity in guiding the development of personalized treatment strategies.

CONCLUSIONS

This narrative review provides fresh perspectives for future research, ultimately enhancing patient outcomes and optimizing management approaches in ARDS.

Comparative outcomes of corticosteroids, neuromuscular blocking agents, and inhaled nitric oxide in ARDS: a systematic review and network meta-analysis

Objectives

Acute respiratory distress syndrome (ARDS) is associated with high rates of morbidity and mortality. However, the evidence regarding the effectiveness of commonly used treatments, including corticosteroids, neuromuscular blocking agents (NMBAs), and inhaled nitric oxide (iNO), remains uncertain. Therefore, this study aimed to compare and rank these three treatments to identify the most effective option.

Data sources

We searched PubMed, Embase, Cochrane Library, and Web of Science for clinical trials from the earliest records to 1 May 2024.

Study selection and data extraction

Clinical trials evaluating three interventions compared with the control group for ARDS were included, with restrictions on any language. Data were extracted by two independent reviewers. Frequentist network meta-analysis (NMA) was performed to identify the most effective intervention, and treatments were ranked using the surface under the cumulative ranking (SUCRA) curve. The primary outcome was 28-day mortality, while secondary outcomes included ventilator-free days up to 28 days, ICU mortality, in-hospital mortality, and the incidence of new infection events.

Data synthesis

Data from 26 clinical trials encompassing 5,071 patients were analyzed. Vecuronium bromide was the most effective strategy for reducing 28-day mortality compared to conventional treatment, iNO, methylprednisolone, and placebo (OR 0.38, 95% CI 0.15-1.00, and OR 0.30, 95% CI 0.10-0.85 and OR 0.25, 95% CI 0.08-0.74 and OR 0.23, 95% CI 0.08-0.65; SUCRA: 96.6%). Dexamethasone was identified as the most effective treatment option for increasing ventilator-free days at 28 days compared to conventional therapy and cisatracurium (MD 3.60, 95% CI 1.77-5.43, and MD 3.40, 95% CI 0.87-5.92; SUCRA: 93.2%). Methylprednisolone demonstrated the highest effectiveness for preventing ICU mortality (SUCRA: 88.5%). Although dexamethasone, cisatracurium, conventional therapy, methylprednisolone, and iNO treatment did not show significant superiority in reducing in-hospital mortality, dexamethasone showed the highest probability of being the most effective treatment option (SUCRA: 79.7%). Furthermore, dexamethasone treatment showed the highest safety in reducing the incidence of new infection events compared with placebo and iNO (OR 0.61, 95% CI 0.42-0.88, and OR 0.33, 95% CI 0.19-0.58; SUCRA: 91.8%).

Conclusion

This NMA suggests that corticosteroids may provide benefits to patients with ARDS. While the application of NMBAs may reduce 28-day mortality, iNO did not demonstrate a significant beneficial effect as a therapeutic measure.

Systematic review registration

PROSPERO, CRD42022333165 https://www.crd.york.ac.uk/PROSPERO/.

Inflammation and aging-related disease: A transdisciplinary inflammaging framework

Inflammaging, a state of chronic, progressive low-grade inflammation during aging, is associated with several adverse clinical outcomes, including frailty, disability, and death. Chronic inflammation is a hallmark of aging and is linked to the pathogenesis of many aging-related diseases. Anti-inflammatory therapies are also increasingly being studied as potential anti-aging treatments, and clinical trials have shown benefits in selected aging-related diseases. Despite promising advances, significant gaps remain in defining, measuring, treating, and integrating inflammaging into clinical geroscience research. The Clin-STAR Inflammation Research Interest Group was formed by a group of transdisciplinary clinician-scientists with the goal of advancing inflammaging-related clinical research and improving patient-centered care for older adults. Here, we integrate insights from nine medical subspecialties to illustrate the widespread impact of inflammaging on diseases linked to aging, highlighting the extensive opportunities for targeted interventions. We then propose a transdisciplinary approach to enhance understanding and treatment of inflammaging that aims to improve comprehensive care for our aging patients.

[Acute respiratory distress syndrome : Pathophysiology, definition and treatment strategies]

Acute respiratory distress syndrome (ARDS) is defined as an acute inflammatory syndrome leading to increased pulmonary capillary leakage and subsequent interstitial and alveolar pulmonary edema. Hypoxia is the predominant symptom. The definition of ARDS comprises acute onset, bilateral patchy infiltration on chest X‑ray and a reduction of the ratio of arterial partial pressure of oxygen (PaO2) to the fraction of inspired oxygen (FiO2), which also determines the classification into mild (≤ 300), moderate (≤ 200) and severe (≤ 100) ARDS. Treating the underlying cause is the only causal treatment measure. The aim of adjunctive therapy is the maintenance of life or organ functions by ensuring an adequate gas exchange without further damaging the lungs. Adjunctive therapy consists mainly of individually adapted "protective" ventilation treatment and the prone position. In severest ARDS, the use of venovenous extracorporeal membrane oxygenation (VV-ECMO) can improve survival if strict criteria for indications and contraindications are followed.

Is prone positioning a valid intervention for ARDS in the deployed intensive care unit?

Prone positioning is an intervention used for patients with acute respiratory distress syndrome (ARDS) whose hypoxia is worsening despite conventional treatment. Previously used infrequently, it became an important treatment escalation strategy for hypoxia during the COVID-19 pandemic. Current evidence for prone positioning suggests increased survivability in intubated patients with moderate to severe ARDS who are prone for >12 hours a day. As a relatively low-cost, low-tech intervention with a growing evidence base, the viability of prone positioning in the deployed land environment is considered in this article. The practical technique of prone positioning is easy to teach to healthcare staff experienced in manual handling. However, it requires significant resources, in particular staff numbers, and time to execute and maintain, and necessitates a pressure-minimising mattress. Additionally, staff are placed at increased risk of musculoskeletal injuries and potential exposure to aerosolised microbes if there is a disconnection of the breathing system. We conclude that in the deployed 2/1/2/12 facility (or larger), with access to higher staff numbers and high-specification mattresses, prone positioning is a valid escalation technique for intubated hypoxic patients with ARDS. However, in smaller facilities where resources are constrained, its implementation is unlikely to be achievable.

Evaluating the impact of ESICM 2023 guidelines and the new global definition of ARDS on clinical outcomes: insights from MIMIC-IV cohort data

BACKGROUND

In 2023, the European Society of Intensive Care Medicine (ESICM) recommended updated criteria for acute respiratory distress syndrome (ARDS). In 2024, Matthay et al. updated the global ARDS definition in AJRCCM, titled "A New Global Definition of Acute Respiratory Distress Syndrome." However, the impact of this new definition on ARDS treatments is currently unknown.

OBJECTIVE

This study aims to determine the effect of the new ARDS definition on patients with hypoxemic respiratory failure and study the heterogeneity of patients in the new definition to guide treatment.

METHODS

Clinical consultation data from the Medical Information Mart for Intensive Care IV database were extracted using Structured Query Language based on the PostgreSQL tool (version 10.0). Data were analyzed using Python (version 3.9) and the deep learning framework Pytorch. Kaplan-Meier survival analysis was used to compare survival between the old and new definitions. A hierarchical clustering approach was applied to identify potential ARDS clinical subtypes.

RESULTS

The new definition diagnosed ARDS earlier and included individuals with lower mortality rates compared with the Berlin definition. Patients meeting the new definition but not the Berlin criteria exhibited a favorable response to non-invasive ventilation strategies (p = 0.009). The XGBoost classifier, trained to predict subphenotypes, achieved an AUC of 0.88 ± 0.02 on the training set. Additionally, mortality was significantly associated with patients with hypoxemia compared with survivors, particularly regarding respiratory parameters. Easily accessible metrics, such as respiratory rate and urea nitrogen (BUN), can help diagnose ARDS in high-risk populations in resource-limited settings.

CONCLUSIONS

The new ARDS definition offers advantages in earlier detection, more accurate grading, and more precise diagnosis in resource-limited settings compared with the Berlin definition. This study also established a robust prediction model for early ARDS identification, improving the patient prognosis and reducing the mortality rate.

Factors Associated with the Initiation of Renal Replacement Therapy in Patients on VV-ECMO: A Case-Control Study

Acute Kidney Injury (AKI) is a common complication in patients with Acute Respiratory Distress Syndrome (ARDS) receiving VV-ECMO support, carrying a high risk of progression to Renal Replacement Therapy (RRT). Both AKI and RRT are linked to an increased risk of mortality. This study aims to evaluate the risk factors associated with the need for RRT in patients undergoing VV-ECMO. Methods: This is a retrospective case-control study involving patients on VV-ECMO therapy admitted to the intensive care unit (ICU) between 2019 and 2023. Patients on VV ECMO support, with or without RRT, were included and their severity scores and associated mortality were calculated. A multivariate logistic regression analysis was performed to assess the variable RRT using odds ratios (OR) with their corresponding confidence intervals (CI) for the outcome variables. Results: A total of 192 subjects were included, with a mortality rate of 39.6%. Of these, 68.7% were male, with an average ICU stay of 25.1 days and a need for RRT in 19.7% of cases. The multivariate analysis independently associated the use of vasopressors with RRT norepinephrine OR 5.61 (95% CI, 1.64-19.1) and vasopressin OR 4.64 (95% CI, 2.15-10.0)). An increase in creatinine levels before ECMO support is associated with an increased risk OR 2.21 (95% CI 1.54-3.18), and 24 h after ECMO support, the risk rises further adjusted odds ratio (AOR) 3.32 (95% IC 1.55-7.09). The accuracy of severity scores presented weak discrimination and similar behavior, except for DEOx for the primary outcome, with an AUC of 0.79 (95% CI, 0.72-0.87), and APACHE II with an AUC of 0.68 (95% CI, 0.59-0.78). Conclusions: The prediction of RRT in patients on VV-ECMO support was superior for DEOx, which is influenced by the use of vasopressors, creatinine levels, and platelet transfusion prior to cannulation. This could be useful for predicting early interventions in this patient population.

Rethinking ARDS classification: oxygenation impairment fails to predict VILI risk

PURPOSE

The selection and intensity of respiratory support for ARDS are guided by PaO2/FiO2. However, ventilator-induced lung injury (VILI) is linked to respiratory mechanics and ventilator settings. We explored whether the VILI risk is related to ARDS severity based on oxygenation.

METHODS

We analysed data on 228 ARDS subjects with PaO2/FiO2 < 200 mmHg, categorized into three severity groups: one based on PaO2/FiO2 ratio, and the others based on tertiles of predictors of VILI: mechanical power ratio (MPR) and driving pressure (DP). In each group of oxygenation-based ARDS severity and MPR and DP tertiles, we measured CT anatomy, gas exchange, respiratory mechanics, VILI prerequisites (lung elastance and lung gas volume), and VILI determinants (tidal volume, PEEP, airway pressures).

RESULTS

Predictors of VILI, such as MPR and DP, were similar across ARDS severity groups based on PaO2/FiO2 ratio, while oxygenation remained comparable across different levels of VILI risk defined by MPR and DP. Oxygenation impairment was associated with increased lung weight, recruitability, and reduced well-inflated tissue. In contrast, MPR and DP tertiles affected variables associated with the baby lung size, such as lung gas volume and well-inflated tissue. Mechanical ventilation intensity increased progressively across MPR and DP tertiles, but remained similar across PaO2/FiO2 severity groups.

CONCLUSIONS

ARDS severity based on oxygenation impairment does not reflect the prerequisites and determinants of VILI. This should prompt a reconsideration of recommending respiratory support based on oxygenation impairment, rather than VILI determinants.

ARDS Ventilation, The Man Behind the Evolution

How to cite this article: Prayag S. ARDS Ventilation, The Man Behind the Evolution. Indian J Crit Care Med 2025;29(1):12-13.

What proteins and albumins in bronchoalveolar lavage fluid and serum could tell us in COVID-19 and influenza acute respiratory distress syndrome on mechanical ventilation patient - A prospective double center study

Introduction

The extent of in vivo damage to the alveolar-capillary membrane in patients with primary lung injury remains unclear. In cases of ARDS related to COVID-19 and Influenza type A, the complexity of the damage increases further, as viral pneumonia cannot currently be treated with a causal approach.

Aims of the study

Our primary goal is to enhance the understanding of Acute Respiratory Distress Syndrome (ARDS) by demonstrating damage to the alveocapillary membrane in critically ill patients with COVID-19 and influenza type A. We will achieve this by measuring the levels of proteins and albumin in bronchoalveolar fluid (BAL) and serum. Our secondary objective is to assess patient outcomes related to elevated protein and albumin levels in both BAL and blood serum, which will deepen our understanding of this complex condition.

Materials and methods

Bronchoalveolar lavage (BAL) fluid and serum samples were meticulously collected from a total of 64 patients, categorized into three distinct groups: 30 patients diagnosed with COVID-19-related acute respiratory distress syndrome (ARDS), 14 patients with influenza type A (H1N1 strain), also experiencing ARDS, and a control group consisting of 20 patients who were preoperatively prepared for elective surgical procedures without any diagnosed lung disease. The careful selection and categorization of patients ensure the robustness of our study. BAL samples were taken within the first 24 hours following the commencement of invasive mechanical ventilation in the intensive care unit, alongside measurements of serum albumin levels. In the control group, BAL and serum samples were collected after the induction of general endotracheal anaesthesia.

Results

Patients in the COVID-19 group are significantly older than those in the Influenza type A (H1N1) group, with median ages of 72.5 years and 62 years, respectively (p < 0.01, Mann-Whitney U test). Furthermore, serum albumin levels (measured in g/L) revealed significant differences across all three groups in the overall sample, yielding a p-value of less than 0.01 according to ANOVA. In terms of treatment outcomes, serum albumin levels also exhibited a significant correlation, with a p-value of 0.03 (Mann-Whitney U test). A reduction in serum albumin levels (below 35 g/L), combined with elevated protein levels in bronchoalveolar lavage (BAL), serves as a predictor of poor outcomes in patients with acute respiratory distress syndrome (ARDS), as indicated by a p-value of less than 0.01 (ANOVA).

Conclusions

Our findings indicate that protein and albumin levels in bronchoalveolar lavage (BAL) fluid are elevated in severe acute respiratory distress syndrome (ARDS) cases. This suggests that BAL can effectively evaluate protein levels and fractions, which could significantly assist in assessing damage to the alveolocapillary membrane. Additionally, the increased albumin levels in BAL, often accompanied by a decrease in serum albumin levels, may serve as a valuable indicator of compromised integrity of the alveolar-capillary membrane in ARDS, with potential implications for patient care.

Studying the interfacial activity and structure of pulmonary surfactant complexes

Pulmonary surfactant (PS) is a membranous complex that coats the respiratory air-liquid interface in air-breathing animal lungs. Its main function is to minimize the surface tension at the end of expiration, what is needed for preventing alveolar collapse. Although the tension reduction capabilities of surfactant depend on the formation of air-exposed phospholipid-enriched monolayers, the interfacial surfactant films are far from simple monolayers. Surfactant surface films are dynamically interconnected to continuously secreted newly synthetized material thanks to the action of a pair of very hydrophobic proteins, termed SP-B and SP-C, which are responsible to modulate the biophysical behavior of the complex. Other proteins in the system, such as the hydrophilic SP-A and SP-D, are integrated into different surfactant structures but participate primarily in the immune defense of the lung. In spite of countless studies on the structure and chemico-physical properties of surfactant membranes, the full complexity of surfactant three-dimensional structure is far from being completely understood. Here we review some of the most useful techniques that have allowed the characterization of the PS system along the years to develop the current models interpreting surfactant structure-function relationships.

Genetic predisposition to acute lung injury in cardiac surgery 'The VEGF Factor': Review article and bibliometric analysis

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are among the most prevalent complications associated with cardiac surgery involving extracorporeal circulation (ECC), contributing to adverse outcomes and representing a significant impediment to successful cardiac surgical procedures. Vascular endothelial growth factor (VEGF) is implicated in the etiology of ALI/ARDS; however, its precise role remains a subject of debate due to the presence of somewhat contradictory findings in the literature, necessitating further investigation. To date, numerous studies have explored the role of VEGF in the pathophysiology of ALI/ARDS, with ongoing discussions regarding whether VEGF exerts a protective or detrimental effect. The genetic polymorphism of the VEGF gene is a significant factor in the development of ALI/ARDS. Research has indicated that the prevalence of the VEGF polymorphic gene is markedly higher in postoperative cardiac surgery patients who develop ALI/ARDS compared to the general population. Furthermore, the mortality rate among patients possessing the VEGF polymorphic gene is significantly elevated. Concurrently, it has been demonstrated that ARDS patients who are positive for the VEGF polymorphism exhibit a reduction in VEGF levels within alveolar lavage fluid, which correlates with an exacerbation of lung injury. The present paper provides a comprehensive review of the genetic polymorphisms of VEGF and their implications in the pathophysiological alterations observed in postoperative cardiac surgery patients with ALI/ARDS, thereby offering novel insights and evidence to further elucidate the mechanisms underlying ALI/ARDS.

Navigating Heart-Lung Interactions in Mechanical Ventilation: Pathophysiology, Diagnosis, and Advanced Management Strategies in Acute Respiratory Distress Syndrome and Beyond

Patients in critical condition who require mechanical ventilation experience intricate interactions between their respiratory and cardiovascular systems. These complex interactions are crucial for clinicians to understand as they can significantly influence therapeutic decisions and patient outcomes. A deep understanding of heart-lung interactions is essential, particularly under the stress of mechanical ventilation, where the right ventricle plays a pivotal role and often becomes a primary concern. Positive pressure ventilation, commonly used in mechanical ventilation, impacts right and left ventricular pre- and afterload as well as ventricular interplay. The right ventricle is especially susceptible to these changes, and its function can be critically affected, leading to complications such as right heart failure. Clinicians must be adept at recognizing and managing these interactions to optimize patient care. This perspective will analyze this matter comprehensively, covering the pathophysiology of these interactions, the monitoring of heart-lung dynamics using the latest methods (including ECHO), and management and treatment strategies for related conditions. In particular, the analysis will delve into the efficacy and limitations of various treatment modalities, including pharmaceutical interventions, nuanced ventilator management strategies, and advanced devices such as extracorporeal membrane oxygenation (ECMO). Each approach will be examined for its impact on optimizing right ventricular function, mitigating complications, and ultimately improving patient outcomes in the context of mechanical ventilation.

Liang-Ge-San Decoction Ameliorates Acute Respiratory Distress Syndrome via Suppressing p38MAPK-NF-κ B Signaling Pathway

OBJECTIVE

To explore the potential effects and mechanisms of Liang-Ge-San (LGS) for the treatment of acute respiratory distress syndrome (ARDS) through network pharmacology analysis and to verify LGS activity through biological experiments.

METHODS

The key ingredients of LGS and related targets were obtained from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform. ARDS-related targets were selected from GeneCards and DisGeNET databases. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were performed using the Metascape Database. Molecular docking analysis was used to confirm the binding affinity of the core compounds with key therapeutic targets. Finally, the effects of LGS on key signaling pathways and biological processes were determined by in vitro and in vivo experiments.

RESULTS

A total of LGS-related targets and 496 ARDS-related targets were obtained from the databases. Network pharmacological analysis suggested that LGS could treat ARDS based on the following information: LGS ingredients luteolin, wogonin, and baicalein may be potential candidate agents. Mitogen-activated protein kinase 14 (MAPK14), recombinant V-Rel reticuloendotheliosis viral oncogene homolog A (RELA), and tumor necrosis factor alpha (TNF-α) may be potential therapeutic targets. Reactive oxygen species metabolic process and the apoptotic signaling pathway were the main biological processes. The p38MAPK/NF-κ B signaling pathway might be the key signaling pathway activated by LGS against ARDS. Moreover, molecular docking demonstrated that luteolin, wogonin, and baicalein had a good binding affinity with MAPK14, RELA, and TNF α. In vitro experiments, LGS inhibited the expression and entry of p38 and p65 into the nucleation in human bronchial epithelial cells (HBE) cells induced by LPS, inhibited the inflammatory response and oxidative stress response, and inhibited HBE cell apoptosis (P<0.05 or P<0.01). In vivo experiments, LGS improved lung injury caused by ligation and puncture, reduced inflammatory responses, and inhibited the activation of p38MAPK and p65 (P<0.05 or P<0.01).

CONCLUSION

LGS could reduce reactive oxygen species and inflammatory cytokine production by inhibiting p38MAPK/NF-κ B signaling pathway, thus reducing apoptosis and attenuating ARDS.

Definitions of Acute Respiratory Distress Syndrome: Present Recommendations and Challenges

Acute respiratory distress syndrome (ARDS) is an acute inflammatory process resulting in diffuse lung injury precipitated by an underlying risk factor. However, current definitions may pose barriers to the accurate diagnosis of this syndrome. These include changes in risk factors and associated disease evolution of ARDS, changes in contemporary clinical practice, and access to diagnostic tools required to diagnose ARDS in resource-limited settings. A consensus conference has proposed changes for an expanded global definition of ARDS. In this review article, we review challenges in defining ARDS and present recommendations of the global definition of ARDS.

Pharmacological mechanisms of traditional Chinese medicine against acute lung injury: From active ingredients to herbal formulae

BACKGROUND

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are the leading causes of acute respiratory failure in many critical diseases and are among the main respiratory diseases with high clinical mortality. The global outbreak of coronavirus disease 2019 (COVID-19) can cause severe ARDS, resulting in a steep rise in the number of patient deaths. Therefore, it is important to explore the pathogenesis of ALI and find effective therapeutic agents. In recent years, thanks to modern biomedical tools, some progress has been made in the application of traditional Chinese medicine (TCM) treatment principles based on syndromic differentiation and holistic concepts in clinical and experimental studies of ALI. More and more TCM effective components and formulae have been verified to have significant curative effects, which have a certain guiding significance for clinical practice.

PURPOSE

It is hoped to provide reference for the clinical research of ALI/ARDS and provide theoretical basis and technical support for the scientific application of TCM in respiratory related diseases.

METHODS

We performed a literature survey using traditional books of Chinese medicine and online scientific databases including PubMed, Web of Science, Google Scholar, ScienceDirect, China National Knowledge Infrastructure (CNKI), and others up to January 2023.

RESULTS

In recent years, thanks to modern biomedical tools, some progress has been made in the application of TCM treatment principles based on syndromic differentiation and holistic concepts in clinical and experimental studies of ALI. This paper mainly reviews the research progress of ALI/ARDS mechanism, the understanding of its etiology and pathogenesis by TCM, and the therapeutic effects of TCM formulae and active ingredients of Chinese medicine. A large number of studies have shown that the effective components and formulae of TCM can prevent or treat ALI/ARDS in vivo and in vitro experiments.

CONCLUSION

TCM effective components and formulae play an important role in the prevention and treatment of ALI/ARDS through multiple approaches and multiple targets, and provide necessary theoretical support for the further development and utilization of TCM resources.

Deciphering the therapeutic potential of Myeloid-Specific JAK2 inhibition in acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a life-threatening condition characterized by severe inflammation and pulmonary dysfunction. Despite advancements in critical care, effective pharmacological interventions for ARDS remain elusive. While Janus kinase 2 (JAK2) inhibitors have emerged as an innovative treatment for numerous autoinflammatory diseases, their therapeutic potential in ARDS remains unexplored. In this study, we investigated the contribution of JAK2 and its underlying mechanisms in ARDS utilizing myeloid-specific JAK2 knockout murine models alongside a pharmacological JAK2 inhibitor. Notably, myeloid-specific JAK2 knockout led to a notable attenuation of ARDS induced by intratracheal administration of LPS, accompanied by reduced levels of neutrophils and inflammatory cytokines in bronchoalveolar lavage fluid (BALF) and lung tissue. Intriguingly, the ameliorative effects were abolished upon the depletion of monocyte-derived alveolar macrophages (Mo-AMs) rather than tissue-resident alveolar macrophages (TR-AMs). JAK2 deficiency markedly reversed LPS-induced activation of STAT5 in macrophages. Remarkably, pharmacological JAK2 inhibition using baricitinib failed to substantially alleviate neutrophils infiltration, implying that specific inhibition of JAK2 in Mo-AMs is imperative for ARDS amelioration. Collectively, our data suggest that JAK2 may mitigate ARDS progression through the JAK2 pathway in Mo-AMs, underscoring JAK2 in alveolar macrophages, particularly Mo-AMs, as a promising therapeutic target for ARDS treatment.

Acute respiratory distress syndrome: A review of ARDS across the life course

Acute respiratory distress syndrome (ARDS) is a multifactorial, inflammatory lung disease with significant morbidity and mortality that predominantly requires supportive care in its management. Although initially described in adult patients, the diagnostic definitions for ARDS have evolved over time to accurately describe this disease process in pediatric and, more recently, neonatal patients. The management of ARDS in each age demographic has converged in the application of lung-protective ventilatory strategies to mitigate the primary disease process and prevent its exacerbation by limiting ventilator-induced lung injury. However, differences arise in the preferred ventilatory strategies or adjunctive pulmonary therapies used to mitigate each type of ARDS. In this review, we compare and contrast the epidemiology, common etiologies, pathophysiology, diagnostic criteria, and outcomes of ARDS across the lifespan. Additionally, we discuss in detail the different management strategies used for each subtype of ARDS and spotlight how these strategies were applied to mitigate poor outcomes during the COVID-19 pandemic. This review is geared toward both clinicians and clinician-scientists as it not only summarizes the latest information on disease pathogenesis and patient management in ARDS across the lifespan but also highlights knowledge gaps for further investigative efforts. We conclude by projecting how future studies can fill these gaps in research and what improvements may be envisioned in the management of NARDS and PARDS based on the current breadth of literature on adult ARDS treatment strategies.

Iron Overload-Dependent Ferroptosis Aggravates LPS-Induced Acute Lung Injury by Impairing Mitochondrial Function

Ferroptosis is a newly proposed form of programmed cell death that is iron-dependent and closely linked to oxidative stress. Its specific morphological changes include shrunken mitochondria, increased density of mitochondrial membrane, and rupture or disappearance of mitochondrial cristae. The main mechanism of ferroptosis involves excessive free iron reacting with membrane phospholipids, known as the Fenton reaction, resulting in lipid peroxidation. However, the role of iron in acute lung injury (ALI) remains largely unknown. In this study, LPS was instilled into the airway to induce ALI in mice. We observed a significant increase in iron concentration during ALI, accompanied by elevated levels of lipid peroxidation markers such as malonaldehyde (MDA) and 4-hydroxynonenal (4-HNE). Treatment with the iron chelator deferoxamine (DFO) or ferroptosis inhibitor ferrostatin-1 (Fer-1) reversed lipid peroxidation and significantly attenuates lung injury. Similarly, DFO or Fer-1 treatment improved the cell survival significantly in vitro. These results demonstrated that ferroptosis occurs during ALI and that targeting ferroptosis is an effective treatment strategy. Interestingly, we found that the increased iron was primarily concentrated in mitochondria and DFO treatment effectively restored normal mitochondria morphology. To further confirm the damaging effect of iron on mitochondria, we performed mitochondrial stress tests in vitro, which revealed that iron stimulation led to mitochondrial dysfunction, characterized by impaired basal respiratory capacity, ATP production capacity, and maximum respiratory capacity. MitoTEMPO, an antioxidant targeting mitochondria, exhibited superior efficacy in improving iron-induced mitochondrial dysfunction compared to the broad-spectrum antioxidant NAC. Treatment with MitoTEMPO more effectively alleviated ALI. In conclusion, ferroptosis contributes to the pathogenesis of ALI and aggravates ALI by impairing mitochondrial function.

Precision Medicine in Acute Respiratory Distress Syndrome: Progress, Challenges, and the Road ahead

Several novel high-dimensional biologic measurements are increasingly being applied to biomedical sciences. Acute respiratory distress syndrome (ARDS) is a theoretically fertile ground for such approaches. Not only are these biologic and analytic tools available to better understand ARDS but also arguably, simpler approaches such as respiratory physiology has been vastly underutilized as a means of delivering precision-based care in the field. Here we review the progress made in ARDS toward discovering biologically homogeneous phenotypes, treatment responsive subgroups, the challenges to implement these discoveries at the bedside, and the road ahead that will enable precision medicine in ARDS.

Early Rehabilitation in Acute Respiratory Distress Syndrome

Providing early rehabilitation during critical illness is considered best practice; however, the respiratory compromise suffered by patients with ARDS often limits their capacity to participate in active exercise. This article outlines the current evidence regarding early rehabilitation in the ICU with a specific focus on the considerations for this cohort. It provides some practical recommendations to assist clinicians in the identification of appropriate early rehabilitation techniques, taking into account disease severity and medical management strategies. It outlines methods to ensure the safe implementation of early rehabilitation with the aim of improving the outcomes of ARDS survivors.

Pediatric pulmonology year in review-Pediatric pulmonary critical care

Pediatric pulmonary critical care literature has continued to grow in recent years. Our aim in this review is to narrowly focus on publications providing clinically-relevant advances in pediatric pulmonary critical care in 2023.

Therapeutic targeting of hypoxia inducible factor in acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is characterized by bilateral chest infiltration and acute hypoxic respiratory failure. ARDS carries significant morbidity and mortality despite advancements in medical management, calling for the development of novel therapeutic targets. Hypoxia-inducible factor (HIF) is a heterodimeric protein involved in various essential pathways, including metabolic reprogramming, immune modulation, angiogenesis and cell cycle regulation. HIF is routinely degraded in homeostasis conditions via the prolyl hydroxylase domain/von Hippel-Lindau protein pathway. However, HIF is stabilized in ARDS via various mechanisms (oxygen-dependent and independent) as an endogenous protective pathway and plays multifaceted roles in different cell populations. This review focuses on the functional role of HIF and its target genes during ARDS, as well as how HIF has evolved as a therapeutic target in current medical management.

Acute respiratory distress syndrome

The understanding of acute respiratory distress syndrome (ARDS) has evolved greatly since it was first described in a 1967 case series, with several subsequent updates to the definition of the syndrome. Basic science advances and clinical trials have provided insight into the mechanisms of lung injury in ARDS and led to reduced mortality through comprehensive critical care interventions. This review summarizes the current understanding of the epidemiology, pathophysiology, and management of ARDS. Key highlights include a recommended new global definition of ARDS and updated guidelines for managing ARDS on a backbone of established interventions such as low tidal volume ventilation, prone positioning, and a conservative fluid strategy. Future priorities for investigation of ARDS are also highlighted.

Risk factors for in-hospital mortality in older patients with acute respiratory distress syndrome due to COVID-19: a retrospective cohort study

BACKGROUND

Advancing age is associated with an increase in mortality among patients with acute respiratory distress syndrome (ARDS) due to coronavirus disease 2019 (COVID-19). This study aimed to determine risk factors for in-hospital mortality in patients over 60 years old with COVID-19-related ARDS (C-ARDS).

METHODS

This was an observational, analytical, retrospective study conducted on a cohort that included all patients aged 60 years or older diagnosed with COVID-ARDSwho were admitted to a high-complexity hospital in Bogotá, Colombia, between March 2020 and July 2021.

RESULTS

A total of 1563 patients were included in the analysis, with a median age of 73 years (interquartile range [IQR]: 67-80) and 811 deaths (51.8%). Independent risk factors for in-hospital mortality were identified as follows: patients aged 71-80 [OR 1.87 (95% CI 1.33-2.64)], age > 80 [OR 8.74 (95% CI 5.34-14.31)], lactate dehydrogenase (LDH) [OR 1.009 (95% CI 1.003-1.0015)], severe C-ARDS [OR 2.16 (95% CI 1.50-3.11)], use of invasive mechanical ventilation (IMV) [OR 12.94 (95% CI 9.52-17.60)], and use of steroids [OR 1.49 (95% CI 1.09-2.03)]. In patients over 80 years of age (n = 388), the primary risk factor associated with in-hospital mortality was the use of IMV (n = 76) [OR 6.26 (95% CI 2.67-14.69)], resulting in an in-hospital mortality rate of 89.4% (n = 68) when this therapy was implemented.

CONCLUSIONS

The primary risk factors for in-hospital mortality in patients older than 60 years were age, the use of IMV, the severity of C-ARDS, use of steroids and elevated LDH values. Among patients older than 80 years, the main risk factor for in-hospital mortality was the use of IMV. In cases of C-ARDS in older patients, the decision to initiate IMV should always be individualized; therefore, the use of alternative oxygen delivery systems as the first-line approach can be considered.

Revisiting ARDS Classification: Are We There Yet?

How to cite this article: Mishra S. Revisiting ARDS Classification: Are We There Yet? Indian J Crit Care Med 2024;28(10):899-900.