Oxygen Toxicity in Critically Ill Adults

NIR triggered polydopamine coated cerium dioxide nanozyme for ameliorating acute lung injury via enhanced ROS scavenging

Acute lung injury (ALI) is a life threatening disease in critically ill patients, and characterized by excessive reactive oxygen species (ROS) and inflammatory factors levels in the lung. Multiple evidences suggest that nanozyme with diversified catalytic capabilities plays a vital role in this fatal lung injury. At present, we developed a novel class of polydopamine (PDA) coated cerium dioxide (CeO2) nanozyme (Ce@P) that acts as the potent ROS scavenger for scavenging intracellular ROS and suppressing inflammatory responses against ALI. Herein, we aimed to identify that Ce@P combining with NIR irradiation could further strengthen its ROS scavenging capacity. Specifically, NIR triggered Ce@P exhibited the most potent antioxidant and anti-inflammatory behaviors in lipopolysaccharide (LPS) induced macrophages through decreasing the intracellular ROS levels, down-regulating the levels of TNF-α, IL-1β and IL-6, up-regulating the level of antioxidant cytokine (SOD-2), inducing M2 directional polarization (CD206 up-regulation), and increasing the expression level of HSP70. Besides, we performed intravenous (IV) injection of Ce@P in LPS induced ALI rat model, and found that it significantly accumulated in the lung tissue for 6 h after injection. It was also observed that Ce@P + NIR presented the superior behaviors of decreasing lung inflammation, alleviating diffuse alveolar damage, as well as promoting lung tissue repair. All in all, it has developed the strategy of using Ce@P combining with NIR irradiation for the synergistic enhanced treatment of ALI, which can serve as a promising therapeutic strategy for the clinical treatment of ROS derived diseases as well.

Hyperoxemia and hypoxemia impair cellular oxygenation: a study in healthy volunteers

INTRODUCTION

Administration of oxygen therapy is common, yet there is a lack of knowledge on its ability to prevent cellular hypoxia as well as on its potential toxicity. Consequently, the optimal oxygenation targets in clinical practice remain unresolved. The novel PpIX technique measures the mitochondrial oxygen tension in the skin (mitoPO2) which allows for non-invasive investigation on the effect of hypoxemia and hyperoxemia on cellular oxygen availability.

RESULTS

During hypoxemia, SpO2 was 80 (77-83)% and PaO2 45(38-50) mmHg for 15 min. MitoPO2 decreased from 42(35-51) at baseline to 6(4.3-9)mmHg (p < 0.001), despite 16(12-16)% increase in cardiac output which maintained global oxygen delivery (DO2). During hyperoxic breathing, an FiO2 of 40% decreased mitoPO2 to 20 (9-27) mmHg. Cardiac output was unaltered during hyperoxia, but perfused De Backer density was reduced by one-third (p < 0.01). A PaO2 < 100 mmHg and > 200 mmHg were both associated with a reduction in mitoPO2.

CONCLUSIONS

Hypoxemia decreases mitoPO2 profoundly, despite complete compensation of global oxygen delivery. In addition, hyperoxemia also decreases mitoPO2, accompanied by a reduction in microcirculatory perfusion. These results suggest that mitoPO2 can be used to titrate oxygen support.

Impact of hyperoxia on the gut during critical illnesses

Molecular oxygen is typically delivered to patients via oxygen inhalation or extracorporeal membrane oxygenation (ECMO), potentially resulting in systemic hyperoxia from liberal oxygen inhalation or localized hyperoxia in the lower body from peripheral venoarterial (VA) ECMO. Consequently, this exposes the gastrointestinal tract to excessive oxygen levels. Hyperoxia can trigger organ damage due to the overproduction of reactive oxygen species and is associated with increased mortality. The gut and gut microbiome play pivotal roles in critical illnesses and even small variations in oxygen levels can have a dramatic influence on the physiology and ecology of gut microbes. Here, we reviewed the emerging preclinical evidence which highlights how excessive inhaled oxygen can provoke diffuse villous damage, barrier dysfunction in the gut, and gut dysbiosis. The hallmark of this dysbiosis includes the expansion of oxygen-tolerant pathogens (e.g., Enterobacteriaceae) and the depletion of beneficial oxygen-intolerant microbes (e.g., Muribaculaceae). Furthermore, we discussed potential impact of oxygen on the gut in various underlying critical illnesses involving inspiratory oxygen and peripheral VA-ECMO. Currently, the available findings in this area are somewhat controversial, and a consensus has not yet to be reached. It appears that targeting near-physiological oxygenation levels may offer a means to avoid hyperoxia-induced gut injury and hypoxia-induced mesenteric ischemia. However, the optimal oxygenation target may vary depending on special clinical conditions, including acute hypoxia in adults and neonates, as well as particular patients undergoing gastrointestinal surgery or VA-ECMO support. Last, we outlined the current challenges and the need for future studies in this area. Insights into this vital ongoing research can assist clinicians in optimizing oxygenation for critically ill patients.

Effects of Oxygenation Targets on Mortality in Critically Ill Patients in Intensive Care Units: A Systematic Review and Meta-Analysis

BACKGROUND

The effects of oxygenation targets (partial pressure of arterial oxygen [Pao2], arterial oxygen saturation [Sao2]/peripheral oxygen saturation [Spo2], or inspiratory oxygen concentration [Fio2] on clinical outcomes in critically ill patients remains controversial. We reviewed the existing literature to assess the effects of lower and higher oxygenation targets on the mortality rates of critically ill intensive care unit (ICU) patients.

METHODS

MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and Web of Science databases were searched from their dates of inception to December 31, 2022, for randomized controlled trials (RCTs) comparing lower and higher oxygenation targets for critically ill patients ≥18 years of age undergoing mechanical ventilation, nasal cannula, oxygen mask, or high-flow oxygen therapy in the ICU. Data extraction was conducted independently, and RoB 2.0 software was used to evaluate the quality of each RCT. A random-effects model was used for the meta-analysis to calculate the relative risk (RR). We used the I2 statistic as a measure of statistical heterogeneity. Certainty of evidence was assessed according to the Grading of Recommendations Assessment, Development and Evaluation (GRADE) guidelines.

RESULTS

We included 12 studies with a total of 7416 patients participating in RCTs. Oxygenation targets were extremely heterogeneous between studies. The meta-analysis found no differences in mortality between lower and higher oxygenation targets for critically ill ICU patients (relative risk [RR], 1.00; 95% confidence interval [CI], 0.93-1.09; moderate certainty). The incidence of serious adverse events (RR, 0.93; 95% CI, 0.85-1.00; high certainty), mechanical ventilation-free days through day 28 (mean difference [MD], -0.05; 95%CI, -1.23 to 1.13; low certainty), the number of patients requiring renal replacement therapy (RRT) (RR, 0.96; 95% CI, 0.84-1.10; low certainty), and ICU length of stay (MD, 1.05; 95% CI, -0.04 to 2.13; very low certainty) also did not differ among patients with lower or higher oxygenation targets.

CONCLUSIONS

Critically ill ICU patients ≥18 years of age managed with lower and higher oxygenation targets did not differ in terms of mortality, RRT need, mechanical ventilation-free days through day 28, or ICU length of stay. However, due to considerable heterogeneity between specific targets in individual studies, no conclusion can be drawn regarding the effect of oxygenation targets on ICU outcomes.

Sigma-1 receptor regulates the endoplasmic reticulum stress pathway in the protective mechanism of dexmedetomidine against hyperoxia-induced lung injury

Perioperative hyperoxia therapy is of great significance to save the lives of patients, but little is known about the possible mechanisms that induce hyperoxia-induced acute lung injury (HALI) and the measures for clinical prevention and treatment. In this experiment, the models were established with a feeding chamber with automatic regulation of oxygen concentration. The results showed that with the increase in inhaled oxygen concentration and the prolongation of exposure time, the severity of lung injury also increases significantly, reaching the diagnostic indication of HALI after 48 h of inhaling 95 % oxygen concentration. Subsequently, according to the dynamic changes of apoptosis in lung specimens, and the expression changes in Sig-1R-regulated ER stress pathway proteins (Sig-1R, GRP78, p-PERK, ATF6, IRE1, Caspase-12, ATF4, CHOP, Caspase-3 and p-JNK), it was confirmed that the Sig-1R-regulated ER stress signaling pathway was involved in the occurrence of HALI. To explore the preventive and therapeutic effects of routine clinical medication on HALI during the perioperative period, our research group selected dexmedetomidine (Dex) with lung protection. The experimental results revealed that Dex partially reversed the changes in the expression levels of Sig-1R-regulated ER stress pathway proteins. These results preliminarily confirmed that Dex may inhibit apoptosis induced by high oxygen concentration through the Sig-1R-regulated ER stress signaling pathway, thus playing a protective role in HALI.

Ventilatory Management of Patients with Acute Respiratory Distress Syndrome Due to SARS-CoV-2

The emergence of the new SARS-CoV-2 in December 2019 caused a worldwide pandemic of the resultant disease, COVID-19. There was a massive surge in admissions to intensive care units (ICU), notably of patients with hypoxaemic acute respiratory failure. In these patients, optimal oxygen therapy was crucial. In this article, we discuss tracheal intubation to provide mechanical ventilation in patients with hypoxaemic acute respiratory failure due to SARS-CoV-2. We first describe the pathophysiology of respiratory anomalies leading to acute respiratory distress syndrome (ARDS) due to infection with SARS-CoV-2, and then briefly review management, focusing particularly on the ventilation strategy. Overall, the ventilatory management of ARDS due to SARS-CoV-2 infection is largely the same as that applied in ARDS from other causes, and lung-protective ventilation is recommended. The difference lies in the initial clinical presentation, with profound hypoxaemia often observed concomitantly with near-normal pulmonary compliance.

TRPA1: A promising target for pulmonary fibrosis?

Pulmonary fibrosis is a disease characterized by progressive scar formation and the ultimate manifestation of numerous lung diseases. It is known as "cancer that is not cancer" and has attracted widespread attention. However, its formation process is very complex, and the mechanism of occurrence has not been fully elucidated. Current research has found that TRPA1 may be a promising target in the pathogenesis of pulmonary fibrosis. The TRPA1 channel was first successfully isolated in human lung fibroblasts, and it was found to have a relatively concentrated distribution in the lungs and respiratory tract. It is also involved in various acute and chronic inflammatory processes of lung diseases and may even play a core role in the progression and/or prevention of pulmonary fibrosis. Natural ligands targeting TRPA1 could offer a promising alternative treatment for pulmonary diseases. Therefore, this review delves into the current understanding of pulmonary fibrogenesis, analyzes TRPA1 biological properties and regulation of lung disease with a focus on pulmonary fibrosis, summarizes the TRPA1 molecular structure and its biological function, and summarizes TRPA1 natural ligand sources, anti-pulmonary fibrosis activity and potential mechanisms. The aim is to decipher the exact role of TRPA1 channels in the pathophysiology of pulmonary fibrosis and to consider their potential in the development of new therapeutic strategies.

The effect of conservative oxygen therapy on mortality in adult critically ill patients: A systematic review and meta-analysis of randomised controlled trials

Background

Oxygen is the commonest intervention provided to critically ill patients requiring mechanical ventilation. Despite this, it is unclear how much oxygen should be administered to patients in order to promote the best clinical outcomes and it has been suggested that a strategy of conservative oxygen therapy (COT) may be advantageous. We therefore sought to answer the question of whether COT versus usual or liberal oxygen therapy was beneficial to adult patients receiving mechanical ventilation on an intensive care unit (ICU) by performing a systematic review and meta-analysis.

Methods

Studies were included if they were randomised controlled trials comparing COT to liberal or usual oxygen therapy strategies in acutely ill adults (aged ⩾18 years) admitted to an ICU, and reported an outcome of interest. Studies were excluded if they were limited to a specific single disease diagnosis. The review was registered on PROSPERO (CRD42022308436). Risk of bias was assessed using a modified Cochrane Risk of Bias assessment tool. Effect estimates were pooled using a random effects model with the between study variance estimated using restricted maximum likelihood and standard errors calculated using the method of Hartung-Knapp/Sidik-Jonkman. Between study heterogeneity was quantified using the I2 statistic. The certainty in the body of evidence was assessed using GRADE criteria.

Results

Nine eligible studies with 5727 participants fulfilled all eligibility criteria. Trials varied in their definitions of COT and liberal or usual oxygen therapy. The pooled estimate of risk ratio for 90 day mortality for COT versus comparator was 0.99 (95% confidence interval 0.88-1.12, 95% prediction interval 0.82-1.21). There was low heterogeneity among studies (I2 = 22.4%). The finding that mortality was similar for patients managed with COT or usual/liberal oxygen therapy was graded as moderate certainty.

Conclusions

In critically ill adults admitted to an ICU, COT is neither beneficial nor harmful when compared to usual or liberal oxygen therapy. Trials to date have been inconsistent in defining both COT and liberal or usual oxygen therapy, which may have had an impact on the results of this meta-analysis. Future research should focus on unifying definitions and outcome measures.

Hyperoxic exposure alters intracellular bioenergetics distribution in human pulmonary cells

AIMS

Pulmonary oxygen toxicity is caused by exposure to a high fraction of inspired oxygen, which damages multiple cell types within the lung. The cellular basis for pulmonary oxygen toxicity includes mitochondrial dysfunction. The aim of this study was to identify the effects of hyperoxic exposure on mitochondrial bioenergetic and dynamic functions in pulmonary cells.

MAIN METHODS

Mitochondrial respiration, inner membrane potential, dynamics (including motility), and distribution of mitochondrial bioenergetic capacity in two intracellular regions were quantified using cultured human lung microvascular endothelial cells, human pulmonary artery endothelial cells and A549 cells. Hyperoxic (95 % O₂) exposures lasted 24, 48 and 72 h, durations relevant to mechanical ventilation in intensive care settings.

KEY FINDINGS

Mitochondrial motility was altered following all hyperoxic exposures utilized in experiments. Inhomogeneities in inner membrane potential and respiration parameters were present in each cell type following hyperoxia. The partitioning of ATP-linked respiration was also hyperoxia-duration and cell type dependent. Hyperoxic exposure lasting 48 h or longer provoked the largest alterations in mitochondrial motility and the greatest decreases in ATP-linked respiration, with a suggestion of decreases in respiration complex protein levels.

SIGNIFICANCE

Hyperoxic exposures of different durations produce intracellular inhomogeneities in mitochondrial dynamics and bioenergetics in pulmonary cells. Oxygen therapy is utilized commonly in clinical care and can induce undesirable decrements in bioenergy function needed to maintain pulmonary cell function and viability. There may be adjunctive or prophylactic measures that can be employed during hyperoxic exposures to prevent the mitochondrial dysfunction that signals the presence of oxygen toxcity.

Mechanical Ventilation during ECMO: Best Practices

Adults and children who require extracorporeal membrane oxygenation for respiratory failure remain at risk for ongoing lung injury if ventilator management is not optimized. This review serves as a guide to assist the bedside clinician in ventilator titration for patients on extracorporeal membrane oxygenation, with a focus on lung-protective strategies. Existing data and guidelines for extracorporeal membrane oxygenation ventilator management are reviewed, including non-conventional ventilation modes and adjunct therapies.

Oxygenation target in acute respiratory distress syndrome

Determining oxygenation targets in acute respiratory distress syndrome (ARDS) remains a challenge. Although oxygenation targets have been used since ARDS was first described, they have not been investigated in detail. However, recent retrospective and prospective trials have evaluated the optimal oxygenation threshold in patients admitted to the general intensive care unit. In view of the lack of prospective data, clinicians continue to rely on data from the few available trials to identify the optimal oxygenation strategy. Assessment of the cost-benefit ratio of the fraction of inspired oxygen (FiO₂) to the partial pressure of oxygen in the arterial blood (PaO₂) is an additional challenge. A high FiO₂ has been found to be responsible for respiratory failure and deaths in numerous animal models. Low and high PaO₂ values have also been demonstrated to be potential risk factors in experimental and clinical situations. The findings from this literature review suggest that PaO₂ values ranging between 80 mmHg and 90 mmHg are acceptable in patients with ARDS. The costs of rescue maneuvers needed to reach these targets have been discussed. Several recent papers have highlighted the risk of disagreement between arterial oxygen saturation (SaO₂) and peripheral oxygen saturation (SpO₂) values. In order to avoid discrepancies and hidden hypoxemia, SpO₂ readings need to be compared with those of SaO₂. Higher SpO₂ values may be needed to achieve the recommended PaO₂ and SaO₂ values.

Effect of low-to-moderate hyperoxia on lung injury in preclinical animal models: a systematic review and meta-analysis

BACKGROUND

Extensive animal investigation informed clinical practice regarding the harmful effects of high fractional inspired oxygen concentrations (FiO₂s > 0.60). Since questions persist whether lower but still supraphysiologic FiO₂ ≤ 0.60 and > 0.21 (FiO₂ ≤ 0.60/ > 0.21) are also harmful with inflammatory lung injury in patients, we performed a systematic review examining this question in animal models.

METHODS

Studies retrieved from systematic literature searches of three databases, that compared the effects of exposure to FiO₂ ≤ 0.60/ > 0.21 vs. FiO₂ = 0.21 for ≥ 24 h in adult in vivo animal models including an inflammatory challenge or not were analyzed. Survival, body weight and/or lung injury measures were included in meta-analysis if reported in ≥ 3 studies.

RESULTS

More than 600 retrieved reports investigated only FiO₂s > 0.60 and were not analyzed. Ten studies with an inflammatory challenge (6 infectious and 4 noninfectious) and 14 studies without, investigated FiO₂s ≤ 0.60/ > 0.21 and were analyzed separately. In seven studies with an inflammatory challenge, compared to FiO₂ = 0.21, FiO₂ ≤ 0.60/ > 0.21 had consistent effects across animal types on the overall odds ratio of survival (95%CI) that was on the side of harm but not significant [0.68 (0.38,1.23), p = 0.21; I² = 0%, p = 0.57]. However, oxygen exposure times were only 1d in 4 studies and 2-4d in another. In a trend approaching significance, FiO₂ ≤ 0.60/ > 0.21 with an inflammatory challenge consistently increased the standardized mean difference (95%CI) (SMD) in lung weights [0.47 (- 0.07,1.00), p = 0.09; I² = 0%, p = 0.50; n = 4 studies] but had inconsistent effects on lung lavage protein concentrations (n = 3), lung pathology scores (n = 4) and/or arterial oxygenation (n = 4) (I² ≥ 43%, p ≤ 0.17). Studies without an inflammatory challenge had consistent effects on lung lavage protein concentration (n = 3) SMDs on the side of being increased that was not significant [0.43 (- 0.23,1.09), p = 0.20; I² = 0%, p = 0.40] but had inconsistent effects on body and lung weights (n = 6 and 8 studies, respectively) (I² ≥ 71%, p < 0.01). Quality of evidence for studies was weak.

INTERPRETATION

Limited animal studies have investigated FiO₂ ≤ 0.60/ > 0.21 with clinically relevant models and endpoints but suggest even these lower FiO₂s may be injurious. Given the influence animal studies examining FiO₂ > 0.60 have had on clinical practice, additional ones investigating FiO₂ ≤ 0.60/ > 0.21 appear warranted, particularly in pneumonia models.

Mechanisms of impaired alveolar fluid clearance

Impaired alveolar fluid clearance (AFC) is an important cause of alveolar edema fluid accumulation in patients with acute respiratory distress syndrome (ARDS). Alveolar edema leads to insufficient gas exchange and worse clinical outcomes. Thus, it is important to understand the pathophysiology of impaired AFC in order to develop new therapies for ARDS. Over the last few decades, multiple experimental studies have been done to understand the molecular, cellular, and physiological mechanisms that regulate AFC in the normal and the injured lung. This review provides a review of AFC in the normal lung, focuses on the mechanisms of impaired AFC, and then outlines the regulation of AFC. Finally, we summarize ongoing challenges and possible future research that may offer promising therapies for ARDS.

Hypoxia signaling in cancer: Implications for therapeutic interventions

Hypoxia is a persistent physiological feature of many different solid tumors and a key driver of malignancy, and in recent years, it has been recognized as an important target for cancer therapy. Hypoxia occurs in the majority of solid tumors due to a poor vascular oxygen supply that is not sufficient to meet the needs of rapidly proliferating cancer cells. A hypoxic tumor microenvironment (TME) can reduce the effectiveness of other tumor therapies, such as radiotherapy, chemotherapy, and immunotherapy. In this review, we discuss the critical role of hypoxia in tumor development, including tumor metabolism, tumor immunity, and tumor angiogenesis. The treatment methods for hypoxic TME are summarized, including hypoxia-targeted therapy and improving oxygenation by alleviating tumor hypoxia itself. Hyperoxia therapy can be used to improve tissue oxygen partial pressure and relieve tumor hypoxia. We focus on the underlying mechanisms of hyperoxia and their impact on current cancer therapies and discuss the prospects of hyperoxia therapy in cancer treatment.

Prognostic value of the novel P/FPE index to classify ARDS severity: A cohort study

OBJECTIVE

To evaluate the impact of the novel P/FP_E index to classify ARDS severity on mortality of patients with ARDS.

DESIGN

A retrospective cohort study.

SETTING

Twelve-bed medical and surgical intensive care unit from January 2018 to December 2020.

PATIENTS

A total of 217 ARDS patients managed with invasive mechanical ventilation >48h.

INTERVENTIONS

None.

VARIABLES

ARDS severity on day 1 and day 3 was measured based on PaO₂/FiO₂ ratio and P/FP_E index [PaO₂/(FiO₂×PEEP)]. Primary outcome was the hospital mortality.

RESULTS

Hospital mortality rate was 59.9%. Relative to PaO₂/FiO₂ ratio, 31.8% of patients on day 1 and 77.0% on day 3 were reclassified into a different category of ARDS severity by P/FP_E index. The level of PEEP was lower by P/FP_E index-based ARDS severity classification than by using PaO₂/FiO₂ ratio. The performance for predicting mortality of P/FP_E index was superior to PaO₂/FiO₂ ratio in term of AROC (day 1: 0.72 vs. 0.62; day 3: 0.87 vs. 0.68) and CORR (day 1: 0.370 vs. 0.213; day 3: 0.634 vs. 0.301). P/FP_E index improved prediction of risk of death compared to PaO₂/FiO₂ ratio as showed by the qNRI (day 1: 72.0%, p<0.0001; day 3: 132.4%, p<0.0001) and IDI (day 1: 0.09, p<0.0001; day 3: 0.31, p<0.0001).

CONCLUSIONS

Assessment of ARDS severity based on P/FP_E index seems better than PaO₂/FiO₂ ratio for predicting mortality. The value of P/FP_E index for clinical decision-making requires confirmation by randomized controlled trials.

Factors to be Considered in Advancing Pediatric Critical Care Across the World

This article reviews the many factors that have to be taken into account as we consider the advancement of pediatric critical care (PCC) in multiple settings across the world. The extent of PCC and the range of patients who are cared for in this environment are considered. Along with a review of the ongoing treatment and technology advances in the PCC setting, the structures and systems required to support these services are also considered. Finally the question of how PCC can be made sustainable in a volatile world with the impacts of global crises such as climate change is addressed.

Sivelestat improves clinical outcomes and decreases ventilator-associated lung injury in children with acute respiratory distress syndrome: a retrospective cohort study

BACKGROUND

Sivelestat, a neutrophil elastase inhibitor, is a selective and targeted therapy for acute respiratory distress syndrome (ARDS) in adults; and it is also reported to apply to children with ARDS. However, there is little evidence of its efficacy in children.

METHODS

This study recruited 212 patients ranging in age from 28 days to 18 years old, and who met the diagnostic criteria for pediatric ARDS (PARDS) while hospitalized in the Intensive Care Department of the Affiliated Children's Hospital of Xi'an Jiaotong University. A total of 125 patients (case group) received sivelestat treatment, and 87 were assigned to the control group. There were no significant differences in gender (P=0.445) or age (P=0.521). Control group data were collected from the Electronic Case Information System for pediatric patients diagnosed with ARDS between March 2017 to January 2020. Data for the case group were collected from the Electronic Case Information System between February 2020 to February 2022. Demographic data, clinically relevant indicators, respiratory parameters were recorded. The 28-day mortality was the primary endpoint; the Kaplan-Meier and log-rank tests were used to evaluate cumulative survival rate.

RESULTS

For general demographic and clinical characteristics, no significant differences were observed between the two groups. Compared to the control group, the case group displayed significant improvements in PaO₂/FiO₂ at 48 h (141±45 vs. 115±21, P<0.001) and 72 h (169±61 vs. 139±40, P<0.001) post-admission, and plateau pressure was lower than that in the control group at 24 h (24±3 vs. 28±7, P<0.001), 48 h (21±4 vs. 26±7, P<0.001), and 72 h (20±2 vs. 25±6, P<0.001) post-admission. Interleukin-8 levels were lower in the case group at 48 and 72 h post-admission. Overall, 28-day mortality was 25.47% (54/212). Twenty-five children died in the sivelestat group, 29 children died in the control group. Survival analysis revealed that cumulative survival in the case group was higher than that in the control group (P=0.028).

CONCLUSIONS

ARDS is expected to have high morbidity and mortality in critical care medicine, and precise targeted drugs are lacking. Our study showed that sivelestat improved prognosis and reduces mortality in children with ARDS.

Intubation Timing in COVID-19 Based on ROX Index and Association With Patient Outcomes

BACKGROUND

Timing of intubation in COVID-19 is controversial. We sought to determine the association of the ROX (Respiratory rate-OXygenation) index defined as [Formula: see text] divided by [Formula: see text] divided by breathing frequency at the time of intubation with clinical outcomes.

METHODS

We conducted a retrospective cohort study of patients with COVID-19 who were intubated by using a database composed of electronic health record data from patients with COVID-19 from 62 institutions. Multivariable logistic regression was used to evaluate the impact of ROX index score on mortality. We analyzed the ROX index as a continuous variable as well as a categorical variable by using cutoffs previously described as predicting success with high-flow nasal cannula.

RESULTS

Of 1,087 subjects in the analysis group, the median age was 64 years, and more than half had diabetes; 55.2% died, 1.8% were discharged to hospice, 7.8% were discharged to home, 27.3% were discharged to another institution, and 7.8% had another disposition. Increasing age and a longer time from admission to intubation were associated with mortality. After adjusting for sex, race, age, comorbidities, and days from admission to intubation, an increasing ROX index score at the time of intubation was associated with a lower risk of death. In a logistic regression model, each increase in the ROX index score by 1 at the time of intubation was associated with an 8% reduction in odds of mortality (odds ratio 0.92, 95% CI 0.88-0.95). We also found an odds ratio for death of 0.62 (95% CI 0.47-0.81) for subjects with an ROX index score ≥ 4.88 at the time of intubation.

CONCLUSIONS

Among a cohort of subjects with COVID-19 who were ultimately intubated, a higher ROX index at the time of intubation was positively associated with survival.

Dual effects of supplemental oxygen on pulmonary infection, inflammatory lung injury, and neuromodulation in aging and COVID-19

Clinical studies have shown a significant positive correlation between age and the likelihood of being infected with SARS-CoV-2. This increased susceptibility is positively correlated with chronic inflammation and compromised neurocognitive functions. Postmortem analyses suggest that acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), with systemic and lung hyperinflammation, can cause significant morbidity and mortality in COVID-19 patients. Supraphysiological supplemental oxygen, also known as hyperoxia, is commonly used to treat decreased blood oxygen saturation in COVID-19 patients. However, prolonged exposure to hyperoxia alone can cause oxygen toxicity, due to an excessive increase in the levels of reactive oxygen species (ROS), which can overwhelm the cellular antioxidant capacity. Subsequently, this causes oxidative cellular damage and increased levels of aging biomarkers, such as telomere shortening and inflammaging. The oxidative stress in the lungs and brain can compromise innate immunity, resulting in an increased susceptibility to secondary lung infections, impaired neurocognitive functions, and dysregulated hyperinflammation, which can lead to ALI/ARDS, and even death. Studies indicate that lung inflammation is regulated by the central nervous system, notably, the cholinergic anti-inflammatory pathway (CAIP), which is innervated by the vagus nerve and α7 nicotinic acetylcholine receptors (α7nAChRs) on lung cells, particularly lung macrophages. The activation of α7nAChRs attenuates oxygen toxicity in the lungs and improves clinical outcomes by restoring hyperoxia-compromised innate immunity. Mechanistically, α7nAChR agonist (e.g., GAT 107 and GTS-21) can regulate redox signaling by 1) activating Nrf2, a master regulator of the antioxidant response and a cytoprotective defense system, which can decrease cellular damage caused by ROS and 2) inhibiting the activation of the NF-κB-mediated inflammatory response. Notably, GTS-21 has been shown to be safe and it improves neurocognitive functions in humans. Therefore, targeting the α7nAChR may represent a viable therapeutic approach for attenuating dysregulated hyperinflammation-mediated ARDS and sepsis in COVID-19 patients receiving prolonged oxygen therapy.

Time-varying intensity of oxygen exposure is associated with mortality in critically ill patients with mechanical ventilation

BACKGROUND

There is no consensus exists regarding the association between oxygen exposure (arterial oxygen tension or fraction of inspired oxygen) and outcomes for patients with mechanical ventilation. Additionally, whether the association remains persistent over time is unknown. We aimed to explore the association between exposure to different intensities of oxygen exposure over time and 28-day mortality in patients with mechanical ventilation.

METHODS

We obtained data from the Medical Information Mart for Intensive Care IV (MIMIC-IV), which included adult (≥ 18 years) patients who received invasive mechanical ventilation for at least 48 h. We excluded patients who received extracorporeal membrane oxygenation (ECMO) or who initiated ventilation more than 24 h after ICU admission. The primary outcome was 28-day mortality. Piece-wise exponential additive mixed models were employed to estimate the strength of associations over time.

RESULTS

A total of 7784 patients were included in the final analysis. Patients had a median duration of invasive mechanical ventilation of 8.1 days (IQR: 3.8-28 days), and the overall 28-day mortality rate was 26.3%. After adjustment for baseline and time-dependent confounders, both daily time-weighted average (TWA) arterial oxygen tension (PaO₂) and fraction of inspired oxygen (FiO₂) were associated with increased 28-day mortality, and the strength of the association manifested predominantly in the early-middle course of illness. A significant increase in the hazard of death was found to be associated with daily exposure to TWA-PaO₂ ≥ 120 mmHg (Hazard ratio 1.166, 95% CI 1.059-1.284) or TWA-FiO₂ ≥ 0.5 (Hazard ratio 1.496, 95% CI 1.363-1.641) during the entire course. A cumulative effect of harmful exposure (TWA-PaO₂ ≥ 120 mmHg or TWA-FiO₂ ≥ 0.5) was also observed.

CONCLUSION

PaO₂ and FiO₂ should be carefully monitored in patients with mechanical ventilation, especially during the early-middle course after ICU admission. Cumulative exposure to higher intensities of oxygen exposure was associated with an increased risk of death.

Rationale and design of a randomized controlled clinical trial; Titration of Oxygen Levels (TOOL) during mechanical ventilation

BACKGROUND

Both hyperoxemia and hypoxemia are deleterious in critically ill patients. Targeted oxygenation is recommended to prevent both of these extremes, however this has not translated to the bedside. Hyperoxemia likely persists more than hypoxemia due to absence of immediate discernible adverse effects, cognitive biases and delay in prioritization of titration.

METHODS

We present the methodology for the Titration Of Oxygen Levels (TOOL) trial, an open label, randomized controlled trial of an algorithm-based FiO2 titration with electronic medical record-based automated alerts. We hypothesize that the study intervention will achieve targeted oxygenation by curbing episodes of hyperoxemia while preventing hypoxemia. In the intervention arm, electronic alerts will be used to titrate FiO2 if SpO2 is ≥94% with FiO2 levels ≥0.4 over 45 min. FiO2 will be titrated per standard practice in the control arm. This study is being carried out with deferred consent. The sample size to determine efficacy is 316 subjects, randomized in a 1:1 ratio to the intervention vs. control arm. The primary outcome is proportion of time during mechanical ventilation spent with FiO2 ≥ 0.4 and SpO2 ≥ 94%. We will also assess proportion of time during mechanical ventilation spent with SpO2 < 88%, duration of mechanical ventilation, length of ICU and hospital stay, hospital mortality, and adherence to electronic alerts as secondary outcomes.

CONCLUSION

This study is designed to evaluate the efficacy of a high fidelity, bioinformatics-based, electronic medical record derived electronic alert system to improve targeted oxygenation in mechanically ventilated patients by reducing excessive FiO2 exposure.

Dangers of hyperoxia

Oxygen (O2) toxicity remains a concern, particularly to the lung. This is mainly related to excessive production of reactive oxygen species (ROS). Supplemental O2, i.e. inspiratory O2 concentrations (FIO2) > 0.21 may cause hyperoxaemia (i.e. arterial (a) PO2 > 100 mmHg) and, subsequently, hyperoxia (increased tissue O2 concentration), thereby enhancing ROS formation. Here, we review the pathophysiology of O2 toxicity and the potential harms of supplemental O2 in various ICU conditions. The current evidence base suggests that PaO2 > 300 mmHg (40 kPa) should be avoided, but it remains uncertain whether there is an "optimal level" which may vary for given clinical conditions. Since even moderately supra-physiological PaO2 may be associated with deleterious side effects, it seems advisable at present to titrate O2 to maintain PaO2 within the normal range, avoiding both hypoxaemia and excess hyperoxaemia.