Routine use of oxygen in the treatment of myocardial infarction: systematic review

Excessive Oxygen Administration in High-Risk Patients Admitted to Medical and Surgical Wards Monitored by Wireless Pulse Oximeter

The monitoring of oxygen therapy when patients are admitted to medical and surgical wards could be important because exposure to excessive oxygen administration (EOA) may have fatal consequences. We aimed to investigate the association between EOA, monitored by wireless pulse oximeter, and nonfatal serious adverse events (SAEs) and mortality within 30 days. We included patients in the Capital Region of Copenhagen between 2017 and 2018. Patients were hospitalized due to acute exacerbation of chronic obstructive pulmonary disease (AECOPD) or after major elective abdominal cancer surgery, and all were treated with oxygen supply. Patients were divided into groups by their exposure to EOA: no exposure, exposure for 1-59 min or exposure over 60 min. The primary outcome was SAEs or mortality within 30 days. We retrieved data from 567 patients for a total of 43,833 h, of whom, 63% were not exposed to EOA, 26% had EOA for 1-59 min and 11% had EOA for ≥60 min. Nonfatal SAEs or mortality within 30 days developed in 24%, 12% and 22%, respectively, and the adjusted odds ratio for this was 0.98 (95% CI, 0.96-1.01) for every 10 min. increase in EOA, without any subgroup effects. In conclusion, we did not observe higher frequencies of nonfatal SAEs or mortality within 30 days in patients exposed to excessive oxygen administration.

Oxygen saturation targets for children with respiratory distress: a systematic review

Background

In children with respiratory distress, supplemental oxygen is indicated at peripheral oxygen saturation (SpO2) thresholds of 90-94%. However, these thresholds are poorly studied. We conducted a systematic review to summarise the existing evidence for SpO2 thresholds in children with respiratory distress.

Methods

Electronic databases and registries were searched for original articles published from 1 January 2010 to 7 January 2022 comparing two or more SpO2 thresholds in children with respiratory distress. Primary outcomes were safety, including mortality, neurocognitive outcomes and readmissions, and effectiveness, including admission rate and length of hospital stay. Methodological appraisal was performed using the Cochrane Risk of Bias 2 (RoB-2) or Risk of Bias in Non-Randomized Studies - of Interventions (ROBINS-I) tools. Results were narratively synthesised.

Results

We retrieved 3384 results; seven studies were included. Lower thresholds ranged from 80% to 92% and were compared with higher thresholds ranging from 92% to 94%. Studies were highly heterogeneous in setting, design, population and outcomes. Risk of bias varied from low to high. Lower SpO2 thresholds had equivalent mortality, neurocognitive outcomes and readmissions or re-attendance to healthcare to higher thresholds. Lower SpO2 thresholds showed a significant decrease in admission rates by up to 40% and shortened hospitalisation duration by 10-18 h.

Conclusions

The current SpO2 thresholds of 90-94% in children with respiratory distress may be too high, which could lead to unnecessary hospitalisations and prolonged hospitalisation duration. SpO2 thresholds as low as 88% are potentially safe in children with respiratory distress and may reduce hospitalisation rates and length of stay. However, high-quality evidence is needed to support this.

Doctors' and Nurses' Knowledge and Perceived Barriers Regarding Acute Oxygen Therapy in a Tertiary Care Hospital in Nigeria

PURPOSE

Oxygen may cause serious consequences when administered wrongly. This study aimed to assess doctors' and nurses' knowledge of acute oxygen therapy and perceived delivery barriers.

PARTICIPANTS AND METHODS

We conducted a cross sectional study among 202 healthcare providers (134 doctors and 68 nurses) in a Nigerian hospital. The validated Acute Oxygen Therapy Questionnaire (AOTQ), which consisted of 21 knowledge assessment questions, was self administered by participants. Provider's knowledge was classified as good if the score was≥80% and poor if < 60%.

RESULTS

Overall, 26.7% (37.3% doctors and 5.9% nurses) had good knowledge of acute oxygen therapy (AOT), 35.9% were aware, and 19.3% used the AOT guidelines. The commonest source of knowledge on oxygen therapy was medical /nursing school (75.2%). The participants' mean knowledge score was 14.75 ± 2.83(possible score of 0-21). Doctors in postgraduate (PG) training obtained the highest score (15.96±2.48) among the participants (F=12.45, df=4, p<0.001). Most doctors (62%) and 23.5% of nurses considered oxygen as a drug. More doctors (52.2%) than nurses (14.7%) believed that a doctor's order was mandatory before oxygen administration, contrary to guidelines recommendations. Most nurses did not know that breathlessness does not always signify hypoxemia and that asymptomatic anemia was not an indication for oxygen. Concerning oxygen prescription, 39.7% of nurses and 64.2% of doctors knew that it should be prescribed to achieve a target saturation range rather than a fixed dose. In acute oxygen delivery in COPD, doctors and nurses exhibited poor knowledge of the appropriate device and flow rate. The reported barriers to oxygen delivery were: a shortage of oxygen supply, inadequate delivery devices, power outages and out of pocket costs.

CONCLUSION

A significant proportion of doctors and nurses had poor knowledge of acute oxygen therapy, poor awareness and infrequently used AOT guidelines, and reported pertinent delivery barriers that warrant educational and administrative interventions.

Mitochondria and oxygen homeostasis

Molecular oxygen possesses a dual nature due to its highly reactive free radical property: it is capable of oxidizing metabolic substrates to generate cellular energy, but can also serve as a substrate for genotoxic reactive oxygen species generation. As a labile substance upon which aerobic life depends, the mechanisms for handling cellular oxygen have been fine-tuned and orchestrated in evolution. Protection from atmospheric oxygen toxicity as originally posited by the Endosymbiotic Theory of the Mitochondrion is likely to be one basic principle underlying oxygen homeostasis. We briefly review the literature on oxygen homeostasis both in vitro and in vivo with a focus on the role of the mitochondrion where the majority of cellular oxygen is consumed. The insights gleaned from these basic mechanisms are likely to be important for understanding disease pathogenesis and developing strategies for maintaining health.

Hyperoxia Reprogrammes Microvascular Endothelial Cell Response to Hypoxia in an Organ-Specific Manner

Organ function relies on microvascular networks to maintain homeostatic equilibrium, which varies widely in different organs and during different physiological challenges. The endothelium role in this critical process can only be evaluated in physiologically relevant contexts. Comparing the responses to oxygen flux in primary murine microvascular EC (MVEC) obtained from brain and lung tissue reveals that supra-physiological oxygen tensions can compromise MVEC viability. Brain MVEC lose mitochondrial activity and undergo significant alterations in electron transport chain (ETC) composition when cultured under standard, non-physiological atmospheric oxygen levels. While glycolytic capacity of both lung and brain MVEC are unchanged by environmental oxygen, the ability to trigger a metabolic shift when oxygen levels drop is greatly compromised following exposure to hyperoxia. This is particularly striking in MVEC from the brain. This work demonstrates that the unique metabolism and function of organ-specific MVEC (1) can be reprogrammed by external oxygen, (2) that this reprogramming can compromise MVEC survival and, importantly, (3) that ex vivo modelling of endothelial function is significantly affected by culture conditions. It further demonstrates that physiological, metabolic and functional studies performed in non-physiological environments do not represent cell function in situ, and this has serious implications in the interpretation of cell-based pre-clinical models.

IDENTIFYING THE EFFECTS OF SUPPLEMENTAL OXYGEN ADMINISTRATION ON THE HEALTH OUTCOMES OF PATIENTS PRESENTING WITH ACUTE CORONARY SYNDROME AND OXYGEN SATURATION >93% - A SYSTEMATIC REVIEW

OBJECTIVES

Oxygen was commonly used in the early management of patients presenting with Acute Coronary Syndrome (ACS) regardless of their oxygen saturation. Inappropriate administration of supplemental oxygen could potentially result in adverse patient health outcomes.

AIM

To identify the effects of supplemental oxygen administration on the health outcomes of patients presenting with ACS and oxygen saturations >93%.

METHOD

Systematic review. The CINAHL, PubMed, Cochrane and Medline databases were searched for relevant literature. Inclusion criteria included articles published from 2008-2019, adult participants, primary studies, and participants with uncomplicated ACS and have oxygen saturation >93%. Eligible studies were assessed for rigour using a critical appraisal tool.

RESULTS

Seven randomised controlled studies were included for analysis. Themes were also used to group the assessed endpoints. The three main outcomes analysed were: infarct size and cardiac function; adverse cardiac events; and mortality. Two of the seven studies found a statistically significant relationship between oxygen administration, infarct size, and adverse cardiac events. Conversely, five of the seven studies reported that supplemental oxygen did not have statistically significant benefit over room air.

CONCLUSION

This review identified that oxygen should not be administered to patients who present with ACS and have oxygen saturations >93%. This is due to the potential risk of adverse outcomes: increased infarct size, mortality, and adverse events.

IMPACT STATEMENT

Recent update of guidelines despite evidence opposing oxygen delivery in ACS means the education of nurses is imperative for safe practice.

Lifesaving Medications Use By Athletic Trainers

The athletic trainer's (AT) emergency management skill set requires competency in the delivery of basic lifesaving medications. Some lifesaving medications have been a part of athletic training practice for decades, but that list has grown as ATs' practice setting has expanded - increasing the types of em ergent conditions that the AT may have to treat. The 2020 CAATE curricular standards require athletic training students be trained to administer the following: supplemental oxygen, nitroglycerine, low dose aspirin, bronchodilators, epinephrine using automated injection device, glucagon, and naloxone. Clinically, the conditions treated by these medications can be categorized as follows: cardiac, respiratory, hypoglycemia, or anaphylaxis. All ATs should know the indications, contraindications, administration methods, and the details of patient monitoring for each medication. Generally, these medications are safe, have clear indications for use, and few contraindications. While ATs are trained to administer these medications, they must consider state laws and local policies.

Intraoperative Fractions of Inspiratory Oxygen Are Associated With Recurrence-Free Survival After Elective Cancer Surgery

Background: Choice of the fraction of inspiratory oxygen (FiO₂) is controversial. The objective of this analysis was to evaluate whether intraoperative FiO₂ was associated with recurrence-free survival after elective cancer surgery.

Methods and Analysis: In this single-center, retrospective study, we analyzed 1,084 patients undergoing elective resection of pancreatic (n = 652), colorectal (n = 405), or hepatic cancer (n = 27) at Heidelberg University Hospital between 2009 and 2016. Intraoperative mean FiO₂ values were calculated. For unstratified analyses, the study cohort was equally divided into a low- and a high-FiO₂ group. For cancer-stratified analyses, this division was done within cancer-strata. The primary outcome measure was recurrence-free survival until the last known follow-up. Groups were compared using Kaplan–Meier analysis. A stratified log rank test was used to control for different FiO₂ levels and survival times between the cancer strata. Cox-regression analyses were used to control for covariates. Sepsis, reoperations, surgical-site infections, and cardiovascular events during hospital stay and overall survival were secondary outcomes.

Results: Median FiO₂ was 40.9% (Q1–Q3, 38.3–42.9) in the low vs. 50.4% (Q1–Q3, 47.4–54.7) in the high-FiO₂ group. Median follow-up was 3.28 (Q1–Q3, 1.68–4.97) years. Recurrence-free survival was considerable higher in the high-FiO₂ group (p < 0.001). This effect was also confirmed when stratified for the different tumor entities (p = 0.007). In colorectal cancer surgery, increased FiO₂ was independently associated with increased recurrence-free survival. The hazard for the primary outcome decreased by 3.5% with every 1% increase in FiO₂. The effect was not seen in pancreatic cancer surgery and we did not find differences in any of the secondary endpoints.

Conclusions: Until definite evidence from large-scale trials is available and in the absence of relevant clinical conditions warranting specific FiO₂ values, perioperative care givers should aim for an intraoperative FiO₂ of 50% in abdominal cancer surgery as this might benefit oncological outcomes.

Oxygen Delivery Approaches to Augment Cell Survival After Myocardial Infarction: Progress and Challenges

Myocardial infarction (MI), triggered by blockage of a coronary artery, remains the most common cause of death worldwide. After MI, the capability of providing sufficient blood and oxygen significantly decreases in the heart. This event leads to depletion of oxygen from cardiac tissue and consequently leads to massive cardiac cell death due to hypoxemia. Over the past few decades, many studies have been carried out to discover acceptable approaches to treat MI. However, very few have addressed the crucial role of efficient oxygen delivery to the injured heart. Thus, various strategies were developed to increase the delivery of oxygen to cardiac tissue and improve its function. Here, we have given an overall discussion of the oxygen delivery mechanisms and how the current technologies are employed to treat patients suffering from MI, including a comprehensive view on three major technical approaches such as oxygen therapy, hemoglobin-based oxygen carriers (HBOCs), and oxygen-releasing biomaterials (ORBs). Although oxygen therapy and HBOCs have shown promising results in several animal and clinical studies, they still have a few drawbacks which limit their effectiveness. More recent studies have investigated the efficacy of ORBs which may play a key role in the future of oxygenation of cardiac tissue. In addition, a summary of conducted studies under each approach and the remaining challenges of these methods are discussed.

Recommendation for Inclusion of Surface Echocardiography in Evaluation of Chest Pain in Acute Emergency Care

Objective  A significant number of conditions may mimic acute myocardial infarction when patients present to acute emergency care (AEC) with chest pain. A proportion of such patients may exhibit ST segment abnormality on the electrocardiogram (ECG) which is due to conditions other than acute coronary syndromes (ACS) or myocardial infarction. The American Heart Association/American College of Cardiology guidelines (2015) algorithm for ACS does not include echocardiographic evaluation in the assessment of chest pain. Patients with chest pain may be subjected to investigations and interventions based on ECG leading unwarranted invasive procedures, which may prove unnecessary, futile, and even detrimental. This study was performed to determine if a bedside echocardiography would help identify the conditions that do not need intervention and might possibly change the treatment pathway at the right time.

Materials and Methods In a prospective observational study design, adult patients presenting to AEC with chest pain were included in the study. After the assessment of airway, breathing and circulation, and initiation of bed side monitoring, a 12-lead ECG was obtained. Patients exhibiting a significant ST change on ECG were subjected to bedside echocardiography, that is, two-dimensional (2D) transthoracic echocardiography (2D-TTE) with a cross reference to a consultant cardiologist for the precise assessment and diagnosis. The findings of echocardiography were correlated with electrocardiogram for possible diagnostic coronary angiography and percutaneous coronary intervention. The results of ECG, echocardiography, and coronary angiography (if done) were analyzed to determine the sensitivity and specificity of echocardiography for ACS.

Results Among 385 patients in the study, 312 were suspected to suffer acute coronary syndrome; among these patients, eight patients turned out to have chest pain due to non-ACS. Of the 73 patients, the chest pain was suspected to be not of cardiac ischemia origin; among these patients, 66 patients were true negative and 7 patients were false positive. Echocardiography was the predictive of ischemic chest pain with a predictive value of 97.7%. The specificity of echocardiography calculated from the above confusion matrix was 90.4% and sensitivity was 97.4%. The positive predictive value of 2D-TTE was 97.7% and negative predictive value was 89.1%. The overall accuracy of bedside 2D-TTE was 96.1%.

Conclusion Echocardiography was found to be an effective tool in aiding diagnosis of a patient presenting to AEC with chest pain and ST-T changes in ECG. A significant percentage of patients (18.7%) presented to AEC with chest pain, ST-T changes and found to have causes other than ACS, and screening echocardiography (2D-TTE) was able to identify 90.4% of those cases. From this study, we conclude that bedside echocardiography had high specificity (90.4%) and sensitivity (97.43%) in identifying regional wall motion abnormality due to ACS. Hence, bedside echocardiography is recommended in patients with chest pain and ST-segment abnormality to avoid unnecessary delay in diagnosis and invasive interventions in non-ACS.

Hypoxemia During One-Lung Ventilation: Does It Really Matter?

PURPOSE OF REVIEW

Hypoxemia during one-lung ventilation, while decreasing in frequency, persists as an intraoperative challenge for anesthesiologists. Discerning when desaturation and resultant hypoxemia correlates to tissue hypoxia is challenging in the perioperative setting and requires a thorough understanding of the physiology of oxygen delivery and tissue utilization.

RECENT FINDINGS

Oxygen delivery is not directly correlated with peripheral oxygen saturation in patients undergoing one-lung ventilation, emphasizing the importance of hemoglobin concentration and cardiac output in avoiding tissue hypoxia. While healthy humans can tolerate acute hypoxemia without long-term consequences, there is a paucity of evidence from patients undergoing thoracic surgery. Increasingly recognized is the potential harm of hyperoxic states, particularly in the setting of complex patients with comorbid diseases.

SUMMARY

Anesthesiologists are left to determine an acceptable oxygen saturation nadir that is individualized to the patient and procedure based on an understanding of oxygen supply, demand, and the consequences of interventions.

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.

Automated closed-loop versus standard manual oxygen administration after major abdominal or thoracic surgery: an international multicentre randomised controlled study

Introduction

Hypoxaemia and hyperoxaemia may occur after surgery, with related complications. This multicentre randomised trial evaluated the impact of automated closed-loop oxygen administration after high-risk abdominal or thoracic surgeries in terms of optimising the oxygen saturation measured by pulse oximetry time within target range.

Methods

After extubation, patients with an intermediate to high risk of post-operative pulmonary complications were randomised to “standard” or “automated” closed-loop oxygen administration. The primary outcome was the percentage of time within the oxygenation range, during a 3-day frame. The secondary outcomes were the time with hypoxaemia and hyperoxaemia under oxygen.

Results

Among the 200 patients, time within range was higher in the automated group, both initially (≤3 h; 91.4±13.7% versus 40.2±35.1% of time, difference +51.0% (95% CI −42.8–59.2%); p<0.0001) and during the 3-day period (94.0±11.3% versus 62.1±23.3% of time, difference +31.9% (95% CI 26.3–37.4%); p<0.0001). Periods of hypoxaemia were reduced in the automated group (≤3 days; 32.6±57.8 min (1.2±1.9%) versus 370.5±594.3 min (5.0±11.2%), difference −10.2% (95% CI −13.9–−6.6%); p<0.0001), as well as hyperoxaemia under oxygen (≤3 days; 5.1±10.9 min (4.8±11.2%) versus 177.9±277.2 min (27.0±23.8%), difference −22.0% (95% CI −27.6–−16.4%); p<0.0001). Kaplan–Meier analysis depicted a significant difference in terms of hypoxaemia (p=0.01) and severe hypoxaemia (p=0.0003) occurrence between groups in favour of the automated group. 25 patients experienced hypoxaemia for >10% of the entire monitoring time during the 3 days within the standard group, as compared to the automated group (p<0.0001).

Conclusion

Automated closed-loop oxygen administration promotes greater time within the oxygenation target, as compared to standard manual administration, thus reducing the occurrence of hypoxaemia and hyperoxaemia.

The Association between Supraphysiologic Arterial Oxygen Levels and Mortality in Critically Ill Patients. A Multicenter Observational Cohort Study

Rationale: There is conflicting evidence on harm related to exposure to supraphysiologic Pa_O2 (hyperoxemia) in critically ill patients.

Objectives: To examine the association between longitudinal exposure to hyperoxemia and mortality in patients admitted to ICUs in five United Kingdom university hospitals.

Methods: A retrospective cohort of ICU admissions between January 31, 2014, and December 31, 2018, from the National Institute of Health Research Critical Care Health Informatics Collaborative was studied. Multivariable logistic regression modeled death in ICU by exposure to hyperoxemia.

Measurements and Main Results: Subsets with oxygen exposure windows of 0 to 1, 0 to 3, 0 to 5, and 0 to 7 days were evaluated, capturing 19,515, 10,525, 6,360, and 4,296 patients, respectively. Hyperoxemia dose was defined as the area between the Pa_O2 time curve and a boundary of 13.3 kPa (100 mm Hg) divided by the hours of potential exposure (24, 72, 120, or 168 h). An association was found between exposure to hyperoxemia and ICU mortality for exposure windows of 0 to 1 days (odds ratio [OR], 1.15; 95% compatibility interval [CI], 0.95–1.38; P = 0.15), 0 to 3 days (OR 1.35; 95% CI, 1.04–1.74; P = 0.02), 0 to 5 days (OR, 1.5; 95% CI, 1.07–2.13; P = 0.02), and 0 to 7 days (OR, 1.74; 95% CI, 1.11–2.72; P = 0.02). However, a dose–response relationship was not observed. There was no evidence to support a differential effect between hyperoxemia and either a respiratory diagnosis or mechanical ventilation.

Conclusions: An association between hyperoxemia and mortality was observed in our large, unselected multicenter cohort. The absence of a dose–response relationship weakens causal interpretation. Further experimental research is warranted to elucidate this important question.

Oxygen therapy for patients with acute myocardial infarction: a meta-analysis of randomized controlled clinical trials

BACKGROUND

Oxygen therapy is widely used for patients with acute myocardial infarction (AMI). However, there is uncertainty about its safety and benefits. The aim of this study is to perform a systematic review and meta-analysis to assess the effectiveness and safety of oxygen therapy for patients with AMI.

MATERIALS AND METHODS

We searched MEDLINE, CINAHL, EMBASE, Cochrane Central Register of Controlled Trials from 1 January 1967, through 31 December 2017. We included randomized controlled clinical trials that used oxygen therapy for patients with suspected or confirmed AMI less than 24 h of symptoms onset. Hyperbaric and aqueous oxygen therapy trials were excluded.

RESULTS

A total of six randomized controlled clinical trials with 7190 individuals were included in this meta-analysis. Compared with no oxygen group, oxygen therapy did not reduce the risk of all-cause mortality [pooled risk ratio (RR): 1.06, 95% confidence interval (CI): 0.56-2.02, P=0.19], recurrent myocardial infarction (pooled RR: 1.57, 95% CI: 0.88-2.80, P=0.18), and pain (pooled RR: 0.97, 95% CI: 0.82-1.14, P=0.25).

CONCLUSION

In this meta-analysis, oxygen inhalation did not benefit patients with AMI with normal oxygen saturation.

Dose variability of supplemental oxygen therapy with open patient interfaces based on in vitro measurements using a physiologically realistic upper airway model

BACKGROUND

Supplemental oxygen therapy is widely used in hospitals and in the home for chronic care. However, there are several fundamental problems with the application of this therapy such that patients are often exposed to arterial oxygen concentrations outside of the intended target range. This paper reports volume-averaged tracheal oxygen concentration measurements (FtO2) from in vitro experiments conducted using a physiologically realistic upper airway model. The goal is to provide data to inform a detailed discussion of the delivered oxygen dose.

METHODS

A baseline FtO2 dataset using a standard, straight adult nasal cannula was established by varying tidal volume (Vt), breathing frequency (f), and continuous oxygen flow rate (QO2) between the following levels to create a factorial design: Vt = 500, 640, or 800 ml; f = 12, 17, or 22 min- 1; QO2 = 2, 4, or 6 l/min. Further experiments were performed to investigate the influence on FtO2 of variation in inspiratory/expiratory ratio, inclusion of an inspiratory or expiratory pause, patient interface selection (e.g. nasal cannula versus a facemask), and rapid breathing patterns in comparison with the baseline measurements.

RESULTS

Oxygen concentration measured at the trachea varied by as much as 60% (i.e. from 30.2 to 48.0% of absolute oxygen concentration) for the same oxygen supply flow rate due to variation in simulated breathing pattern. Among the baseline cases, the chief reasons for variation were 1) the influence of variation in tidal volume leading to variable FiO2 and 2) variation in breathing frequency affecting volume of supplemental oxygen delivered through the breath.

CONCLUSION

For oxygen administration using open patient interfaces there was variability in the concentration and quantity of oxygen delivered to the trachea over the large range of scenarios studied. Of primary importance in evaluating the oxygen dose is knowledge of the breathing parameters that determine the average inhalation flow rate relative to the oxygen flow rate. Otherwise, the oxygen dose cannot be determined.

A comparison of two designs for earcons conveying pulse oximetry information

We performed a randomised controlled trial comparing two kinds of earcons that could provide intermittent pulse oximetry information about a patient's oxygen saturation (SpO₂) and heart rate (HR). Timbre-earcons represented SpO₂ levels with different levels of timbre, and pitch-earcons with different levels of pitch. Both kinds of earcons represented HR with tremolo. Participants using pitch-earcons identified SpO₂ levels alone, and both SpO₂ plus HR levels, significantly better than participants using timbre-earcons: p < .001 in both cases. However, there was no difference between earcon conditions in how effectively HR was identified, p = .422. For both kinds of earcons, identification of SpO₂ levels was more compromised by simultaneous changes in HR than identification of HR levels was compromised by simultaneous changes in SpO₂, suggesting asymmetric integrality. Overall, pitch-earcons may provide a better intermittent auditory pulse oximetry display than timbre-earcons, especially for clinical contexts when quiet is needed.

Supporting multiple patient monitoring with head-worn displays and spearcons

In hospitals, clinicians often need to monitor several patients while performing other tasks. However, visual displays that show patients' vital signs are in fixed locations and auditory alarms intended to alert clinicians may be missed. Information such as spearcons (time-compressed speech earcons) that 'travels' with the clinician and is delivered by earpiece and/or head-worn displays (HWDs), might overcome these problems. In this study, non-clinicians monitored five simulated patients in three 10-min scenarios while performing a demanding tracking task. Monitoring accuracy was better for participants using spearcons and a HWD (88.7%) or a HWD alone (86.2%) than for participants using spearcons alone (74.1%). Participants using the spearcons and HWD (37.7%) performed the tracking task no differently from participants using spearcons alone (37.1%) but participants using the HWD alone performed worse overall (33.1%). The combination of both displays may be a suitable solution for monitoring multiple patients.

Practice patterns and perceptions of Australian and New Zealand anaesthetists towards perioperative oxygen therapy

We conducted a survey of Australian and New Zealand anaesthetists to determine self-reported practice of perioperative oxygen administration and to quantify perceptions regarding the perceived benefits and risks resulting from liberal oxygen therapy delivered in a manner consistent with the current World Health Organization guidelines. In addition, we sought feedback on the acceptability of several proposed clinical trial designs aiming to assess the overall effect of liberal and restricted perioperative oxygen regimens on patient outcomes. We developed a 23-question electronic survey that was emailed to 972 randomly selected Australian and New Zealand College of Anaesthetists (ANZCA) Fellows. We received responses from 282 of 972 invitees (response rate 29%). The majority of survey participants indicated that they routinely titrate inspired oxygen to a level they feel is safe (164/282, 58%) or minimise oxygen administration (82/282, 29%), while 5% of respondents indicated that they aim to maximise oxygen administration. The mean value for targeted intraoperative fraction inspired oxygen (FiO2) was 0.41 (standard deviation 0.12). Of the survey respondents, 2/282 (0.7%) indicated they believe that routine intra- and postoperative administration of ≥80% oxygen reduces the risk of surgical site infection. Well-designed and conducted randomised trials on this topic may help to better direct clinicians' choices. A high level of willingness to participate (80% of responses) in a study designed to investigate the impact of differing approaches to perioperative oxygen administration suggests that recruitment is likely to be feasible in a future study.

Development and validation of a questionnaire to assess the doctors and nurses knowledge of acute oxygen therapy

BACKGROUND

Prescription and administration of oxygen in emergencies by healthcare providers are reported to be inappropriate in most settings. There is a huge gap in the knowledge of health care providers on various aspects of oxygen therapy, and this may be a barrier to optimal oxygen administration. Hence, it is essential to ascertain providers' knowledge of acute oxygen therapy so that appropriate educational interventions are instituted for better delivery. There is no available validated instrument to assess knowledge of acute oxygen therapy. The study aimed to develop, validate and evaluate the test-retest reliability of a questionnaire to determine the doctors and nurses understanding of acute oxygen therapy.

METHODS

This study involved the development of the questionnaire contents by a literature review, assessment of face validity (n = 5), content validity, using a panel of experts (n = 10), item analysis and test-retest reliability among a sample (n = 121) of doctors and nurses.

RESULTS

Face validity indicated that the questionnaire was quick to complete (10-15 min), most items were easy to follow and comprehensible. The global content validity index (S-CVI) was 0.85. The test-retest reliability statistics showed a kappa coefficient of 0.546-0.897 (all P<0.001) and percentage agreement of 80-98.3% indicating high temporal stability in the target population. In total, 90% of the items fulfilled the reliability acceptance criteria. Item discrimination analysis showed that most questions were at an acceptable level. The final questionnaire included 37 item questions and eight sections.

CONCLUSION

The designed questionnaire is a reliable and valid tool for assessing knowledge of acute oxygen therapy among doctors and nurses.

Automated oxygen administration versus conventional oxygen therapy after major abdominal or thoracic surgery: study protocol for an international multicentre randomised controlled study

INTRODUCTION

Hypoxemia and hyperoxia may occur after surgery with potential related complications. The FreeO₂ PostOp trial is a prospective, multicentre, randomised controlled trial that evaluates the clinical impact of automated O₂ administration versus conventional O₂ therapy after major abdominal or thoracic surgeries. The study is powered to demonstrate benefits of automated oxygen titration and weaning in term of oxygenation, which is an important surrogate for complications after such interventions.

METHODS AND ANALYSIS

After extubation, patients are randomly assigned to the Standard (manual O₂ administration) or FreeO₂ group (automated closed-loop O₂ administration). Stratification is performed for the study centre and a medical history of chronic obstructive pulmonary disease (COPD). Primary outcome is the percentage of time spent in the target zone of oxygen saturation, during a 3-day time frame. In both groups, patients will benefit from continuous oximetry recordings. The target zone of oxygen saturation is SpO₂=88%-92% for patients with COPD and 92%-96% for patients without COPD. Secondary outcomes are the nursing workload assessed by the number of manual O₂ flow adjustments, the time spent with severe desaturation (SpO₂ <85%) and hyperoxia area (SpO₂ >98%), the time spent in a hyperoxia area (SpO₂ >98%), the VO₂, the duration of oxygen administration during hospitalisation, the frequency of use of mechanical ventilation (invasive or non-invasive), the duration of the postrecovery room stay, the hospitalisation length of stay and the survival rate.

ETHICS AND DISSEMINATION

The FreeO₂ PostOp study is conducted in accordance with the declaration of Helsinki and was registered on 11 September 2015 (http://www.clinicaltrials.gov). First patient inclusion was performed on 14 January 2016. The results of the study will be presented at academic conferences and submitted to peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT02546830.

Human brain blood flow and metabolism during isocapnic hyperoxia: the role of reactive oxygen species

KEY POINTS

It is unknown whether excessive reactive oxygen species (ROS) production drives the isocapnic hyperoxia (IH)-induced decline in human cerebral blood flow (CBF) via reduced nitric oxide (NO) bioavailability and leads to disruption of the blood-brain barrier (BBB) or neural-parenchymal damage. Cerebral metabolic rate for oxygen (CMR O 2 ) and transcerebral exchanges of NO end-products, oxidants, antioxidants and neural-parenchymal damage markers were simultaneously quantified under IH with intravenous saline and ascorbic acid infusion. CBF and CMR O 2 were reduced during IH, responses that were followed by increased oxidative stress and reduced NO bioavailability when saline was infused. No indication of neural-parenchymal damage or disruption of the BBB was observed during IH. Antioxidant defences were increased during ascorbic acid infusion, while CBF, CMR O 2 , oxidant and NO bioavailability markers remained unchanged. ROS play a role in the regulation of CBF and metabolism during IH without evidence of BBB disruption or neural-parenchymal damage.

ABSTRACT

To test the hypothesis that isocapnic hyperoxia (IH) affects cerebral blood flow (CBF) and metabolism through exaggerated reactive oxygen species (ROS) production, reduced nitric oxide (NO) bioavailability, disturbances in the blood-brain barrier (BBB) and neural-parenchymal homeostasis, 10 men (24 ± 1 years) were exposed to a 10 min IH trial (100% O₂ ) while receiving intravenous saline and ascorbic acid (AA, 3 g) infusion. Internal carotid artery blood flow (ICABF), vertebral artery blood flow (VABF) and total CBF (tCBF, Doppler ultrasound) were determined. Arterial and right internal jugular venous blood was sampled to quantify the cerebral metabolic rate of oxygen (CMR O 2 ), transcerebral exchanges (TCE) of NO end-products (plasma nitrite), antioxidants (AA and AA plus dehydroascorbic acid (AA+DA)) and oxidant biomarkers (thiobarbituric acid-reactive substances (TBARS) and 8-isoprostane), and an index of BBB disruption and neuronal-parenchymal damage (neuron-specific enolase; NSE). IH reduced ICABF, tCBF and CMR O 2 , while VABF remained unchanged. Arterial 8-isoprostane and nitrite TCE increased, indicating that CBF decline was related to ROS production and reduced NO bioavailability. AA, AA+DA and NSE TCE did not change during IH. AA infusion did not change the resting haemodynamic and metabolic parameters but raised antioxidant defences, as indicated by increased AA/AA+DA concentrations. Negative AA+DA TCE, unchanged nitrite, reductions in arterial and venous 8-isoprostane, and TBARS TCE indicated that AA infusion effectively inhibited ROS production and preserved NO bioavailability. Similarly, AA infusion prevented IH-induced decline in regional and total CBF and re-established CMR O 2 . These findings indicate that ROS play a role in CBF regulation and metabolism during IH without evidence of BBB disruption or neural-parenchymal damage.

Effect of oxygen therapy on myocardial salvage in ST elevation myocardial infarction: the randomized SOCCER trial

OBJECTIVE

Recent studies suggest that administration of O2 in patients with acute myocardial infarction may have negative effects. With the use of cardiac MRI (CMR), we evaluated the effects of supplemental O2 in patients with ST elevation myocardial infarction (STEMI) accepted for acute percutaneous coronary intervention (PCI).

MATERIALS AND METHODS

This study was a randomized-controlled trial conducted at two university hospitals in Sweden. Normoxic STEMI patients were randomized in the ambulance to either supplemental O2 (10 l/min) or room air until the conclusion of the PCI. CMR was performed 2-6 days after the inclusion. The primary endpoint was the myocardial salvage index assessed by CMR. The secondary endpoints included infarct size and myocardium at risk.

RESULTS

At inclusion, the O2 (n=46) and air (n=49) patient groups had similar patient characteristics. There were no significant differences in myocardial salvage index [53.9±25.1 vs. 49.3±24.0%; 95% confidence interval (CI): -5.4 to 14.6], myocardium at risk (31.9±10.0% of the left ventricle in the O2 group vs. 30.0±11.8% in the air group; 95% CI: -2.6 to 6.3), or infarct size (15.6±10.4% of the left ventricle vs. 16.0±11.0%; 95% CI: -4.7 to 4.1).

CONCLUSION

In STEMI patients undergoing acute PCI, we found no effect of high-flow oxygen compared with room air on the size of ischemia before PCI, myocardial salvage, or the resulting infarct size. These results support the safety of withholding supplemental oxygen in normoxic STEMI patients.

Supplemental Oxygen Protects Heart Against Acute Myocardial Infarction

Myocardial infarction (MI), which occurs often due to acute ischemia followed by reflow, is associated with irreversible loss (death) of cardiomyocytes. If left untreated, MI will lead to progressive loss of viable cardiomyocytes, deterioration of cardiac function, and congestive heart failure. While supplemental oxygen therapy has long been in practice to treat acute MI, there has not been a clear scientific basis for the observed beneficial effects. Further, there is no rationale for the amount or duration of administration of supplemental oxygenation for effective therapy. The goal of the present study was to determine an optimum oxygenation protocol that can be clinically applicable for treating acute MI. Using EPR oximetry, we studied the effect of exposure to supplemental oxygen cycling (OxCy) administered by inhalation of 21–100% oxygen for brief periods (15–90 min), daily for 5 days, using a rat model of acute MI. Myocardial oxygen tension (pO₂), cardiac function and pro-survival/apoptotic signaling molecules were used as markers of treatment outcome. OxCy resulted in a significant reduction of infarct size and improvement of cardiac function. An optimal condition of 30-min OxCy with 95% oxygen + 5% CO₂ under normobaric conditions was found to be effective for cardioprotection.

Highs and lows of hyperoxia: physiological, performance, and clinical aspects

Molecular oxygen (O₂) is a vital element in human survival and plays a major role in a diverse range of biological and physiological processes. Although normobaric hyperoxia can increase arterial oxygen content ([Formula: see text]), it also causes vasoconstriction and hence reduces O₂ delivery in various vascular beds, including the heart, skeletal muscle, and brain. Thus, a seemingly paradoxical situation exists in which the administration of oxygen may place tissues at increased risk of hypoxic stress. Nevertheless, with various degrees of effectiveness, and not without consequences, supplemental oxygen is used clinically in an attempt to correct tissue hypoxia (e.g., brain ischemia, traumatic brain injury, carbon monoxide poisoning, etc.) and chronic hypoxemia (e.g., severe COPD, etc.) and to help with wound healing, necrosis, or reperfusion injuries (e.g., compromised grafts). Hyperoxia has also been used liberally by athletes in a belief that it offers performance-enhancing benefits; such benefits also extend to hypoxemic patients both at rest and during rehabilitation. This review aims to provide a comprehensive overview of the effects of hyperoxia in humans from the "bench to bedside." The first section will focus on the basic physiological principles of partial pressure of arterial O₂, [Formula: see text], and barometric pressure and how these changes lead to variation in regional O₂ delivery. This review provides an overview of the evidence for and against the use of hyperoxia as an aid to enhance physical performance. The final section addresses pathophysiological concepts, clinical studies, and implications for therapy. The potential of O₂ toxicity and future research directions are also considered.

[Management of acute coronary syndrome without ST-segment elevation]

Acute coronary syndrome without persistent ST-segment elevation (non-ST segment elevation myocardial infarction and instable angina pectoris NSTEMI-ACS) is common and is associated with a high mortality. In addition to 12-channel echocardiograph (ECG) assessment, measurement of cardiac troponins I and T are important for risk stratification and diagnosis. The introduction of high-sensitivity cardiac troponin assays and their implementation into clinical practice has influenced risk stratification and treatment of these patients. Additional diagnostic validation must supplement routine clinical chemistry testing following the initial measurement to distinguish between different possible causes of troponin elevation above the 99th percentile. The time point for the additional troponin measurement depends on the different protocols and troponin assays and is stipulated in the current guidelines. The use of both 1‑hour and 3‑hour protocols together with the clinical presentation and work-up of possible differential diagnoses provide optimal care of patients. Patients who test positive for troponin dynamics should undergo invasive diagnostics and treatment within 24 h of presentation and within 2 h is recommended for unstable patients. Clopidogrel is indicated only in patients requiring oral anticoagulation.

The oxygen reserve index (ORI): a new tool to monitor oxygen therapy

Supplemental oxygen is administered in the vast majority of patients in the perioperative setting and in the intensive care unit to prevent the potentially deleterious effects of hypoxia. On the other hand, the administration of high concentrations of oxygen may induce hyperoxia that may also be associated with significant complications. Oxygen therapy should therefore be precisely titrated and accurately monitored. Although pulse oximetry has become an indispensable monitoring technology to detect hypoxemia, its value in assessing the oxygenation status beyond the range of maximal arterial oxygen saturation (SpO₂ ≥97%) is very limited. In this hyperoxic range, we need to rely on blood gas analysis, which is intermittent, invasive and sometimes delayed. The oxygen reserve index (ORI) is a new continuous non-invasive variable that is provided by the new generation of pulse oximeters that use multi-wavelength pulse co-oximetry. The ORI is a dimensionless index that reflects oxygenation in the moderate hyperoxic range (PaO₂ 100-200 mmHg). The ORI may provide an early alarm when oxygenation deteriorates well before any changes in SpO₂ occur, may reflect the response to oxygen administration (e.g., pre-oxygenation), and may facilitate oxygen titration and prevent unintended hyperoxia. In this review we describe this new variable, summarize available data and preliminary experience, and discuss its potential clinical utilities in the perioperative and intensive care settings.

Automaticversusmanual oxygen administration in the emergency department

Oxygen is commonly administered in hospitals, with poor adherence to treatment recommendations.

We conducted a multicentre randomised controlled study in patients admitted to the emergency department requiring O2≥3 L·min−1. Patients were randomised to automated closed-loop or manual O2titration during 3 h. Patients were stratified according to arterial carbon dioxide tension (PaCO2) (hypoxaemicPaCO2≤45 mmHg; or hypercapnicPaCO2>45–≤55 mmHg) and study centre. Arterial oxygen saturation measured by pulse oximetry (SpO2) goals were 92–96% for hypoxaemic, or 88–92% for hypercapnic patients. Primary outcome was % time withinSpO2target. Secondary endpoints were hypoxaemia and hyperoxia prevalence, O2weaning, O2duration and hospital length of stay.

187 patients were randomised (93 automated, 94 manual) and baseline characteristics were similar between the groups. Time within theSpO2target was higher under automated titration (81±21%versus51±30%, p<0.001). Time with hypoxaemia (3±9%versus5±12%, p=0.04) and hyperoxia under O2(4±9%versus22±30%, p<0.001) were lower with automated titration. O2could be weaned at the end of the study in 14.1%versus4.3% patients in the automated and manual titration group, respectively (p<0.001). O2duration during the hospital stay was significantly reduced (5.6±5.4versus7.1±6.3 days, p=0.002).

Automated O2titration in the emergency department improved oxygenation parameters and adherence to guidelines, with potential clinical benefits.

Oxygen therapy for acute myocardial infarction

BACKGROUND

Oxygen (O₂) is widely used in people with acute myocardial infarction (AMI). Previous systematic reviews concluded that there was insufficient evidence to know whether oxygen reduced, increased or had no effect on heart ischaemia or infarct size. Our first Cochrane review in 2010 also concluded there was insufficient evidence to know whether oxygen should be used. Since 2010, the lack of evidence to support this widely used intervention has attracted considerable attention, prompting further trials of oxygen therapy in myocardial infarction patients. It is thus important to update this Cochrane review.

OBJECTIVES

To assess the effects of routine use of inhaled oxygen for acute myocardial infarction (AMI).

SEARCH METHODS

We searched the following bibliographic databases on 6 June 2015: the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, MEDLINE (OVID), Embase (OVID), CINAHL (EBSCO) and Web of Science (Thomson Reuters). LILACS (Latin American and Caribbean Health Sciences Literature) was last searched in September 2016. We also contacted experts to identify eligible studies. We applied no language restrictions.

SELECTION CRITERIA

Randomised controlled trials in people with suspected or proven AMI (ST-segment elevation myocardial infarction (STEMI) or non-STEMI) within 24 hours after onset, in which the intervention was inhaled oxygen (at normal pressure) compared to air, regardless of co-therapies provided to participants in both arms of the trial.

DATA COLLECTION AND ANALYSIS

Two authors independently reviewed the titles and abstracts of identified studies to see if they met the inclusion criteria and independently undertook the data extraction. We assessed the quality of studies and the risk of bias according to guidance in the Cochrane Handbook for Systematic Reviews of Interventions. The primary outcome was death. The measure of effect used was the risk ratio (RR) with a 95% confidence interval (CI). We used the GRADE approach to evaluate the quality of the evidence and the GRADE profiler (GRADEpro) to import data from Review Manager 5 and create 'Summary of findings' tables.

MAIN RESULTS

The updated search yielded one new trial, for a total of five included studies involving 1173 participants, 32 of whom died. The pooled risk ratio (RR) of all-cause mortality in the intention-to-treat analysis was 0.99 (95% CI 0.50 to 1.95; 4 studies, N = 1123; I² = 46%; quality of evidence: very low) and 1.02 (95% CI 0.52 to 1.98; 4 studies, N = 871; I² = 49%; quality of evidence: very low) when only analysing participants with confirmed AMI. One trial measured pain directly, and two others measured it by opiate usage. The trial showed no effect, with a pooled RR of 0.97 for the use of opiates (95% CI 0.78 to 1.20; 2 studies, N = 250). The result on mortality and pain are inconclusive. There is no clear effect for oxygen on infarct size (the evidence is inconsistent and low quality).

AUTHORS' CONCLUSIONS

There is no evidence from randomised controlled trials to support the routine use of inhaled oxygen in people with AMI, and we cannot rule out a harmful effect. Given the uncertainty surrounding the effect of oxygen therapy on all-cause mortality and on other outcomes critical for clinical decision, well-conducted, high quality randomised controlled trials are urgently required to inform guidelines in order to give definitive recommendations about the routine use of oxygen in AMI.

Oxygen deteriorates arterial function in type 1 diabetes

AIMS

Although oxygen is commonly used to treat various medical conditions, it has recently been shown to worsen vascular function (arterial stiffness) in healthy volunteers and even more in patients in whom vascular function might already be impaired. The effects of oxygen on arterial function in patients with type 1 diabetes (T1D) are unknown, although such patients display disturbed vascular function already at rest. Therefore, we tested whether short-term oxygen administration may alter the arterial function in patients with T1D.

METHODS

We estimated arterial stiffness by augmentation index (AIx) and the pulse wave velocity equivalent (SI-DVP) in 98 patients with T1D and 49 age- and sex-matched controls at baseline and during hyperoxia by obtaining continuous noninvasive finger pressure waveforms using a recently validated method.

RESULTS

AIx and SI-DVP increased in patients (P < 0.05) but not in controls in response to hyperoxia. The increase in AIx (P = 0.05), systolic (P < 0.05), and diastolic (P < 0.05) blood pressure was higher in the patients than in the controls.

CONCLUSIONS

Short-term oxygen administration deteriorates arterial function in patients with T1D compared to non-diabetic control subjects. Since disturbed arterial function plays a major role in the development of diabetic complications, these findings may be of clinical relevance.

Statin drugs mitigate cellular inflammatory response after ST elevation myocardial infarction, but do not affect in-hospital mortality

Introduction: The objective was to examine the role of statins in modulating post-STEMI inflammation and related mortality.

Methods: A total of 404 patients with STEMI were reviewed. Demographics, comorbidities, laboratory values, and outcomes were collected. The patients were grouped as STATIN and NOSTAT based on the use of statin drugs at the time of admission. Ninety-seven patients were receiving statin drugs.

Results: The patients in the STATIN group were more likely to be hypertensive (53.6%), diabetic (37.1%) and to have previous coronary revascularization (9.3%). Following propensity matching of 89 patients in STATIN group to an equal number of patients in NOSTAT controls had lower neutrophil count 7.8 (6.8-8.4) compared to those in the NOSTAT group 9.1 (7.9-10.1). Although there was no difference in-hospital mortality between the two groups, the incidence of pump failure was lower in the STATIN group (5.6% vs. 15.7%; P < 0.01).

Conclusion: Statin treatment prior to STEMI mitigates the cellular inflammatory response after the myocardial infarction, as evidenced by lower leukocyte and neutrophil cell counts in the STATIN group.

Cardiac Usage of Reducible Poly(oligo-D-arginine) As a Gene Carrier for Vascular Endothelial Growth Factor Expression

Developments of non-viral carriers have headed toward reducing cytotoxicity, which results from the use of conventional gene carriers, and enhancing gene delivery efficiency. Cys-(d-R9)-Cys repeated reducible poly(oligo-D-arginine) (rPOA) is one of the most efficient non-viral carriers for gene therapy; however, while its efficiency has been verified in the lung and brain, it is necessary to confirm its activity in each organ or tissue since there are differences of gene carrier susceptibility to among tissue types. We therefore tested the compatibility of rPOA in cardiac tissue by in vitro or in vivo experiments and confirmed its high transfection efficiency and low cytotoxicity. Moreover, substantial regenerative effects were observed following transfection with rPOA/pVEGF expression vector complexes (79% decreased infarct size) compared to polyethyleneimine (PEI) (34% decreased infarct size) in a rat myocardial infarction (MI) model. These findings suggest that rPOA efficiently enables DNA transfection in cardiac tissue and can be used as a useful non-viral therapeutic gene carrier for gene therapy in ischemic heart disease.

Bench-to-bedside review: the effects of hyperoxia during critical illness

Oxygen administration is uniformly used in emergency and intensive care medicine and has life-saving potential in critical conditions. However, excessive oxygenation also has deleterious properties in various pathophysiological processes and consequently both clinical and translational studies investigating hyperoxia during critical illness have gained increasing interest. Reactive oxygen species are notorious by-products of hyperoxia and play a pivotal role in cell signaling pathways. The effects are diverse, but when the homeostatic balance is disturbed, reactive oxygen species typically conserve a vicious cycle of tissue injury, characterized by cell damage, cell death, and inflammation. The most prominent symptoms in the abundantly exposed lungs include tracheobronchitis, pulmonary edema, and respiratory failure. In addition, absorptive atelectasis results as a physiological phenomenon with increasing levels of inspiratory oxygen. Hyperoxia-induced vasoconstriction can be beneficial during vasodilatory shock, but hemodynamic changes may also impose risk when organ perfusion is impaired. In this context, oxygen may be recognized as a multifaceted agent, a modifiable risk factor, and a feasible target for intervention. Although most clinical outcomes are still under extensive investigation, careful titration of oxygen supply is warranted in order to secure adequate tissue oxygenation while preventing hyperoxic harm.

Oxygen in the Setting of Acute Myocardial Infarction: Is It Really a Breath of Fresh Air?

INTRODUCTION

Supplemental oxygen has been used in the setting of acute myocardial infarction (AMI). Once an official recommendation in the guidelines for the management of acute ST-segment elevation myocardial infarction, it is now mentioned as an intervention to be considered. Data for the use of supplemental oxygen or AMI are limited, and some data have suggested associated harm.

METHODS

We performed a systematic review of the literature and a subsequent meta-analysis of the data to determine the effect of high concentration oxygen versus titrated oxygen or room air in the setting of AMI. The following end points were studied: in-hospital mortality, opiate use, percentage of infarcted myocardium by magnetic resonance imaging (MRI), and mass of infarcted myocardium by MRI.

RESULTS

No significant difference was noted with end points when comparing those randomized to high-concentration oxygen versus those randomized to titrated oxygen or room air in the setting of AMI. No significant publication bias was identified although this could not be assessed for all end points.

CONCLUSION

High-concentration oxygen may not offer any benefit when compared to titrated oxygen or room air. A large, randomized trial is warranted to further delineate these differences with respect to multiple end points.

Mechanical Ventilation and ARDS in the ED: A Multicenter, Observational, Prospective, Cross-sectional Study

BACKGROUND

There are few data regarding mechanical ventilation and ARDS in the ED. This could be a vital arena for prevention and treatment.

METHODS

This study was a multicenter, observational, prospective, cohort study aimed at analyzing ventilation practices in the ED. The primary outcome was the incidence of ARDS after admission. Multivariable logistic regression was used to determine the predictors of ARDS.

RESULTS

We analyzed 219 patients receiving mechanical ventilation to assess ED ventilation practices. Median tidal volume was 7.6 mL/kg predicted body weight (PBW) (interquartile range, 6.9-8.9), with a range of 4.3 to 12.2 mL/kg PBW. Lung-protective ventilation was used in 122 patients (55.7%). The incidence of ARDS after admission from the ED was 14.7%, with a mean onset of 2.3 days. Progression to ARDS was associated with higher illness severity and intubation in the prehospital environment or transferring facility. Of the 15 patients with ARDS in the ED (6.8%), lung-protective ventilation was used in seven (46.7%). Patients who progressed to ARDS experienced greater duration in organ failure and ICU length of stay and higher mortality.

CONCLUSIONS

Lung-protective ventilation is infrequent in patients receiving mechanical ventilation in the ED, regardless of ARDS status. Progression to ARDS is common after admission, occurs early, and worsens outcome. Patient- and treatment-related factors present in the ED are associated with ARDS. Given the limited treatment options for ARDS, and the early onset after admission from the ED, measures to prevent onset and to mitigate severity should be instituted in the ED.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01628523; URL: www.clinicaltrials.gov.

Oxygen regulates molecular mechanisms of cancer progression and metastasis

Oxygen is the basic molecule which supports life and it truly is "god's gift to life." Despite its immense importance, research on "oxygen biology" has never received the light of the day and has been limited to physiological and biochemical studies. It seems that in modern day biology, oxygen research is summarized in one word "hypoxia." Scientists have focused on hypoxia-induced transcriptomics and molecular-cellular alterations exclusively in disease models. Interestingly, the potential of oxygen to control the basic principles of biology like homeostatic maintenance, transcription, replication, and protein folding among many others, at the molecular level, has been completely ignored. Here, we present a perspective on the crucial role played by oxygen in regulation of basic biological phenomena. Our conclusion highlights the importance of establishing novel research areas like oxygen biology, as there is great potential in this field for basic science discoveries and clinical benefits to the society.

Self-reported attitudes versus actual practice of oxygen therapy by ICU physicians and nurses

BACKGROUND

High inspiratory oxygen concentrations are frequently administered in ventilated patients in the intensive care unit (ICU) but may induce lung injury and systemic toxicity. We compared beliefs and actual clinical practice regarding oxygen therapy in critically ill patients.

METHODS

In three large teaching hospitals in the Netherlands, ICU physicians and nurses were invited to complete a questionnaire about oxygen therapy. Furthermore, arterial blood gas (ABG) analysis data and ventilator settings were retrieved to assess actual oxygen practice in the same hospitals 1 year prior to the survey.

RESULTS

In total, 59% of the 215 respondents believed that oxygen-induced lung injury is a concern. The majority of physicians and nurses stated that minimal acceptable oxygen saturation and partial arterial oxygen pressure (PaO2) ranges were 85% to 95% and 7 to 10 kPa (52.5 to 75 mmHg), respectively. Analysis of 107,888 ABG results with concurrent ventilator settings, derived from 5,565 patient admissions, showed a median (interquartile range (IQR)) PaO2 of 11.7 kPa (9.9 to 14.3) [87.8 mmHg], median fractions of inspired oxygen (FiO2) of 0.4 (0.4 to 0.5), and median positive end-expiratory pressure (PEEP) of 5 (5 to 8) cm H2O. Of all PaO2 values, 73% were higher than the upper limit of the commonly self-reported acceptable range, and in 58% of these cases, neither FiO2 nor PEEP levels were lowered until the next ABG sample was taken.

CONCLUSIONS

Most ICU clinicians acknowledge the potential adverse effects of prolonged exposure to hyperoxia and report a low tolerance for high oxygen levels. However, in actual clinical practice, a large proportion of their ICU patients was exposed to higher arterial oxygen levels than self-reported target ranges.