GMP-compliant extracellular vesicles derived from umbilical cord mesenchymal stromal cells: manufacturing and pre-clinical evaluation in ARDS treatment.

BACKGROUND AIMS: Extracellular vesicles (EVs) represent a new axis of intercellular communication that can be harnessed for therapeutic purposes, as cell-free therapies. The clinical application of mesenchymal stromal cell (MSC)-derived EVs, however, is still in its infancy and faces many challenges. The heterogeneity inherent to MSCs, differences among donors, tissue sources, and variations in manufacturing conditions may influence the release of EVs and their cargo, thus potentially affecting the quality and consistency of the final product. We investigated the influence of cell culture and conditioned medium harvesting conditions on the physicochemical and proteomic profile of human umbilical cord MSC-derived EVs (hUCMSC-EVs) produced under current good manufacturing practice (cGMP) standards. We also evaluated the efficiency of the protocol in terms of yield, purity, productivity, and expression of surface markers, and assessed the biodistribution, toxicity and potential efficacy of hUCMSC-EVs in pre-clinical studies using the LPS-induced acute lung injury model. METHODS: hUCMSCs were isolated from a cord tissue, cultured, cryopreserved, and characterized at a cGMP facility. The conditioned medium was harvested at 24, 48, and 72 h after the addition of EV collection medium. Three conventional methods (nanoparticle tracking analysis, transmission electron microscopy, and nanoflow cytometry) and mass spectrometry were used to characterize hUCMSC-EVs. Safety (toxicity of single and repeated doses) and biodistribution were evaluated in naive mice after intravenous administration of the product. Efficacy was evaluated in an LPS-induced acute lung injury model. RESULTS: hUCMSC-EVs were successfully isolated using a cGMP-compliant protocol. Comparison of hUCMSC-EVs purified from multiple harvests revealed progressive EV productivity and slight changes in the proteomic profile, presenting higher homogeneity at later timepoints of conditioned medium harvesting. Pooled hUCMSC-EVs showed a non-toxic profile after single and repeated intravenous administration to naive mice. Biodistribution studies demonstrated a major concentration in liver, spleen and lungs. HUCMSC-EVs reduced lung damage and inflammation in a model of LPS-induced acute lung injury. CONCLUSIONS: hUCMSC-EVs were successfully obtained following a cGMP-compliant protocol, with consistent characteristics and pre-clinical safety profile, supporting their future clinical development as cell-free therapies.

Comparison between high-flow nasal oxygen (HFNO) alternated with non-invasive ventilation (NIV) and HFNO and NIV alone in patients with COVID-19: a retrospective cohort study.

BACKGROUND: Non-invasive respiratory support (conventional oxygen therapy [COT], non-invasive ventilation [NIV], high-flow nasal oxygen [HFNO], and NIV alternated with HFNO [NIV + HFNO] may reduce the need for invasive mechanical ventilation (IMV) in patients with COVID-19. The outcome of patients treated non-invasively depends on clinical severity at admission. We assessed the need for IMV according to NIV, HFNO, and NIV + HFNO in patients with COVID-19 according to disease severity and evaluated in-hospital survival rates and hospital and intensive care unit (ICU) lengths of stay. METHODS: This cohort study was conducted using data collected between March 2020 and July 2021. Patients ≥ 18 years admitted to the ICU with a diagnosis of COVID-19 were included. Patients hospitalized for < 3 days, receiving therapy (COT, NIV, HFNO, or NIV + HFNO) for < 48 h, pregnant, and with no primary outcome data were excluded. The COT group was used as reference for multivariate Cox regression model adjustment. RESULTS: Of 1371 patients screened, 958 were eligible: 692 (72.2%) on COT, 92 (9.6%) on NIV, 31 (3.2%) on HFNO, and 143 (14.9%) on NIV + HFNO. The results for the patients in each group were as follows: median age (interquartile range): NIV (64 [49-79] years), HFNO (62 [55-70] years), NIV + HFNO (62 [48-72] years) (p = 0.615); heart failure: NIV (54.5%), HFNO (36.3%), NIV + HFNO (9%) (p = 0.003); diabetes mellitus: HFNO (17.6%), NIV + HFNO (44.7%) (p = 0.048). > 50% lung damage on chest computed tomography (CT): NIV (13.3%), HFNO (15%), NIV + HFNO (71.6%) (p = 0.038); SpO2/FiO2: NIV (271 [118-365] mmHg), HFNO (317 [254-420] mmHg), NIV + HFNO (229 [102-317] mmHg) (p = 0.001); rate of IMV: NIV (26.1%, p = 0.002), HFNO (22.6%, p = 0.023), NIV + HFNO (46.8%); survival rate: HFNO (83.9%), NIV + HFNO (63.6%) (p = 0.027); ICU length of stay: NIV (8.5 [5-14] days), NIV + HFNO (15 [10-25] days (p < 0.001); hospital length of stay: NIV (13 [10-21] days), NIV + HFNO (20 [15-30] days) (p < 0.001). After adjusting for comorbidities, chest CT score and SpO2/FiO2, the risk of IMV in patients on NIV + HFNO remained high (hazard ratio, 1.88; 95% confidence interval, 1.17-3.04). CONCLUSIONS: In patients with COVID-19, NIV alternating with HFNO was associated with a higher rate of IMV independent of the presence of comorbidities, chest CT score and SpO2/FiO2. Trial registration ClinicalTrials.gov identifier: NCT05579080.

The Role of Ultrasonography in the Process of Weaning from Mechanical Ventilation in Critically Ill Patients.

Weaning patients from mechanical ventilation (MV) is a complex process that may result in either success or failure. The use of ultrasound at the bedside to assess organs may help to identify the underlying mechanisms that could lead to weaning failure and enable proactive measures to minimize extubation failure. Moreover, ultrasound could be used to accurately identify pulmonary diseases, which may be responsive to respiratory physiotherapy, as well as monitor the effectiveness of physiotherapists' interventions. This article provides a comprehensive review of the role of ultrasonography during the weaning process in critically ill patients.

Understanding the mechanisms of ventilator-induced lung injury using animal models.

Mechanical ventilation is a life-saving therapy in several clinical situations, promoting gas exchange and providing rest to the respiratory muscles. However, mechanical ventilation may cause hemodynamic instability and pulmonary structural damage, which is known as ventilator-induced lung injury (VILI). The four main injury mechanisms associated with VILI are as follows: barotrauma/volutrauma caused by overstretching the lung tissues; atelectrauma, caused by repeated opening and closing of the alveoli resulting in shear stress; and biotrauma, the resulting biological response to tissue damage, which leads to lung and multi-organ failure. This narrative review elucidates the mechanisms underlying the pathogenesis, progression, and resolution of VILI and discusses the strategies that can mitigate VILI. Different static variables (peak, plateau, and driving pressures, positive end-expiratory pressure, and tidal volume) and dynamic variables (respiratory rate, airflow amplitude, and inspiratory time fraction) can contribute to VILI. Moreover, the potential for lung injury depends on tissue vulnerability, mechanical power (energy applied per unit of time), and the duration of that exposure. According to the current evidence based on models of acute respiratory distress syndrome and VILI, the following strategies are proposed to provide lung protection: keep the lungs partially collapsed (SaO2 > 88%), avoid opening and closing of collapsed alveoli, and gently ventilate aerated regions while keeping collapsed and consolidated areas at rest. Additional mechanisms, such as subject-ventilator asynchrony, cumulative power, and intensity, as well as the damaging threshold (stress-strain level at which tidal damage is initiated), are under experimental investigation and may enhance the understanding of VILI.

Therapeutic effects of hypoxia-preconditioned bone marrow-derived mesenchymal stromal cells and their extracellular vesicles in experimental pulmonary arterial hypertension.

AIMS: To evaluate BM-MSCs and their extracellular vesicles (EVs) preconditioned with hypoxia or normoxia in experimental pulmonary arterial hypertension (PAH). MAIN METHODS: BM-MSCs were isolated and cultured under normoxia (MSC-N, 21%O2) or hypoxia (MSC-H, 1%O2) for 48 h. EVs were then isolated from MSCs under normoxia (EV-N) or hypoxia (EV-H). PAH was induced in male Wistar rats (n = 35) with monocrotaline (60 mg/kg); control animals (CTRL, n = 7) were treated with saline. On day 14, PAH animals received MSCs or EVs under normoxia or hypoxia, intravenously (n = 7/group). On day 28, right ventricular systolic pressure (RVSP), pulmonary acceleration time (PAT)/pulmonary ejection time (PET), and right ventricular hypertrophy (RVH) index were evaluated. Perivascular collagen content, vascular wall thickness, and endothelium-mesenchymal transition were analyzed. KEY FINDINGS: PAT/PET was lower in the PAH group (0.26 ± 0.02, P < 0.001) than in CTRLs (0.43 ± 0.02) and only increased in the EV-H group (0.33 ± 0.03, P = 0.014). MSC-N (32 ± 6 mmHg, P = 0.036), MSC-H (31 ± 3 mmHg, P = 0.019), EV-N (27 ± 4 mmHg, P < 0.001), and EV-H (26 ± 5 mmHg, P < 0.001) reduced RVSP compared with the PAH group (39 ± 4 mmHg). RVH was higher in the PAH group than in CTRL and reduced after all therapies. All therapies decreased perivascular collagen fiber content, vascular wall thickness, and the expression of endothelial markers remained unaltered; only MSC-H and EV-H decreased expression of mesenchymal markers in pulmonary arterioles. SIGNIFICANCE: MSCs and EVs, under normoxia or hypoxia, reduced right ventricular hypertrophy, perivascular collagen, and vessel wall thickness. Under hypoxia, MSCs and EVs were more effective at improving endothelial to mesenchymal transition in experimental PAH.

Fluid management strategies and their interaction with mechanical ventilation: from experimental studies to clinical practice.

Patients on mechanical ventilation may receive intravenous fluids via restrictive or liberal fluid management. A clear and objective differentiation between restrictive and liberal fluid management strategies is lacking in the literature. The liberal approach has been described as involving fluid rates ranging from 1.2 to 12 times higher than the restrictive approach. A restrictive fluid management may lead to hypoperfusion and distal organ damage, and a liberal fluid strategy may result in endothelial shear stress and glycocalyx damage, cardiovascular complications, lung edema, and distal organ dysfunction. The association between fluid and mechanical ventilation strategies and how they interact toward ventilator-induced lung injury (VILI) could potentiate the damage. For instance, the combination of a liberal fluids and pressure-support ventilation, but not pressure control ventilation, may lead to further lung damage in experimental models of acute lung injury. Moreover, under liberal fluid management, the application of high positive end-expiratory pressure (PEEP) or an abrupt decrease in PEEP yielded higher endothelial cell damage in the lungs. Nevertheless, the translational aspects of these findings are scarce. The aim of this narrative review is to provide better understanding of the interaction between different fluid and ventilation strategies and how these interactions may affect lung and distal organs. The weaning phase of mechanical ventilation and the deresuscitation phase are not explored in this review.

Serum from patients with asthma potentiates macrophage phagocytosis and human mesenchymal stromal cell therapy in experimental allergic asthma.

BACKGROUND/AIMS: Although several studies have demonstrated that mesenchymal stromal cells (MSCs) exhibit beneficial immunomodulatory properties in preclinical models of allergic asthma, effects on airway remodeling have been controversial. Recent evidence has shown that MSCs modify their in vivo immunomodulatory actions depending on the specific inflammatory environment encountered. Accordingly, we assessed whether the therapeutic properties of human mesenchymal stromal cells (hMSCs) could be potentiated by conditioning these cells with serum (hMSC-serum) obtained from patients with asthma and then transplanted in an experimental model of house dust mite (HDM)-induced allergic asthma. METHODS: hMSC and hMSC-serum were administered intratracheally 24 h after the final HDM challenge. hMSC viability and inflammatory mediator production, lung mechanics and histology, bronchoalveolar lavage fluid (BALF) cellularity and biomarker levels, mitochondrial structure and function as well as macrophage polarization and phagocytic capacity were assessed. RESULTS: Serum preconditioning led to: (i) increased hMSC apoptosis and expression of transforming growth factor-ß, interleukin (IL)-10, tumor necrosis factor-α-stimulated gene 6 protein and indoleamine 2,3-dioxygenase-1; (ii) fission and reduction of the intrinsic respiratory capacity of mitochondria; and (iii) polarization of macrophages to M2 phenotype, which may be associated with a greater percentage of hMSCs phagocytosed by macrophages. Compared with mice receiving hMSCs, administration of hMSC-serum led to further reduction of collagen fiber content, eotaxin levels, total and differential cellularity and increased IL-10 levels in BALF, improving lung mechanics. hMSC-serum promoted greater M2 macrophage polarization as well as macrophage phagocytosis, mainly of apoptotic hMSCs. CONCLUSIONS: Serum from patients with asthma led to a greater percentage of hMSCs phagocytosed by macrophages and triggered immunomodulatory responses, resulting in further reductions in both inflammation and remodeling compared with non-preconditioned hMSCs.

Mesenchymal stromal cell therapy for chronic lung diseases: experimental and clinical evidence.

INTRODUCTION: Cell therapy has emerged as an alternative option for chronic lung diseases with the highest rates of morbidity and mortality rates worldwide. AREAS COVERED: This review addresses the definition of mesenchymal stromal cells (MSCs), their properties, mechanisms of action, as well as preclinical and clinical studies that have used cell therapy in chronic lung diseases such as asthma, chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, pulmonary arterial hypertension, and silicosis. Ongoing clinical trials are also presented. EXPERT OPINION: Experimental evidence has shown that MSCs have immunomodulatory and regenerative properties that could rescue impaired lung function and histoarchitecture. Their beneficial effects have been mainly associated with their ability to communicate with target cells through the secretion of soluble mediators and extracellular vesicles or even through transfer of organelles (e.g. mitochondria). MSC-derived conditioned medium, extracellular vesicles and mitochondria induce beneficial effects in selected scenarios. The initial results in clinical trials were modest compared with the experimental results, therefore researchers were encouraged to move from bedside back to bench to develop new strategies able to potentiate the effects of MSCs.

Development of nintedanib nanosuspension for inhaled treatment of experimental silicosis.

Silicosis is an irreversible and progressive fibrotic lung disease caused by massive inhalation of crystalline silica dust at workplaces, affecting millions of industrial workers worldwide. A tyrosine kinase inhibitor, nintedanib (NTB), has emerged as a potential silicosis treatment due to its inhibitory effects on key signaling pathways that promote silica-induced pulmonary fibrosis. However, chronic and frequent use of the oral NTB formulation clinically approved for treating other fibrotic lung diseases often results in significant side effects. To this end, we engineered a nanocrystal-based suspension formulation of NTB (NTB-NS) possessing specific physicochemical properties to enhance drug retention in the lung for localized treatment of silicosis via inhalation. Our NTB-NS formulation was prepared using a wet-milling procedure in presence of Pluronic F127 to endow the formulation with nonadhesive surface coatings to minimize interactions with therapy-inactivating delivery barriers in the lung. We found that NTB-NS, following intratracheal administration, provided robust anti-fibrotic effects and mechanical lung function recovery in a mouse model of silicosis, whereas a 100-fold greater oral NTB dose given with a triple dosing frequency failed to do so. Importantly, several key pathological phenotypes were fully normalized by NTB-NS without displaying notable local or systemic adverse effects. Overall, NTB-NS may open a new avenue for localized treatment of silicosis and potentially other fibrotic lung diseases.

A Prototype Implantable Artificial Bronchus Reduces Lung Hyperinflation in Recently Deceased Patients with Emphysema.

BACKGROUND: Several minimally invasive treatments have been offered to patients with severe emphysema over the last two decades. Currently, endobronchial valves (EBVs) are the only approved therapeutic option, but this method has drawbacks: only a few can undergo this therapy and the incidence of pneumothorax remains high. A minimally invasive technique, appropriate for a broader patient population and posing fewer risks, would represent a desirable alternative to improve lung function in these patients. OBJECTIVE: The objective of this study was to demonstrate whether a new prototype implantable artificial bronchus (IAB) releases trapped air from the lungs of recently deceased patients with emphysema. METHOD: Seven recently deceased patients with emphysema were mechanically ventilated and the respiratory rate increased from 12 bpm (resting) to 30 bpm (exercise), inducing air trapping and dynamic hyperinflation. This protocol was performed twice, before and after IAB placement. Ventilation parameters and the fraction of inspired oxygen were similar in all patients. Respiratory system plateau pressure (Pplat,rs) and intrinsic positive end-expiratory pressure (iPEEP) were measured. RESULTS: IAB implantation significantly reduced Pplat,rs (p = 0.017) in 6 of 7 deceased patients with emphysema and iPEEP (p = 0.03) in 5 of 7 patients. CONCLUSIONS: Placement of one or two IABs in segmental bronchi (up to 15th generation) proved to be feasible and improved lung function. These findings should provide a basis for subsequent clinical studies to assess the safety and efficacy of IAB in patients with emphysema, as well as identify short- and long-term effects of this innovative procedure.

Lung Injury Is Induced by Abrupt Increase in Respiratory Rate but Prevented by Recruitment Maneuver in Mild Acute Respiratory Distress Syndrome in Rats.

BACKGROUND: Gradually changing respiratory rate (RR) during time to reduce ventilation-induced lung injury has not been investigated. The authors hypothesized that gradual, compared with abrupt, increments in RR would mitigate ventilation-induced lung injury and that recruitment maneuver before abruptly increasing RR may prevent injurious biologic impact. METHODS: Twenty-four hours after intratracheal administration of Escherichia coli lipopolysaccharide, 49 male Wistar rats were anesthetized and mechanically ventilated (tidal volume, 6 ml/kg; positive end-expiratory pressure, 3 cm H2O) with RR increase patterns as follows (n = 7 per group): (1) control 1, RR = 70 breaths/min for 2 h; (2) and (3) abrupt increases of RR for 1 and 2 h, respectively, both for 2 h; (4) shorter RR adaptation, gradually increasing RR (from 70 to 130 breaths/min during 30 min); (5) longer RR adaptation, more gradual increase in RR (from 70 to 130 breaths/min during 60 min), both for 2 h; (6) control 2, abrupt increase of RR maintained for 1 h; and (7) control 3, recruitment maneuver (continuous positive airway pressure, 30 cm H2O for 30 s) followed by control-2 protocol. RESULTS: At the end of 1 h of mechanical ventilation, cumulative diffuse alveolar damage scores were lower in shorter (11.0 [8.0 to 12.0]) and longer (13.0 [11.0 to 14.0]) RR adaptation groups than in animals with abrupt increase of RR for 1 h (25.0 [22.0 to 26.0], P = 0.035 and P = 0.048, respectively) and 2 h (35.0 [32.0 to 39.0], P = 0.003 and P = 0.040, respectively); mechanical power and lung heterogeneity were lower, and alveolar integrity was higher, in the longer RR adaptation group compared with abruptly adjusted groups; markers of lung inflammation (interleukin-6), epithelial (club cell secretory protein [CC-16]) and endothelial cell damage (vascular cell adhesion molecule 1 [VCAM-1]) were higher in both abrupt groups, but not in either RR adaptation group, compared with controls. Recruitment maneuver prevented the increase in VCAM-1 and CC-16 gene expressions in the abruptly increased RR groups. CONCLUSIONS: In mild experimental acute respiratory distress syndrome in rats, gradually increasing RR, compared with abruptly doing so, can mitigate the development of ventilation-induced lung injury. In addition, recruitment maneuver prevented the injurious biologic impact of abrupt increases in RR.

Morphological and functional findings in COVID-19 lung disease as compared to Pneumonia, ARDS, and High-Altitude Pulmonary Edema.

Coronavirus disease-2019 (COVID-19) may severely affect respiratory function and evolve to life-threatening hypoxia. The clinical experience led to the implementation of standardized protocols assuming similarity to severe acute respiratory syndrome (SARS-CoV-2). Understanding the histopathological and functional patterns is essential to better understand the pathophysiology of COVID-19 and then develop new therapeutic strategies. Epithelial and endothelial cell damage can result from the virus attack, thus leading to immune-mediated response. Pulmonary histopathological findings show the presence of Mallory bodies, alveolar coating cells with nuclear atypia, reactive pneumocytes, reparative fibrosis, intra-alveolar hemorrhage, moderate inflammatory infiltrates, micro-abscesses, microthrombus, hyaline membrane fragments, and emphysema-like lung areas. COVID-19 patients may present different respiratory stages from silent to critical hypoxemia, are associated with the degree of pulmonary parenchymal involvement, thus yielding alteration of ventilation and perfusion relationships. This review aims to: discuss the morphological (histopathological and radiological) and functional findings of COVID-19 compared to acute interstitial pneumonia, acute respiratory distress syndrome (ARDS), and high-altitude pulmonary edema (HAPE), four entities that share common clinical traits, but have peculiar pathophysiological features with potential implications to their clinical management.

Mild hypothermia combined with dexmedetomidine reduced brain, lung, and kidney damage in experimental acute focal ischemic stroke.

BACKGROUND: Sedatives and mild hypothermia alone may yield neuroprotective effects in acute ischemic stroke (AIS). However, the impact of this combination is still under investigation. We compared the effects of the combination of mild hypothermia or normothermia with propofol or dexmedetomidine on brain, lung, and kidney in experimental AIS. AIS-induced Wistar rats (n = 30) were randomly assigned, after 24 h, to normothermia or mild hypothermia (32-35 °C) with propofol or dexmedetomidine. Histologic injury score and molecular biomarkers were evaluated not only in brain, but also in lung and kidney. Hemodynamics, ventilatory parameters, and carotid Doppler ultrasonography were analyzed for 60 min. RESULTS: In brain: (1) hypothermia compared to normothermia, regardless of sedative, decreased tumor necrosis factor (TNF)-α expression and histologic injury score; (2) normothermia + dexmedetomidine reduced TNF-α and histologic injury score compared to normothermia + propofol; (3) hypothermia + dexmedetomidine increased zonula occludens-1 expression compared to normothermia + dexmedetomidine. In lungs: (1) hypothermia + propofol compared to normothermia + propofol reduced TNF-α and histologic injury score; (2) hypothermia + dexmedetomidine compared to normothermia + dexmedetomidine reduced histologic injury score. In kidneys: (1) hypothermia + dexmedetomidine compared to normothermia + dexmedetomidine decreased syndecan expression and histologic injury score; (2) hypothermia + dexmedetomidine compared to hypothermia + propofol decreased histologic injury score. CONCLUSIONS: In experimental AIS, the combination of mild hypothermia with dexmedetomidine reduced brain, lung, and kidney damage.

Proteomics profile of mesenchymal stromal cells and extracellular vesicles in normoxic and hypoxic conditions.

BACKGROUND AIMS: Although bone marrow-derived mesenchymal stromal cells (MSCs) have demonstrated success in pre-clinical studies, they have shown only mild therapeutic effects in clinical trials. Hypoxia pre-conditioning may optimize the performance of bone marrow-derived MSCs because it better reflects the physiological conditions of their origin. It is not known whether changes in the protein profile caused by hypoxia in MSCs can be extended to the extracellular vesicles (EVs) released from them. The aim of this study was to evaluate the proteomics profile of MSCs and their EVs under normoxic and hypoxic conditions. METHODS: Bone marrow-derived MSCs were isolated from six healthy male Wistar rats. After achieving 80% confluence, MSCs were subjected to normoxia (MSC-Norm) (21% oxygen, 5% carbon dioxide, 74% nitrogen) or hypoxia (MSC-Hyp) (1% oxygen, 5% carbon dioxide, 94% nitrogen) for 48 h. Cell viability and oxygen consumption rate were assessed. EVs were extracted from MSCs for each condition (EV-Norm and EV-Hyp) by ultracentrifugation. Total proteins were isolated from MSCs and EVs and prepared for mass spectrometry. EVs were characterized by nanoparticle tracking analysis. Proteomics data were analyzed by PatternLab 4.0, Search Tool for the Retrieval of Interacting Genes/Proteins, Gene Ontology, MetaboAnalyst and Reactome software. RESULTS: Cell viability was higher in MSC-Hyp than MSC-Norm (P = 0.007). Basal respiration (P = 0.001), proton leak (P = 0.004) and maximal respiration (P = 0.014) were lower in MSC-Hyp than MSC-Norm, and no changes in adenosine triphosphate-linked and residual respiration were observed. The authors detected 2177 proteins in MSC-Hyp and MSC-Norm, of which 147 were identified in only MSC-Hyp and 512 were identified in only MSC-Norm. Furthermore, 718 proteins were identified in EV-Hyp and EV-Norm, of which 293 were detected in only EV-Hyp and 30 were detected in only EV-Norm. Both MSC-Hyp and EV-Hyp showed enrichment of pathways and biological processes related to glycolysis, the immune system and extracellular matrix organization. CONCLUSIONS: MSCs subjected to hypoxia showed changes in their survival and metabolic activity. In addition, MSCs under hypoxia released more EVs, and their content was related to expression of regulatory proteins of the immune system and extracellular matrix organization. Because of the upregulation of proteins involved in glycolysis, gluconeogenesis and glucose uptake during hypoxia, production of reactive oxygen species and expression of immunosuppressive properties may be affected.

Effects of different fluid management on lung and kidney during pressure-controlled and pressure-support ventilation in experimental acute lung injury.

Optimal fluid management is critical during mechanical ventilation to mitigate lung damage. Under normovolemia and protective ventilation, pulmonary tensile stress during pressure-support ventilation (PSV) results in comparable lung protection to compressive stress during pressure-controlled ventilation (PCV) in experimental acute lung injury (ALI). It is not yet known whether tensile stress can lead to comparable protection to compressive stress in ALI under a liberal fluid strategy (LF). A conservative fluid strategy (CF) was compared with LF during PSV and PCV on lungs and kidneys in an established model of ALI. Twenty-eight male Wistar rats received endotoxin intratracheally. After 24 h, they were treated with CF (minimum volume of Ringer's lactate to maintain normovolemia and mean arterial pressure ≥70 mmHg) or LF (~4 times higher than CF) combined with PSV or PCV (VT  = 6 ml/kg, PEEP = 3 cmH2 O) for 1 h. Nonventilated animals (n = 4) were used for molecular biology analyses. CF-PSV compared with LF-PSV: (1) decreased the diffuse alveolar damage score (10 [7.8-12] vs. 25 [23-31.5], p = 0.006), mainly due to edema in axial and alveolar parenchyma; (2) increased birefringence for occludin and claudin-4 in lung tissue and expression of zonula-occludens-1 and metalloproteinase-9 in lung. LF compared with CF reduced neutrophil gelatinase-associated lipocalin and interleukin-6 expression in the kidneys in PSV and PCV. In conclusion, CF compared with LF combined with PSV yielded less lung epithelial cell damage in the current model of ALI. However, LF compared with CF resulted in less kidney injury markers, regardless of the ventilatory strategy.

Rationale and limitations of the SpO2/FiO2 as a possible substitute for PaO2/FiO2 in different preclinical and clinical scenarios. / Justificativa e limitações da SpO2/FiO2 como possível substituta da PaO2/FiO2 em diferentes cenários pré-clínicos e clínicos.

Although the PaO 2/FiO 2 derived from arterial blood gas analysis remains the gold standard for the diagnosis of acute respiratory failure, the SpO2/FiO2 has been investigated as a potential substitute. The current narrative review presents the state of the preclinical and clinical literature on the SpO2/FiO2 as a possible substitute for PaO2/FiO2 and for use as a diagnostic and prognostic marker; provides an overview of pulse oximetry and its limitations, and assesses the utility of SpO2/ FiO2 as a surrogate for PaO2/FiO2 in COVID-19 patients. Overall, 49 studies comparing SpO2/FiO2 and PaO2/FiO2 were found according to a minimal search strategy. Most were conducted on neonates, some were conducted on adults with acute respiratory distress syndrome, and a few were conducted in other clinical scenarios (including a very few on COVID-19 patients). There is some evidence that the SpO2/ FiO2 criteria can be a surrogate for PaO2/FiO2 in different clinical scenarios. This is reinforced by the fact that unnecessary invasive procedures should be avoided in patients with acute respiratory failure. It is undeniable that pulse oximeters are becoming increasingly widespread and can provide costless monitoring. Hence, replacing PaO2/FiO2 with SpO2/FiO2may allow resourcelimited facilities to objectively diagnose acute respiratory failure.

Embora a PaO2/FiO2 derivada da gasometria arterial continue sendo o padrão-ouro do diagnóstico de insuficiência respiratória aguda, a SpO2/FiO2 tem sido investigada como potencial substituta. Esta revisão narrativa apresenta o estado da literatura pré-clínica e clínica sobre a SpO2/FiO2 como possível substituta da PaO2/FiO2 e para uso como marcador diagnóstico e prognóstico; ainda, é fornecida uma visão geral da oximetria de pulso e suas limitações, além da avaliação da utilidade da SpO2/ FiO2 como substituta da PaO2/FiO2 em pacientes com COVID-19. Ao todo, foram encontrados 49 estudos comparando SpO2/FiO2 e PaO2/ FiO2 com base em uma estratégia de pesquisa mínima. A maioria dos estudos foi realizada em recémnascidos, alguns foram realizados em adultos com síndrome do desconforto respiratório agudo, e outros foram realizados em outros cenários clínicos (incluindo poucos em pacientes com COVID-19). Há certa evidência de que os critérios de SpO2/FiO2 podem substituir a PaO2/FiO2 em diferentes cenários clínicos. Isso é reforçado pelo fato de que devem ser evitados procedimentos invasivos desnecessários em pacientes com insuficiência respiratória aguda. É inegável que os oxímetros de pulso estão cada vez mais difundidos e podem proporcionar um monitoramento sem custos. Portanto, substituir a PaO2/FiO2 pela SpO2/FiO2 pode permitir que instalações com recursos limitados diagnostiquem a insuficiência respiratória aguda de maneira objetiva.

Clinical features, electroencephalogram, and biomarkers in pediatric sepsis-associated encephalopathy.

To date, no specific diagnostic criteria for sepsis-associated encephalopathy (SAE) have been established. We studied 33 pediatric patients with sepsis prospectively and evaluated the level of consciousness, the presence of delirium, electroencephalographic (EEG) findings, and plasma levels of neuron-specific enolase and S100-calcium-binding protein-B. A presumptive diagnosis of SAE was primarily considered in the presence of a decreased level of consciousness and/or delirium (clinical criteria), but specific EEG abnormalities were also considered (EEG criteria). The time course of the biomarkers was compared between groups with and without clinical or EEG criteria. The Functional Status Scale (FSS) was assessed at admission, discharge, and 3-6 months post-discharge. Clinical criteria were identified in 75.8% of patients, EEG criteria in 26.9%, both in 23.1%, and none in 23.1%. Biomarkers did not differ between groups. Three patients had an abnormal FSS at discharge, but no one on follow-up. A definitive diagnostic pattern for SAE remained unclear. Clinical criteria should be the basis for diagnosis, but sedation may be a significant confounder, also affecting EEG interpretation. The role of biomarkers requires a better definition. The diagnosis of SAE in pediatric patients remains a major challenge. New consensual diagnostic definitions and mainly prognostic studies are needed.

Justificativa e limitações da SpO2/FiO2 como possível substituta da PaO2/FiO2 em diferentes cenários pré-clínicos e clínicos / Rationale and limitations of the SpO2/FiO2 as a possible substitute for PaO2/FiO2 in different preclinical and clinical scenarios

RESUMO Embora a PaO2/FiO2 derivada da gasometria arterial continue sendo o padrão-ouro do diagnóstico de insuficiência respiratória aguda, a SpO2/FiO2 tem sido investigada como potencial substituta. Esta revisão narrativa apresenta o estado da literatura pré-clínica e clínica sobre a SpO2/FiO2 como possível substituta da PaO2/FiO2 e para uso como marcador diagnóstico e prognóstico; ainda, é fornecida uma visão geral da oximetria de pulso e suas limitações, além da avaliação da utilidade da SpO2/ FiO2 como substituta da PaO2/FiO2 em pacientes com COVID-19. Ao todo, foram encontrados 49 estudos comparando SpO2/FiO2 e PaO2/ FiO2 com base em uma estratégia de pesquisa mínima. A maioria dos estudos foi realizada em recémnascidos, alguns foram realizados em adultos com síndrome do desconforto respiratório agudo, e outros foram realizados em outros cenários clínicos (incluindo poucos em pacientes com COVID-19). Há certa evidência de que os critérios de SpO2/FiO2 podem substituir a PaO2/FiO2 em diferentes cenários clínicos. Isso é reforçado pelo fato de que devem ser evitados procedimentos invasivos desnecessários em pacientes com insuficiência respiratória aguda. É inegável que os oxímetros de pulso estão cada vez mais difundidos e podem proporcionar um monitoramento sem custos. Portanto, substituir a PaO2/FiO2 pela SpO2/FiO2 pode permitir que instalações com recursos limitados diagnostiquem a insuficiência respiratória aguda de maneira objetiva.

ABSTRACT Although the PaO 2/FiO 2 derived from arterial blood gas analysis remains the gold standard for the diagnosis of acute respiratory failure, the SpO2/FiO2 has been investigated as a potential substitute. The current narrative review presents the state of the preclinical and clinical literature on the SpO2/FiO2 as a possible substitute for PaO2/FiO2 and for use as a diagnostic and prognostic marker; provides an overview of pulse oximetry and its limitations, and assesses the utility of SpO2/ FiO2 as a surrogate for PaO2/FiO2 in COVID-19 patients. Overall, 49 studies comparing SpO2/FiO2 and PaO2/FiO2 were found according to a minimal search strategy. Most were conducted on neonates, some were conducted on adults with acute respiratory distress syndrome, and a few were conducted in other clinical scenarios (including a very few on COVID-19 patients). There is some evidence that the SpO2/ FiO2 criteria can be a surrogate for PaO2/FiO2 in different clinical scenarios. This is reinforced by the fact that unnecessary invasive procedures should be avoided in patients with acute respiratory failure. It is undeniable that pulse oximeters are becoming increasingly widespread and can provide costless monitoring. Hence, replacing PaO2/FiO2 with SpO2/FiO2may allow resourcelimited facilities to objectively diagnose acute respiratory failure.

Testosterone Therapy and Diaphragm Performance in a Male Patient with COVID-19: A Case Report.

Low levels of testosterone may lead to reduced diaphragm excursion and inspiratory time during COVID-19 infection. We report the case of a 38-year-old man with a positive result on a reverse transcriptase-polymerase chain reaction test for SARS-CoV-2, admitted to the intensive care unit with acute respiratory failure. After several days on mechanical ventilation and use of rescue therapies, during the weaning phase, the patient presented dyspnea associated with low diaphragm performance (diaphragm thickness fraction, amplitude, and the excursion-time index during inspiration were 37%, 1.7 cm, and 2.6 cm/s, respectively) by ultrasonography and reduced testosterone levels (total testosterone, bioavailable testosterone and sex hormone binding globulin (SHBG) levels were 9.3 ng/dL, 5.8 ng/dL, and 10.5 nmol/L, respectively). Testosterone was administered three times 2 weeks apart (testosterone undecanoate 1000 mg/4 mL intramuscularly). Diaphragm performance improved significantly (diaphragm thickness fraction, amplitude, and the excursion-time index during inspiration were 70%, 2.4 cm, and 3.0 cm/s, respectively) 45 and 75 days after the first dose of testosterone. No adverse events were observed, although monitoring was required after testosterone administration. Testosterone replacement therapy led to good diaphragm performance in a male patient with COVID-19. This should be interpreted with caution due to the exploratory nature of the study.

Effects of time-controlled adaptive ventilation on cardiorespiratory parameters and inflammatory response in experimental emphysema.

The time-controlled adaptive ventilation (TCAV) method attenuates lung damage in acute respiratory distress syndrome. However, so far, no study has evaluated the impact of the TCAV method on ventilator-induced lung injury (VILI) and cardiac function in emphysema. We hypothesized that the use of the TCAV method to achieve an expiratory flow termination/expiratory peak flow (EFT/EPF) of 25% could reduce VILI and improve right ventricular function in elastase-induced lung emphysema in rats. Five weeks after the last intratracheal instillation of elastase, animals were anesthetized and mechanically ventilated for 1 h using TCAV adjusted to either EFT/EPF 25% or EFT/EPF 75%, the latter often applied in acute respiratory distress syndrome (ARDS). Pressure-controlled ventilation (PCV) groups with positive end-expiratory pressure levels similar to positive end-release pressure in TCAV with EFT/EPF 25% and EFT/EPF 75% were also analyzed. Echocardiography and lung ultrasonography were monitored. Lung morphometry, alveolar heterogeneity, and biological markers related to inflammation [interleukin 6 (IL-6), CINC-1], alveolar pulmonary stretch (amphiregulin), lung matrix damage [metalloproteinase 9 (MMP-9)] were assessed. EFT/EPF 25% reduced respiratory system peak pressure, mean linear intercept, B lines at lung ultrasonography, and increased pulmonary acceleration time/pulmonary ejection time ratio compared with EFT/EPF 75%. The volume fraction of mononuclear cells, neutrophils, and expression of IL-6, CINC-1, amphiregulin, and MMP-9 were lower with EFT/EPF 25% than with EFT/EPF 75%. In conclusion, TCAV with EFT/EPF 25%, compared with EFT/EPF 75%, led to less lung inflammation, hyperinflation, and pulmonary arterial hypertension, which may be a promising strategy for patients with emphysema.NEW & NOTEWORTHY The TCAV method reduces lung damage in ARDS. However, so far, no study has evaluated the impact of the TCAV method on ventilator-induced lung injury and cardiac function in experimental emphysema. The TCAV method at EFT/EPF ratio of 25%, compared with EFT/EPF of 75% (frequently used in ARDS), reduced lung inflammation, alveolar heterogeneity and hyperinflation, and pulmonary arterial hypertension in elastase-induced emphysema. TCAV may be a promising and personalized ventilation strategy for patients with emphysema.