Clinicians' response to hyperoxia in ventilated patients in a Dutch ICU depends on the level of FiO2

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 [Pa o2 ], arterial oxygen saturation [Sa o2 ]/peripheral oxygen saturation [Sp o2 ], or inspiratory oxygen concentration [Fi o2 ] 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 I 2 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.

Hyperoxemia among Pediatric Intensive Care Unit Patients Receiving Oxygen Therapy

Supratherapeutic oxygen levels consistently cause oxygen toxicity in the lungs and other organs. The prevalence and severity of hyperoxemia among pediatric intensive care unit (PICU) patients remain unknown. This was the first study to examine the prevalence and duration of hyperoxemia in PICU patients receiving oxygen therapy. This is a retrospective chart review. This was performed in a setting of 36-bed PICU in a quaternary-care children's hospital. All the patients were children aged <18 years, admitted to the PICU for ≥24 hours, receiving oxygen therapy for ≥12 hours who had at least one arterial blood gas during this time. There was no intervention. Of 5,251 patients admitted to the PICU, 614 were included in the study. On average, these patients received oxygen therapy for 91% of their time in the PICU and remained hyperoxemic, as measured by pulse oximetry, for 65% of their time on oxygen therapy. Patients on oxygen therapy remained hyperoxemic for a median of 38 hours per patient and only 1.1% of patients did not experience any hyperoxemia. Most of the time (87.5%) patients received oxygen therapy through a fraction of inspired oxygen (FiO 2 )-adjustable device. Mean FiO 2 on noninvasive support was 0.56 and on invasive support was 0.37. Mean partial pressure of oxygen (PaO 2 ) on oxygen therapy was 108.7 torr and 3,037 (42.1%) of PaO 2 measurements were >100 torr. Despite relatively low FiO 2 , PICU patients receiving oxygen therapy are commonly exposed to prolonged hyperoxemia, which may contribute to ongoing organ injury.

Hyperoxemia in invasively ventilated COVID-19 patients-Insights from the PRoVENT-COVID study

OBJECTIVE

We determined the prevalences of hyperoxemia and excessive oxygen use, and the epidemiology, ventilation characteristics and outcomes associated with hyperoxemia in invasively ventilated patients with coronavirus disease 2019 (COVID-19).

METHODS

Post hoc analysis of a national, multicentre, observational study in 22 ICUs. Patients were classified in the first two days of invasive ventilation as 'hyperoxemic' or 'normoxemic'. The co-primary endpoints were prevalence of hyperoxemia (PaO2 > 90 mmHg) and prevalence of excessive oxygen use (FiO2 ≥ 60% while PaO2 > 90 mmHg or SpO2 > 92%). Secondary endpoints included ventilator settings and ventilation parameters, duration of ventilation, length of stay (LOS) in ICU and hospital, and mortality in ICU, hospital, and at day 28 and 90. We used propensity matching to control for observed confounding factors that may influence endpoints.

RESULTS

Of 851 COVID-19 patients, 225 (26.4%) were classified as hyperoxemic. Excessive oxygen use occurred in 385 (45.2%) patients. Acute respiratory distress syndrome (ARDS) severity was lowest in hyperoxemic patients. Hyperoxemic patients were ventilated with higher positive end-expiratory pressure (PEEP), while rescue therapies for hypoxemia were applied more often in normoxemic patients. Neither in the unmatched nor in the matched analysis were there differences between hyperoxemic and normoxemic patients with regard to any of the clinical outcomes.

CONCLUSION

In this cohort of invasively ventilated COVID-19 patients, hyperoxemia occurred often and so did excessive oxygen use. The main differences between hyperoxemic and normoxemic patients were ARDS severity and use of PEEP. Clinical outcomes were not different between hyperoxemic and normoxemic patients.

Effect of postoperative oxygen therapy regimen modification on oxygenation in patients with acute type A aortic dissection

Objective

In this study, we investigated the effect of various oxygen therapy regimens on oxygenation in patients with acute type A aortic dissection (AAD).

Methods

A quasi-randomized controlled trial was conducted, in which patients with AAD hospitalized for surgery from June to September 2021 were assigned to the control group (patients received conventional oxygen therapy after postoperative mechanical ventilation, weaning, and extubation) and those who were admitted from October to December 2021 were assigned to the observation group [patients underwent optimally adjusted therapy based on the treatment of the control group, which mainly included prioritized elevation of positive end-expiratory pressure (PEEP) and restricted use of the fraction of inspired oxygen (FiO2)].The postoperative oxygenation index, blood gas analysis, and duration of mechanical ventilation were compared between the two groups.

Results

There were significant differences in oxygenation observed at 2 h postoperatively between the groups. 12, 24, and 72 h postoperatively, the oxygenation index varied significantly between the two groups. There were statistically significant differences in the time effects of the oxygenation index and PaO2 between the two groups, as well as significant differences in the length of stay in the intensive care unit.

Conclusion

For the postoperative care of patients with AAD, it is suggested that the minimum FiO2 required for oxygenation of patients be maintained. In addition, it is possible to enhance PEEP as a priority when PaO2 is low.

Conservative versus liberal oxygen therapy for intensive care unit patients: meta-analysis of randomized controlled trials

BACKGROUND

It remains unclear whether conservative oxygen therapy (COT) or liberal oxygen therapy (LOT) is more beneficial to the clinical outcomes of intensive care unit (ICU) patients. We systematically reviewed the efficacy and safety of conservative versus liberal oxygen therapy for ICU patients.

METHODS

We systematically searched PubMed, Embase, Web of Science, Scopus, Cochrane Central Register of Controlled Trials, ClinicalTrials.gov, MedRxiv, and BioRxiv for reports on randomized controlled trials (RCTs) that compared the effects of COT versus LOT on the clinical outcomes of ICU patients published in English before April 2024. The primary outcome was the mortality rate, secondary outcomes included ICU and hospital length of stay, days free from mechanical ventilation support (MVF), vasopressor-free time (VFT), and adverse events.

RESULTS

In all, 13 RCTs involving 10,632 patients were included in analyses. Meta-analysis showed COT did not reduce mortality at 30-day (risk ratio [RR] = 1.01, 95% confidence interval [CI] 0.94 to 1.09, I2 = 42%, P = 0.78), 90-day (RR = 1.01, 95% CI 0.95 to 1.08, I2 = 9%, P = 0.69), or longest follow-up (RR = 1.00, 95% CI 0.95 to 1.06, I2 = 22%, P = 0.95) compared to LOT in ICU patients. In subgroup analyses, no significant difference was observed between the two groups in terms of the different ICU, baseline P/F, and actual PaO2. In addition, COT did not affect ICU length of stay, hospital length of stay, or VFT, it only affected MVF days.

CONCLUSIONS

COT did not reduce all-cause mortality in ICU patients. Further RCTs are urgently needed to confirm the impact of COT strategy on specific populations.

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.

Effectiveness of the oxygen reserve index in detecting and preventing hyperoxia in critically ill patients on mechanical ventilation: a randomized controlled trial

AIM

To assess the effectiveness of fraction of inspired oxygen (FiO2) titration guided by oxygen reserve index (ORi) in preventing hyperoxia in intensive care unit (ICU) patients receiving mechanical ventilator support.

METHODS

Patients aged 18 years and older who were admitted to a tertiary ICU and required mechanical ventilator support were randomly divided into two groups: the control group (n=30) and the oxygen saturation (SpO2) +ORi group (n=30). In the SpO2+ORi group, the goal was to maintain SpO2 between 95% and 98% and ORi at 0.00. In both groups, SpO2, ORi, partial pressure of oxygen (PaO2), partial pressure of carbon dioxide, positive end-expiratory pressure, FiO2, and hemodynamic parameters were recorded every six hours for two consecutive days.

RESULTS

A very strong positive linear correlation was found between PaO2 and ORi (r=0.937; P<0.001). In the ORi+SpO2 group, PaO2 values were significantly lower and decreased with FiO2 titration over time. Severe hyperoxia was observed in 24.8% of the control group and in only 3.3% of the ORi+SpO2 group. When PaO2>120 mm Hg, FiO2>0.40 was found in 83.5% of the control group, and in 40% of the ORi+SpO2 group.

CONCLUSION

FiO2 titration guided by ORi+SpO2 effectively prevents hyperoxia and reduces the exposure time to hyperoxia in critically ill patients.

Higher versus lower fractions of inspired oxygen or targets of arterial oxygenation for adults admitted to the intensive care unit

BACKGROUND

This is an updated review concerning 'Higher versus lower fractions of inspired oxygen or targets of arterial oxygenation for adults admitted to the intensive care unit'. Supplementary oxygen is provided to most patients in intensive care units (ICUs) to prevent global and organ hypoxia (inadequate oxygen levels). Oxygen has been administered liberally, resulting in high proportions of patients with hyperoxemia (exposure of tissues to abnormally high concentrations of oxygen). This has been associated with increased mortality and morbidity in some settings, but not in others. Thus far, only limited data have been available to inform clinical practice guidelines, and the optimum oxygenation target for ICU patients is uncertain. Because of the publication of new trial evidence, we have updated this review.

OBJECTIVES

To update the assessment of benefits and harms of higher versus lower fractions of inspired oxygen (FiO2) or targets of arterial oxygenation for adults admitted to the ICU.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, Science Citation Index Expanded, BIOSIS Previews, and LILACS. We searched for ongoing or unpublished trials in clinical trial registers and scanned the reference lists and citations of included trials. Literature searches for this updated review were conducted in November 2022.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared higher versus lower FiO2 or targets of arterial oxygenation (partial pressure of oxygen (PaO2), peripheral or arterial oxygen saturation (SpO2 or SaO2)) for adults admitted to the ICU. We included trials irrespective of publication type, publication status, and language. We excluded trials randomising participants to hypoxaemia (FiO2 below 0.21, SaO2/SpO2 below 80%, or PaO2 below 6 kPa) or to hyperbaric oxygen, and cross-over trials and quasi-randomised trials.

DATA COLLECTION AND ANALYSIS

Four review authors independently, and in pairs, screened the references identified in the literature searches and extracted the data. Our primary outcomes were all-cause mortality, the proportion of participants with one or more serious adverse events (SAEs), and quality of life. We analysed all outcomes at maximum follow-up. Only three trials reported the proportion of participants with one or more SAEs as a composite outcome. However, most trials reported on events categorised as SAEs according to the International Conference on Harmonisation Good Clinical Practice (ICH-GCP) criteria. We, therefore, conducted two analyses of the effect of higher versus lower oxygenation strategies using 1) the single SAE with the highest reported proportion in each trial, and 2) the cumulated proportion of participants with an SAE in each trial. Two trials reported on quality of life. Secondary outcomes were lung injury, myocardial infarction, stroke, and sepsis. No trial reported on lung injury as a composite outcome, but four trials reported on the occurrence of acute respiratory distress syndrome (ARDS) and five on pneumonia. We, therefore, conducted two analyses of the effect of higher versus lower oxygenation strategies using 1) the single lung injury event with the highest reported proportion in each trial, and 2) the cumulated proportion of participants with ARDS or pneumonia in each trial. We assessed the risk of systematic errors by evaluating the risk of bias in the included trials using the Risk of Bias 2 tool. We used the GRADEpro tool to assess the overall certainty of the evidence. We also evaluated the risk of publication bias for outcomes reported by 10b or more trials.

MAIN RESULTS

We included 19 RCTs (10,385 participants), of which 17 reported relevant outcomes for this review (10,248 participants). For all-cause mortality, 10 trials were judged to be at overall low risk of bias, and six at overall high risk of bias. For the reported SAEs, 10 trials were judged to be at overall low risk of bias, and seven at overall high risk of bias. Two trials reported on quality of life, of which one was judged to be at overall low risk of bias and one at high risk of bias for this outcome. Meta-analysis of all trials, regardless of risk of bias, indicated no significant difference from higher or lower oxygenation strategies at maximum follow-up with regard to mortality (risk ratio (RR) 1.01, 95% confidence interval (C)I 0.96 to 1.06; I2 = 14%; 16 trials; 9408 participants; very low-certainty evidence); occurrence of SAEs: the highest proportion of any specific SAE in each trial RR 1.01 (95% CI 0.96 to 1.06; I2 = 36%; 9466 participants; 17 trials; very low-certainty evidence), or quality of life (mean difference (MD) 0.5 points in participants assigned to higher oxygenation strategies (95% CI -2.75 to 1.75; I2 = 34%, 1649 participants; 2 trials; very low-certainty evidence)). Meta-analysis of the cumulated number of SAEs suggested benefit of a lower oxygenation strategy (RR 1.04 (95% CI 1.02 to 1.07; I2 = 74%; 9489 participants; 17 trials; very low certainty evidence)). However, trial sequential analyses, with correction for sparse data and repetitive testing, could reject a relative risk increase or reduction of 10% for mortality and the highest proportion of SAEs, and 20% for both the cumulated number of SAEs and quality of life. Given the very low-certainty of evidence, it is necessary to interpret these findings with caution. Meta-analysis of all trials indicated no statistically significant evidence of a difference between higher or lower oxygenation strategies on the occurrence of lung injuries at maximum follow-up (the highest reported proportion of lung injury RR 1.08, 95% CI 0.85 to 1.38; I2 = 0%; 2048 participants; 8 trials; very low-certainty evidence). Meta-analysis of all trials indicated harm from higher oxygenation strategies as compared with lower on the occurrence of sepsis at maximum follow-up (RR 1.85, 95% CI 1.17 to 2.93; I2 = 0%; 752 participants; 3 trials; very low-certainty evidence). Meta-analysis indicated no differences regarding the occurrences of myocardial infarction or stroke.

AUTHORS' CONCLUSIONS

In adult ICU patients, it is still not possible to draw clear conclusions about the effects of higher versus lower oxygenation strategies on all-cause mortality, SAEs, quality of life, lung injuries, myocardial infarction, stroke, and sepsis at maximum follow-up. This is due to low or very low-certainty evidence.

Investigation and Analysis of the Current Status of Rationality and Standardization of Oxygen Therapy in Hospitalized Adult Patients

Objective

To investigate the rationality and standardization of oxygen therapy for hospitalized adult patients, so as to provide a basis for improving the quality of oxygen therapy care.

Methods

Self-designed "Inpatient Oxygen Therapy Status Questionnaire", using a cross-sectional survey, surveyed 185 oxygen inhalation patients in a tertiary general hospital from August 3-15, 2020, based on the formulation and promulgation of the Chinese Nursing Association The "Nursing care for adult patient with oxygen therapy" standard evaluates the rationality of clinical oxygen therapy implementation and the standardization of nursing measures.

Results

The reasonable rate of oxygen therapy for hospitalized adult patients was 19.46%, and the standardized rate of nursing measures was 54.52%. The reasonable and standardized rates of medical wards were higher than those of surgical and specialized wards, and were statistically significant (P<0.05). The incidence of complications of oxygen therapy was positively correlated with the rationality of oxygen therapy and the standardized data of nursing measures.

Conclusion

The clinical oxygen therapy nursing practice and the standard of "Nursing care for adult patient with oxygen therapy" are quite inadequate. There are differences in the quality of oxygen therapy in different wards. Nursing managers should strengthen training and management, standardize nursing behaviors, and improve the quality of oxygen therapy and ensure oxygen therapy for patients' safety.

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).

Higher versus lower oxygenation strategies in the general intensive care unit population: A systematic review, meta-analysis and meta-regression of randomized controlled trials

PURPOSE

Oxygen therapy is vital in adult intensive care unit (ICU) patients, but it is indistinct whether higher or lower oxygen targets are favorable. Our aim was to update the findings of randomized controlled trials (RTCs) comparing higher and lower oxygen strategies.

MATERIALS AND METHODS

MEDLINE, EMBASE, and Web of Science were searched. RCTs comparing higher (liberal, hyperoxia) and lower (conservative, normoxia) oxygen in adult mechanically ventilated ICU patients were included. The main outcome was 90-day mortality; other outcomes include serious adverse events (SAE), support free days and length of stay (LOS).

RESULTS

No significant difference was observed for 90-day mortality. A lower incidence was found for SAEs, favoring lower oxygenation (OR, 0.86; 95%CI, 0.77-0.96; I ² 13%). No differences were observed in either support free days at day 28 or ICU and hospital LOS.

CONCLUSIONS

No difference was found for 90-day mortality, support free days and ICU and hospital LOS. However, a lower incidence of SAEs was found for lower oxygenation. These findings may have clinical implications for practice guidelines, yet it remains of paramount importance to continue conducting clinical trials, comparing groups with a clinically relevant contrast and focusing on the impact of important side effects.

Development and validation of an online nomogram for predicting the outcome of open tracheotomy decannulation: a two-center retrospective analysis

BACKGROUND

Tracheotomy decannulation is critical for patients in the intensive care unit (ICU) to recover. In this study, we developed and validated an intuitive nomogram to predict the success rate of tracheotomy decannulation.

METHODS

We collected the data of 627 ICU patients before open tracheotomy decannulation from two medical institutions, including 466 patients (135 success and 331 failure) from the First Affiliated Hospital of Anhui Medical University as a training cohort, and 161 patients (57 success and 104 failure) from the Second Affiliated Hospital of Anhui Medical University as an external validation cohort. A least absolute shrinkage and multivariate logistic regression analysis were performed to determine the independent risk factors and construct the nomogram. The area under the receiver operating characteristic curve (AUC) was used to assess discrimination and the calibration plots were used to assess consistency. The clinical application was assessed using decision curve analysis and the clinical impact curve.

RESULTS

7 independent risk factors were eventually included in the prediction model. The AUC of the training cohort, internal validation and external validation were 0.932, 0.926, and 0.915, showing good discrimination. The model performed well in terms of calibration, decision curve analysis, and clinical impact curves. The superior performance of the model was also confirmed by external validation.

CONCLUSION

This nomogram can help ICU physicians identify high-risk patients for decannulation and plan their pre-decannulation treatment accordingly.

Impacts of a fraction of inspired oxygen adjustment protocol in COVID-19 patients under mechanical ventilation: A prospective cohort study

OBJECTIVE

We examined weather a protocol for fraction of inspired oxygen (FiO₂) adjustment can reduce hyperoxemia and excess oxygen use in COVID-19 patients mechanically ventilated.

DESIGN

Prospective cohort study.

SETTING

Two intensive care units (ICUs) dedicated to COVID-19 patients in Brazil.

PATIENTS

Consecutive patients with COVID-19 mechanically ventilated.

INTERVENTIONS

One ICU followed a FiO₂ adjustment protocol based on SpO₂ (conservative-oxygen ICU) and the other, which did not follow the protocol, constituted the control ICU.

MAIN VARIABLES OF INTEREST

Prevalence of hyperoxemia (PaO₂>100mmHg) on day 1, sustained hyperoxemia (present on days 1 and 2), and excess oxygen use (FiO₂>0.6 in patients with hyperoxemia) were compared between the two ICUs.

RESULTS

Eighty two patients from the conservative-oxygen ICU and 145 from the control ICU were included. The conservative-oxygen ICU presented lower prevalence of hyperoxemia on day 1 (40.2% vs. 75.9%, p<0.001) and of sustained hyperoxemia (12.2% vs. 49.6%, p<0.001). Excess oxygen use was less frequent in the conservative-oxygen ICU on day 1 (18.3% vs. 52.4%, p<0.001). Being admitted in the control ICU was independently associated with hyperoxemia and excess oxygen use. Multivariable analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FiO₂ use and adverse clinical outcomes.

CONCLUSIONS

Following FiO₂ protocol was associated with lower hyperoxemia and less excess oxygen use. Although those results were not associated with better clinical outcomes, adopting FiO₂ protocol may be useful in a scenario of depleted oxygen resources, as was seen during the COVID-19 pandemic.

Epidermal Growth Factor Receptor Inhibition Is Protective in Hyperoxia-Induced Lung Injury

Aims

Studies have linked severe hyperoxia, or prolonged exposure to very high oxygen levels, with worse clinical outcomes. This study investigated the role of epidermal growth factor receptor (EGFR) in hyperoxia-induced lung injury at very high oxygen levels (>95%).

Results

Effects of severe hyperoxia (100% oxygen) were studied in mice with genetically inhibited EGFR and wild-type littermates. Despite the established role of EGFR in lung repair, EGFR inhibition led to improved survival and reduced acute lung injury, which prompted an investigation into this protective mechanism. Endothelial EGFR genetic knockout did not confer protection. EGFR inhibition led to decreased levels of cleaved caspase-3 and poly (ADP-ribosyl) polymerase (PARP) and decreased terminal dUTP nick end labeling- (TUNEL-) positive staining in alveolar epithelial cells and reduced ERK activation, which suggested reduced apoptosis in vivo. EGFR inhibition decreased hyperoxia (95%)-induced apoptosis and ERK in murine alveolar epithelial cells in vitro, and CRISPR-mediated EGFR deletion reduced hyperoxia-induced apoptosis and ERK in human alveolar epithelial cells in vitro. Innovation. This work defines a protective role of EGFR inhibition to decrease apoptosis in lung injury induced by 100% oxygen. This further characterizes the complex role of EGFR in acute lung injury and outlines a novel hyperoxia-induced cell death pathway that warrants further study.

Conclusion

In conditions of severe hyperoxia (>95% for >24 h), EGFR inhibition led to improved survival, decreased lung injury, and reduced cell death. These findings further elucidate the complex role of EGFR in acute lung injury.

Too much tolerance for hyperoxemia in mechanically ventilated patients with SARS-CoV-2 pneumonia? Report from an Italian intensive care unit

Background

In COVID-19 patients requiring mechanical ventilation, the administration of high oxygen (O2) doses for prolonged time periods may be necessary. Although life-saving in most cases, O2 may exert deleterious effects if administered in excessive concentrations. We aimed to describe the prevalence of hyperoxemia and excessive O2 administration in mechanically ventilated patients with SARS-CoV-2 pneumonia and determine whether hyperoxemia is associated with mortality in the Intensive Care Unit (ICU) or the onset of ventilator-associated pneumonia (VAP).

Materials and methods

Retrospective single-center study on adult patients with SARS-CoV-2 pneumonia requiring invasive mechanical ventilation for ≥48 h. Patients undergoing extracorporeal respiratory support were excluded. We calculated the excess O2 administered based on the ideal arterial O2 tension (PaO2) target of 55-80 mmHg. We defined hyperoxemia as PaO2 > 100 mmHg and hyperoxia + hyperoxemia as an inspired O2 fraction (FiO2) > 60% + PaO2 > 100 mmHg. Risk factors for ICU-mortality and VAP were assessed through multivariate analyses.

Results

One hundred thirty-four patients were included. For each day of mechanical ventilation, each patient received a median excess O2 of 1,121 [829-1,449] L. Hyperoxemia was found in 38 [27-55]% of arterial blood gases, hyperoxia + hyperoxemia in 11 [5-18]% of cases. The FiO2 was not reduced in 69 [62-76]% of cases of hyperoxemia. Adjustments were made more frequently with higher PaO2 or initial FiO2 levels. ICU-mortality was 32%. VAP was diagnosed in 48.5% of patients. Hyperoxemia (OR 1.300 95% CI [1.097-1.542]), time of exposure to hyperoxemia (OR 2.758 [1.406-5.411]), hyperoxia + hyperoxemia (OR 1.144 [1.008-1.298]), and daily excess O2 (OR 1.003 [1.001-1.005]) were associated with higher risk for ICU-mortality, independently of age, Sequential Organ failure Assessment score at ICU-admission and mean PaO2/FiO2. Hyperoxemia (OR 1.033 [1.006-1.061]), time of exposure to hyperoxemia (OR 1.108 [1.018-1.206]), hyperoxia + hyperoxemia (OR 1.038 [1.003-1.075]), and daily excess O2 (OR 1.001 [1.000-1.001]) were identified as risk factors for VAP, independently of body mass index, blood transfusions, days of neuromuscular blocking agents (before VAP), prolonged prone positioning and mean PaO2/FiO2 before VAP.

Conclusion

Excess O2 administration and hyperoxemia were common in mechanically ventilated patients with SARS-CoV-2 pneumonia. The exposure to hyperoxemia may be associated with ICU-mortality and greater risk for VAP.

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.

Impacts of a fraction of inspired oxygen adjustment protocol in COVID-19 patients under mechanical ventilation: A prospective cohort study

OBJECTIVE

We examined weather a protocol for fraction of inspired oxygen (FiO₂) adjustment can reduce hyperoxemia and excess oxygen use in COVID-19 patients mechanically ventilated.

DESIGN

Prospective cohort study.

SETTING

Two intensive care units (ICUs) dedicated to COVID-19 patients in Brazil.

PATIENTS

Consecutive patients with COVID-19 mechanically ventilated.

INTERVENTIONS

One ICU followed a FiO₂ adjustment protocol based on SpO₂ (conservative-oxygen ICU) and the other, which did not follow the protocol, constituted the control ICU.

MAIN VARIABLES OF INTEREST

Pprevalence of hyperoxemia (PaO₂>100 mmHg) on day 1, sustained hyperoxemia (present on days 1 and 2), and excess oxygen use (FiO₂>0.6 in patients with hyperoxemia) were compared between the two ICUs.

RESULTS

82 patients from the conservative-oxygen ICU and 145 from the control ICU were included. The conservative-oxygen ICU presented lower prevalence of hyperoxemia on day 1 (40.2% vs. 75.9%, p<0.001) and of sustained hyperoxemia (12.2% vs. 49.6%, p<0.001). Excess oxygen use was less frequent in the conservative-oxygen ICU on day 1 (18.3% vs. 52.4%, p<0.001). Being admitted in the control ICU was independently associated with hyperoxemia and excess oxygen use. Multivariable analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FiO₂ use and adverse clinical outcomes.

CONCLUSIONS

Following FiO₂ protocol was associated with lower hyperoxemia and less excess oxygen use. Although those results were not associated with better clinical outcomes, adopting FiO₂ protocol may be useful in a scenario of depleted oxygen resources, as was seen during the COVID-19 pandemic.

Effect of Automated Closed-loop ventilation versus convenTional VEntilation on duration and quality of ventilation in critically ill patients (ACTiVE) - study protocol of a randomized clinical trial

BACKGROUND

INTELLiVENT-Adaptive Support Ventilation (ASV) is a fully automated closed-loop mode of ventilation for use in critically ill patients. Evidence for benefit of INTELLiVENT-ASV in comparison to ventilation that is not fully automated with regard to duration of ventilation and quality of breathing is largely lacking. We test the hypothesis that INTELLiVENT-ASV shortens time spent on a ventilator and improves the quality of breathing.

METHODS

The "Effects of Automated Closed-loop VenTilation versus Conventional Ventilation on Duration and Quality of Ventilation" (ACTiVE) study is an international, multicenter, two-group randomized clinical superiority trial. In total, 1200 intensive care unit (ICU) patients with an anticipated duration of ventilation of > 24 h will be randomly assigned to one of the two ventilation strategies. Investigators screen patients aged 18 years or older at start of invasive ventilation in the ICU. Patients either receive automated ventilation by means of INTELLiVENT-ASV, or ventilation that is not automated by means of a conventional ventilation mode. The primary endpoint is the number of days free from ventilation and alive at day 28; secondary endpoints are quality of breathing using granular breath-by-breath analysis of ventilation parameters and variables in a time frame of 24 h early after the start of invasive ventilation, duration of ventilation in survivors, ICU and hospital length of stay (LOS), and mortality rates in the ICU and hospital, and at 28 and 90 days.

DISCUSSION

ACTiVE is one of the first randomized clinical trials that is adequately powered to compare the effects of automated closed-loop ventilation versus conventional ventilation on duration of ventilation and quality of breathing in invasively ventilated critically ill patients. The results of ACTiVE will support intensivist in their choices regarding the use of automated ventilation.

TRIAL REGISTRATION

ACTiVE is registered in clinicaltrials.gov (study identifier: NCT04593810 ) on 20 October 2020.

Effects of hyperoxemia on aneurysmal subarachnoid hemorrhage outcomes: a systematic review and meta-analysis

OBJECTIVE

In recent years, hyperoxemia in the intensive care unit has received attention as potentially contributing to negative outcomes in the setting of cardiac arrest, ischemic stroke, and traumatic brain injury. The authors sought to evaluate whether hyperoxemia contributes to worse outcomes in the setting of aneurysmal subarachnoid hemorrhage (aSAH) and to summarize suggested pathophysiological mechanisms.

METHODS

A systematic literature review was conducted without date restrictions on the PubMed and Web of Science databases on September 15, 2021. All studies that assessed the relationship between patients treated for aSAH and hyperoxemia were eligible independent of the criteria used to define hyperoxemia. All nonclinical studies and studies that did not report outcome data specific to patients with aSAH were excluded. A total of 102 records were found and screened, resulting in assessment of 10 full-text studies, of which 7 met eligibility criteria. Risk of bias was assessed using the Downs and Black checklist. A meta-analysis on the pooled 2602 patients was performed, and forest plots were constructed. Additionally, a review of the literature was performed to summarize available data regarding the pathophysiology of hyperoxemia.

RESULTS

The included studies demonstrated an association between hyperoxemia and increased morbidity and mortality following aSAH. The criteria used to determine hyperoxemia varied among studies. Pooling of univariate data showed hyperoxemia to be associated with poor neurological outcome (OR 2.26, 95% CI 1.66-3.07; p < 0.001), delayed cerebral ischemia (DCI) (OR 1.91, 95% CI 1.31-2.78; p < 0.001), and increased incidence of poor neurological outcome or mortality as a combined endpoint (OR 2.36, 95% CI 1.87-2.97; p < 0.001). Pooling of multivariable effect sizes showed the same relationship for poor neurological outcome (OR 1.28, 95% CI 1.07-1.55; p = 0.01) and poor neurological outcome and mortality as a combined endpoint (OR 1.17, 95% CI 1.11-1.23; p < 0.001). Additionally, review of preclinical studies underlined the contribution of oxidative stress due to hyperoxemia to acute secondary brain injury and DCI.

CONCLUSIONS

Reported outcomes from the available studies have indicated that hyperoxemia is associated with worse neurological outcome, mortality, and DCI. These findings provide a general guideline toward avoiding hyperoxemia in the acute setting of aSAH. Further studies are needed to determine the optimal ventilation and oxygenation parameters for acute management of this patient population.

Outcomes and Predictors of Severe Hyperoxemia in Patients Receiving Mechanical Ventilation: A Single-Center Cohort Study

RATIONALE

Supplemental oxygen is among the most commonly administered therapies in intensive care units. High supplemental oxygen exposure has been associated with harm in observational human studies and animal models. Yet no consensus exists regarding which dose and duration of high oxygen constitutes harmful hyperoxemia, and little is known regarding the clinical factors that predict potentially injurious exposure.

OBJECTIVES

To determine the level and duration of arterial oxygen (PaO2) associated with mortality among mechanically ventilated patients, and to identify the clinical factors that predict this exposure.

METHODS

We performed a retrospective cohort study of patients who received invasive mechanical ventilation at a single academic institution in 2017 and 2018. We used a generalized additive model to visualize the relationship between the measured PaO2 via arterial blood gases (ABGs) and 30-day mortality. We used multivariable logistic regression to identify patient- and hospital-level factors that predict exposure to harmful hyperoxemia.

RESULTS

We analyzed 2,133 patients with 33,310 ABGs obtained during mechanical ventilation. We identified a U-shaped relationship between PaO2 and mortality, where PaO2 was positively correlated with mortality above a threshold of 200 mmHg. 1,184 patients (55.5%) had at least one PaO2 level above this threshold. If patients spent an entire day exposed to PaO2 > 200 mmHg, they had 2.19 (95% CI 1.33 - 3.60, p = 0.002) greater odds of 30-day mortality in an adjusted analysis. Any exposure to severe hyperoxemia (PaO2 > 200 mmHg), was associated with mortality (OR 1.29, 95% CI 1.04 - 1.59, p = 0.021). The strongest clinical predictor of severe hyperoxemia exposure was the identity of the ICU in which mechanical ventilation was delivered.

CONCLUSIONS

Exposure to high arterial oxygen concentrations is common among mechanically ventilated patients, and the dose and duration of PaO2 ≥ 200 mmHg is associated with mortality. Severe hyperoxemia is highly variable across ICUs, and is far more common in clinical practice than in recent randomized trials of oxygen targeting strategies. Efforts to minimize this common and injurious exposure level are needed.

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.

Role of SatO2, PaO2/FiO2 Ratio and PaO2 to Predict Adverse Outcome in COVID-19: A Retrospective, Cohort Study

COVID-19 respiratory failure is a life-threatening condition. Oxygenation targets were evaluated in a non-ICU setting. In this retrospective, observational study, we enrolled all patients admitted to the University Hospital of Genoa, Italy, between 1 February and 31 May 2020 with an RT-PCR positive for SARS-CoV-2. PaO2, PaO2/FiO2 and SatO2% were collected and analyzed at time 0 and in case of admission, patients who required or not C-PAP (groups A and B) were categorized. Each measurement was correlated to adverse outcome. A total of 483 patients were enrolled, and 369 were admitted to hospital. Of these, 153 required C-PAP and 266 had an adverse outcome. Patients with PaO2 <60 and >100 had a higher rate of adverse outcome at time 0, in groups A and B (OR 2.52, 3.45, 2.01, respectively). About the PaO2/FiO2 ratio, the OR for < 300 was 3.10 at time 0, 4.01 in group A and 4.79 in group B. Similar odds were found for < 200 in any groups and < 100 except for group B (OR 11.57). SatO2 < 94% showed OR 1.34, 3.52 and 19.12 at time 0, in groups A and B, respectively. PaO2 < 60 and >100, SatO2 < 94% and PaO2/FiO2 ratio < 300 showed at least two- to three-fold correlation to adverse outcome. This may provide simple but clear targets for clinicians facing COVID-19 respiratory failure in a non ICU-setting.

Impact of Permissive Hypoxia and Hyperoxia Avoidance on Clinical Outcomes in Septic Patients Receiving Mechanical Ventilation: A Retrospective Single-Center Study

BACKGROUND

Septic patients often require mechanical ventilation due to respiratory dysfunction, and effective ventilatory strategies can improve survival. The effects of the combination of permissive hypoxia and hyperoxia avoidance for managing mechanically ventilated patients are unknown. This study examines these effects on outcomes in mechanically ventilated septic patients.

METHODS

In a retrospective before-and-after study, we examined adult septic patients (aged ≥18 years) requiring mechanical ventilation at a university hospital. On April 1, 2017, our mechanical ventilation policy changed from a conventional oxygenation target (SpO2: ≥96%) to more conservative targets with permissive hypoxia (SpO2: 88-92% or PaO2: 60 mmHg) and hyperoxia avoidance (reduced oxygenation for PaO2 > 110 mmHg). Patients were divided into a prechange group (April 2015 to March 2017; n = 83) and a postchange group (April 2017 to March 2019; n = 130). Data were extracted from clinical records and insurance claims. Using a multiple logistic regression model, we examined the association of the postchange group (permissive hypoxia and hyperoxia avoidance) with intensive care unit (ICU) mortality after adjusting for variables such as Sequential Organ Failure Assessment (SOFA) score and PaO2/FiO2 ratios.

RESULTS

The postchange group did not have significantly lower adjusted ICU mortality (0.67, 0.33-1.43; P = 0.31) relative to the prechange group. However, there were significant intergroup differences in mechanical ventilation duration (prechange: 11.0 days, postchange: 7.0 days; P = 0.01) and ICU stay (prechange: 11.0 days, postchange: 9.0 days; P = 0.02).

CONCLUSIONS

Permissive hypoxia and hyperoxia avoidance had no significant association with reduced ICU mortality in mechanically ventilated septic patients. However, this approach was significantly associated with shorter mechanical ventilation duration and ICU stay, which can improve patient turnover and ventilator access.

Liberal or conservative oxygen therapy for ventilated patients in the ICU: a meta-analysis of randomized controlled trials

Background

The acknowledgment that conservative oxygen therapy (COT) was related to better prognosis in the intensive care unit (ICU) was challenged recently. We conducted an updated meta-analysis aimed to determine whether liberal oxygen therapy (LOT) or COT is associated with better improve clinical outcomes.

Methods

We systematically searched the electronic databases (PubMed, Web of Science and Embase) up to May 2021 for randomized controlled trials (RCTs). The primary outcome was the mortality of the final follow-up time and secondary outcomes were ICU mortality, the ICU length of stay and the number of ventilator-free days.

Results

A total of 7 RCTs were included, with 2166 patients admitted to the ICU. There was no significant difference in the primary outcome between the LOT and COT. Additionally, LOT could not significantly increase ICU mortality and the ICU length of stay compared with COT.

Conclusions

The present study showed that COT was not significantly superior to LOT in clinical outcomes. Therefore, additional high-quality studies with novel designs are required to further elucidate this controversy.

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.

A quasiexperimental study of targeted normoxia in critically ill trauma patients

BACKGROUND

Avoidance of hypoxia and hyperoxia may reduce morbidity and mortality in critically ill civilian and military trauma patients. The objective of this study was to determine if a multimodal quality improvement intervention increases adherence to a consensus-based, targeted normoxia strategy. We hypothesized that this intervention would safely improve compliance with targeted normoxia.

METHODS

This is a pre/postquasiexperimental pilot study to improve adherence to normoxia, defined as a pulse oximetry (SpO2) of 90% to 96% or an arterial partial pressure oxygen (PaO2) of 60 to 100 mm Hg. We used a multimodal informatics and educational intervention guiding clinicians to safely titrate supplemental oxygen to normoxia based on SpO2 monitoring in critically ill trauma patients admitted to the surgical-trauma or neurosurgical intensive care unit within 24 hours of emergency department arrival. The primary outcome was effectiveness in delivering targeted normoxia (i.e., an increase in the probability of being in the targeted normoxia range and/or a reduction in the probability of being on a higher fraction-inspired oxygen concentration [FiO2]).

RESULTS

Analysis included 371 preintervention subjects and 201 postintervention subjects. Preintervention and postintervention subjects were of similar age, race/ethnicity, and sex and had similar comorbidities and Acute Physiologic and Chronic Health Evaluation II scores. Overall, the adjusted probability of being hyperoxic while on supplemental oxygen was reduced during the postintervention period (adjusted odds ratio, 0.74; 95% confidence interval, 0.57-0.97). There was a higher probability of being on room air (FiO2, 0.21) in the postintervention period (adjusted odds ratio, 1.38; 95% confidence interval, 0.83-2.30). In addition, there was a decreased amount of patient time spent on higher levels of FiO2 (FiO2, >40%) without a concomitant increase in hypoxia.

CONCLUSION

A multimodal intervention targeting normoxia in critically ill trauma patients increased normoxia and lowered the use of supplemental oxygen. A large clinical trial is needed to validate the impact of this protocol on patient-centered clinical outcomes.

LEVEL OF EVIDENCE

Therapeutic/care management, level II.

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.

Conservative oxygen supplementation versus usual oxygen supplementation among septic medical intensive care units patients: A before-after investigation

Patients admitted in the intensive care unit (ICU) are always managed with excessive high fraction of inspired oxygen and have hyperoxia for a significant period of time, which has potential harms. The guidelines for the management of patients in ICUs do not provide the target values for partial pressure of oxygen or arterial oxyhemoglobin saturations. The study was a before-after investigation comparing two time periods in which different oxygenation strategies were applied. Data of oxygen control, outcome measures, and mortality of a total of 273 patients (>18 years) admitted at least for 2 days in ICUs and received treatment for the sepsis were retrospectively collected and analyzed. Patients were received usual oxygen supplementation (targeted partial pressure of oxygen: 150 mmHg; a high fraction of inspired oxygen: 0.4; UOS cohort; n = 142) or conservative oxygen supplementation (targeted partial pressure of oxygen: 70-100 mmHg; a high fraction of inspired oxygen as low as possible; COS cohort; n = 131). Mechanical ventilation-free hours were significantly higher for patients of COS cohort than those of UOS cohort (77.99 ± 21.26 h/patient vs 70.01 ± 23.57 h/patient, p = 0.016). ICUs length of stays of patients of COS cohort was fewer than those of UOS cohort (7.05 ± 2.13 days/patient vs 7.69 ± 2.43 days/patients, p = 0.016). The probability of survival of patients was higher among patients of COS cohort than those of UOS cohort (p = 0.049). A higher number of patients from UOS cohort needed vasopressors than those from COS cohort (55 vs 35, p = 0.039). Conservative oxygen supplementation to maintain partial pressure of oxygen was improved outcome measures and decreases mortality as compared to that of usual oxygen supplementation.Level of Evidence: III.Technical Efficacy Stage: 4.

Hyperoxia After Return of Spontaneous Circulation in Cardiac Arrest Patients

Current guidelines emphasize the use of 100% oxygen during cardiopulmonary resuscitation after cardiac arrest. When patients are ventilated for variable periods after return of spontaneous circulation (ROSC), hyperoxia causes increased morbidity and mortality by overproduction of reactive oxygen species. Various patient, volunteer, and animal studies have shown the harmful effects of hyperoxia. This mini-review article aims to expand the potential clinical spectrum of hyperoxia on individual organ systems leading to organ dysfunction. A framework to achieve and maintain normoxia after ROSC is proposed. Despite the harmful considerations of hyperoxia in critically ill patients, additional safety studies including dose-effect, level and onset of the reactive oxygen species effect, and safe hyperoxia applicability period after ROSC, need to be performed in various animal and human models to further elucidate the role of oxygen therapy after cardiac arrest.

Intensivists' response to hyperoxemia in mechanical ventilation patients: The status quo and related factors

BACKGROUND

Due to the still sparse literature in China, the investigation of hyperoxemia management is required. Thus, we aim to conduct a retrospective study to provide more information about hyperoxemia management in intensive care unit (ICU) patients.

METHODS

We retrospectively screened the medical records of adult patients (age ≥18 years) who required mechanical ventilation (MV) ≥24 hours from January 1, 2018, to December 31, 2018. All arterial blood gas (ABG) tested during MV was retrieved, and MV settings were recorded. The median arterial partial pressure of oxygen (PaO₂) >120 mmHg (1 mmHg=0.133 kPa) was defined as mild to moderate hyperoxemia, and PaO₂ >300 mmHg as extreme hyperoxemia. Intensivists' response to hyperoxemia was assessed based on the reduction of fraction of inspired oxygen (FiO₂) within one hour after hyperoxemia was recorded. Multivariable logistic regression analysis was performed to determine the independent factors associated with the intensivists' response to hyperoxemia.

RESULTS

A total of 592 patients were finally analyzed. The median Acute Physiology and Chronic Health Evaluation II (APACHE II) score was 21 (15-26). The PaO₂, arterial oxygen saturation (SaO₂), FiO₂, and positive end expiratory pressure (PEEP) were 96.4 (74.0-126.0) mmHg, 97.8% (95.2%-99.1%), 0.4 (0.4-0.5), and 5 (3-6) cmH₂O, respectively. Totally 174 (29.39%) patients had PaO₂ >120 mmHg, and 19 (3.21%) patients had extreme hyperoxemia at PaO₂ >300 mmHg. In cases of mild to moderate hyperoxemia with FiO₂ ≤0.4, only 13 (2.20%) patients had a decrease in FiO₂ within one hour. The multivariable logistic regression analysis showed that a positive response was independently associated with FiO₂ (odds ratio [OR] 1.09, 95% confidence interval [CI] 1.06-1.12, P<0.001), PaO₂ (OR 1.01, 95% CI 1.00-1.01, P=0.002), and working shifts (OR 5.09, 95% CI 1.87-13.80, P=0.001).

CONCLUSIONS

Hyperoxemia occurs frequently and is neglected in most cases, particularly when mild to moderate hyperoxemia, hyperoxemia with lower FiO₂, hyperoxemia during night and middle-night shifts, or FiO₂ less likely to be decreased. Patients may be at a risk of oxygen toxicity because of the liberal oxygen strategy. Therefore, further research is needed to improve oxygen management for patients with MV in the ICUs.

Hyperoxemia during the hyperacute phase of aneurysmal subarachnoid hemorrhage is associated with delayed cerebral ischemia and poor outcome: a retrospective observational study

OBJECTIVE

The harmful effects of hyperoxemia have been reported in critically ill patients with various disorders, including those with brain injuries. However, the effect of hyperoxemia on aneurysmal subarachnoid hemorrhage (aSAH) patients is unclear. In this study the authors aimed to determine whether hyperoxemia during the hyperacute or acute phase in patients with aSAH is associated with delayed cerebral ischemia (DCI) and poor neurological outcome.

METHODS

In this single-center retrospective study, data from patients with aSAH treated between January 2011 and June 2017 were reviewed. The patients were classified into groups according to whether they experienced DCI (DCI group and non-DCI group) and whether they had a poor outcome at discharge (poor outcome group and favorable outcome group). The background characteristics and time-weighted average (TWA) PaO2 during the first 24 hours after arrival at the treatment facility (TWA24h-PaO2) and between the first 24 hours after arrival and day 6 (TWA6d-PaO2), the hyperacute and acute phases, respectively, were compared between the groups. Factors related to DCI and poor outcome were evaluated with logistic regression analyses.

RESULTS

Of 197 patients with aSAH, 42 patients experienced DCI and 82 patients had a poor outcome at discharge. TWA24h-PaO2 was significantly higher in the DCI group than in the non-DCI group (186 [141-213] vs 161 [138-192] mm Hg, p = 0.029) and in the poor outcome group than in the favorable outcome group (176 [154-205] vs 156 [136-188] mm Hg, p = 0.004). TWA6d-PaO2 did not differ significantly between the groups. Logistic regression analyses revealed that higher TWA24h-PaO2 was an independent risk factor for DCI (OR 1.09, 95% CI 1.01-1.17, p = 0.037) and poor outcome (OR 1.17, 95% CI 1.06-1.29, p = 0.002).

CONCLUSIONS

Hyperoxemia during the first 24 hours was associated with DCI and a poor outcome in patients with aSAH. Excessive oxygen therapy might have an adverse effect in the hyperacute phase of aSAH.

Perioperative Lung Protection: Clinical Implications

In the past, it was common practice to use a high tidal volume (VT) during intraoperative ventilation, because this reduced the need for high oxygen fractions to compensate for the ventilation-perfusion mismatches due to atelectasis in a time when it was uncommon to use positive end-expiratory pressure (PEEP) in the operating room. Convincing and increasing evidence for harm induced by ventilation with a high VT has emerged over recent decades, also in the operating room, and by now intraoperative ventilation with a low VT is a well-adopted approach. There is less certainty about the level of PEEP during intraoperative ventilation. Evidence for benefit and harm of higher PEEP during intraoperative ventilation is at least contradicting. While some PEEP may prevent lung injury through reduction of atelectasis, higher PEEP is undeniably associated with an increased risk of intraoperative hypotension that frequently requires administration of vasoactive drugs. The optimal level of inspired oxygen fraction (FIO2) during surgery is even more uncertain. The suggestion that hyperoxemia prevents against surgical site infections has not been confirmed in recent research. In addition, gas absorption-induced atelectasis and its association with adverse outcomes like postoperative pulmonary complications actually makes use of a high FIO2 less attractive. Based on the available evidence, we recommend the use of a low VT of 6-8 mL/kg predicted body weight in all surgery patients, and to restrict use of a high PEEP and high FIO2 during intraoperative ventilation to cases in which hypoxemia develops. Here, we prefer to first increase FIO2 before using high PEEP.

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.

Arterial oxygen pressure targets in critically ill patients: Analysis of a large ICU database

BACKGROUND

Providing supplemental oxygen is common in the management of critically ill patients, yet the optimal oxygen regimen remains unclear.

OBJECTIVES

To explore the optimal range of PaO₂ in critically ill patients.

METHODS

This is a retrospective study conducted in the Medical Information Mart for Intensive Care III (MIMIC-III) database. The patients with a least 48 h of oxygen therapy were included. Nonlinear regression was used to analyze the association between PaO₂ and mortality. We derived an optimal range of PaO₂ and evaluated the association between the proportion of PaO₂ measurements within this range and mortality.

RESULTS

In total, 8401 patients were included in the study. A J-shaped relationship was observed between median PaO₂ and hospital mortality. Compared with the reference group of 100-120 mmHg, patients with values of 80-100 mmHg and 120-140 mmHg had higher hospital mortality (adjusted odds ratio [aOR], 1.23; 95% CI, 1.05-1.43 and 1.29; 95%CI, 1.08-1.54, respectively). Similarly, mortality rates were significantly higher for PaO₂ <80 mmHg and ≥140 mmHg (aOR, 1.97; 95%CI, 1.58-2.45 and 1.42; 95%CI, 1.19-1.69, respectively). Patients spent a greater proportion of time within 100-120 mmHg tended to have a lower mortality rate.

CONCLUSION

Among critically ill patients, the relationship between median PaO₂ and hospital mortality was J-shaped. The lowest rates of mortality was observed in those with PaO₂ levels within 100 to 120 mmHg.

Hyperoxia and modulation of pulmonary vascular and immune responses in COVID-19

Oxygen is the most commonly used therapy in hospitalized patients with COVID-19. In those patients who develop worsening pneumonia and acute respiratory distress syndrome (ARDS), high concentrations of oxygen may need to be administered for prolonged time periods, often together with mechanical ventilation. Hyperoxia, although lifesaving and essential for maintaining adequate oxygenation in the short term, may have adverse long-term consequences upon lung parenchymal structure and function. How hyperoxia per se impacts lung disease in COVID-19 has remained largely unexplored. Numbers of experimental studies have previously established that hyperoxia is associated with deleterious outcomes inclusive of perturbations in immunologic responses, abnormal metabolic function, and alterations in hemodynamics and alveolar barrier function. Such changes may ultimately progress into clinically evident lung injury and adverse remodeling and result in parenchymal fibrosis when exposure is prolonged. Given that significant exposure to hyperoxia in patients with severe COVID-19 may be unavoidable to preserve life, these sequelae of hyperoxia, superimposed on the cytopathic effects of SARS-CoV-2 virus, may well impact pathogenesis of COVID-19-induced ARDS.

Oxygen reserve index, a new method of monitoring oxygenation status: what do we need to know?

The oxygen reserve index (ORI) is a new technology that provides real-time, non-invasive, and continuous monitoring of patients’ oxygenation status. This review aimed to discuss its clinical utility, prospect and limitations. A systematic literature search of PubMed, MEDLINE, Google Scholar, and ScienceDirect was performed with the keywords of “oxygen reserve index,” “ORI,” “oxygenation,” “pulse oximetry,” “monitoring,” and “hyperoxia.” Original articles, reviews, case reports, and other relevant articles were reviewed. All articles on ORI were selected. ORI can provide an early warning before saturation begins to decrease and expands the ability to monitor the human body's oxygenation status noninvasively and continuously with the combination of pulse oximetry so as to avoid unnecessary hyperoxia or unanticipated hypoxia. Although the technology is so new that it is rarely known and has not been applied to routine practices in hospitals, it shows good prospects for critical care, oxygen therapy, and intraoperative monitoring.

Lung injury induced by short-term mechanical ventilation with hyperoxia and its mitigation by deferoxamine in rats

BACKGROUND

Long-term mechanical ventilation with hyperoxia can induce lung injury. General anesthesia is associated with a very high incidence of hyperoxaemia, despite it usually lasts for a relatively short period of time. It remains unclear whether short-term mechanical ventilation with hyperoxia has an adverse impact on or cause injury to the lungs. The present study aimed to assess whether short-term mechanical ventilation with hyperoxia may cause lung injury in rats and whether deferoxamine (DFO), a ferrous ion chelator, could mitigate such injury to the lungs and explore the possible mechanism.

METHODS

Twenty-four SD rats were randomly divided into 3 groups (n = 8/group): mechanical ventilated with normoxia group (MV group, FiO2 = 21%), with hyperoxia group (HMV group, FiO2 = 90%), or with hyperoxia + DFO group (HMV + DFO group, FiO2 = 90%). Mechanical ventilation under different oxygen concentrations was given for 4 h, and ECG was monitored. The HMV + DFO group received continuous intravenous infusion of DFO at 50 mg•kg- 1•h- 1, while the MV and HMV groups received an equal volume of normal saline. Carotid artery cannulation was carried out to monitor the blood gas parameters under mechanical ventilation for 2 and 4 h, respectively, and the PaO2/FiO2 ratio was calculated. After 4 h ventilation, the right anterior lobe of the lung and bronchoalveolar lavage fluid from the right lung was sampled for pathological and biochemical assays.

RESULTS

PaO2 in the HMV and HMV + DFO groups were significantly higher, but the PaO2/FiO2 ratio were significantly lower than those of the MV group (all p < 0.01), while PaO2 and PaO2/FiO2 ratio between HMV + DFO and HMV groups did not differ significantly. The lung pathological scores and the wet-to-dry weight ratio (W/D) in the HMV and HMV + DFO groups were significantly higher than those of the MV group, but the lung pathological score and the W/D ratio were reduced by DFO (p < 0.05, HMV + DFO vs. HMV). Biochemically, HMV resulted in significant reductions in Surfactant protein C (SP-C), Surfactant protein D (SP-D), and Glutathion reductase (GR) levels and elevation of xanthine oxidase (XOD) in both the Bronchoalveolar lavage fluid and the lung tissue homogenate, and all these changes were prevented or significantly reverted by DFO.

CONCLUSIONS

Mechanical ventilation with hyperoxia for 4 h induced oxidative injury of the lungs, accompanied by a dramatic reduction in the concentrations of SP-C and SP-D. DFO could mitigate such injury by lowering XOD activity and elevating GR activity.

Hyperoxemia and excess oxygen use in early acute respiratory distress syndrome: insights from the LUNG SAFE study

Background

Concerns exist regarding the prevalence and impact of unnecessary oxygen use in patients with acute respiratory distress syndrome (ARDS). We examined this issue in patients with ARDS enrolled in the Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE (LUNG SAFE) study.

Methods

In this secondary analysis of the LUNG SAFE study, we wished to determine the prevalence and the outcomes associated with hyperoxemia on day 1, sustained hyperoxemia, and excessive oxygen use in patients with early ARDS. Patients who fulfilled criteria of ARDS on day 1 and day 2 of acute hypoxemic respiratory failure were categorized based on the presence of hyperoxemia (PaO₂ > 100 mmHg) on day 1, sustained (i.e., present on day 1 and day 2) hyperoxemia, or excessive oxygen use (FIO₂ ≥ 0.60 during hyperoxemia).

Results

Of 2005 patients that met the inclusion criteria, 131 (6.5%) were hypoxemic (PaO₂ < 55 mmHg), 607 (30%) had hyperoxemia on day 1, and 250 (12%) had sustained hyperoxemia. Excess FIO₂ use occurred in 400 (66%) out of 607 patients with hyperoxemia. Excess FIO₂ use decreased from day 1 to day 2 of ARDS, with most hyperoxemic patients on day 2 receiving relatively low FIO₂. Multivariate analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FIO₂ use and adverse clinical outcomes. Mortality was 42% in patients with excess FIO₂ use, compared to 39% in a propensity-matched sample of normoxemic (PaO₂ 55–100 mmHg) patients (P = 0.47).

Conclusions

Hyperoxemia and excess oxygen use are both prevalent in early ARDS but are most often non-sustained. No relationship was found between hyperoxemia or excessive oxygen use and patient outcome in this cohort.

Trial registration

LUNG-SAFE is registered with ClinicalTrials.gov, NCT02010073

Higher versus lower fraction of inspired oxygen or targets of arterial oxygenation for adults admitted to the intensive care unit

BACKGROUND

The mainstay treatment for hypoxaemia is oxygen therapy, which is given to the vast majority of adults admitted to the intensive care unit (ICU). The practice of oxygen administration has been liberal, which may result in hyperoxaemia. Some studies have indicated an association between hyperoxaemia and mortality, whilst other studies have not. The ideal target for supplemental oxygen for adults admitted to the ICU is uncertain. Despite a lack of robust evidence of effectiveness, oxygen administration is widely recommended in international clinical practice guidelines. The potential benefit of supplemental oxygen must be weighed against the potentially harmful effects of hyperoxaemia.

OBJECTIVES

To assess the benefits and harms of higher versus lower fraction of inspired oxygen or targets of arterial oxygenation for adults admitted to the ICU.

SEARCH METHODS

We identified trials through electronic searches of CENTRAL, MEDLINE, Embase, Science Citation Index Expanded, BIOSIS Previews, CINAHL, and LILACS. We searched for ongoing or unpublished trials in clinical trials registers. We also scanned the reference lists of included studies. We ran the searches in December 2018.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that compared higher versus lower fraction of inspired oxygen or targets of arterial oxygenation for adults admitted to the ICU. We included trials irrespective of publication type, publication status, and language. We included trials with a difference between the intervention and control groups of a minimum 1 kPa in partial pressure of arterial oxygen (PaO2), minimum 10% in fraction of inspired oxygen (FiO2), or minimum 2% in arterial oxygen saturation of haemoglobin/non-invasive peripheral oxygen saturation (SaO2/SpO2). We excluded trials randomizing participants to hypoxaemia (FiO2 below 0.21, SaO2/SpO2 below 80%, and PaO2 below 6 kPa) and to hyperbaric oxygen.

DATA COLLECTION AND ANALYSIS

Three review authors independently, and in pairs, screened the references retrieved in the literature searches and extracted data. Our primary outcomes were all-cause mortality, the proportion of participants with one or more serious adverse events, and quality of life. None of the trials reported the proportion of participants with one or more serious adverse events according to the International Conference on Harmonisation Good Clinical Practice (ICH-GCP) criteria. Nonetheless, most trials reported several serious adverse events. We therefore included an analysis of the effect of higher versus lower fraction of inspired oxygen, or targets using the highest reported proportion of participants with a serious adverse event in each trial. Our secondary outcomes were lung injury, acute myocardial infarction, stroke, and sepsis. None of the trials reported on lung injury as a composite outcome, however some trials reported on acute respiratory distress syndrome (ARDS) and pneumonia. We included an analysis of the effect of higher versus lower fraction of inspired oxygen or targets using the highest reported proportion of participants with ARDS or pneumonia in each trial. To assess the risk of systematic errors, we evaluated the risk of bias of the included trials. We used GRADE to assess the overall certainty of the evidence.

MAIN RESULTS

We included 10 RCTs (1458 participants), seven of which reported relevant outcomes for this review (1285 participants). All included trials had an overall high risk of bias, whilst two trials had a low risk of bias for all domains except blinding of participants and personnel. Meta-analysis indicated harm from higher fraction of inspired oxygen or targets as compared with lower fraction or targets of arterial oxygenation regarding mortality at the time point closest to three months (risk ratio (RR) 1.18, 95% confidence interval (CI) 1.01 to 1.37; I2 = 0%; 4 trials; 1135 participants; very low-certainty evidence). Meta-analysis indicated harm from higher fraction of inspired oxygen or targets as compared with lower fraction or targets of arterial oxygenation regarding serious adverse events at the time point closest to three months (estimated highest proportion of specific serious adverse events in each trial RR 1.13, 95% CI 1.04 to 1.23; I2 = 0%; 1234 participants; 6 trials; very low-certainty evidence). These findings should be interpreted with caution given that they are based on very low-certainty evidence. None of the included trials reported any data on quality of life at any time point. Meta-analysis indicated no evidence of a difference between higher fraction of inspired oxygen or targets as compared with lower fraction or targets of arterial oxygenation on lung injury at the time point closest to three months (estimated highest reported proportion of lung injury RR 1.03, 95% CI 0.78 to 1.36; I2 = 0%; 1167 participants; 5 trials; very low-certainty evidence). None of the included trials reported any data on acute myocardial infarction or stroke, and only one trial reported data on the effects on sepsis.

AUTHORS' CONCLUSIONS

We are very uncertain about the effects of higher versus lower fraction of inspired oxygen or targets of arterial oxygenation for adults admitted to the ICU on all-cause mortality, serious adverse events, and lung injuries at the time point closest to three months due to very low-certainty evidence. Our results indicate that oxygen supplementation with higher versus lower fractions or oxygenation targets may increase mortality. None of the trials reported the proportion of participants with one or more serious adverse events according to the ICH-GCP criteria, however we found that the trials reported an increase in the number of serious adverse events with higher fractions or oxygenation targets. The effects on quality of life, acute myocardial infarction, stroke, and sepsis are unknown due to insufficient data.

Use of excessive supplemental oxygen in mechanically ventilated patients is based on unit culture. A multiple-methods study in a regional intensive care unit

BACKGROUND

Administration of supplemental oxygen is widely used in the management of critically ill patients; however, there is evidence that excessive supplemental oxygen exposure is associated with increased mortality. There is limited research evaluating what factors clinicians take into consideration when managing oxygenation in critically ill adults.

OBJECTIVES

The purpose of this study was to explore intensive care unit (ICU) clinicians' experience and decision-making when managing supplemental oxygen therapy in mechanically ventilated patients in a regional intensive care unit.

METHODS

A multiple-methods observational study that included (i) a cross-sectional ICU staff survey and (ii) focus group discussions with critical care nurses was conducted. Descriptive statistics were used to summarise the key outcomes of the staff survey. Thematic analysis was used to analyse the focus group discussions and open-ended questions on the staff survey. The staff survey was completed by 49 ICU clinicians, and 11 critical care nurses participated in the two focus group discussions.

RESULTS

Survey data showed that staff acknowledged the problem of excessive oxygen exposure; 79.6% (n = 39) reported that the minimum acceptable fraction of inspired oxygen for mechanically ventilated patients was 0.3. The majority (89.8%, n = 44) reported that there was an interdisciplinary approach to decision-making in the unit. Two major themes were chosen from the focus group discussions and staff survey data: (i) Decision-making is based on unit culture rather than evidence and (ii) the process of weaning is driven by interdisciplinary team collaboration. Participants acknowledged that there needed to be a culture change from a liberal approach to oxygen therapy.

CONCLUSIONS

Although participants acknowledged the adverse consequences of excessive oxygen use, achieving oxygenation targets with the minimum level of supplemental oxygen was not a key focus of care. The findings highlight the need to develop and evaluate evidence-based protocols to support a conservative approach to supplemental oxygen management.

The Search for Optimal Oxygen Saturation Targets in Critically Ill Patients: Observational Data From Large ICU Databases

BACKGROUND

Although low oxygen saturations are generally regarded as deleterious, recent studies in ICU patients have shown that a liberal oxygen strategy increases mortality. However, the optimal oxygen saturation target remains unclear. The goal of this study was to determine the optimal range by using real-world data.

METHODS

Replicate retrospective analyses were conducted of two electronic medical record databases: the eICU Collaborative Research Database (eICU-CRD) and the Medical Information Mart for Intensive Care III database (MIMIC). Only patients with at least 48 h of oxygen therapy were included. Nonlinear regression was used to analyze the association between median pulse oximetry-derived oxygen saturation (Spo₂) and hospital mortality. We derived an optimal range of Spo₂ and analyzed the association between the percentage of time within the optimal range of Spo₂ and hospital mortality. All models adjusted for age, BMI, sex, and Sequential Organ Failure Assessment score. Subgroup analyses included ICU types, main diagnosis, and comorbidities.

RESULTS

The analysis identified 26,723 patients from eICU-CRD and 8,564 patients from MIMIC. The optimal range of Spo₂ was 94% to 98% in both databases. The percentage of time patients were within the optimal range of Spo₂ was associated with decreased hospital mortality (OR of 80% vs 40% of the measurements within the optimal range, 0.42 [95% CI, 0.40-0.43] for eICU-CRD and 0.53 [95% CI, 0.50-0.55] for MIMIC). This association was consistent across subgroup analyses.

CONCLUSIONS

The optimal range of Spo₂ was 94% to 98% and should inform future trials of oxygen therapy.

Oxygen Exposure Resulting in Arterial Oxygen Tensions Above the Protocol Goal Was Associated With Worse Clinical Outcomes in Acute Respiratory Distress Syndrome

OBJECTIVES

High fractions of inspired oxygen may augment lung damage to exacerbate lung injury in patients with acute respiratory distress syndrome. Participants enrolled in Acute Respiratory Distress Syndrome Network trials had a goal partial pressure of oxygen in arterial blood range of 55-80 mm Hg, yet the effect of oxygen exposure above this arterial oxygen tension range on clinical outcomes is unknown. We sought to determine if oxygen exposure that resulted in a partial pressure of oxygen in arterial blood above goal (> 80 mm Hg) was associated with worse outcomes in patients with acute respiratory distress syndrome.

DESIGN

Longitudinal analysis of data collected in these trials.

SETTING

Ten clinical trials conducted at Acute Respiratory Distress Syndrome Network hospitals between 1996 and 2013.

SUBJECTS

Critically ill patients with acute respiratory distress syndrome.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We defined above goal oxygen exposure as the difference between the fraction of inspired oxygen and 0.5 whenever the fraction of inspired oxygen was above 0.5 and when the partial pressure of oxygen in arterial blood was above 80 mm Hg. We then summed above goal oxygen exposures in the first five days to calculate a cumulative above goal oxygen exposure. We determined the effect of a cumulative 5-day above goal oxygen exposure on mortality prior to discharge home at 90 days. Among 2,994 participants (mean age, 51.3 yr; 54% male) with a study-entry partial pressure of oxygen in arterial blood/fraction of inspired oxygen that met acute respiratory distress syndrome criteria, average cumulative above goal oxygen exposure was 0.24 fraction of inspired oxygen-days (interquartile range, 0-0.38). Participants with above goal oxygen exposure were more likely to die (adjusted interquartile range odds ratio, 1.20; 95% CI, 1.11-1.31) and have lower ventilator-free days (adjusted interquartile range mean difference of -0.83; 95% CI, -1.18 to -0.48) and lower hospital-free days (adjusted interquartile range mean difference of -1.38; 95% CI, -2.09 to -0.68). We observed a dose-response relationship between the cumulative above goal oxygen exposure and worsened clinical outcomes for participants with mild, moderate, or severe acute respiratory distress syndrome, suggesting that the observed relationship is not primarily influenced by severity of illness.

CONCLUSIONS

Oxygen exposure resulting in arterial oxygen tensions above the protocol goal occurred frequently and was associated with worse clinical outcomes at all levels of acute respiratory distress syndrome severity.

Handling Oxygenation Targets in the Intensive Care Unit (HOT-ICU)-Protocol for a randomised clinical trial comparing a lower vs a higher oxygenation target in adults with acute hypoxaemic respiratory failure

BACKGROUND

Acutely ill adults with hypoxaemic respiratory failure are at risk of life-threatening hypoxia, and thus oxygen is often administered liberally. Excessive oxygen use may, however, increase the number of serious adverse events, including death. Establishing the optimal oxygenation level is important as existing evidence is of low quality. We hypothesise that targeting an arterial partial pressure of oxygen (PaO₂ ) of 8 kPa is superior to targeting a PaO₂ of 12 kPa in adult intensive care unit (ICU) patients with acute hypoxaemic respiratory failure.

METHODS

The Handling Oxygenation Targets in the ICU (HOT-ICU) trial is an outcome assessment blinded, multicentre, randomised, parallel-group trial targeting PaO₂ in acutely ill adults with hypoxaemic respiratory failure within 12 hours after ICU admission. Patients are randomised 1:1 to one of the two PaO₂ targets throughout ICU stay until a maximum of 90 days. The primary outcome is 90-day mortality. Secondary outcomes are serious adverse events in the ICU, days alive without organ support and days alive out of hospital in the 90-day period; mortality, health-related quality-of-life at 1-year follow-up as well as 1-year cognitive and pulmonary function in a subgroup; and an overall health economic analysis. To detect or reject a 20% relative risk reduction, we aim to include 2928 patients. An interim analysis is planned after 90-day follow-up of 1464 patients.

CONCLUSION

The HOT-ICU trial will test the hypothesis that a lower oxygenation target reduces 90-day mortality compared with a higher oxygenation target in adult ICU patients with acute hypoxaemic respiratory failure.

Untreated Relative Hypotension Measured as Perfusion Pressure Deficit During Management of Shock and New-Onset Acute Kidney Injury-A Literature Review

Maintaining an optimal blood pressure (BP) during shock is a fundamental tenet of critical care. Optimal BP targets may be different for different patients. In current practice, too often, uniform BP targets are pursued which may result in inadvertently accepting a degree of untreated relative hypotension, i.e., the deficit between patients' usual premorbid basal BP and the achieved BP, during vasopressor support. Relative hypotension is a common but an under-recognized and an under-treated sign among patients with potential shock state. From a physiological perspective, any relative reduction in the net perfusion pressure across an organ (e.g., renal) vasculature has a potential to overwhelm autoregulatory mechanisms, which are already under stress during shock. Such perfusion pressure deficit may consequently impact organs' ability to function or recover from an injured state. This review discusses such pathophysiologic mechanisms in detail with a particular focus on the risk of new-onset acute kidney injury (AKI). To review current literature, databases of Medline, Embase, and Google scholar were searched to retrieve articles that either adjusted BP targets based on patients' premorbid BP levels or considered relative hypotension as an exposure endpoint and assessed its association with clinical outcomes among acutely ill patients. There were no randomized controlled trials. Only seven studies could be identified and these were reviewed in detail. These studies indicated a significant association between the degree of relative hypotension that was inadvertently accepted in real-world practice and new-onset organ dysfunction or subsequent AKI. However, this is not a high-quality evidence. Therefore, well-designed randomized controlled trials are needed to evaluate whether adoption of individualized BP targets, which are initially guided by patient's premorbid basal BP and then tailored according to clinical response, is superior to conventional BP targets for vasopressor therapy, particularly among patients with vasodilatory shock states.

Changes in ventilator settings and ventilation-induced lung injury in burn patients-A systematic review

OBJECTIVE

Ventilation strategies aiming at prevention of ventilator-induced lung injury (VILI), including low tidal volumes (V_T) and use of positive end-expiratory pressures (PEEP) are increasingly used in critically ill patients. It is uncertain whether ventilation practices changed in a similar way in burn patients. Our objective was to describe applied ventilator settings and their relation to development of VILI in burn patients.

DATA SOURCES

Systematic search of the literature in PubMed and EMBASE using MeSH, EMTREE terms and keywords referring to burn or inhalation injury and mechanical ventilation.

STUDY SELECTION

Studies reporting ventilator settings in adult or pediatric burn or inhalation injury patients receiving mechanical ventilation during the ICU stay.

DATA EXTRACTION

Two authors independently screened abstracts of identified studies for eligibility and performed data extraction.

DATA SYNTHESIS

The search identified 35 eligible studies. V_T declined from 14 ml/kg in studies performed before to around 8 ml/kg predicted body weight in studies performed after 2006. Low-PEEP levels (<10 cmH₂O) were reported in 70% of studies, with no changes over time. Peak inspiratory pressure (PIP) values above 35 cmH₂O were frequently reported. Nevertheless, 75% of the studies conducted in the last decade used limited maximum airway pressures (≤35 cmH₂O) compared to 45% of studies conducted prior to 2006. Occurrence of barotrauma, reported in 45% of the studies, ranged from 0 to 29%, and was more frequent in patients ventilated with higher compared to lower airway pressures.

CONCLUSION

This systematic review shows noticeable trends of ventilatory management in burn patients that mirrors those in critically ill non-burn patients. Variability in available ventilator data precluded us from drawing firm conclusions on the association between ventilator settings and the occurrence of VILI in burn patients.

Controversies in the Postoperative Management of the Critically Ill Heart Transplant Patient

Heart transplant recipients are susceptible to a number of complications in the immediate postoperative period. Despite advances in surgical techniques, mechanical circulatory support (MCS), and immunosuppression, evidence supporting optimal management strategies of the critically ill transplant patient is lacking on many fronts. This review identifies some of these controversies with the aim of stimulating further discussion and development into these gray areas.