Emergency department hyperoxia is associated with increased mortality in mechanically ventilated patients: a cohort study

Respiratory Therapist-Driven Mechanical Ventilation Protocol Is Associated With Increased Lung Protective Ventilation

BACKGROUND

Mechanical ventilation is a common life-saving procedure but can lead to serious complications, including ARDS and oxygen toxicity. Nonadherence to lung-protective ventilation guidelines is common. We hypothesized that a respiratory therapist-driven mechanical ventilation bundle could increase adherence to lung-protective ventilation and decrease the incidence of pulmonary complications in the ICU.

METHODS

A respiratory therapist-driven protocol was implemented on August 1, 2018, in all adult ICUs of a Midwestern academic tertiary center. The protocol targeted low tidal volume, adequate PEEP, limiting oxygen, adequate breathing frequency, and head of the bed elevation. Adherence to lung-protective guidelines and clinical outcomes were retrospectively observed in adult subjects admitted to the ICU and on ventilation for ≥ 24 h between January 2011 and December 2019.

RESULTS

We included 666 subjects; 68.5% were in the pre-intervention group and 31.5% were in the post-intervention group. After adjusting for body mass index and intubation indication, a significant increase in overall adherence to lung-protective ventilation guidelines was observed in the post-intervention period (adjusted odds ratio 2.48, 95% CI 1.73-3.56). Fewer subjects were diagnosed with ARDS in the post-intervention group (adjusted odds ratio 0.22, 95% CI 0.08-0.65) than in the pre-intervention group. There was no difference in the incidence of ventilator-associated pneumonia, ventilator-free days, ICU mortality, or death within 1 month of ICU discharge.

CONCLUSIONS

A respiratory therapist-driven protocol increased adherence to lung-protective mechanical ventilation guidelines in the ICU and was associated with decreased ARDS incidence.

Association Between Early Hyperoxemia Exposure and Intensive Care Unit Mortality in Intracerebral Hemorrhage: An Observational Cohort Analysis

BACKGROUND

Supraphysiologic levels of oxygen could have potential adverse effects on the brain that may be dose and time dependent in patients with brain injury. We therefore aimed to assess whether exposure to excess supplemental oxygen, measured as time-weighted mean exposure to hyperoxemia, was associated with intensive care unit (ICU) mortality in patients with intracerebral hemorrhage (ICH).

METHODS

In this single-center retrospective cohort study, we included all patients admitted to our ICU with a diagnosis of primary spontaneous ICH. To provide a longitudinal measure of hyperoxemia exposure, we calculated the hyperoxemia dose, defined as the area under the partial pressure of oxygen in arterial blood (PaO2) time curve above the threshold PaO2 value of 100 mm Hg (13.3 kPa) divided by the number of hours of potential exposure. To provide consistent potential exposure windows and limit bias from informative censoring, nested subsets were created with progressively longer exposure periods (0-1 day, 0-2 days, 0-3 days, 0-4 days, 0-5 days, 0-6 days, 0-7 days). We used multivariable Cox regression, with hyperoxemia dose as a time-dependent covariate, to model ICU mortality. Admission ICH and Acute Physiology and Chronic Health Evaluation II scores were included as predictor covariables. A step-function extended Cox model was also fitted.

RESULTS

Between September 2019 and July 2022, 275 patients met the inclusion criteria, with 24,588 arterial blood gas results available for analysis. The mean age was 57.19 years (± 13.99), 59.64% were male, 23.64% had an infratentorial origin of hemorrhage, and ICU mortality was 35.64%. Almost all patients (97.45%) were exposed to hyperoxemia during their ICU admission. Cox regression modeling showed an association between hyperoxemia dose and ICU mortality (hazard ratio 1.15, confidence interval 1.05-1.25, p = 0.003). This association was observed in the 0-1 day subset in the step-function extended Cox model (hazard ratio 1.19, confidence interval 1.06-1.35, p = 0.005) but not in any of the subsequent exposure periods.

CONCLUSIONS

In patients with ICH admitted to the ICU, we observed an association between hyperoxemia dose and ICU mortality. Further prospective study is required to inform guidance on early systemic oxygen targets in ICH.

Hyperoxia and brain: the link between necessity and injury from a molecular perspective

Oxygen (O2) supplementation is commonly used to treat hypoxia in patients with respiratory failure. However, indiscriminate use can lead to hyperoxia, a condition detrimental to living tissues, particularly the brain. The brain is sensitive to reactive oxygen species (ROS) and inflammation caused by high concentrations of O2, which can result in brain damage and mitochondrial dysfunction, common features of neurodegenerative disorders. Hyperoxia leads to increased production of ROS, causing oxidative stress, an imbalance between oxidants and antioxidants, which can damage tissues. The brain is particularly vulnerable to oxidative stress due to its lipid composition, high O2 consumption rate, and low levels of antioxidant enzymes. Moreover, hyperoxia can cause vasoconstriction and decreased O2 supply to the brain, posing a challenge to redox balance and neurodegenerative processes. Studies have shown that the severity of hyperoxia-induced brain damage varies with inspired O2 concentration and duration of exposure. Therefore, careful evaluation of the balance between benefits and risks of O2 supplementation, especially in clinical settings, is crucial.

Hyperoxemia Induced by Oxygen Therapy in Nonsurgical Critically Ill Patients

BACKGROUND

Hyperoxemia, often overlooked in critically ill patients, is common and may have adverse consequences.

OBJECTIVE

To evaluate the incidence of hyperoxemia induced by oxygen therapy in nonsurgical critically ill patients at intensive care unit (ICU) admission and the association of hyperoxemia with hospital mortality.

METHODS

This prospective cohort study included all consecutive admissions of nonsurgical patients aged 18 years or older who received oxygen therapy on admission to the Hospital Santa Luzia Rede D'Or São Luiz adult ICU from July 2018 through June 2021. Patients were categorized into 3 groups according to Pao2 level at ICU admission: hypoxemia (Pao2<60 mm Hg), normoxemia (Pao2= 60-120 mm Hg), and hyperoxemia (Pao2 >120 mm Hg).

RESULTS

Among 3088 patients, hyperoxemia was present in 1174 (38.0%) and was independently associated with hospital mortality (odds ratio [OR], 1.32; 95% CI, 1.04-1.67; P=.02). Age (OR, 1.02; 95% CI, 1.02-1.02; P<.001) and chronic kidney disease (OR, 1.55; 95% CI, 1.02-2.36; P=.04) were associated with a higher rate of hyperoxemia. Factors associated with a lower rate of hyperoxemia were Sequential Organ Failure Assessment score (OR, 0.88; 95% CI, 0.83-0.93; P<.001); late-night admission (OR, 0.80; 95% CI, 0.67-0.96; P=.02); and renal/metabolic (OR, 0.22; 95% CI, 0.13-1.39; P<.001), neurologic (OR, 0.02; 95% CI, 0.01-0.05; P<.001), digestive (OR, 0.23; 95% CI, 0.13-0.41; P<.001), and soft tissue/skin/orthopedic (OR, 0.32; 95% CI, 0.13-0.79; P=.01) primary reasons for hospital admission.

CONCLUSION

Hyperoxemia induced by oxygen therapy was common in critically ill patients and was linked to increased risk of hospital mortality. Health care professionals should be aware of this condition because of its potential risks and unnecessary costs.

Short-term hyperoxia induced mitochondrial respiratory chain complexes dysfunction and oxidative stress in lung of rats

BACKGROUND

Oxygen therapy is an alternative for many patients with hypoxemia. However, this practice can be dangerous as oxygen is closely associated with the development of oxidative stress.

METHODS

Male Wistar rats were exposed to hyperoxia with a 40% fraction of inspired oxygen (FIO2) and hyperoxia (FIO2 = 60%) for 120 min. Blood and lung tissue samples were collected for gas, oxidative stress, and inflammatory analyses.

RESULTS

Hyperoxia (FIO2 = 60%) increased PaCO2 and PaO2, decreased blood pH and caused thrombocytopenia and lymphocytosis. In lung tissue, neutrophil infiltration, nitric oxide concentration, carbonyl protein formation and the activity of complexes I and II of the mitochondrial respiratory chain increased. FIO2 = 60% decreased SOD activity and caused several histologic changes.

CONCLUSION

In conclusion, we have experimentally demonstrated that short-term exposure to high FIO2 can cause oxidative stress in the lung.

The Effect of Early Severe Hyperoxia in Adults Intubated in the Prehosptial Setting or Emergency Department: A Scoping Review

BACKGROUND

The detrimental effects of hyperoxia exposure have been well-described in patients admitted to intensive care units. However, data evaluating the effects of short-term, early hyperoxia exposure in patients intubated in the prehospital setting or emergency department (ED) have not been systematically reviewed.

OBJECTIVE

Our aim was to quantify and describe the existing literature examining the clinical outcomes in ED patients exposed to hyperoxia within the first 24 h of mechanical ventilation.

METHODS

This review was performed in concordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for scoping reviews. Two rounds of review using Rayyan QCRI software were performed for title and abstract screening and full-text search. Of the 2739 articles, 27 articles were retrieved after initial screening, of which 5 articles were excluded during the full-text screening, leaving 22 articles for final review and data extraction.

RESULTS

Of 22 selected publications, 9 described patients with traumatic brain injury, 6 with cardiac arrest, 3 with multisystem trauma, 1 with stroke, 2 with septic shock, and 1 was heterogeneous. Three studies were randomized controlled trials. The available data have widely heterogeneous definitions of hyperoxia exposure, outcomes, and included populations, limiting conclusions.

CONCLUSIONS

There is a paucity of data that examined the effects of severe hyperoxia exposure in the acute, post-intubation phase of the prehospital and ED settings. Further research with standardized definitions is needed to provide more detailed guidance regarding early oxygen titration in intubated patients.

Arterial to end-tidal carbon dioxide gap and its characterization in mechanically ventilated adults in the emergency department

PURPOSE

To evaluate early measurement of the arterial to end-tidal carbon dioxide (PaCO2-PetCO2) gap, a surrogate for physiologic dead space, and its association with clinical outcomes in intubated adults in the emergency department (ED).

MATERIALS AND METHODS

Observational cohort study of invasively mechanically ventilated adults in an academic medical center (years 2009 to 2016). The association of the PaCO2-PetCO2 gap was evaluated with respect to clinical outcomes; the primary outcome was in-hospital mortality.

RESULTS

519 patients were included. 325 (63%) patients had an elevated (>5 mmHg) PaCO2-PetCO2. Patients with an elevated PaCO2-PetCO2 were significantly older, had higher APACHE II scores, more frequently had chronic obstructive pulmonary disease (COPD), had lower arterial oxygen to fraction of inspired oxygen (P:F) ratios, and were more likely to be intubated for exacerbation of COPD or sepsis. There was no difference in mortality for patients with an elevated PaCO2-PetCO2 (25% vs 26%) in unadjusted analysis (p = 0.829) or adjusted analysis (aOR = 0.81 [95% CI: 0.53-1.26]), as compared to a non-elevated PaCO2-PetCO2.

CONCLUSIONS

An elevated PaCO2-PetCO2 gap is common in the post-intubation period in the ED, but not significantly associated with clinical outcomes.

A vanguard randomised feasibility trial comparing three regimens of peri-operative oxygen therapy on recovery after major surgery

International recommendations encourage liberal administration of oxygen to patients having surgery under general anaesthesia, ostensibly to reduce surgical site infection. However, the optimal oxygen regimen to minimise postoperative complications and enhance recovery from surgery remains uncertain. The hospital operating theatre randomised oxygen (HOT-ROX) trial is a multicentre, patient- and assessor-blinded, parallel-group, randomised clinical trial designed to assess the effect of a restricted, standard care, or liberal peri-operative oxygen therapy regimen on days alive and at home after surgery in adults undergoing prolonged non-cardiac surgery under general anaesthesia. Here, we report the findings of the internal vanguard feasibility phase of the trial undertaken in four large metropolitan hospitals in Australia and New Zealand that included the first 210 patients of a planned overall 2640 trial sample, with eight pre-specified endpoints evaluating protocol implementation and safety. We screened a total of 956 participants between 1 September 2019 and 26 January 2021, with data from 210 participants included in the analysis. Median (IQR [range]) time-weighted average intra-operative Fi O2 was 0.30 (0.26-0.35 [0.20-0.59]) and 0.47 (0.44-0.51 [0.37-0.68]) for restricted and standard care, respectively (mean difference (95%CI) 0.17 (0.14-0.20), p < 0.001). Median time-weighted average intra-operative Fi O2 was 0.83 (0.80-0.85 [0.70-0.91]) for liberal oxygen therapy (mean difference (95%CI) compared with standard care 0.36 (0.33-0.39), p < 0.001). All feasibility endpoints were met. There were no significant patient adverse events. These data support the feasibility of proceeding with the HOT-ROX trial without major protocol modifications.

Machine learning based prediction of prolonged duration of mechanical ventilation incorporating medication data

Rationale

Duration of mechanical ventilation is associated with adverse outcomes in critically ill patients and increased use of resources. The increasing complexity of medication regimens has been associated with increased mortality, length of stay, and fluid overload but has never been studied specifically in the setting of mechanical ventilation.

Objective

The purpose of this analysis was to develop prediction models for mechanical ventilation duration to test the hypothesis that incorporating medication data may improve model performance.

Methods

This was a retrospective cohort study of adults admitted to the ICU and undergoing mechanical ventilation for longer than 24 hours from October 2015 to October 2020. Patients were excluded if it was not their index ICU admission or if the patient was placed on comfort care in the first 24 hours of admission. Relevant patient characteristics including age, sex, body mass index, admission diagnosis, morbidities, vital signs measurements, severity of illness, medication regimen complexity as measured by the MRC-ICU, and medical treatments before intubation were collected. The primary outcome was area under the receiver operating characteristic (AUROC) of prediction models for prolonged mechanical ventilation (defined as greater than 5 days). Both logistic regression and supervised learning techniques including XGBoost, Random Forest, and Support Vector Machine were used to develop prediction models.

Results

The 318 patients [age 59.9 (SD 16.9), female 39.3%, medical 28.6%] had mean 24-hour MRC-ICU score of 21.3 (10.5), mean APACHE II score of 21.0 (5.4), mean SOFA score of 9.9 (3.3), and ICU mortality rate of 22.6% (n=72). The strongest performing logistic model was the base model with MRC-ICU added, with AUROC of 0.72, positive predictive value (PPV) of 0.83, and negative prediction value (NPV) of 0.92. The strongest overall model was Random Forest with an AUROC of 0.78, a PPV of 0.53, and NPV of 0.90. Feature importance analysis using support vector machine and Random Forest revealed severity of illness scores and medication related data were the most important predictors.

Conclusions

Medication regimen complexity is significantly associated with prolonged duration of mechanical ventilation in critically ill patients, and prediction models incorporating medication information showed modest improvement in this prediction.

Oxygen Therapy Part 2 - Indications and Toxicity

Oxygen Therapy Part 2: Indications and ToxicityWemple et al. continue their review of oxygen therapy, discussing the acute and chronic indications for oxygen and the delivery of supplemental oxygen (and its potential adverse effects and toxicity).

The European guideline on management of major bleeding and coagulopathy following trauma: sixth edition

BACKGROUND

Severe trauma represents a major global public health burden and the management of post-traumatic bleeding continues to challenge healthcare systems around the world. Post-traumatic bleeding and associated traumatic coagulopathy remain leading causes of potentially preventable multiorgan failure and death if not diagnosed and managed in an appropriate and timely manner. This sixth edition of the European guideline on the management of major bleeding and coagulopathy following traumatic injury aims to advise clinicians who care for the bleeding trauma patient during the initial diagnostic and therapeutic phases of patient management.

METHODS

The pan-European, multidisciplinary Task Force for Advanced Bleeding Care in Trauma included representatives from six European professional societies and convened to assess and update the previous version of this guideline using a structured, evidence-based consensus approach. Structured literature searches covered the period since the last edition of the guideline, but considered evidence cited previously. The format of this edition has been adjusted to reflect the trend towards concise guideline documents that cite only the highest-quality studies and most relevant literature rather than attempting to provide a comprehensive literature review to accompany each recommendation.

RESULTS

This guideline comprises 39 clinical practice recommendations that follow an approximate temporal path for management of the bleeding trauma patient, with recommendations grouped behind key decision points. While approximately one-third of patients who have experienced severe trauma arrive in hospital in a coagulopathic state, a systematic diagnostic and therapeutic approach has been shown to reduce the number of preventable deaths attributable to traumatic injury.

CONCLUSION

A multidisciplinary approach and adherence to evidence-based guidelines are pillars of best practice in the management of severely injured trauma patients. Further improvement in outcomes will be achieved by optimising and standardising trauma care in line with the available evidence across Europe and beyond.

The Practice Change and Clinical Impact of Lung-Protective Ventilation Initiated in the Emergency Department: A Secondary Analysis of Individual Patient-Level Data From Prior Clinical Trials and Cohort Studies

OBJECTIVES

Mechanically ventilated emergency department (ED) patients experience high morbidity and mortality. In a prior trial at our center, ED-based lung-protective ventilation was associated with improved care delivery and outcomes. Whether this strategy has persisted in the years after the trial remains unclear. The objective was to assess practice change and clinical outcomes associated with ED lung-protective ventilation.

DESIGN

Secondary analysis of individual patient-level data from prior clinical trials and cohort studies.

SETTING

ED and ICUs of a single academic center.

PATIENTS

Mechanically ventilated adults.

INTERVENTIONS

A lung-protective ventilator protocol used as the default approach in the ED.

MEASUREMENTS AND MAIN RESULTS

The primary ventilator-related outcome was tidal volume, and the primary clinical outcome was hospital mortality. Secondary outcomes included ventilator-, hospital-, and ICU-free days. Multivariable logistic regression, propensity score (PS)-adjustment, and multiple a priori subgroup analyses were used to evaluate outcome as a function of the intervention. A total of 1,796 patients in the preintervention period and 1,403 patients in the intervention period were included. In the intervention period, tidal volume was reduced from 8.2 mL/kg predicted body weight (PBW) (7.3-9.1) to 6.5 mL/kg PBW (6.1-7.1), and low tidal volume ventilation increased from 46.8% to 96.2% ( p < 0.01). The intervention period was associated with lower mortality (35.9% vs 19.1%), remaining significant after multivariable logistic regression analysis (adjusted odds ratio [aOR], 0.43; 95% CI, 0.35-0.53; p < 0.01). Similar results were seen after PS adjustment and in subgroups. The intervention group had more ventilator- (18.8 [10.1] vs 14.1 [11.9]; p < 0.01), hospital- (12.2 [9.6] vs 9.4 [9.5]; p < 0.01), and ICU-free days (16.6 [10.1] vs 13.1 [11.1]; p < 0.01).

CONCLUSIONS

ED lung-protective ventilation has persisted in the years since implementation and was associated with improved outcomes. These data suggest the use of ED-based lung-protective ventilation as a means to improve outcome.

Changes of blood gas analysis in moderate-to-severe acute respiratory distress syndrome patients during long-term prone position ventilation: a retrospective cohort study

Background

Prone position ventilation (PPV) has been recommended for patients with acute respiratory distress syndrome (ARDS) to improve oxygenation. However, whether prolonged prone ventilation will aggravate hyperoxia and whether abdominal compression will aggravate permissive hypercapnia acidosis are topics of concern. We carried out a retrospective analysis to investigate the issues above.

Methods

Clinical data were collected from 97 moderate-to-severe ARDS patients who received PPV as part of their treatment in the intensive care unit (ICU) of the First Affiliated Hospital of Guangzhou Medical University from November 2015 to May 2021. We collected arterial blood gas of patients according to the 3 periods: supine position ventilation (SPV), PPV early stage (within 4 hours), and PPV middle and late stage (6 hours or later). We established a linear mixed-effects models with "body position changes, times of PPV, gender, age, baseline SOFA, and baseline APACHE II" as fixed effects, and individual and the number of prone positions as random intercept and random slope to investigate the effect of body position changes on blood gas analysis.

Results

Among the 97 patients received PPV included, 51 were ICU survivors. Arterial partial pressure of oxygen (PaO₂) and PaO₂/fraction of inspired oxygen (FiO₂) ratio were significantly higher at the early, middle and late stages of PPV than those in SPV [PFR (mmHg): 158 (118.00, 203.00) vs. 161 (129.00, 202.75) vs. 123 (91.75, 163.00), P<0.05]. Despite the synchronized reduction of FiO₂, the incidence of hyperoxia in the prone position was still significantly higher than that in the supine position [hyperoxia (%):33.33 vs. 33.56 vs. 12.42, P<0.05]; there was no significant change in arterial carbon dioxide partial pressure (PaCO₂) at each stage of PPV, but there was a significant increase in PH at PPV middle and late stages than those at early stage [PH: 7.39 (7.34, 7.42) vs. 7.37 (7.31, 7.41), P<0.05].

Conclusions

Although PPV improves the patients' oxygenation, the associated incidence of hyperoxia exceeds 33%. Down-regulate FiO₂ more sharply after PPV is necessary, if oxygenation conditions permit. PPV may alleviate the acidosis associated with permissive hypercapnia in ARDS patients treated with lung protective ventilation strategy (LPVS).

AA, Kudriaeva AA, Bugrimov DY, Krasnorutskaya ON, Murashev AN. Derinat® has an immunomodulatory and anti-inflammatory effect on the model of acute lung injury in male SD rats

To simulate acute lung injury (ALI) in SD male rats they we administered intratracheally with lipopolysaccharide (LPS) followed by hyperventilation of the lungs (HVL), which lead to functional changes in the respiratory system and an increase in the blood serum concentration of inflammatory cytokines. LPS + HVL after 4 h lead to pronounced histological signs of lung damage. We have studied the effectiveness of Derinat^® when administered intramuscularly at dose of 7.5 mg/kg for 8 days in the ALI model. Derinat^® administration lead to an increase in the concentration of most of the studied cytokines in a day. In the ALI model the administration of Derinat^® returned the concentration of cytokines to its original values already 48 h after LPS + HVL, and also normalized the parameters of pulmonary respiration in comparison with animals without treatment. By the eighth day after LPS + HVL, respiratory parameters and cytokine levels, as well as biochemical and hematological parameters did not differ between groups, while histological signs of residual effects of lung damage were found in all animals, and were more pronounced in Derinat^® group, which may indicate stimulation of the local immune response. Thus, the administration of Derinat^® stimulates the immune response, has a pronounced protective effect against cytokinemia and respiratory failure caused by ALI, has immunomodulatory effect, and also stimulates a local immune response in lung tissues. Thus, Derinat^® is a promising treatment for ALI.

Impact of age and sex on hyperoxia-induced cardiovascular pathophysiology

Hyperoxia is characterized by pronounced inflammatory responses, pulmonary cell apoptosis, and adverse cardiac remodeling due to an excess supply of oxygen. Hyperoxic episodes are frequent in mechanically ventilated patients and are associated with in-hospital mortality. This study extends the analysis of prior published research by our group as it investigates the influence of age in male and female rodents exposed to hyperoxic conditions. Age is an independent cardiovascular risk factor, often compounded by variables like obesity, diabetes, and a decline in sex hormones and their receptors. This study simulates clinical hyperoxia by subjecting rodents to > 90 % of oxygen for 72 h and compares the changes in cardiac structural and functional parameters with those exposed to normal air. While in both sexes conduction abnormalities with ageing were discernible, aged females owing to their inherent higher baseline QTc, were at a higher risk of developing arrhythmias as compared to age-matched males. Quantitative real-time RT-PCR and western blot analysis reflected altered expression of cardiac potassium channels, resulting in conduction abnormalities in aged female rodents. Unaffected by age and sex, hyperoxia-treated mice had altered body composition, as evidenced by a considerable reduction in body weight. Interestingly, compensatory hypertrophy observed as a protective mechanism in young males was absent in aged males, whereas protection of hearts from hyperoxia-induced cardiac hypertrophy was absent in aged female mice, both of which may be at least in part due to a reduction in sex steroid receptors and the systemic steroid levels. Finally, statistical analysis revealed that hyperoxia had the greatest impact on most of the cardiac parameters, followed by age and then sex. This data established an imperative finding that can change the provision of care for aged individuals admitted to ICU by elucidating the impact of intrinsic aging on hyperoxia-induced cardiac remodeling.

Closed–loop oxygen control improves oxygenation in pediatric patients under high–flow nasal oxygen—A randomized crossover study

Background

We assessed the effect of a closed–loop oxygen control system in pediatric patients receiving high–flow nasal oxygen therapy (HFNO).

Methods

A multicentre, single–blinded, randomized, and cross–over study. Patients aged between 1 month and 18 years of age receiving HFNO for acute hypoxemic respiratory failure (AHRF) were randomly assigned to start with a 2–h period of closed–loop oxygen control or a 2–h period of manual oxygen titrations, after which the patient switched to the alternative therapy. The endpoints were the percentage of time spent in predefined SpO2 ranges (primary), FiO2, SpO2/FiO2, and the number of manual adjustments.

Findings

We included 23 patients, aged a median of 18 (3–26) months. Patients spent more time in a predefined optimal SpO2 range when the closed–loop oxygen controller was activated compared to manual oxygen titrations [91⋅3% (IQR 78⋅4–95⋅1%) vs. 63⋅0% (IQR 44⋅4–70⋅7%)], mean difference [28⋅2% (95%–CI 20⋅6–37⋅8%); P &lt; 0.001]. Median FiO2 was lower [33⋅3% (IQR 26⋅6–44⋅6%) vs. 42⋅6% (IQR 33⋅6–49⋅9%); P = 0.07], but median SpO2/FiO2 was higher [289 (IQR 207–348) vs. 194 (IQR 98–317); P = 0.023] with closed–loop oxygen control. The median number of manual adjustments was lower with closed–loop oxygen control [0⋅0 (IQR 0⋅0–0⋅0) vs. 0⋅5 (IQR 0⋅0–1⋅0); P &lt; 0.001].

Conclusion

Closed-loop oxygen control improves oxygenation therapy in pediatric patients receiving HFNO for AHRF and potentially leads to more efficient oxygen use. It reduces the number of manual adjustments, which may translate into decreased workloads of healthcare providers.

Clinical trial registration

[www.ClinicalTrials.gov], identifier [NCT 05032365].

Hyperoxia by short-term promotes oxidative damage and mitochondrial dysfunction in rat brain

Oxygen (O₂) therapy is used as a therapeutic protocol to prevent or treat hypoxia. However, a high inspired fraction of O₂ (FIO₂) promotes hyperoxia, a harmful condition for the central nervous system (CNS). The present study evaluated parameters of oxidative stress and mitochondrial dysfunction in the brain of rats exposed to different FIO₂. Male Wistar rats were exposed to hyperoxia (FIO₂ 40 % and 60 %) compared to the control group (FIO₂ 21 %) for 2 h. Oxidative stress, neutrophilic infiltration, and mitochondrial respiratory chain enzymes were determined in the hippocampus, striatum, cerebellum, cortex, and prefrontal cortex after O₂ exposure. The animals exposed to hyperoxia showed increased lipid peroxidation, formation of carbonyl proteins, N/N concentration, and neutrophilic infiltration in some brain regions, like hippocampus, striatum, and cerebellum being the most affected. Furthermore, CAT activity and activity of mitochondrial enzyme complexes were also altered after exposure to hyperoxia. Rats exposed to hyperoxia showed increase in oxidative stress parameters and mitochondrial dysfunction in brain structures.

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.

Early Titration of Oxygen During Mechanical Ventilation Reduces Hyperoxemia in a Pilot, Feasibility, Randomized Control Trial for Automated Titration of Oxygen Levels

Timely regulation of oxygen (Fio₂) is essential to prevent hyperoxemia or episodic hypoxemia. Exposure to excessive Fio₂ is often noted early after onset of mechanical ventilation. In this pilot study, we examined the feasibility, safety, and efficacy of a clinical trial to prioritize Fio₂ titration with electronic alerts to respiratory therapists.

Recomendaciones para el uso de oxígeno y sus dispositivos básicos y avanzados: racionalidad y seguridad en tiempos de pandemia por SARS-CoV-2 en Colombia

En medio de la pandemia de COVID-19, y ante la inminencia de desabastecimiento de oxígeno en Colombia, la red de Gestión y Transferencia de Conocimiento, integrada por 19 sociedades científicas, instituciones de salud y universidades, genera una actualización al documento liderado por la Asociación Colombiana de Medicina Crítica e incluye nuevos lineamientos informados en evidencia para el manejo racional de la oxigenoterapia, así como los dispositivos básicos y avanzados para la oxigenoterapia. Las recomendaciones se refieren a: uso racional de oxígeno orientado por metas, estandarización del seguimiento y ajuste de dosis, uso adecuado de los dispositivos de oxigenoterapia, uso racional de ventilación mecánica invasiva y uso racional de la terapia con membrana de oxigenación extracorpórea. Al ejercer su juicio, se espera que los profesionales y equipos de atención tengan en cuenta estos lineamientos, con el fin de hacer un uso racional y seguro de la oxigenoterapia y sus dispositivos básicos y avanzados, junto con las necesidades individuales y preferencias de las personas que están bajo su cuidado.

The ability of Oxygen Reserve Index® to detect hyperoxia in critically ill patients

Background

Hyperoxia is associated with increased morbidity and mortality in the intensive care unit. Classical noninvasive measurements of oxygen saturation with pulse oximeters are unable to detect hyperoxia. The Oxygen Reserve Index (ORI) is a continuous noninvasive parameter provided by a multi-wave pulse oximeter that can detect hyperoxia. Primary objective was to evaluate the diagnostic accuracy of the ORI for detecting arterial oxygen tension (PaO₂) > 100 mmHg in neurocritical care patients. Secondary objectives were to test the ability of ORI to detect PaO₂ > 120 mmHg and the ability of pulse oximetry (SpO₂) to detect PaO₂ > 100 mmHg and PaO₂ > 120 mmHg.

Methods

In this single-center study, we collected ORI and arterial blood samples every 6 h for 3 consecutive days. Diagnostic performance was estimated using the area under the receiver operating characteristic curve (AUROC).

Results

There were 696 simultaneous measurements of ORI and PaO₂ in 62 patients. Considering the repeated measurements, the correlation between ORI and PaO₂ was r = 0.13. The area under the receiver operating characteristic curve (AUROC), obtained to test the ability of ORI to detect PaO₂ > 100 mmHg, was 0.567 (95% confidence interval = 0.566–0.569) with a sensitivity of 0.233 (95%CI = 0.230–0.235) and a specificity of 0.909 (95%CI = 0.907–0.910). The AUROC value obtained to test the ability of SpO₂ to detect a PaO₂ > 100 mmHg was 0.771 (95%CI = 0.770–0.773) with a sensitivity of 0.715 (95%CI = 0.712–0.718) and a specificity of 0.700 (95%CI = 0.697–0.703). The diagnostic performance of ORI and SpO₂ for detecting PaO₂ > 120 mmHg was AUROC = 0.584 (95%CI = 0.582–0.586) and 0.764 (95%CI = 0.762–0.766), respectively. The AUROC obtained for SpO₂ was significantly higher than that for ORI (p < 0.01). Diagnostic performance was not affected by sedation, norepinephrine infusion, arterial partial pressure of carbon dioxide, hemoglobin level and perfusion index.

Conclusion

In a specific population of brain-injured patients hospitalized in a neurointensive care unit, our results suggest that the ability of ORI to diagnose hyperoxia is relatively low and that SpO₂ provides better detection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-022-01012-w.

Supplemental oxygen administration during mechanical ventilation reduces diaphragm blood flow and oxygen delivery

During mechanical ventilation (MV), supplemental oxygen (O2) is commonly administered to critically ill patients to combat hypoxemia. Previous studies demonstrate that hyperoxia exacerbates MV-induced diaphragm oxidative stress and contractile dysfunction. Whereas normoxic MV (i.e., 21% O2) diminishes diaphragm perfusion and O2 delivery in the quiescent diaphragm, the effect of MV with 100% O2 is unknown. We tested the hypothesis that MV supplemented with hyperoxic gas (100% O2) would increase diaphragm vascular resistance and reduce diaphragmatic blood flow and O2 delivery to a greater extent than MV alone. Female Sprague-Dawley rats (4-6 mo) were randomly divided into two groups: 1) MV + 100% O2 followed by MV + 21% O2 (n = 9) or 2) MV + 21% O2 followed by MV + 100% O2 (n = 10). Diaphragmatic blood flow (mL/min/100 g) and vascular resistance were determined, via fluorescent microspheres, during spontaneous breathing (SB), MV + 100% O2, and MV + 21% O2. Compared with SB, total diaphragm vascular resistance was increased, and blood flow was decreased with both MV + 100% O2 and MV + 21% O2 (all P < 0.05). Medial costal diaphragmatic blood flow was lower with MV + 100% O2 (26 ± 6 mL/min/100 g) versus MV + 21% O2 (51 ± 15 mL/min/100 g; P < 0.05). Second, the addition of 100% O2 during normoxic MV exacerbated the MV-induced reductions in medial costal diaphragm perfusion (23 ± 7 vs. 51 ± 15 mL/min/100 g; P < 0.05) and O2 delivery (3.4 ± 0.2 vs. 6.4 ± 0.3 mL O2/min/100 g; P < 0.05). These data demonstrate that administration of supplemental 100% O2 during MV increases diaphragm vascular resistance and diminishes perfusion and O2 delivery to a significantly greater degree than normoxic MV. This suggests that prolonged bouts of MV (i.e., 6 h) with hyperoxia may accelerate MV-induced vascular dysfunction in the quiescent diaphragm and potentially exacerbate downstream contractile dysfunction.NEW & NOTEWORTHY This is the first study, to our knowledge, demonstrating that supplemental oxygen (i.e., 100% O2) during mechanical ventilation (MV) augments the MV-induced reductions in diaphragmatic blood flow and O2 delivery. The accelerated reduction in diaphragmatic blood flow with hyperoxic MV would be expected to potentiate MV-induced diaphragm vascular dysfunction and consequently, downstream contractile dysfunction. The data presented herein provide a putative mechanism for the exacerbated oxidative stress and diaphragm dysfunction reported with prolonged hyperoxic MV.

Early Outcomes of a High PaO2/FiO2 Ratio during Cardiopulmonary Bypass

Background: In cardiac surgery, supraphysiological oxygen levels are frequently applied perioperatively. In this study, we examined the postoperative effect of perioperative hyperoxemia in cardiac surgery. Methods: All patients who underwent mitral valve replacement via the standard sternotomy method between 2010 and 2021 were analyzed by scanning the hospital data system. The patients were divided into 2 groups: the hyperoxemic group (partial pressure of oxygen/fraction of inspired oxygen [PaO₂/FiO₂] > 500 mmHg) (Group I) and the normoxemic group (300 mmHg < PaO₂/FiO₂ < 500 mmHg) (Group II) according to the mean of 3 PaO₂/FiO₂ values calculated by using 3 PaO₂ and 3 FiO₂ levels. Postoperative complications, the mechanical ventilation time, the need for noninvasive mechanical ventilator support, the length of intensive care unit (ICU) stay, the hospitalization period, and the mortality rate of the groups were compared. Results: A total of 78 patients were included in the study, and 53 of the patients (67.9%) were female. The mean age of the patients was 58.89±12.60 years. The total mechanical ventilation time was significantly higher in the hyperoxemic group than in Group II (P<0.001) (18.18±12.90 h and 11.45±7.85 h, respectively). The amount of postoperative bleeding was significantly higher in Group I (P=0.003) (539.47±201.74 mL and 417.50±186.93 mL, respectively). The total amount of blood products administered during surgery and ICU stay was higher in Group I (P=0.041) (3.55±1.59 units and 2.87±1.89 units, respectively). Conclusion: We observed that the group with hyperoxemia during cardiopulmonary bypass had a higher amount of postoperative bleeding and the need for transfusion, as well as a longer duration of mechanical ventilation and intensive care.

Oxygen Targets During Mechanical Ventilation in the ICU: A Systematic Review and Meta-Analysis

Patients admitted to intensive care often require treatment with invasive mechanical ventilation and high concentrations of oxygen. Mechanical ventilation can cause acute lung injury that may be exacerbated by oxygen therapy. Uncertainty remains about which oxygen therapy targets result in the best clinical outcomes for these patients. This review aims to determine whether higher or lower oxygenation targets are beneficial for mechanically ventilated adult patients.

Oxygen therapy for sepsis and prevention of complications

Patients with sepsis have a wide range of respiratory disorders that can be treated with oxygen therapy. Experimental data in animal sepsis models show that oxygen therapy significantly increases survival, while clinical data on the use of different oxygen therapy protocols are ambiguous. Oxygen therapy, especially hyperbaric oxygenation, in patients with sepsis can aggravate existing oxidative stress and contribute to the development of disseminated intravascular coagulation. The purpose of this article is to compare experimental and clinical data on oxygen therapy in animals and humans, to discuss factors that can influence the results of oxygen therapy for sepsis treatment in humans, and to provide some recommendations for reducing oxidative stress and preventing disseminated intravascular coagulation during oxygen therapy.

Initiation of a Lung Protective Ventilation Strategy in the Emergency Department: Does an Emergency Department-Based ICU Make a Difference?

BACKGROUND:

Lung protective ventilation (LPV) is a key component in the management of acute respiratory distress syndrome and other acute respiratory pathology. Initiation of LPV in the emergency department (ED) is associated with improved patient-centered and system outcomes, but adherence to LPV among ED patients is low. The impact of an ED-based ICU (ED-ICU) on LPV adherence is not known.

METHODS:

This single-center, retrospective, cohort study analyzed rates of adherence to a multifaceted LPV strategy pre- and post-implementation of an ED-ICU. LPV strategy components included low tidal volume ventilation, avoidance of severe hyperoxia and high plateau pressures, and positive end-expiratory pressure settings in alignment with best-evidence recommendations. The primary outcome was adherence to the LPV strategy at time of ED departure.

RESULTS AND CONCLUSIONS:

A total of 561 ED visits were included in the analysis, of which 60.0% received some portion of their emergency care in the ED-ICU. Adherence to the LPV strategy was statistically significantly higher in the ED-ICU cohort compared with the pre-ED-ICU cohort (65.8% vs 41.4%; p < 0.001) and non-ED-ICU cohort (65.8% vs 43.1%; p < 0.001). Among the ED-ICU cohort, 92.8% of patients received low tidal volume ventilation. Care in the ED-ICU was also associated with shorter ICU and hospital length of stay. These findings suggest improved patient and resource utilization outcomes for mechanically ventilated ED patients receiving care in an ED-ICU.

Prehospital Mechanical Ventilation: An NAEMSP Position Statement and Resource Document

Airway emergencies and respiratory failure frequently occur in the prehospital setting. Patients undergoing advanced airway management customarily receive manual ventilations. However, manual ventilation is associated with hypo- and hyperventilation, variable tidal volumes, and barotrauma, among other potential complications. Portable mechanical ventilators offer an important strategy for optimizing ventilation and mitigating ventilatory complications.EMS clinicians, including those performing emergency response as well as interfacility transports, should consider using mechanical ventilation after advanced airway insertion.Prehospital mechanical ventilation techniques, strategies, and parameters should be disease-specific and should mirror in-hospital best practices.EMS clinicians must receive training in the general principles of mechanical ventilation as well as detailed training in the operation of the specific system(s) used by the EMS agency.Patients undergoing mechanical ventilation must receive appropriate sedation and analgesia.

Optimizing Physiology During Prehospital Airway Management: An NAEMSP Position Statement and Resource Document

Airway management is a critical component of resuscitation but also carries the potential to disrupt perfusion, oxygenation, and ventilation as a consequence of airway insertion efforts, the use of medications, and the conversion to positive-pressure ventilation. NAEMSP recommends:Airway management should be approached as an organized system of care, incorporating principles of teamwork and operational awareness.EMS clinicians should prevent or correct hypoxemia and hypotension prior to advanced airway insertion attempts.Continuous physiological monitoring must be used during airway management to guide the timing of, limit the duration of, and inform decision making during advanced airway insertion attempts.Initial and ongoing confirmation of advanced airway placement must be performed using waveform capnography. Airway devices must be secured using a reliable method.Perfusion, oxygenation, and ventilation should be optimized before, during, and after advanced airway insertion.To mitigate aspiration after advanced airway insertion, EMS clinicians should consider placing a patient in a semi-upright position.When appropriate, patients undergoing advanced airway placement should receive suitable pharmacologic anxiolysis, amnesia, and analgesia. In select cases, the use of neuromuscular blocking agents may be appropriate.

A high fraction of inspired oxygen may increase mortality in intubated trauma patients - A retrospective cohort study

BACKGROUND

Mechanical ventilation of trauma patients is common, and many will require a higher than normal fraction of inspired oxygen (FiO₂) to avoid hypoxaemia. The primary objective of this study was to assess the association between FiO₂ and all-cause, one-year mortality in intubated trauma patients.

METHODS

Adult trauma patients intubated in the initial phase post-trauma between 2015 and 2017 were retrospectively identified. Information on FiO₂ during the first 24 hours of hospitalisation and mortality was registered. For each patient the number of hours of the first 24 hours exposed to an FiO₂ ≥ 80%, ≥ 60%, and ≥ 40%, respectively, were determined and categorised into exposure durations. The associations of these FiO₂ exposures with mortality were evaluated using Cox regression adjusting for age, sex, body mass index (BMI), Injury Severity Score (ISS), prehospital Glasgow Coma Scale (GCS) score, and presence of thoracic injuries.

RESULTS

We included 218 intubated trauma patients. The median prehospital GCS score was 6 and the median ISS was 25. One-year mortality was significantly increased when patients had received an FiO₂ above 80% for 3-4 hours compared to <2 hours (hazard ratio (95% CI) 2.7 (1.3-6.0), p= 0.011). When an FiO₂ above 80% had been administered for more than 4 hours, there was a trend towards a higher mortality as well, but this was not statistically significant. There was a significant, time-dependent increase in mortality for patients who had received an FiO₂ ≥ 60%. There was no significant relationship observed between mortality and the duration of FiO₂ ≥ 40%.

CONCLUSION

A fraction of inspired oxygen above 60% for more than 2 hours during the first 24 hours of admission was associated with increased mortality in intubated trauma patients in a duration-dependent manner. However, given the limitations of this retrospective study, the findings need to be confirmed in a larger, randomized set-up.

The Evaluation of End Tidal Carbon Dioxide Values in Intubated Patients with COVID-19

BACKGROUND

The aim of this study is to establish the value of PETCO2 in COVID-19 patients intubated in emergency department, and its effects on mortality.  Objectives: Between May 15, 2020 and January 15, 2021, The patients aged ≥18 years and diagnosed COVID-19, scheduled for urgent intubation in the emergency department were included.

METHOD

Single-center, prospective and observational study. Age, gender, vital signs, laboratory findings are recorded. Immediately after intubation as measured by the capnography, the initial PETCO2_1 and at post-ventilation 15 min, PETCO2_2 and first, second arterial blood gas analysis are recorded.

RESULTS

The mean age of the 48 patients was 74 years. The PETCO2_1 and PETCO2_2 measurements were statistically significantly different between the patients who survived and those who died (p=0.014, p=0.015). The patients with a high first PETCO2_1 value and a decrease to the normal level survived, but those with a low PETCO2_1 value that could not increase to a normal value died (p=0.038, p=0.031). Increased levels of SpO2, PETCO2_1, PETCO2_2 and PaCO2_2 decreased the risk of mortality, while an increased level of PaO2_2 increased the risk of mortality.

CONCLUSION

Capnography is non-invasive and provides continuous measurement. Assessment of changes in PETCO2 value would contribute to patient survival.

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.

Effect of early hyperoxemia on mortality in mechanically ventilated septic shock patients according to Sepsis-3 criteria: analysis of the MIMIC-III database

BACKGROUND AND IMPORTANCE

Hyperoxemia may be associated with increased mortality in emergency room or ICU patients. However, its effect during septic shock is still debated.

OBJECTIVE

To evaluate the effect of hyperoxemia on ICU mortality, during the first 24 h of ICU stay, in mechanically ventilated patients with septic shock according to SEPSIS-3 criteria.

DESIGN, SETTINGS AND PARTICIPANTS

A retrospective cohort study of ICU admissions recorded in the Medical Information Mart for Intensive Care-III, a retrospective ICU database, was performed.

INTERVENTION

Two oxygen exposures during the first 24 h were compared: average PaO2 (TWA-PaO2) between 70 and 120 mmHg in the normoxemia group and above 120 mmHg in the hyperoxemia group.

OUTCOME MEASURES AND ANALYSIS

The primary outcome was mortality during ICU stay.

MAIN RESULTS

Four hundred eighty-eight ICU admissions met the inclusion criteria: 214 in the normoxemia group and 274 in the hyperoxemia group. The median TWA-PaO2 was 99.1 (88.9-107.6) mmHg in the normoxemia group and 151.5 (133.6-180.2) mmHg in the hyperoxemia group. ICU mortality was lower in the hyperoxemia group than in the normoxemia group in univariate analysis [29.6 vs. 39.7%, respectively; OR 0.64 (0.44-0.93); P = 0.024], but not in multivariate analysis [OR 0.98 (0.62-1.56); P = 0.93]. There was no difference between the two groups in ICU length of stay [8.0 (4.3-15.0) vs. 8.4 (4.7-15.0) days; P = 0.82].

CONCLUSION

We did not find any impact of early hyperoxemia on mortality in this population of mechanically ventilated patients with SEPSIS-3 septic shock criteria.

The implications of hyperoxia, type 1 diabetes and sex on cardiovascular physiology in mice

Oxygen supplementation, although a cornerstone of emergency and cardiovascular medicine, often results in hyperoxia, a condition characterized by excessive tissue oxygen which results in adverse cardiac remodeling and subsequent injurious effects to physiological function. Cardiac remodeling is further influenced by various risk factors, including pre-existing conditions and sex. Thus, the purpose of this experiment was to investigate cardiac remodeling in Type I Diabetic (Akita) mice subjected to hyperoxic treatment. Overall, we demonstrated that Akita mice experience distinct challenges from wild type (WT) mice. Specifically, Akita males at both normoxia and hyperoxia showed significant decreases in body and heart weights, prolonged PR, QRS, and QTc intervals, and reduced %EF and %FS at normoxia compared to WT controls. Moreover, Akita males largely resemble female mice (both WT and Akita) with regards to the parameters studied. Finally, statistical analysis revealed hyperoxia to have the greatest influence on cardiac pathophysiology, followed by sex, and finally genotype. Taken together, our data suggest that Type I diabetic patients may have distinct cardiac pathophysiology under hyperoxia compared to uncomplicated patients, with males being at high risk. These findings can be used to enhance provision of care in ICU patients with Type I diabetes as a comorbid condition.

The Impact of Hyperoxia Treatment on Neurological Outcomes and Mortality in Moderate to Severe Traumatic Brain Injured Patients

Background

Traumatic brain injury is a leading cause of morbidity and mortality worldwide. The relationship between hyperoxia and outcomes in patients with TBI remains controversial. We assessed the effect of persistent hyperoxia on the neurological outcomes and survival of critically ill patients with moderate-severe TBI.

Method

This was a retrospective cohort study of all adults with moderate-severe TBI admitted to the ICU between 1st January 2016 and 31st December 2019 and who required invasive mechanical ventilation. Arterial blood gas data was recorded within the first 3 hours of intubation and then after 6-12 hours and 24-48 hours. The patients were divided into two categories: Group I had a PaO2 < 120mmHg on at least two ABGs undertaken in the first twelve hours post intubation and Group II had a PaO2 ≥ 120mmHg on at least two ABGs in the same period. Multivariable logistic regression was performed to assess predictors of hospital mortality and good neurologic outcome (Glasgow outcome score ≥ 4).

Results

The study included 309 patients: 54.7% (n=169) in Group I and 45.3% (n=140) in Group II. Hyperoxia was not associated with increased mortality in the ICU (20.1% vs. 17.9%, p=0.62) or hospital (20.7% vs. 17.9%, p=0.53), moreover, the hospital discharge mean (SD) Glasgow Coma Scale (11.0(5.1) vs. 11.2(4.9), p=0.70) and mean (SD) Glasgow Outcome Score (3.1(1.3) vs. 3.1(1.2), p=0.47) were similar. In multivariable logistic regression analysis, persistent hyperoxia was not associated with increased mortality (adjusted odds ratio [aOR] 0.71, 95% CI 0.34-1.35, p=0.29). PaO2 within the first 3 hours was also not associated with mortality: 121-200mmHg: aOR 0.58, 95% CI 0.23-1.49, p=0.26; 201-300mmHg: aOR 0.66, 95% CI 0.27-1.59, p=0.35; 301-400mmHg: aOR 0.85, 95% CI 0.31-2.35, p=0.75 and >400mmHg: aOR 0.51, 95% CI 0.18-1.44, p=0.20; reference: PaO2 60-120mmHg within 3 hours. However, hyperoxia >400mmHg was associated with being less likely to have good neurological (GOS ≥4) outcome on hospital discharge (aOR 0.36, 95% CI 0.13-0.98, p=0.046; reference: PaO2 60-120mmHg within 3 hours.

Conclusion

In intubated patients with moderate-severe TBI, hyperoxia in the first 48 hours was not independently associated with hospital mortality. However, PaO2 >400mmHg may be associated with a worse neurological outcome on hospital discharge.

Incidence of hyperoxia in trauma patients receiving pre-hospital emergency anaesthesia: results of a 5-year retrospective analysis

Background

Previous studies have demonstrated an association between hyperoxia and increased mortality in various patient groups. Critically unwell and injured patients are routinely given high concentration oxygen in the pre-hospital phase of care. We aim to investigate the incidence of hyperoxia in major trauma patients receiving pre-hospital emergency anesthesia (PHEA) in the pre-hospital setting and determine factors that may help guide clinicians with pre-hospital oxygen administration in these patients.

Methods

A retrospective cohort study was performed of all patients who received PHEA by a single helicopter emergency medical service (HEMS) between 1 October 2014 and 1 May 2019 and who were subsequently transferred to one major trauma centre (MTC). Patient and treatment factors were collected from the electronic patient records of the HEMS service and the MTC. Hyperoxia was defined as a PaO₂ > 16 kPA on the first arterial blood gas analysis upon arrival in the MTC.

Results

On arrival in the MTC, the majority of the patients (90/147, 61.2%) had severe hyperoxia, whereas 30 patients (20.4%) had mild hyperoxia and 26 patients (19.7%) had normoxia. Only 1 patient (0.7%) had hypoxia. The median PaO₂ on the first arterial blood gas analysis (ABGA) after HEMS handover was 36.7 [IQR 18.5–52.2] kPa, with a range of 7.0–86.0 kPa. SpO₂ pulse oximetry readings before handover were independently associated with the presence of hyperoxia. An SpO₂ ≥ 97% was associated with a significantly increased odds of hyperoxia (OR 3.99 [1.58–10.08]), and had a sensitivity of 86.7% [79.1–92.4], a specificity of 37.9% [20.7–57.8], a positive predictive value of 84.5% [70.2–87.9] and a negative predictive value of 42.3% [27.4–58.7] for the presence of hyperoxemia.

Conclusion

Trauma patients who have undergone PHEA often have profound hyperoxemia upon arrival at hospital. In the pre-hospital setting, where arterial blood gas analysis is not readily available a titrated approach to oxygen therapy should be considered to reduce the incidence of potentially harmful tissue hyperoxia.

Hyperoxaemia and hypoxaemia are associated with harm in patients with ARDS

BACKGROUND

Oxygen therapy is routinely administered to mechanically ventilated patients. However, there remains uncertainty about the optimal oxygen titration target in patients with the acute respiratory distress syndrome (ARDS).

METHODS

Prospectively identified adult patients meeting the Berlin definition of ARDS between 1st January 2014 and 13th December 2016 were analyzed. Oxygen exposure variables were collected at 6-hourly intervals. The primary exposure was the average time-weighted partial pressure of arterial oxygen (PaO2) calculated over a maximum of 7 days from meeting ARDS criteria. The primary outcome was ICU mortality. Univariable and multivariable logistic regression analyses were performed to assess the impact of exposure variables on clinical outcomes. Results are presented as odds ratio [95% confidence interval].

RESULTS

202 patients were included in the final analysis. Overall ICU mortality was 31%. The average time-weighted PaO2 during the first 7 days of ARDS was similar between non-survivors and survivors (11.3 kPa [10.2, 12.5] (84.8 mmHg [76.5, 93.8]) vs. 11.9 kPa [10.9, 12.6] (89.3 mmHg [81.8, 94.5]); p = 0.08). In univariable and multivariable analysis, average time-weighted PaO2 demonstrated a U-shaped relationship with ICU mortality. There was a similar relationship identified with hospital mortality.

CONCLUSIONS

In patients with ARDS, the predicted probability of both ICU and hospital mortality was lowest when the average time-weighted PaO2 was between 12.5 and 14 kPa (93.8-105.0 mmHg), suggesting this is a reasonable oxygenation target for clinicians to aim for.

Variable oxygen administration in surgical and medical wards evaluated by 30-day mortality-An observational study

BACKGROUND

Several studies in surgery and initial management of critical illness have indicated harmful effects of short-term exposure to hyperoxia. Exposure to and consequences of excessive oxygen administration in hospital wards are sparsely investigated. The aim of this study was to investigate the association between excessive oxygen administration in patients admitted to surgical or medical wards and 30-day mortality.

METHODS

We included patients in the Capital Region of Denmark who were admitted to hospital in 2014 for either myocardial infarction, acute exacerbation of chronic obstructive pulmonary disease (COPD), hip fracture or open abdominal surgery. We defined groups of inadequate, adequate or excessive oxygen administration based on peripheral oxygen saturation and oxygen administration values in the first 48 hours after admission. The primary outcome was mortality within 30 days, and data were analysed with multivariable logistic regression for age, gender and comorbidities.

RESULTS

We retrieved data from 11 196 patients, of which 81% had adequate, 18% had excessive and 1.8% inadequate oxygen administration. Mortality at 30 days was 4.2%, 7.6% and 27%, respectively, OR 1.46 (95%CI 1.16-1.84), P = .001 for patients with excessive compared to adequate oxygen administration. The association was significant in subgroups of patients admitted for acute exacerbation of COPD (OR 1.67, 95%CI 1.19-2.34) and myocardial infarction (OR 3.50, 95%CI 1.55-7.89).

CONCLUSION

Patients who received excessive oxygen administration in surgical and medical wards during the first 48 hours of admission had a higher mortality risk within 30 days compared to patients with adequate oxygen administration. However, inadequate oxygen therapy still renders highest mortality and should be avoided.

Target arterial PO2 according to the underlying pathology: a mini-review of the available data in mechanically ventilated patients

There is an ongoing discussion whether hyperoxia, i.e. ventilation with high inspiratory O2 concentrations (FIO2), and the consecutive hyperoxaemia, i.e. supraphysiological arterial O2 tensions (PaO2), have a place during the acute management of circulatory shock. This concept is based on experimental evidence that hyperoxaemia may contribute to the compensation of the imbalance between O2 supply and requirements. However, despite still being common practice, its use is limited due to possible oxygen toxicity resulting from the increased formation of reactive oxygen species (ROS) limits, especially under conditions of ischaemia/reperfusion. Several studies have reported that there is a U-shaped relation between PaO2 and mortality/morbidity in ICU patients. Interestingly, these mostly retrospective studies found that the lowest mortality coincided with PaO2 ~ 150 mmHg during the first 24 h of ICU stay, i.e. supraphysiological PaO2 levels. Most of the recent large-scale retrospective analyses studied general ICU populations, but there are major differences according to the underlying pathology studied as well as whether medical or surgical patients are concerned. Therefore, as far as possible from the data reported, we focus on the need of mechanical ventilation as well as the distinction between the absence or presence of circulatory shock. There seems to be no ideal target PaO2 except for avoiding prolonged exposure (> 24 h) to either hypoxaemia (PaO2 < 55-60 mmHg) or supraphysiological (PaO2 > 100 mmHg). Moreover, the need for mechanical ventilation, absence or presence of circulatory shock and/or the aetiology of tissue dysoxia, i.e. whether it is mainly due to impaired macro- and/or microcirculatory O2 transport and/or disturbed cellular O2 utilization, may determine whether any degree of hyperoxaemia causes deleterious side effects.

Determining a target SpO2 to maintain PaO2 within a physiological range

OBJECTIVE

In the context of an ongoing debate on the potential risks of hypoxemia and hyperoxemia, it seems prudent to maintain the partial arterial oxygen pressure (PaO2) in a physiological range during administration of supplemental oxygen. The PaO2 and peripheral oxygen saturation (SpO2) are closely related and both are used to monitor oxygenation status. However, SpO2 values cannot be used as an exact substitute for PaO2. The aim of this study in acutely ill and stable patients was to determine at which SpO2 level PaO2 is more or less certain to be in the physiological range.

METHODS

This is an observational study prospectively collecting data pairs of PaO2 and SpO2 values in patients admitted to the emergency room or intensive care unit (Prospective Inpatient Acutely ill cohort; PIA cohort). A second cohort of retrospective data of patients who underwent pulmonary function testing was also included (Retrospective Outpatient Pulmonary cohort; ROP cohort). Arterial hypoxemia was defined as PaO2 < 60 mmHg and hyperoxemia as PaO2 > 125 mmHg. The SpO2 cut-off values with the lowest risk of hypoxemia and hyperoxemia were determined as the 95th percentile of the observed SpO2 values corresponding with the observed hypoxemic and hyperoxemic PaO2 values.

RESULTS

220 data pairs were collected in the PIA cohort. 95% of hypoxemic PaO2 measurements occurred in patients with an SpO2 below 94%, and 95% of hyperoxemic PaO2 measurements occurred in patients with an SpO2 above 96%. Additionally in the 1379 data pairs of the ROP cohort, 95% of hypoxemic PaO2 measurements occurred in patients with an SpO2 below 93%.

CONCLUSION

The SpO2 level marking an increased risk of arterial hypoxemia is not substantially different in acutely ill versus stable patients. In acutely ill patients receiving supplemental oxygen an SpO2 target of 95% maximizes the likelihood of maintaining PaO2 in the physiological range.

Electronic Medical Record-Based Pager Notification Reduces Excess Oxygen Exposure in Mechanically Ventilated Subjects

BACKGROUND

Liberal oxygenation during mechanical ventilation is harmful in critically ill patients and in certain subsets of patients, including those with stroke, acute myocardial infarction, and cardiac arrest. Surveillance through electronic medical records improves safety of mechanical ventilation in the ICU. To date, this practice has not been used for oxygen titration ([Formula: see text]) in adults. We hypothesize that a surveillance system based on the electronic medical record to alert respiratory therapists to titrate [Formula: see text] is feasible, safe, and efficacious.

METHODS

In this pilot study, mechanically ventilated subjects were randomized to respiratory therapist-driven [Formula: see text] titration after an electronic alert versus standard of care (ie, titration based on physician order). An automated surveillance system utilizing a hyperoxemia-detection algorithm generated an electronic alert to a respiratory therapist's pager. Hyperoxemia was defined as [Formula: see text] > 0.5 and [Formula: see text] > 95% for > 30 min. No other aspects of treatment were changed. We assessed feasibility, safety, and preliminary efficacy. Primary outcome was duration of hyperoxemia during mechanical ventilation. An unsafe outcome was identified as hypoxemia ([Formula: see text] < 88%) within 1 h after titration per alert. Feasibility was assessed by a survey of respiratory therapists.

RESULTS

Of 226 randomized subjects, 31 were excluded (eg, programming errors of the electronic alerts, no consent, physician discretion). We included 195 subjects, of whom 86 were in the intervention arm. Alert accuracy was 78%, and respiratory therapists responded to 64% of the alerts. During mechanical ventilation, exposure to hyperoxemia significantly decreased in the intervention group (median 13.5 h [interquartile range 6.2-29.4] vs 18.8 h [interquartile range 9.6-37.4]). No episodes of significant hypoxemia were registered. Most respiratory therapists agreed that the alert was helpful in reducing excessive oxygen exposure.

CONCLUSIONS

Use of an electronic surveillance system to titrate [Formula: see text] was safe and feasible and showed preliminary efficacy in reducing hyperoxemia. Our study serves to justify larger randomized controlled trials for [Formula: see text] titration.

[Oxygen therapy in emergency and intensive care medicine]

Oxygen treatment is being widely used in intensive care and emergency medicine and is required to maintain aerobic metabolism. It may be administered by nasal cannula, face mask, high-flow therapy, and by ventilation. Under clinical circumstances, blood oxygen concentration is not relevantly increased above a partial pressure of 80 mmHg. Although oxygen therapy is often life-saving, it has recently been shown that its indiscriminate administration may increase morbidity and mortality, presumably due to a formation of reactive-oxygen species.For ventilated critically ill patients the optimal targets need to be further defined but harm has been shown for mild hyperoxia. For patients with acute exacerbation of chronic obstructive lung disease hyperoxia may lead to an increase of hypercarbia. Hyperoxia may increase myocardial necrosis in myocardial infarction. For patients with stroke, data do not show any benefit or harm from oxygen administration.On the other hand, hyperoxia shall be used for treatment in patients with cardiac arrest until return of spontaneous circulation and in patients with carbon monoxide poisoning.For other conditions, no benefit has been shown for hyperoxia, but undoubtedly, hypoxemia must be avoided, as well. Therefore, a normoxic oxygenation strategy should be employed. The optimal oxygenation targets for distinct conditions need to be further defined.

Effect of Blood Pressure Variability on Outcomes in Emergency Patients with Intracranial Hemorrhage

Introduction

Patients with spontaneous intracranial hemorrhage (sICH) have high mortality and morbidity, which are associated with blood pressure variability. Additionally, blood pressure variability is associated with acute kidney injury (AKI) in critically ill patients, but its association with sICH patients in emergency departments (ED) is unclear. Our study investigated the association between blood pressure variability in the ED and the risk of developing AKI during sICH patients’ hospital stay.

Methods

We retrospectively analyzed patients with sICH, including those with subarachnoid and intraparenchymal hemorrhage, who were admitted from any ED and who received an external ventricular drain at our academic center. Patients were identified by the International Classification of Diseases, Ninth Revision (ICD-9). Outcomes were the development of AKI, mortality, and being discharged home. We performed multivariable logistic regressions to measure the association of clinical factors and interventions with outcomes.

Results

We analyzed the records of 259 patients: 71 (27%) patients developed AKI, and 59 (23%) patients died. Mean age (± standard deviation [SD]) was 58 (14) years, and 150 (58%) were female. Patients with AKI had significantly higher blood pressure variability than patients without AKI. Each millimeter of mercury increment in one component of blood pressure variability, SD in systolic blood pressure (SBP_SD), was significantly associated with 2% increased likelihood of developing AKI (odds ratio [OR] 1.02, 95% confidence interval [CI], 1.005–1.03, p = 0.007). Initiating nicardipine infusion in the ED (OR 0.35, 95% CI, 0.15–0.77, p = 0.01) was associated with lower odds of in-hospital mortality. No ED interventions or blood pressure variability components were associated with patients’ likelihood to be discharged home.

Conclusion

Our study suggests that greater SBP_SD during patients’ ED stay is associated with higher likelihood of AKI, while starting nicardipine infusion is associated with lower odds of in-hospital mortality. Further studies about interventions and outcomes of patients with sICH in the ED are needed to confirm our observations.

Emergency Department Management of Severe Hypoxemic Respiratory Failure in Adults With COVID-19

Background

While emergency physicians are familiar with the management of hypoxemic respiratory failure, management of mechanical ventilation and advanced therapies for oxygenation in the emergency department have become essential during the coronavirus disease 2019 (COVID-19) pandemic.

Objective

We review the current evidence on hypoxemia in COVID-19 and place it in the context of known evidence-based management of hypoxemic respiratory failure in the emergency department.

Discussion

COVID-19 causes mortality primarily through the development of acute respiratory distress syndrome (ARDS), with hypoxemia arising from shunt, a mismatch of ventilation and perfusion. Management of patients developing ARDS should focus on mitigating derecruitment and avoiding volutrauma or barotrauma.

Conclusions

High flow nasal cannula and noninvasive positive pressure ventilation have a more limited role in COVID-19 because of the risk of aerosolization and minimal benefit in severe cases, but can be considered. Stable patients who can tolerate repositioning should be placed in a prone position while awake. Once intubated, patients should be managed with ventilation strategies appropriate for ARDS, including targeting lung-protective volumes and low pressures. Increasing positive end-expiratory pressure can be beneficial. Inhaled pulmonary vasodilators do not decrease mortality but may be given to improve refractory hypoxemia. Prone positioning of intubated patients is associated with a mortality reduction in ARDS and can be considered for patients with persistent hypoxemia. Neuromuscular blockade should also be administered in patients who remain dyssynchronous with the ventilator despite adequate sedation. Finally, patients with refractory severe hypoxemic respiratory failure in COVID-19 should be considered for venovenous extracorporeal membrane oxygenation.

The Oxygen Reserve Index as a determinant of the necessary amount of postoperative supplemental oxygen

BACKGROUND

Although blood gas analysis (BGA) is important for supplemental oxygen titration, it is invasive, intermittent, costly, and burdensome for staff. We assessed whether the Oxygen Reserve Index (ORi™), a novel pulse oximeter-based index that reflects the partial pressure of oxygen (PaO<inf>2</inf>), could determine the amount of postoperative supplemental oxygen. We also evaluated the extent of hyperoxia and hypoxia.

METHODS

Fifty patients scheduled to undergo breast surgery were randomly assigned to receive ORi-based oxygen (group O) or conventional postoperative oxygen (group C) treatments. Postoperatively, patients were transported to the Post-Anesthesia Care Unit (PACU) and then to general wards. In group O, oxygen was administered at 4 L·min^-1 in the operation room after extubation and was decreased if the ORi was >0.00 until a continuous index of 0.00 was achieved for 30 min in the PACU and wards. In group C, oxygen was administered at 4 L·min^-1 throughout the evaluation period. BGA was performed 1 h after anesthesia induction (T0), after extubation (T1), before PACU exit (T2), and on the first postoperative morning (T3). Percutaneous oxygen saturation was measured every two seconds from 9 PM after surgery to 6 AM the next morning.

RESULTS

The supplemental oxygen amount and PaO<inf>2</inf> were significantly lower in group O than group C at T2 (1.5 [0.5-3.0] vs. 4.0 [4.0-4.0] L/min, 117.3 [26.8] vs. 170.0 [42.8] mmHg) and T3 (1.0 [0.5-3.0] vs. 4.0 [4.0-4.0] L/min, 107.5 [16.5] vs. 157.1 [28.4] mmHg; median [interquartile ranges] and mean [1 SD]; P<0.01). No patient exhibited hypoxia.

CONCLUSIONS

Based on our results, ORi might be useful to titrate postoperative oxygen supplementation.

Early hyperoxemia is associated with lower adjusted mortality after severe trauma: results from a French registry

BACKGROUND

Hyperoxemia has been associated with increased mortality in critically ill patients, but little is known about its effect in trauma patients. The objective of this study was to assess the association between early hyperoxemia and in-hospital mortality after severe trauma. We hypothesized that a PaO2 ≥ 150 mmHg on admission was associated with increased in-hospital mortality.

METHODS

Using data issued from a multicenter prospective trauma registry in France, we included trauma patients managed by the emergency medical services between May 2016 and March 2019 and admitted to a level I trauma center. Early hyperoxemia was defined as an arterial oxygen tension (PaO2) above 150 mmHg measured on hospital admission. In-hospital mortality was compared between normoxemic (150 > PaO2 ≥ 60 mmHg) and hyperoxemic patients using a propensity-score model with predetermined variables (gender, age, prehospital heart rate and systolic blood pressure, temperature, hemoglobin and arterial lactate, use of mechanical ventilation, presence of traumatic brain injury (TBI), initial Glasgow Coma Scale score, Injury Severity Score (ISS), American Society of Anesthesiologists physical health class > I, and presence of hemorrhagic shock).

RESULTS

A total of 5912 patients were analyzed. The median age was 39 [26-55] years and 78% were male. More than half (53%) of the patients had an ISS above 15, and 32% had traumatic brain injury. On univariate analysis, the in-hospital mortality was higher in hyperoxemic patients compared to normoxemic patients (12% versus 9%, p < 0.0001). However, after propensity score matching, we found a significantly lower in-hospital mortality in hyperoxemic patients compared to normoxemic patients (OR 0.59 [0.50-0.70], p < 0.0001).

CONCLUSION

In this large observational study, early hyperoxemia in trauma patients was associated with reduced adjusted in-hospital mortality. This result contrasts the unadjusted in-hospital mortality as well as numerous other findings reported in acutely and critically ill patients. The study calls for a randomized clinical trial to further investigate this association.

Automatic oxygen administration and weaning in patients following mechanical ventilation

PURPOSE

To evaluate efficacy of FreeO2 device in oxygen weaning of patients after being liberated from mechanical ventilation (MV).

METHODS

Prospective crossover cohort study in patients admitted to ICU and after MV weaning. FreeO2 curves were recorded during constant flow and FreeO2 modes. Oxygenation parameters and O2 consumption were assessed.

RESULTS

Fifty one records were obtained in 51 patients (median age, 62 years, 54.9% had COPD, admission for acute respiratory failure in 96%). NIV was used initially in 68.6%. For a median records duration of 2.04 h, the time spent within target SpO2 range was significantly higher with FreeO2 mode compared to constant O2 flow mode [86.92% (77.11-92.39) vs 43.17% (5.08-75.37); p < 0.001]. Time with hyperoxia was lower with FreeO2 mode: 8.68% (2.96-15.59) vs 38.28% (2.02-86.34). Times with hypoxaemia, and with severe desaturation, were similar. At the end of FreeO2 mode, O2 flow was lower than 1 l/min in 28 patients (54.9%), with a median of 0.99 l/min.

CONCLUSIONS

For the purpose of oxygen weaning in patients recovering from MV, automatic O2 titration with FreeO2 was associated with a substantial reduction in O2 delivery and better oxygenation parameters in comparison with constant O2 flow.

Interactions among Genetic Background, Anesthetic Agent, and Oxygen Concentration Shape Blunt Traumatic Brain Injury Outcomes in Drosophila melanogaster

Following traumatic brain injury (TBI), the time window during which secondary injuries develop provides a window for therapeutic interventions. During this time, many TBI victims undergo exposure to hyperoxia and anesthetics. We investigated the effects of genetic background on the interaction of oxygen and volatile general anesthetics with brain pathophysiology after closed-head TBI in the fruit fly Drosophila melanogaster. To test whether sevoflurane shares genetic risk factors for mortality with isoflurane and whether locomotion is affected similarly to mortality, we used a device that generates acceleration–deceleration forces to induce TBI in ten inbred fly lines. After TBI, we exposed flies to hyperoxia alone or in combination with isoflurane or sevoflurane and quantified mortality and locomotion 24 and 48 h after TBI. Modulation of TBI–induced mortality and locomotor impairment by hyperoxia with or without anesthetics varied among fly strains and among combinations of agents. Resistance to increased mortality from hyperoxic isoflurane predicted resistance to increased mortality from hyperoxic sevoflurane but did not predict the degree of locomotion impairment under any condition. These findings are important because they demonstrate that, in the context of TBI, genetic background determines the latent toxic potentials of oxygen and anesthetics.

The management of coronavirus disease 2019 (COVID-19)

In December 2019, a novel coronavirus causing severe acute respiratory disease occurred in Wuhan, China. It is an emerging infectious disease with widespread and rapid infectiousness. The World Health Organization declared the coronavirus outbreak to be a public health emergency of international concern on 31 January 2020. Severe COVID-19 patients should be managed and treated in a critical care unit. Performing a chest X-ray/CT can judge the severity of the disease. The management of COVID-19 patients includes epidemiological risk and patient isolation; treatment entails general supportive care, respiratory support, symptomatic treatment, nutritional support, psychological intervention, etc. The prognosis of the patients depends upon the severity of the disease, the patient's age, the underlying diseases of the patients, and the patient's overall medical condition. The management of COVID-19 should focus on early diagnosis, immediate isolation, general and optimized supportive care, and infection prevention and control.

Investigating Disturbances of Oxygen Homeostasis: From Cellular Mechanisms to the Clinical Practice

Soon after its discovery in the 18th century, oxygen was applied as a therapeutic agent to treat severely ill patients. Lack of oxygen, commonly termed as hypoxia, is frequently encountered in different disease states and is detrimental to human life. However, at the end of the 19th century, Paul Bert and James Lorrain Smith identified what is known as oxygen toxicity. The molecular basis of this phenomenon is oxygen's readiness to accept electrons and to form different variants of aggressive radicals that interfere with normal cell functions. The human body has evolved to maintain oxygen homeostasis by different molecular systems that are either activated in the case of oxygen under-supply, or to scavenge and to transform oxygen radicals when excess amounts are encountered. Research has provided insights into cellular mechanisms of oxygen homeostasis and is still called upon in order to better understand related diseases. Oxygen therapy is one of the prime clinical interventions, as it is life saving, readily available, easy to apply and economically affordable. However, the current state of research also implicates a reconsidering of the liberal application of oxygen causing hyperoxia. Increasing evidence from preclinical and clinical studies suggest detrimental outcomes as a consequence of liberal oxygen therapy. In this review, we summarize concepts of cellular mechanisms regarding different forms of disturbed cellular oxygen homeostasis that may help to better define safe clinical application of oxygen therapy.