Management of severe acute respiratory distress syndrome: a primer

Human fetal lung mesenchymal stem cells ameliorate lung injury in an animal model

Acute lung injury (ALI) is a critical condition with limited treatment options. This study evaluates the therapeutic potential of human fetal lung-derived mesenchymal stem cells (hFL-MSCs) in an experimental model of ALI. Our proof-of-concept findings suggest a paradigm shift in the approach to cell sourcing for lung diseases, proposing that fetal lung cells may be potential targets for stem cell differentiation studies when the derived cells are intended to be used for lung cell therapy. After characterizing hFL-MSCs, 18-week fetal lung cells were intratracheally instilled into rats with bleomycin-induced ALI. All the animals were evaluated on days 3 - 28 post-injury for cell count and the cytokines in bronchoalveolar lavage fluid (BALF), lung wet/dry weight ratio, lung tissue histological staining and expression of an extracellular matrix component, inflammatory and fibrotic genes. The findings confirm mesenchymal stem cell identity of the isolated cells and stability in their cell cycle distribution. Analysis of BALF showed that immune cell response to acute inflammation and adaptive immunity was significantly ameliorated by cell therapy with hFL-MSCs. Same results were confirmed by the levels of IL-6, TNF-α, IL-10 and NO in BALF, the lung wet/dry weight ratio and histopathological analysis of lung tissues after H&E and Masson's trichrome staining. Effective modulation of key pro-inflammatory (Il6, Tnf, Il1b), pro-fibrotic (Tgfb1) and Col1a1 genes were also confirmed after therapy with hFL-MSCs. Our findings suggest that fetal lung tissue-specific stem cells are viable options for lung cell therapy and could be considered as targets for engineering of regenerative cells for lung diseases.

Acute respiratory distress syndrome (ARDS): from mechanistic insights to therapeutic strategies

Acute respiratory distress syndrome (ARDS) is a clinical syndrome of acute hypoxic respiratory failure caused by diffuse lung inflammation and edema. ARDS can be precipitated by intrapulmonary factors or extrapulmonary factors, which can lead to severe hypoxemia. Patients suffering from ARDS have high mortality rates, including a 28-day mortality rate of 34.8% and an overall in-hospital mortality rate of 40.0%. The pathophysiology of ARDS is complex and involves the activation and dysregulation of multiple overlapping and interacting pathways of systemic inflammation and coagulation, including the respiratory system, circulatory system, and immune system. In general, the treatment of inflammatory injuries is a coordinated process that involves the downregulation of proinflammatory pathways and the upregulation of anti-inflammatory pathways. Given the complexity of the underlying disease, treatment needs to be tailored to the problem. Hence, we discuss the pathogenesis and treatment methods of affected organs, including 2019 coronavirus disease (COVID-19)-related pneumonia, drowning, trauma, blood transfusion, severe acute pancreatitis, and sepsis. This review is intended to provide a new perspective concerning ARDS and offer novel insight into future therapeutic interventions.

Knowledge, attitudes and practices of intensive care unit physicians towards the management of acute respiratory distress syndrome in China: a cross-sectional survey

OBJECTIVES

This study aimed to assess the knowledge, attitudes and practices (KAP) of intensive care unit (ICU) physicians in China towards acute respiratory distress syndrome (ARDS).

DESIGN

A cross-sectional study was conducted between September and November 2022.

PARTICIPANTS

A total of 497 ICU physicians participated, with 258 (51.91%) being male and the majority aged 30-40 years (56.74%).

INTERVENTIONS

Participants were surveyed to evaluate their KAP regarding ARDS, with mediation analysis employed to elucidate the association between demographic characteristics and KAP scores.

PRIMARY AND SECONDARY OUTCOME MEASURES

The mean scores for KAP were 11.89±2.64 (range: 0-17), 44.73±4.85 (range: 12-60) and 18.26±3.43 (range: 1-48), respectively. Pearson correlation analysis showed positive correlations between knowledge and attitude (0.367), knowledge and practice (0.582) and attitude and practice (0.314) (all p<0.001).

RESULTS

Mediation analysis indicated that attitude (β=0.07, p<0.001) and hospital type (β=-0.84, p=0.005) had direct effects on practice, while knowledge had significant direct (β=0.68, p<0.001) and indirect (β=0.03, p=0.019) effects. Additionally, education (β=0.47, p<0.001), work experience (β=0.25, p<0.001), hospital classification (β=-0.91, p<0.001), ICU type (β=-0.61, p=0.001) and ARDS experience (β=-1.57, p<0.001) showed various indirect effects on practice.

CONCLUSIONS

ICU physicians in China exhibited inadequate knowledge, moderate attitudes and suboptimal practices regarding ARDS management. Enhancing education and work experience is crucial, along with practical, scenario-based training, to improve KAP in ARDS management.

Effects of different ventilatory settings on alveolar and pulmonary microvessel dimensions in pigs

Mechanical ventilation with high tidal volume (TV) or positive end-expiratory pressure (PEEP) may induce lung overinflation and increased pulmonary vascular resistance to flow. In 8 healthy mechanically ventilated pigs, we evaluated whether incident dark field (IDF) vital microscopy, applied through a small thoracotomy, could be used to evaluate changes in alveolar and pulmonary microvessel dimensions under different ventilator settings. High TV (12 ml/kg) increased alveolar diameters (from 99 ± 13 to 114 ± 6 μm, p < 0.05 repeated measures one way analysis of variance) and reduced septal capillary diameters (from 12.1 ± 1.7 to 10.5 ± 1.4 μm, p < 0.001) as compared to 8 ml/kg TV. This effect was more pronounced in non-dependent lung. Alveolar and microvessel diameters did not change with high PEEP (12 cmH2O Vs. 5 cmH2O). High FiO2 (100%) led to pulmonary vasodilation (from 12.1 ± 1.7 to 14.7 ± 1.4 μm, p < 0.001), with no change in alveolar dimensions as compared to 50% FiO2. In conclusion, IDF imaging enabled to obtain high-quality images of subpleural alveoli and microvessels. High TV ventilation may induce alveolar distension with compression of septal capillaries, thus potentially increasing dead space ventilation.

ECMO in the Management of Noncardiogenic Pulmonary Edema with Increased Inflammatory Reaction After Cardiac Surgery: A Case Report and Literature Review

Noncardiogenic pulmonary edema after cardiac surgery is a rare but severe complication. The etiology remains poorly understood; however, the issue may arise from multiple sources. Possible causes include a significant inflammatory response or an autoimmune process. Pulmonary edema resulting from noncardiac etiologies can necessitate extracorporeal membrane oxygenation (ECMO) because most of the cases present a substantial volume of fluid expelled from the lungs and the medical team must manage the inability to achieve effective ventilation. A 64-year-old patient with known heart disease was admitted to our clinic with acute pulmonary edema. His medical history included Barlow's disease, severe mitral regurgitation (IIP2), moderate-severe tricuspid regurgitation, and moderate pulmonary hypertension. The patient had a coronary angiography performed in a prior hospitalization before the surgical intervention which indicated the absence of coronary lesions. Preoperative screening (nasal, pharyngeal exudate, inguinal pouch culture, and urine culture) was negative, with no active dental infections. The patient was stabilized, and 14 days post-admission, mitral and tricuspid valve repair was performed via a thoracoscopic approach. After being admitted to intensive care post-surgery, the patient quickly developed pulmonary edema, producing a large volume (4.5 L) of yellow secretions through the intubation tube followed by hemodynamic instability necessitating high doses of medications to support circulation but no cardiorespiratory arrest. Due to his worsening condition, the patient was urgently taken back to the operating room, where veno-venous extracorporeal membrane oxygenation (VV-ECMO) was initiated to support oxygenation and stabilize the patient.

High-frequency percussive ventilation in acute respiratory failure

Introduction

High-frequency percussive ventilation (HFPV) is a ventilation mode characterised by high-frequency breaths. This study investigated the impact of HFPV on gas exchange and clinical outcomes in acute respiratory failure (ARF) patients during spontaneous breathing, noninvasive ventilation (NIV) and invasive mechanical ventilation (iMV).

Methods

This systematic review included randomised and nonrandomised studies up to August 2023. Inclusion criteria focused on adult ARF patients, HFPV application, comparisons with other ventilation modes, and outcomes related to oxygenation and clinical parameters. A pooled data analysis was performed comparing HFPV with iMV concerning gas exchange, pulmonary infection and mortality.

Results

Of the 51 identified records, 29 met the inclusion criteria. HFPV was safely and effectively applied to ARF patients during spontaneous breathing or NIV, improving oxygenation. For patients who underwent iMV, HFPV significantly enhanced oxygenation and the arterial partial pressure of carbon dioxide, reduced pulmonary infection occurrence and improved survival. Barotrauma rates were not elevated with HFPV, and haemodynamic stability remained unaffected. HFPV was also utilised in patients undergoing extracorporeal membrane oxygenation, resulting in improved lung recruitment and oxygenation.

Conclusion

HFPV had favourable effects on physiological and certain clinical outcomes in ARF patients. However, the overall evidence quality remains weak, necessitating large-scale randomised controlled trials for definitive conclusions.

Human placental mesenchymal stem cells transplantation repairs the alveolar epithelial barrier to alleviate lipopolysaccharides-induced acute lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are accompanied by high mortality rates and few effective treatments. Transplantation of human placental mesenchymal stem cells (hPMSCs) may attenuate ALI and the mechanism is still unclear. Our study aimed to elucidate the potential protective effect and therapeutic mechanism of hPMSCs against lipopolysaccharide (LPS)-induced ALI, An ALI model was induced by tracheal instillation of LPS into wild-type (WT) and angiotensin-converting enzyme 2 (ACE2) knockout (KO) male mice, followed by injection of hPMSCs by tail vein. Treatment with hPMSCs improved pulmonary histopathological injury, reduced pulmonary injury scores, decreased leukocyte count and protein levels in bronchoalveolar lavage fluid(BALF), protected the damaged alveolar epithelial barrier, and reversed LPS-induced upregulation of pro-inflammatory factors Interleukin-6 (IL-6) and Tumor necrosis factor-α(TNF-α) and downregulation of anti-inflammatory factor Interleukin-6(IL-10) in BALF. Moreover, administration of hPMSCs inhibited Angiotensin (Ang)II activation and promoted the expression levels of ACE2 and Ang (1-7) in ALI mice. Pathological damage, inflammation levels, and disruption of alveolar epithelial barrier in ALI mice were elevated after the deletion of ACE2 gene, and the Renin angiotensin system (RAS) imbalance was exacerbated. The therapeutic effect of hPMSCs was significantly reduced in ACE2 KO mice. Our findings suggest that ACE2 plays a key role in hPMSCs repairing the alveolar epithelial barrier to protect against ALI, laying a new foundation for the clinical treatment of ALI.

Management of severe acute respiratory distress syndrome in Australia and New Zealand (SAGE-ANZ): An observational study

Objective

Acute respiratory distress syndrome (ARDS) is associated with significant mortality, morbidity, and cost. We aimed to describe characteristics and management of adult patients admitted to intensive care units (ICUs) in Australia and New Zealand with moderate-severe ARDS, to better understand contemporary practice.

Design

Bi-national, prospective, observational, multi-centre study.

Setting

19 ICUs in Australia and New Zealand.

Participants

Mechanically ventilated patients with moderate-severe ARDS.

Main outcome measures

Baseline demographic characteristics, ventilation characteristics, use of adjunctive support therapy and all-cause mortality to day 28. Data were summarised using descriptive statistics.

Results

200 participants were enrolled, mean (±SD) age 55.5 (±15.9) years, 40% (n = 80) female. Around half (51.5%) had no baseline comorbidities and 45 (31%) tested positive for COVID-19. On day 1, mean SOFA score was 9 ± 3; median (IQR) PaO2/FiO2 ratio 119 (89, 142), median (IQR) FiO2 70% (50%, 99%) and mean (±SD) positive end expiratory pressure (PEEP) 11 (±3) cmH2O. On day one, 10.5% (n = 21) received lung protective ventilation (LPV) (tidal volume ≤6.5 mL/kg predicted body weight and plateau pressure or peak pressure ≤30 cm H2O). Adjunctive therapies were received by 86% (n = 172) of patients at some stage from enrolment to day 28. Systemic steroids were most used (n = 127) followed by neuromuscular blockers (n = 122) and prone positioning (n = 27). Median ventilator-free days (IQR) to day 28 was 5 (0, 20). In-hospital mortality, censored at day 28, was 30.5% (n = 61).

Conclusions

In Australia and New Zealand, compliance with evidence-based practices including LPV and prone positioning was low in this cohort. Therapies with proven benefit in the treatment of patients with moderate-severe ARDS, such as lung protective ventilation and prone positioning, were not routinely employed.

Extracorporeal Membrane Oxygenation for Respiratory Failure: A Narrative Review

Extracorporeal membrane oxygenation support for respiratory failure in the intensive care unit continues to have an expanded role in select patients. While acute respiratory distress syndrome remains the most common indication, extracorporeal membrane oxygenation may be used in other causes of refractory hypoxemia and/or hypercapnia. The most common configuration is veno-venous extracorporeal membrane oxygenation; however, in specific cases of refractory hypoxemia or right ventricular failure, some patients may benefit from veno-pulmonary extracorporeal membrane oxygenation or veno-venoarterial extracorporeal membrane oxygenation. Patient selection and extracorporeal circuit management are essential to successful outcomes. This narrative review explores the physiology of extracorporeal membrane oxygenation, indications and contraindications, ventilator management, extracorporeal circuit management, troubleshooting hypoxemia, complications, and extracorporeal membrane oxygenation weaning in patients with respiratory failure. As the footprint of extracorporeal membrane oxygenation continues to expand, it is essential that clinicians understand the underlying physiology and management of these complex patients.

A deep dive into burn-mediated ARDS severity assessment: a retrospective study on hematological markers

Acute Respiratory Distress Syndrome (ARDS) is a critical form of Acute Lung Injury (ALI), challenging clinical diagnosis and severity assessment. This study evaluates the potential utility of various hematological markers in burn-mediated ARDS, including Neutrophil-to-Lymphocyte Ratio (NLR), Mean Platelet Volume (MPV), MPV-to-Lymphocyte Ratio (MPVLR), Platelet count, and Platelet Distribution Width (PDW). Employing a retrospective analysis of data collected over 12 years, this study focuses on the relationship between these hematological markers and ARDS diagnosis and severity in hospitalized patients. The study establishes NLR as a reliable systemic inflammation marker associated with ARDS severity. Elevated MPV and MPVLR also emerged as significant markers correlating with adverse outcomes. These findings suggest these economical, routinely measured markers can enhance traditional clinical criteria, offering a more objective approach to ARDS diagnosis and severity assessment. Hematological markers such as NLR, MPV, MPVLR, Platelet count, and PDW could be invaluable in clinical settings for diagnosing and assessing ARDS severity. They offer a cost-effective, accessible means to improve diagnostic accuracy and patient stratification in ARDS. However, further prospective studies are necessary to confirm these findings and investigate their integration with other diagnostic tools in diverse clinical settings.

Polyphenols as Therapeutics in Respiratory Diseases: Moving from Preclinical Evidence to Potential Clinical Applications

Respiratory diseases are the most common and severe health complication and a leading cause of death worldwide. Despite breakthroughs in diagnosis and treatment, few safe and effective therapeutics have been reported. Phytochemicals are gaining popularity due to their beneficial effects and low toxicity. Polyphenols are secondary metabolites with high molecular weights found at high levels in natural food sources such as fruits, vegetables, grains, and citrus seeds. Over recent decades, polyphenols and their beneficial effects on human health have been the subject of intense research, with notable successes in preventing major chronic non-communicable diseases. Many respiratory syndromes can be treated effectively with polyphenolic supplements, including acute lung damage, pulmonary fibrosis, asthma, pulmonary hypertension, and lung cancer. This review summarizes the role of polyphenols in respiratory conditions with sufficient experimental data, highlights polyphenols with beneficial effects for each, and identifies those with therapeutic potential and their underlying mechanisms. Moreover, clinical studies and future research opportunities in this area are discussed.

Advanced Respiratory Monitoring during Extracorporeal Membrane Oxygenation

Advanced respiratory monitoring encompasses a diverse range of mini- or noninvasive tools used to evaluate various aspects of respiratory function in patients experiencing acute respiratory failure, including those requiring extracorporeal membrane oxygenation (ECMO) support. Among these techniques, key modalities include esophageal pressure measurement (including derived pressures), lung and respiratory muscle ultrasounds, electrical impedance tomography, the monitoring of diaphragm electrical activity, and assessment of flow index. These tools play a critical role in assessing essential parameters such as lung recruitment and overdistention, lung aeration and morphology, ventilation/perfusion distribution, inspiratory effort, respiratory drive, respiratory muscle contraction, and patient-ventilator synchrony. In contrast to conventional methods, advanced respiratory monitoring offers a deeper understanding of pathological changes in lung aeration caused by underlying diseases. Moreover, it allows for meticulous tracking of responses to therapeutic interventions, aiding in the development of personalized respiratory support strategies aimed at preserving lung function and respiratory muscle integrity. The integration of advanced respiratory monitoring represents a significant advancement in the clinical management of acute respiratory failure. It serves as a cornerstone in scenarios where treatment strategies rely on tailored approaches, empowering clinicians to make informed decisions about intervention selection and adjustment. By enabling real-time assessment and modification of respiratory support, advanced monitoring not only optimizes care for patients with acute respiratory distress syndrome but also contributes to improved outcomes and enhanced patient safety.

Research trends and hotspots in the field of electrical impedance tomography for mechanical ventilation: a bibliometric analysis

Background

Electrical impedance tomography (EIT) is a relatively recent functional imaging technique that is both noninvasive and radiation free. EIT measures the associated voltage when a weak current is applied to the surface of the human body to determine the distribution of electrical resistance within tissues. We performed a bibliometrics-based review to explore the geographic hotspots of current research and future trends developing in the field of EIT for mechanical ventilation.

Methods

The Web of Science database was searched from its inception to June 25, 2023. CiteSpace software was used to visualize and analyze the relevant literature and identify the most impactful literature, trends, and hotspots.

Results

363 articles describing EIT use in mechanical ventilation were identified. A fluctuating growth in the number of publications was observed from 1998 to 2023. Germany had the highest number of articles (n=154), followed by Italy (n=53) and China (n=52). A cluster analysis of keyword co-occurrence revealed that "titration", "ventilator-related lung injury", and "oxygenation" were the most actively researched terms associated with the use of EIT in mechanically ventilated patients.

Conclusions

Significant progress has been made in EIT research for mechanical ventilation. EIT research is limited to a small number of countries with a present research focus on the prevention and treatment of ventilator-related lung injury, oxygenation status, and prone ventilation. These topics are expected to remain research hotspots in the future.

Lung ultrasound score and in-hospital mortality of adults with acute respiratory distress syndrome: a meta-analysis

BACKGROUND

Lung ultrasound (LUS) score could quantitatively reflect the lung aeration, which has been well applied in critically ill patients. The aim of the systematic review and meta-analysis was to evaluate the association between LUS score at admission and the risk of in-hospital mortality of adults with acute respiratory distress syndrome (ARDS).

METHODS

Toachieve the objective of this meta-analysis, we conducted a thorough search of PubMed, Embase, Cochrane Library, and the Web of Science to identify relevant observational studies with longitudinal follow-up. We employed random-effects models to combine the outcomes, considering the potential influence of heterogeneity.

RESULTS

Thirteen cohort studies with 1,022 hospitalized patients with ARDS were included. Among them, 343 patients (33.6%) died during hospitalization. The pooled results suggested that the LUS score at admission was higher in non-survivors as compared to survivors (standardized mean difference = 0.73, 95% confidence interval [CI]: 0.55 to 0.91, p < 0.001; I2 = 25%). Moreover, a high LUS score at admission was associated with a higher risk of in-hospital mortality of patients with ARDS (risk ratio: 1.44, 95% CI: 1.14 to 1.81, p = 0.002; I2 = 46%). Subgroup analyses showed consistent results in studies with LUS score analyzed with 12 or 16 lung regions, and in studies reporting mortality during ICU or within 1-month hospitalization.

CONCLUSION

Our findings suggest that a high LUS score at admission may be associated with a high risk of in-hospital mortality of patients with ARDS.

Metabolic and Other Endocrine Elements with Regard to Lifestyle Choices: Focus on E-Cigarettes

Our objective was to overview recent data on metabolic/endocrine disorders with respect to e-cigarette (e-cig) use. This is a narrative review; we researched English, full-length, original articles on PubMed (between January 2020 and August 2023) by using different keywords in the area of metabolic/endocrine issues. We only included original clinical studies (n = 22) and excluded case reports and experimental studies. 3 studies (N1 = 22,385; N2 = 600,046; N3 = 5101) addressed prediabetes risk; N1 showed a 1.57-fold increased risk of dual vs. never smokers, a higher risk that was not confirmed in N2 (based on self-reported assessments). Current non-smokers (N1) who were dual smokers still have an increased odd of prediabetes (a 1.27-fold risk increase). N3 and another 2 studies addressed type 2 diabetes mellitus (DM): a lower prevalence of DM among dual users (3.3%) vs. cigarette smoking (5.9%) was identified. 6 studies investigated obesity profile (4 of them found positive correlations with e-cig use). One study (N4 = 373,781) showed that e-cig use was associated with obesity in the general population (OR = 1.6, 95%CI: 1.3-2.1, p < 0.05); another (N5 = 7505, 0.82% were e-cig-only) showed that obesity had a higher prevalence in dual smokers (51%) vs. cig-only (41.2%, p < 0.05), while another (N6 = 3055) found that female (not male) e-cig smokers had higher body mass index vs. non-smokers. Data on metabolic syndrome (MS) are provided for dual smokers (n = 2): one case-control study found that female dual smokers had higher odds of MS than non-smokers. The need for awareness with respect to potential e-cig--associated medical issues should be part of modern medicine, including daily anamnesis. Whether the metabolic/endocrine frame is part of the general picture is yet to be determined. Surveillance protocols should help clinicians to easily access the medical background of one subject, including this specific matter of e-cig with/without conventional cigarettes smoking and other habits/lifestyle elements, especially when taking into consideration metabolism anomalies.

Prognostic value of oxygen saturation index trajectory phenotypes on ICU mortality in mechanically ventilated patients: a multi-database retrospective cohort study

BACKGROUND

Heterogeneity among critically ill patients undergoing invasive mechanical ventilation (IMV) treatment could result in high mortality rates. Currently, there are no well-established indicators to help identify patients with a poor prognosis in advance, which limits physicians' ability to provide personalized treatment. This study aimed to investigate the association of oxygen saturation index (OSI) trajectory phenotypes with intensive care unit (ICU) mortality and ventilation-free days (VFDs) from a dynamic and longitudinal perspective.

METHODS

A group-based trajectory model was used to identify the OSI-trajectory phenotypes. Associations between the OSI-trajectory phenotypes and ICU mortality were analyzed using doubly robust analyses. Then, a predictive model was constructed to distinguish patients with poor prognosis phenotypes.

RESULTS

Four OSI-trajectory phenotypes were identified in 3378 patients: low-level stable, ascending, descending, and high-level stable. Patients with the high-level stable phenotype had the highest mortality and fewest VFDs. The doubly robust estimation, after adjusting for unbalanced covariates in a model using the XGBoost method for generating propensity scores, revealed that both high-level stable and ascending phenotypes were associated with higher mortality rates (odds ratio [OR]: 1.422, 95% confidence interval [CI] 1.246-1.623; OR: 1.097, 95% CI 1.027-1.172, respectively), while the descending phenotype showed similar ICU mortality rates to the low-level stable phenotype (odds ratio [OR] 0.986, 95% confidence interval [CI] 0.940-1.035). The predictive model could help identify patients with ascending or high-level stable phenotypes at an early stage (area under the curve [AUC] in the training dataset: 0.851 [0.827-0.875]; AUC in the validation dataset: 0.743 [0.709-0.777]).

CONCLUSIONS

Dynamic OSI-trajectory phenotypes were closely related to the mortality of ICU patients requiring IMV treatment and might be a useful prognostic indicator in critically ill patients.