Revisiting the role of oxygen therapy in cardiac patients

Myocardial protection in cardiac surgery: a comprehensive review of current therapies and future cardioprotective strategies

Cardiac surgery with cardiopulmonary bypass results in global myocardial ischemia-reperfusion injury, leading to significant postoperative morbidity and mortality. Although cardioplegia is the cornerstone of intraoperative cardioprotection, a number of additional strategies have been identified. The concept of preconditioning and postconditioning, despite its limited direct clinical application, provided an essential contribution to the understanding of myocardial injury and organ protection. Therefore, physicians can use different tools to limit perioperative myocardial injury. These include the choice of anesthetic agents, remote ischemic preconditioning, tight glycemic control, optimization of respiratory parameters during the aortic unclamping phase to limit reperfusion injury, appropriate choice of monitoring to optimize hemodynamic parameters and limit perioperative use of catecholamines, and early reintroduction of cardioprotective agents in the postoperative period. Appropriate management before, during, and after cardiopulmonary bypass will help to decrease myocardial damage. This review aimed to highlight the current advancements in cardioprotection and their potential applications during cardiac surgery.

Influence of Age on Hyperoxia-Induced Cardiac Pathophysiology in Type 1 Diabetes Mellitus (T1DM) Mouse Model

Mechanical ventilation often results in hyperoxia, a condition characterized by excess SpO2 levels (>96%). Hyperoxia results in changes in the physiological parameters, severe cardiac remodeling, arrhythmia development, and alteration of cardiac ion channels, all of which can point toward a gradual increase in the risk of developing cardiovascular disease (CVD). This study extends the analysis of our prior work in young Akita mice, which demonstrated that exposure to hyperoxia worsens cardiac outcomes in a type 1 diabetic murine model as compared to wild-type (WT) mice. Age is an independent risk factor, and when present with a major comorbidity, such as type 1 diabetes (T1D), it can further exacerbate cardiac outcomes. Thus, this research subjected aged T1D Akita mice to clinical hyperoxia and analyzed the cardiac outcomes. Overall, aged Akita mice (60 to 68 weeks) had preexisting cardiac challenges compared to young Akita mice. Aged mice were overweight, had an increased cardiac cross-sectional area, and showed prolonged QTc and JT intervals, which are proposed as major risk factors for CVD like intraventricular arrhythmias. Additionally, exposure to hyperoxia resulted in severe cardiac remodeling and a decrease in Kv 4.2 and KChIP2 cardiac potassium channels in these rodents. Based on sex-specific differences, aged male Akita mice had a higher risk of poor cardiac outcomes than aged females. Aged male Akita mice had prolonged RR, QTc, and JT intervals even at baseline normoxic exposure. Moreover, they were not protected against hyperoxic stress through adaptive cardiac hypertrophy, which, at least to some extent, is due to reduced cardiac androgen receptors. This study in aged Akita mice aims to draw attention to the clinically important yet understudied subject of the effect of hyperoxia on cardiac parameters in the presence of preexisting comorbidities. The findings would help revise the provision of care for older T1D patients admitted to ICUs.

Cardiopulmonary outcomes following high flow nasal cannula in pediatric population: A systematic review

BACKGROUND

The high-flow nasal cannula (HFNC) has received much attention in various clinical settings and has been approved recently for application in pediatric care.

OBJECTIVES

To determine whether HFNC use improves cardiopulmonary outcomes in pediatric patients with the cardiac disease more effectively than alternative oxygen therapies.

METHODS

Systematic review was performed using PubMed, Scopus, and Web of Science databases. Randomized controlled trials comparing HFNC with alternative oxygen therapies and observational studies that solely reported on the use of HFNC in the pediatric population were included between 2012 and 2022.

RESULTS

Nine studies with approximately 656 patients were reported in this review. HFNC significantly increased systemic oxygen saturation across all literature investigating this parameter. Other notable outcomes in HFNC patients included normalizing heart rate, partial blood pressure, and PaO₂/FiO₂ ratio. However, some studies reported a complication rate concurrent with traditional oxygen therapies, and a suggested HFNC failure rate of 50% was observed.

CONCLUSIONS

Compared with traditional oxygen therapies, HFNC can reduce anatomical dead space and normalize systemic oxygen saturation, PaO2/FiO2 ratio, heart rate, and partial blood pressure. We advocate using HFNC therapy in children with cardiac diseases as the currently available evidence supports HFNC use over other oxygenation treatments in the pediatric population.

Knowledge, attitude, and practice of health professionals for oxygen therapy working in South Gondar zone hospitals, 2021: multicenter cross-sectional study

INTRODUCTION

Therapeutic oxygen should be administered by competent healthcare providers who possess the required competencies of knowledge, skill, and judgment/abilities to make clinical decisions regarding the administration of oxygen. Therefore, this study aimed to assess the knowledge, attitude, and practice of health professionals towards oxygen therapy.

METHODS

A multicenter institutional-based cross-sectional study was conducted among 218 health professionals. The assessment was done with a total of 31 questions. After data cleanup analysis was done with SPSS software. Descriptive, chi-square test, bivariable and multivariable analysis were done accordingly. A p-value of ≤0.05 was considered to have a significant association with the outcome variables.

RESULTS

Among 218 participants, most of the participants (92.7%) were in the age range of less than 40 years old. Nurses were the most responding professions followed by physicians and midwifes. From the participants, around 54.6, 54.6, and 65.1% of respondents answered above the means score of knowledge, attitude and practice questions respectively. Getting training (AOR- 4.15, CI- 1.15-14.6), work experiences of less than 4 years (AOR- 2.54, 95%CI- (1.28-5.05), and availability of guidelines (AOR- 11.5, CI- 3.35-39.6) were significantly associated with knowledge level. Also work experience of fewer than 4 years (AOR- 3.41, 95%CI- (1.58-7.35) and presence of periodic maintenance and supply of oxygen therapy devices (AOR- 4.32, 95% CI- (1.44-12.9) were associated with practice level. Similarly, work experiences < 4 years (AOR- 8.6, 95%CI- (2.6-29) and getting training (AOR- 21.4, 95%CI-(2.7- 27.3) has a positive (direct) association with the level of attitude, and poor level of knowledge (AOR- 12.1, 95%CI (3.42-42.9) was contributed for negative attitude.

CONCLUSION

This study concluded that 54.6, 54.6, and 65.1% of participants have a good level of knowledge, positive attitude, and good level of practice towards oxygen therapy respectively.

Study design for a randomized crossover study investigating myocardial strain analysis in patients with coronary artery disease at hyperoxia and normoxemia prior to coronary artery bypass graft surgery (StrECHO-O2)

BACKGROUND

Supplemental oxygen (O₂) is used routinely during anesthesia. In the treatment of acute myocardial infarction, it has been established that hyperoxia is to be avoided, whereas information on benefit and risk of hyperoxia in patients with stable coronary artery disease (CAD) remain scarce, especially in the setting of general anesthesia. This study will compare the immediate effects of normoxemia and hyperoxia on cardiac function, with a primary focus on changes in peak longitudinal left-ventricular strain, in anesthetized stable chronic CAD patients using peri-operative transesophageal echocardiography (TEE).

METHODS

A single-center randomized cross-over clinical trial will be conducted, enrolling 106 patients undergoing elective coronary artery bypass graft surgery. After the induction of anesthesia and prior to the start of surgery, cardiac function will be assessed by 2D and 3D TEE. Images will be acquired at two different oxygen states for each patient in randomized order. The fraction of inspired oxygen (F_IO₂) will be titrated to a normoxemic state (oxygen saturation of 95-98%) and adjusted to a hyperoxic state (F_IO₂ = 0.8). TEE images will be analyzed in a blinded manner for standard cardiac function and strain parameters.

CONCLUSION

By using myocardial strain assessed by TEE, early and subtle signs of biventricular systolic and diastolic dysfunction can be promptly measured intraoperatively prior to the onset of severe signs of ischemia. The results may help anesthesiologists to better understand the effects of F_IO₂ on cardiac function and potentially tailor oxygen therapy to patients with CAD undergoing general anesthesia.

Prolonged oxygen exposure causes the mobilization and functional damage of stem or progenitor cells and exacerbates cardiac ischemia or reperfusion injury in healthy mice

Oxygen is often administered to patients and occasionally to healthy individuals as well; however, the cellular toxicity of oxygen, especially following prolonged exposure, is widely known. To evaluate the potential effect of oxygen exposure on circulating stem/progenitor cells and cardiac ischemia/reperfusion (I/R) injury, we exposed healthy adult mice to 100% oxygen for 20 or 60 min. We then examined the c-kit-positive stem/progenitor cells and colony-forming cells and measured the cytokine/chemokine levels in peripheral blood. We also induced cardiac I/R injury in mice at 3 h after 60 min of oxygen exposure and examined the recruitment of inflammatory cells and the fibrotic area in the heart. The proportion of c-kit-positive stem/progenitor cells significantly increased in peripheral blood at 3 and 24 h after oxygen exposure for either 20 or 60 min (p < .01 vs. control). However, the abundance of colony-forming cells in peripheral blood conversely decreased at 3 and 24 h after oxygen exposure for only 60 min (p < .05 vs. control). Oxygen exposure for either 20 or 60 min resulted in significantly decreased plasma vascular endothelial growth factor levels at 3 h, whereas oxygen exposure for only 60 min reduced plasma insulin-like growth factor 1 levels at 24 h (p < .05 vs. control). Protein array indicated the increase in the levels of some cytokines/chemokines, such as CXCL6 (GCP-2) at 24 h after 60 min of oxygen exposure. Moreover, oxygen exposure for 60 min enhanced the recruitment of Ly6g- and CD11c-positive inflammatory cells at 3 days (p < .05 vs. control) and increased the fibrotic area at 14 days in the heart after I/R injury (p < .05 vs. control). Prolonged oxygen exposure induced the mobilization and functional impairment of stem/progenitor cells and likely enhanced inflammatory responses to exacerbate cardiac I/R injury in healthy mice.

Is oxygen therapy beneficial for normoxemic patients with acute heart failure? A propensity score matched study

BACKGROUND

The clinical efficiency of routine oxygen therapy is uncertain in patients with acute heart failure (AHF) who do not have hypoxemia. The aim of this study was to investigate the association between oxygen therapy and clinical outcomes in normoxemic patients hospitalized with AHF using real-world data.

METHODS

Normoxemic patients diagnosed with AHF on ICU admission from the electronic ICU (eICU) Collaborative Research Database were included in the current study, in which the study population was divided into the oxygen therapy group and the ambient-air group. Propensity score matching (PSM) was applied to create a balanced covariate distribution between patients receiving supplemental oxygen and those exposed to ambient air. Linear regression and logistic regression models were performed to assess the associations between oxygen therapy and length of stay (LOS), and all-cause in-hospital as well as ICU mortality rates, respectively. A series of sensitivity and subgroup analyses were conducted to further validate the robustness of our findings.

RESULTS

A total of 2922 normoxemic patients with AHF were finally included in the analysis. Overall, 42.1% (1230/2922) patients were exposed to oxygen therapy, and 57.9% (1692/2922) patients did not receive oxygen therapy (defined as the ambient-air group). After PSM analysis, 1122 pairs of patients were matched: each patient receiving oxygen therapy was matched with a patient without receiving supplemental oxygen. The multivariable logistic model showed that there was no significant interaction between the ambient air and oxygen group for all-cause in-hospital mortality [odds ratio (OR) 1.30; 95% confidence interval (CI) 0.92-1.82; P = 0.138] or ICU mortality (OR 1.39; 95% CI 0.83-2.32; P = 0.206) in the post-PSM cohorts. In addition, linear regression analysis revealed that oxygen therapy was associated with prolonged ICU LOS (OR 1.11; 95% CI 1.06-1.15; P <  0.001) and hospital LOS (OR 1.06; 95% CI 1.01-1.10; P = 0.009) after PSM. Furthermore, the absence of an effect of supplemental oxygen on mortality was consistent in all subgroups.

CONCLUSION

Routine use of supplemental oxygen in AHF patients without hypoxemia was not found to reduce all-cause in-hospital mortality or ICU mortality.

Randomized comparison of early supplemental oxygen versus ambient air in patients with confirmed myocardial infarction: Sex-related outcomes from DETO2X-AMI

BACKGROUND

The purpose of this study is to investigate the impact of oxygen therapy on cardiovascular outcomes in relation to sex in patients with confirmed myocardial infarction (MI).

METHODS

The DETermination of the role of Oxygen in suspected Acute Myocardial Infarction trial randomized 6,629 patients to oxygen at 6 L/min for 6-12 hours or ambient air. In the present subgroup analysis including 5,010 patients (1,388 women and 3,622 men) with confirmed MI, we report the effect of supplemental oxygen on the composite of all-cause death, rehospitalization with MI, or heart failure at long-term follow-up, stratified according to sex.

RESULTS

Event rate for the composite endpoint was 18.1% in women allocated to oxygen, compared to 21.4% in women allocated to ambient air (hazard ratio [HR] 0.83, 95% confidence interval [CI] 0.65-1.05). In men, the incidence was 13.6% in patients allocated to oxygen compared to 13.3% in patients allocated to ambient air (HR 1.03, 95% CI 0.86-1.23). No significant interaction in relation to sex was found (P= .16). Irrespective of allocated treatment, the composite endpoint occurred more often in women compared to men (19.7 vs 13.4%, HR 1.51; 95% CI, 1.30-1.75). After adjustment for age alone, there was no difference between the sexes (HR 1.06, 95% CI 0.91-1.24), which remained consistent after multivariate adjustment.

CONCLUSION

Oxygen therapy in normoxemic MI patients did not significantly affect all-cause mortality or rehospitalization for MI or heart failure in women or men. The observed worse outcome in women was explained by differences in baseline characteristics, especially age.

Routine Oxygen Therapy Does Not Improve Health-Related Quality of Life in Patients With Acute Myocardial Infarction-Insights From the Randomized DETO2X-AMI Trial

Background: After decades of ubiquitous oxygen therapy in all patients with acute myocardial infarction (MI), recent guidelines are more restrictive based on lack of efficacy in contemporary trials evaluating hard clinical outcomes in patients without hypoxemia at baseline. However, no evidence regarding treatment effects on health-related quality of life (HRQoL) exists. In this study, we investigated the impact of routine oxygen supplementation on HRQoL 6–8 weeks after hospitalization with acute MI. Secondary objectives included analyses of MI subtypes, further adjustment for infarct size, and oxygen saturation at baseline and 1-year follow-up.

Methods: In the DETermination of the role of Oxygen in suspected Acute Myocardial Infarction (DETO2X-AMI) trial, 6,629 normoxemic patients with suspected MI were randomized to oxygen at 6 L/min for 6–12 h or ambient air. In this prespecified analysis, patients younger than 75 years of age with confirmed MI who had available HRQoL data by European Quality of Life Five Dimensions questionnaire (EQ-5D) in the national registry were included. Primary endpoint was the EQ-5D index assessed by multivariate linear regression at 6–10 weeks after MI occurrence.

Results: A total of 3,086 patients (median age 64, 22% female) were eligible, 1,518 allocated to oxygen and 1,568 to ambient air. We found no statistically significant effect of oxygen therapy on EQ-5D index (−0.01; 95% CI: −0.03–0.01; p = 0.23) or EQ-VAS score (−0.57; 95% CI: −1.88–0.75; p = 0.40) compared to ambient air after 6–10 weeks. Furthermore, no significant difference was observed between the treatment groups in EQ-5D dimensions. Results remained consistent across MI subtypes and at 1-year follow-up, including further adjustment for infarct size or oxygen saturation at baseline.

Conclusions: Routine oxygen therapy provided to normoxemic patients with acute MI did not improve HRQoL up to 1 year after MI occurrence.

Clinical Trial Registration:ClinicalTrials.gov number, NCT01787110.

The effect of oxygen inhalation on cardiac biomarkers in patients presenting with acute ST-segment elevation myocardial infraction: A randomized clinical trial

Background: It is assumed giving oxygen to patients with acute myocardial infraction may increase the oxygenation of the ischemic tissue; however, the usefulness of oxygen in these patients has become a challenging topic. Thus, the present study aimed to determine the effect of oxygen inhalation on cardiac biomarkers in patients with acute myocardial infarction. Methods: This randomized clinical trial study was performed on 2 groups of intervention and control within 2 days of admission to critical care unit (CCU). A total of 64 patients with ST-segment elevation acute myocardial infarction who referred to Zeyaei hospital, Ardakan, were selected using simple random sampling. In the intervention group, the pulse oximetry was monitored and they only breathed regular air and received supplemental oxygen in case their oxygen level dropped below 94%. The levels of creatine kinase-MB and troponin I enzymes were measured. Data were analyzed using SPSS version 20 through repeated measure ANOVA, t test, and chi-squared test. Significance level was set at 0.05. Results: This study showed that during the 48 hours of hospitalization, there were no significant differences between the 2 groups regarding the levels of creatine kinase-MB (p=0.509) and troponin I (p=0.604). Conclusion: Since the level of cardiac biomarkers is a sign of the extent of infracted area, it is assumed receiving supplemental oxygen in patients with acute myocardial infarction has no effect on decreasing the infracted area.

Admission oxygen saturation and all-cause in-hospital mortality in acute myocardial infarction patients: data from the MIMIC-III database

Background

Acute myocardial infarction (AMI) is mainly caused by a mismatch of blood oxygen supply and demand in the myocardium. However, several studies have suggested that excessively high or low arterial oxygen tension could have deleterious effects on the prognosis of AMI patients. Therefore, the relationship between blood oxygenation and clinical outcomes among AMI patients is unclear, and could be nonlinear. In the critical care setting, blood oxygen level is commonly measured continuously using pulse oximetry-derived oxygen saturation (SpO₂). The present study aimed to determine the association between admission SpO₂ levels and all-cause in-hospital mortality, and to elucidate the optimal SpO₂ range with real-world data.

Methods

Patients diagnosed with AMI on admission in the Medical Information Mart for Intensive Care III (MIMIC-III) database were included. A generalized additive model (GAM) with loess smoothing functions was used to determine and visualize the nonlinear relationship between admission SpO₂ levels within the first 24 hours after ICU admission and mortality. Moreover, the Cox regression model was constructed to confirm the association between SpO₂ and mortality.

Results

We included 1,846 patients who fulfilled our inclusion criteria, among whom 587 (31.80%) died during hospitalization. The GAM showed that the relationship between admission SpO₂ levels and all-cause in-hospital mortality among AMI patients was nonlinear, as a U-shaped curve was observed. In addition, the lowest mortality was observed for an SpO₂ range of 94–96%. Adjusted multivariable Cox regression analysis confirmed that the admission SpO₂ level of 94–96% was independently associated with decreased mortality compared to SpO₂ levels <94% [hazard ratio (HR) 1.352; 95% confidence interval (CI): 1.048–1.715; P=0.028] and >96% (HR 1.315; 95% CI: 1.018–1.658; P=0.030).

Conclusions

The relationship between admission SpO₂ levels and all-cause in-hospital mortality followed a U-shaped curve among patients with AMI. The optimal oxygen saturation range was identified as an SpO₂ range of 94–96%, which was independently associated with increased survival in a large and heterogeneous cohort of AMI patients.

Oxygen Management During Cardiopulmonary Bypass: A Single-Center, 8-Year Retrospective Cohort Study

OBJECTIVE

To characterize the institutional oxygen management practices during cardiopulmonary bypass (CPB) in patients undergoing cardiac surgery, including any potential changes during an 8-year study period.

DESIGN

A retrospective cohort study.

SETTING

A tertiary care cardiac surgical program.

PARTICIPANTS

Patients who underwent cardiac surgery involving CPB, with or without hypothermic circulatory arrest (HCA), between January 1, 2010, and December 31, 2017.

MEASUREMENTS AND MAIN RESULTS

In addition to baseline patient characteristics, the authors recorded the partial pressures of arterial oxygen (Pao₂), fraction of inspired oxygen, and mixed venous oxygen saturation during CPB of 696 randomly selected patients during an 8-year study period. The overall mean Pao₂ was 255 ± 48 mmHg, without any significant change during the 8-year study period (p = 0.30). The mean Pao₂ of HCA patients was significantly higher than in patients without HCA (327 ± 93 mmHg v 252 ± 45 mmHg, respectively; p < 0.001).

CONCLUSIONS

The current approach to oxygen management during CPB at the authors' institution is within the range of hyperoxemic levels, and these practices have not changed over time. The impact of these practices on patients' outcomes is not fully understood, and additional studies are needed to establish firm evidence to guide optimal oxygen management practice during CPB.

Effect of Hyperoxia on Myocardial Oxygenation and Function in Patients With Stable Multivessel Coronary Artery Disease

Background

The impact of hyperoxia, that is, supraphysiological arterial partial pressure of O₂, on myocardial oxygen balance and function in stable multivessel coronary artery disease (CAD) is poorly understood. In this observational study, we assessed myocardial effects of inhalational hyperoxia in patients with CAD using a comprehensive cardiovascular magnetic resonance exam.

Methods and Results

Twenty‐five patients with stable CAD underwent a contrast‐free cardiovascular magnetic resonance exam in the interval between their index coronary angiography and subsequent revascularization. The cardiovascular magnetic resonance exam involved T1 and T2 mapping for tissue characterization (fibrosis, edema) as well as function imaging, from which strain analysis was derived, and oxygenation‐sensitive cardiovascular magnetic resonance imaging. The latter modalities were both acquired at room air and after breathing pure O₂ by face mask at 10 L/min for 5 minutes. In 14 of the 25 CAD patients (56%), hyperoxia induced poststenotic myocardial deoxygenation with a subsequent oxygenation discordance across the myocardium. Extent of deoxygenation was correlated to degree of stenosis (r=−0.434, P=0.033). Hyperoxia‐associated poststenotic deoxygenation was accompanied by ipsiregional reduction of diastolic strain rate (1.39±0.57 versus 1.18±0.65; P=0.045) and systolic radial velocity (37.40±17.22 versus 32.88±13.58; P=0.038). Increased T2, as well as lower cardiac index, and defined abnormal strain parameters on room air were predictive for hyperoxia‐induced abnormalities (P<0.05). Furthermore, in patients with prolonged native T1 (>1220 ms), hyperoxia reduced ejection fraction and peak strain.

Conclusions

Patients with CAD and pre‐existent myocardial injury who respond to hyperoxic challenge with strain abnormalities appear susceptible for hyperoxia‐induced regional deoxygenation and deterioration of myocardial function.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02233634.

Effect of Oxygen Therapy on Cardiovascular Outcomes in Relation to Baseline Oxygen Saturation

OBJECTIVES

The aim of this study was to determine the effect of supplemental oxygen in patients with myocardial infarction (MI) on the composite of all-cause death, rehospitalization with MI, or heart failure related to baseline oxygen saturation. A secondary objective was to investigate outcomes in patients developing hypoxemia.

BACKGROUND

In the DETO2X-AMI (Determination of the Role of Oxygen in Suspected Acute Myocardial Infarction) trial, 6,629 normoxemic patients with suspected MI were randomized to oxygen at 6 l/min for 6 to 12 h or ambient air.

METHODS

The study population of 5,010 patients with confirmed MI was divided by baseline oxygen saturation into a low-normal (90% to 94%) and a high-normal (95% to 100%) cohort. Outcomes are reported within 1 year. To increase power, all follow-up time (between 1 and 4 years) was included post hoc, and interaction analyses were performed with oxygen saturation as a continuous covariate.

RESULTS

The composite endpoint of all-cause death, rehospitalization with MI, or heart failure occurred significantly more often in patients in the low-normal cohort (17.3%) compared with those in the high-normal cohort (9.5%) (p < 0.001), and most often in patients developing hypoxemia (23.6%). Oxygen therapy compared with ambient air was not associated with improved outcomes regardless of baseline oxygen saturation (interaction p values: composite endpoint, p = 0.79; all-cause death, p = 0.33; rehospitalization with MI, p = 0.86; hospitalization for heart failure, p = 0.35).

CONCLUSIONS

Irrespective of oxygen saturation at baseline, we found no clinically relevant beneficial effect of routine oxygen therapy in normoxemic patients with MI regarding cardiovascular outcomes. Low-normal baseline oxygen saturation or development of hypoxemia was identified as an independent marker of poor prognosis. (An Efficacy and Outcome Study of Supplemental Oxygen Treatment in Patients With Suspected Myocardial Infarction; NCT01787110).

Oxygen therapy in ST-elevation myocardial infarction

Aims

To determine whether supplemental oxygen in patients with ST-elevation myocardial infarction (STEMI) impacts on procedure-related and clinical outcomes.

Methods and results

The DETermination of the role of Oxygen in suspected Acute Myocardial Infarction (DETO2X-AMI) trial randomized patients with suspected myocardial infarction (MI) to receive oxygen at 6 L/min for 6-12 h or ambient air. In this pre-specified analysis, we included only STEMI patients who underwent percutaneous coronary intervention (PCI). In total, 2807 patients were included, 1361 assigned to receive oxygen, and 1446 assigned to ambient air. The pre-specified primary composite endpoint of all-cause death, rehospitalization with MI, cardiogenic shock, or stent thrombosis at 1 year occurred in 6.3% (86 of 1361) of patients allocated to oxygen compared to 7.5% (108 of 1446) allocated to ambient air [hazard ratio (HR) 0.85, 95% confidence interval (95% CI) 0.64-1.13; P = 0.27]. There was no difference in the rate of death from any cause (HR 0.86, 95% CI 0.61-1.22; P = 0.41), rate of rehospitalization for MI (HR 0.92, 95% CI 0.57-1.48; P = 0.73), rehospitalization for cardiogenic shock (HR 1.05, 95% CI 0.21-5.22; P = 0.95), or stent thrombosis (HR 1.27, 95% CI 0.46-3.51; P = 0.64). The primary composite endpoint was consistent across all subgroups, as well as at different time points, such as during hospital stay, at 30 days and the total duration of follow-up up to 1356 days.

Conclusions

Routine use of supplemental oxygen in normoxemic patients with STEMI undergoing primary PCI did not significantly affect 1-year all-cause death, rehospitalization with MI, cardiogenic shock, or stent thrombosis.

Oxygen Therapy in Myocardial Infarction Patients With or Without Diabetes: A Predefined Subgroup Analysis From the DETO2X-AMI Trial

OBJECTIVE

To determine the effects of oxygen therapy in myocardial infarction (MI) patients with and without diabetes.

RESEARCH DESIGN AND METHODS

In the Determination of the Role of Oxygen in Suspected Acute Myocardial Infarction (DETO2X-AMI) trial, 6,629 normoxemic patients with suspected MI were randomized to oxygen at 6 L/min for 6-12 h or ambient air. In this prespecified analysis involving 5,010 patients with confirmed MI, 934 had known diabetes. Oxidative stress may be of particular importance in diabetes, and the primary objective was to study the effect of supplemental oxygen on the composite of all-cause death and rehospitalization with MI or heart failure (HF) at 1 year in patients with and without diabetes.

RESULTS

As expected, event rates were significantly higher in patients with diabetes compared with patients without diabetes (main composite end point: hazard ratio [HR] 1.60 [95% CI 1.32-1.93], P < 0.01). In patients with diabetes, the main composite end point occurred in 16.2% (72 of 445) allocated to oxygen as compared with 16.6% (81 of 489) allocated to ambient air (HR 0.93 [95% CI 0.67-1.27], P = 0.81). There was no statistically significant difference for the individual components of the composite end point or the rate of cardiovascular death up to 1 year. Likewise, corresponding end points in patients without diabetes were similar between the treatment groups.

CONCLUSIONS

Despite markedly higher event rates in patients with MI and diabetes, oxygen therapy did not significantly affect 1-year all-cause death, cardiovascular death, or rehospitalization with MI or HF, irrespective of underlying diabetes, in line with the results of the entire study.

Effect of oxygen therapy on the risk of mechanical ventilation in emergency acute pulmonary edema patients

OBJECTIVE

We investigated the effects of hyperoxemia on morbidity and mortality in acute cardiogenic pulmonary edema (ACPE).

METHODS

We conducted a retrospective cohort study of patients in our emergency department (ED) with ACPE who received arterial blood gases. Patients were classified based on the first PaO2 as hypoxemic (<75 mmHg), normoxemic (75-100 mmHg) and hyperoxemic (>100 mmHg). The primary outcome was the rates of mechanical ventilation (MV). We also reported adjusted odds ratios (AOR) and their 95% confidence intervals (CI) of the primary outcome after adjusting for predictors of MV determined a priori. Secondary outcomes were median hospital length of stay (LOS) and in-hospital mortality.

RESULTS

We recruited 335 patients; 34.0% had hyperoxemia. The rates of normoxemia and hypoxemia were 27.5% and 38.5%, respectively. The rates of MV were: hypoxemic 60/129 (46.5%) vs. normoxemic 41/92 (44.6%) vs. hyperoxemic 50/114 (43.9%); P = 0.62. The AORs for MV for the hyperoxemic and hypoxemic groups (reference: normoxemic group) were 0.98 (95% CI: 0.53-1.79) and 1.38 (95% CI: 0.77-2.48), respectively. Intubation rates for the groups were: hypoxemic 15/129 (11.6%) vs. normoxemic 6/92 (6.5%) vs. hyperoxemic 12/114 (10.6%); P = 0.43. The secondary outcomes were comparable among the groups. In-hospital mortality rates were: hypoxemic 6/129 (4.7%) vs. 6/92 (6.5%) vs. 10/114 (8.8%); P = 0.42.

CONCLUSION

Our exploratory study did not report effects on mechanical ventilation, median hospital LOS and in-hospital mortality from hyperoxemia compared to hypoxemic and normoxemic ED patients with ACPE. Further studies are warranted to prove or disprove our findings.

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.

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.

Edward F. Adolph Distinguished Lecture. Contemporary model of muscle microcirculation: gateway to function and dysfunction

This review strikes at the very heart of how the microcirculation functions to facilitate blood-tissue oxygen, substrate, and metabolite fluxes in skeletal muscle. Contemporary evidence, marshalled from animals and humans using the latest techniques, challenges iconic perspectives that have changed little over the past century. Those perspectives include the following: the presence of contractile or collapsible capillaries in muscle, unitary control by precapillary sphincters, capillary recruitment at the onset of contractions, and the notion of capillary-to-mitochondrial diffusion distances as limiting O₂ delivery. Today a wealth of physiological, morphological, and intravital microscopy evidence presents a completely different picture of microcirculatory control. Specifically, capillary red blood cell (RBC) and plasma flux is controlled primarily at the arteriolar level with most capillaries, in healthy muscle, supporting at least some flow at rest. In healthy skeletal muscle, this permits substrate access (whether carried in RBCs or plasma) to a prodigious total capillary surface area. Pathologies such as heart failure or diabetes decrease access to that exchange surface by reducing the proportion of flowing capillaries at rest and during exercise. Capillary morphology and function vary disparately among tissues. The contemporary model of capillary function explains how, following the onset of exercise, muscle O₂ uptake kinetics can be extremely fast in health but slowed in heart failure and diabetes impairing contractile function and exercise tolerance. It is argued that adoption of this model is fundamental for understanding microvascular function and dysfunction and, as such, to the design and evaluation of effective therapeutic strategies to improve exercise tolerance and decrease morbidity and mortality in disease.

Oxygen therapy in suspected acute myocardial infarction and concurrent normoxemic chronic obstructive pulmonary disease: a prespecified subgroup analysis from the DETO2X-AMI trial

BACKGROUND

The DETermination of the role of Oxygen in suspected Acute Myocardial Infarction (DETO2X-AMI) trial did not find any benefit of oxygen therapy compared to ambient air in normoxemic patients with suspected acute myocardial infarction. Patients with chronic obstructive pulmonary disease may both benefit and be harmed by supplemental oxygen. Thus we evaluated the effect of routine oxygen therapy compared to ambient air in normoxemic chronic obstructive pulmonary disease patients with suspected acute myocardial infarction.

METHODS AND RESULTS

A total of 6629 patients with suspected acute myocardial infarction were randomly assigned in the DETO2X-AMI trial to oxygen or ambient air. In the oxygen group (n=3311) and the ambient air group (n=3318), 155 and 141 patients, respectively, had chronic obstructive pulmonary disease (prevalence of 4.5%). Patients with chronic obstructive pulmonary disease were older, had more comorbid conditions and experienced a twofold higher risk of death at one year (chronic obstructive pulmonary disease: 32/296 (10.8%) vs. non-chronic obstructive pulmonary disease: 302/6333 (4.8%)). Oxygen therapy compared to ambient air was not associated with improved outcomes at 365 days (chronic obstructive pulmonary disease: all-cause mortality hazard ratio (HR) 0.99, 95% confidence interval (CI) 0.50-1.99, P_interaction=0.96); cardiovascular death HR 0.80, 95% CI 0.32-2.04, P_interaction=0.59); rehospitalisation with acute myocardial infarction or death HR 1.27, 95% CI 0.71-2.28, P_interaction=0.46); hospitalisation for heart failure or death HR 1.08, 95% CI 0.61-1.91, P_interaction=0.77]); there were no significant treatment-by-chronic obstructive pulmonary disease interactions.

CONCLUSIONS

Although chronic obstructive pulmonary disease patients had twice the mortality rate compared to non-chronic obstructive pulmonary disease patients, this prespecified subgroup analysis from the DETO2X-AMI trial on oxygen therapy versus ambient air in normoxemic chronic obstructive pulmonary disease patients with suspected acute myocardial infarction revealed no evidence for benefit of routine oxygen therapy consistent with the main trial's findings.

CLINICAL TRIALS REGISTRATION

NCT02290080.

Hyperoxygenation in pregnancy exerts a more profound effect on cardiovascular hemodynamics than is observed in the nonpregnant state

BACKGROUND

Supplemental oxygen is administered to pregnant women in many different clinical scenarios in obstetric practice. Despite the accepted uses for maternal hyperoxygenation, the impact of hyperoxia on maternal hemodynamic indices has not been evaluated. As a result, there is a paucity of data in the literature in relation to the physiological changes to the maternal circulation in response to supplemental oxygen.

OBJECTIVE

The hemodynamic effects of oxygen therapy are under-recognized and the impact of hyperoxygenation on maternal hemodynamics is currently unknown. Using noninvasive cardiac output monitoring which employs transthoracic bioreactance, we examined the effect of brief hyperoxygenation on cardiac index, systemic vascular resistance, blood pressure, stroke volume, and heart rate in pregnant mothers during the third trimester, compared with those effects observed in a nonpregnant population subjected to the same period of hyperoxygenation.

STUDY DESIGN

Hemodynamic monitoring was performed in a continuous manner over a 30-minute period using noninvasive cardiac output monitoring. Hyperoxygenation (O₂ 100% v/v inhalational gas) was carried out at a rate of 12 L/min via a partial non-rebreather mask for 10-minutes. Cardiac index, systemic vascular resistance, stroke volume, heart rate, and blood pressure were recorded before hyperoxygenation, at completion of hyperoxygenation, and 10 minutes after the cessation of hyperoxygenation. Two-way analysis of variance with repeated measures was used to assess the change in hemodynamic indices over time and the differences between the 2 groups.

RESULTS

Forty-six pregnant and 20 nonpregnant women with a median age of 33 years (interquartile range, 26-38 years) and 32 years (interquartile range, 28-37 years) were recruited prospectively, respectively (P=.82). The median gestational age was 35 weeks (33-37 weeks). In the pregnant group, there was a fall in cardiac index during the hyperoxygenation exposure period (P=.009) coupled with a rise in systemic vascular resistance with no recovery at 10 minutes after cessation of hyperoxygenation (P=.02). Heart rate decreased after hyperoxygenation exposure and returned to baseline by 10 minutes after cessation of therapy. There was a decrease in stroke volume over the exposure period, with no change in systolic or diastolic blood pressure. In the nonpregnant group, there was no significant change in the cardiac index, systemic vascular resistance, stroke volume, heart rate, or systolic or diastolic blood pressure during the course of exposure to hyperoxygenation.

CONCLUSION

Hyperoxygenation during the third trimester is associated with a fall in maternal cardiac index and a rise in systemic vascular resistance without recovery to baseline levels at 10 minutes after cessation of hyperoxygenation. The hemodynamic changes that were observed in this study in response to hyperoxygenation therapy during pregnancy could counteract any intended increase in oxygen delivery. The observed maternal effects of hyperoxygenation call for a reevaluation of the role of hyperoxygenation treatment in the nonhypoxemic pregnant patient.

Oxygen Requirements for Acutely and Critically Ill Patients

Oxygen administration is often assumed to be required for all patients who are acutely or critically ill. However, in many situations, this assumption is not based on evidence. Injured body tissues and cells throughout the body respond both beneficially and adversely to delivery of supplemental oxygen. Available evidence indicates that oxygen administration is not warranted for patients who are not hypoxemic, and hyperoxia may contribute to increased tissue damage and mortality. Nurses must be aware of implications related to oxygen administration for all types of acutely and critically ill patients. These implications include having knowledge of oxygenation processes and pathophysiology; assessing global, tissue, and organ oxygenation status; avoiding either hypoxia or hyperoxia; and creating partnerships with respiratory therapists. Nurses can contribute to patients' oxygen status well-being by being proficient in determining each patient's specific oxygen needs and appropriate oxygen administration.

Impact of early hyperoxia on 28-day in-hospital mortality in patients with myocardial injury

INTRODUCTION

Despite relevant evidence that supplemental oxygen therapy can be harmful to patients with myocardial injury, the association between hyperoxia and the clinical outcome of such patients has not been evaluated. We assessed whether early hyperoxia negatively affects outcomes in hospitalized patients with myocardial injury.

METHODS

This was a retrospective study conducted at a tertiary referral teaching hospital. Between January 2010 and December 2016, 2,376 consecutive emergency department patients with myocardial injury, defined as a peak troponin-I level ≥ 0.2 ng/mL, within the first 24 hours of presentation were included. The metrics used to define hyperoxia were the maximum average partial pressure of oxygen (PaO2MAX), average partial pressure of oxygen (PaO2AVG), and area under the curve during the first 24 hours (AUC24). The association between early hyperoxia within 24 hours after presentation and clinical outcomes was evaluated using multiple imputation and logistic regression analysis. The primary outcome was 28-day in-hospital mortality. The secondary outcomes were new-onset cardiovascular, coagulation, hepatic, renal, and respiratory dysfunctions (sequential organ failure sub-score ≥ 2).

RESULTS

Compared with normoxic patients, the adjusted odds ratios (ORs) for PaO2MAX, PaO2AVG, and AUC24 were 1.55 (95% confidence interval (CI) 1.05-2.27; p = 0.026), 2.13 (95% CI 1.45-3.12; p = 0.001), and 1.73 (95% CI 1.15-2.61; p = 0.008), respectively, in patients with mild hyperoxia and 6.01 (95% CI 3.98-9.07; p < 0.001), 8.92 (95% CI 3.33-23.88; p < 0.001), and 7.32 (95% CI 2.72-19.70; p = 0.001), respectively, in patients with severe hyperoxia. The incidence of coagulation and hepatic dysfunction (sequential organ failure sub-score ≥ 2) was significantly higher in the mild and severe hyperoxia group.

CONCLUSIONS

Hyperoxia during the first 24 hours of presentation is associated with an increased 28-day in-hospital mortality rate and risks of coagulation and hepatic dysfunction in patients with myocardial injury.

The pharmacological treatment of chronic comorbidities in COPD: mind the gap!

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is commonly associated with other chronic diseases, which poses several diagnostic and therapeutic problems. Indeed, important comorbidities frequently remain unrecognized and, then, untreated, whereas respiratory drugs may have non respiratory side effects, and selected non respiratory drugs may variably affect the respiratory function.

OBJECTIVE

to describe: how COPD affects the presentation and contributes to the diagnostic challenges of its most common comorbidities; how coexisting COPD impacts the therapeutic approach to selected comorbidities and viceversa.

METHODS

we distinguish comorbidities of COPD depending upon whether they are complications of COPD or share risk factors, mainly smoke, with it or, finally, aggravate COPD. We describe atypical presentations of and diagnostic clues to comorbidities and suggest screening procedures. Finally, the main therapeutic problems, as resulting from the risk of untoward effects of therapies of COPD and its comorbidity, with special attention to drug-drug interactions and possible overdosages, are described.

RESULTS

selected complications of COPD, such as osteoporosis, sarcopenia and dysphagia, are rarely recognized and treated, likely due to the poor awareness of them. Important comorbidities, such as coronary artery disease, chronic heart failure, obstructive sleep apnoea syndrome and chronic renal failure, also should be systematically searched for because of their commonly variant presentation. Disease-related symptoms should be distinguished from drug effects or drug-drug interaction effects.

CONCLUSIONS

a truly comprehensive view of the complex COPD patient, hopefully capitalizing on multidimensional geriatric assessment, is needed to dissect the many components of health status impairment and to provide the optimal care. Selected screening procedures are highly desirable to identify frequently missed comorbidities. Pharmacosurveillance is an essential part of the approach to COPD and its comorbidities.

Supplemental oxygen therapy does not affect the systemic inflammatory response to acute myocardial infarction

BACKGROUND

Oxygen therapy has been used routinely in normoxemic patients with suspected acute myocardial infarction (AMI) despite limited evidence supporting a beneficial effect. AMI is associated with a systemic inflammation. Here, we hypothesized that the inflammatory response to AMI is potentiated by oxygen therapy.

METHODS

The DETermination of the role of Oxygen in suspected Acute Myocardial Infarction (DETO2X-AMI) multicentre trial randomized patients with suspected AMI to receive oxygen at 6 L min^-1 for 6-12 h or ambient air. For this prespecified subgroup analysis, we recruited patients with confirmed AMI from two sites for evaluation of inflammatory biomarkers at randomization and 5-7 h later. Ninety-two inflammatory biomarkers were analysed using proximity extension assay technology, to evaluate the effect of oxygen on the systemic inflammatory response to AMI.

RESULTS

Plasma from 144 AMI patients was analysed whereof 76 (53%) were randomized to oxygen and 68 (47%) to air. Eight biomarkers showed a significant increase, whereas 13 were decreased 5-7 h after randomization. The inflammatory response did not differ between the two treatment groups neither did plasma troponin T levels. After adjustment for increase in troponin T over time, age and sex, the release of inflammation-related biomarkers was still similar in the groups.

CONCLUSIONS

In a randomized controlled setting of normoxemic patients with AMI, the use of supplemental oxygen did not have any significant impact on the early release of systemic inflammatory markers.

High frequency percussive ventilation increases alveolar recruitment in early acute respiratory distress syndrome: an experimental, physiological and CT scan study

Background

High frequency percussive ventilation (HFPV) combines diffusive (high frequency mini-bursts) and convective ventilation patterns. Benefits include enhanced oxygenation and hemodynamics, and alveolar recruitment, while providing hypothetic lung-protective ventilation. No study has investigated HFPV-induced changes in lung aeration in patients with early acute respiratory distress syndrome (ARDS).

Methods

Eight patients with early non-focal ARDS were enrolled and five swine with early non-focal ARDS were studied in prospective computed tomography (CT) scan and animal studies, in a university-hospital tertiary ICU and an animal laboratory. Patients were optimized under conventional “open-lung” ventilation. Lung CT was performed using an end-expiratory hold (Conv) to assess lung morphology. HFPV was applied for 1 hour to all patients before new CT scans were performed with end-expiratory (HFPV EE) and end-inspiratory (HFPV EI) holds. Lung volumes were determined after software analysis. At specified time points, blood gases and hemodynamic data were collected. Recruitment was defined as a change in non-aerated lung volumes between Conv, HFPV EE and HFPV EI. The main objective was to verify whether HFPV increases alveolar recruitment without lung hyperinflation. Correlation between pleural, upper airways and HFPV-derived pressures was assessed in an ARDS swine-based model.

Results

One-hour HFPV significantly improved oxygenation and hemodynamics. Lung recruitment significantly rose by 12.0% (8.5–18.0%), P = 0.05 (Conv-HFPV EE) and 12.5% (9.3–16.8%), P = 0.003 (Conv-HFPV EI). Hyperinflation tended to increase by 2.0% (0.5–2.5%), P = 0.89 (Conv-HFPV EE) and 3.0% (2.5–4.0%), P = 0.27 (Conv-HFPV EI). HFPV hyperinflation correlated with hyperinflated and normally-aerated lung volumes at baseline: r = 0.79, P = 0.05 and r = 0.79, P = 0.05, respectively (Conv-HFPV EE); and only hyperinflated lung volumes at baseline: r = 0.88, P = 0.01 (Conv-HFPV EI). HFPV CT-determined tidal volumes reached 5.7 (1.1–8.1) mL.kg^-1 of ideal body weight (IBW). Correlations between pleural and HFPV-monitored pressures were acceptable and end-inspiratory pleural pressures remained below 25cmH₂0.

Conclusions

HFPV improves alveolar recruitment, gas exchanges and hemodynamics of patients with early non-focal ARDS without relevant hyperinflation. HFPV-derived pressures correlate with corresponding pleural or upper airways pressures.

Trial registration

ClinicalTrials.gov, NCT02510105. Registered on 1 June 2015. The trial was retrospectively registered.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1924-6) contains supplementary material, which is available to authorized users.

[Comparison of safe duration of apnea and intubation time in face mask ventilation with air versus 100% oxygen during induction of general anesthesia]

OBJECTIVE

To compare the safe duration of apnea and intubation time between face mask ventilation with air and 100% oxygen during induction of general anesthesia.

METHODS

Eighty adult patients with ASA class I or II without predicted difficult airways were scheduled for elective surgery under general anesthesia. The patients were randomized to receive anesthesia induction with preoxygenation [Group 1, n=40, fraction of inspired oxygen (FiO₂)=1] or without preoxygenation (Group2, n=40, FiO₂=0.21). Two experienced anesthesiologists performed the mask ventilation and tracheal intubation during induction, and the assistants adjusted the oxygen concentration and recorded the pulse oxygen saturation (SpO₂) and other variables. The cases where SpO₂ decreased to below 90% before accomplishment of intubation were considered unsuccessful, and mask ventilation with 100% oxygen was given. After tracheal intubation, mechanical ventilation was not initiated until the SpO₂ decreased to 90%. The number of unsuccessful cases, the safe duration of apnea and intubation time were recorded in the two groups.

RESULTS

There was no unsuccessful case in either groups. The safe duration of apnea was 469.5∓143.0 s in Group 1 and 63.6∓20.0 s in Group 2, and the intubation time was 34.4∓12.6 s and 32.8∓9.6 s, respectively. The safe duration of apnea was significantly longer than the intubation time in both groups (P<0.01). The intubation time and the number of cases with SpO₂≥90% before completion of tracheal intubation were similar between the two groups. The safe duration of apnea was significantly shorter in Group 2 than in Group 1 (P<0.01) and was correlated with the body mass index of the patients (P<0.05).

CONCLUSION

Anesthesia induction without preoxygenation can provide sufficient time for experienced anesthesiologists to complete tracheal intubation.

Oxygen Therapy in Suspected Acute Myocardial Infarction

BACKGROUND

The clinical effect of routine oxygen therapy in patients with suspected acute myocardial infarction who do not have hypoxemia at baseline is uncertain.

METHODS

In this registry-based randomized clinical trial, we used nationwide Swedish registries for patient enrollment and data collection. Patients with suspected myocardial infarction and an oxygen saturation of 90% or higher were randomly assigned to receive either supplemental oxygen (6 liters per minute for 6 to 12 hours, delivered through an open face mask) or ambient air.

RESULTS

A total of 6629 patients were enrolled. The median duration of oxygen therapy was 11.6 hours, and the median oxygen saturation at the end of the treatment period was 99% among patients assigned to oxygen and 97% among patients assigned to ambient air. Hypoxemia developed in 62 patients (1.9%) in the oxygen group, as compared with 254 patients (7.7%) in the ambient-air group. The median of the highest troponin level during hospitalization was 946.5 ng per liter in the oxygen group and 983.0 ng per liter in the ambient-air group. The primary end point of death from any cause within 1 year after randomization occurred in 5.0% of patients (166 of 3311) assigned to oxygen and in 5.1% of patients (168 of 3318) assigned to ambient air (hazard ratio, 0.97; 95% confidence interval [CI], 0.79 to 1.21; P=0.80). Rehospitalization with myocardial infarction within 1 year occurred in 126 patients (3.8%) assigned to oxygen and in 111 patients (3.3%) assigned to ambient air (hazard ratio, 1.13; 95% CI, 0.88 to 1.46; P=0.33). The results were consistent across all predefined subgroups.

CONCLUSIONS

Routine use of supplemental oxygen in patients with suspected myocardial infarction who did not have hypoxemia was not found to reduce 1-year all-cause mortality. (Funded by the Swedish Heart-Lung Foundation and others; DETO2X-AMI ClinicalTrials.gov number, NCT01787110 .).

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.

Hyperoxia Reduces Oxygen Consumption in Children with Pulmonary Hypertension

High inspired oxygen concentration (FiO₂ > 0.85) is administered to test pulmonary vascular reactivity in children with pulmonary hypertension (PH). It is difficult to measure oxygen consumption (VO₂) if the subject is breathing a hyperoxic gas mixture so the assumption is made that baseline VO₂ does not change. We hypothesized that hyperoxia changes VO₂. We sought to compare the VO₂ measured by a thermodilution catheter in room air and hyperoxia. A retrospective review of the hemodynamic data obtained in children with PH who underwent cardiac catheterization was conducted between 2009 and 2014. Cardiac index (CI) was measured by a thermodilution catheter in room air and hyperoxia. VO₂ was calculated using the equation CI = VO₂/arterial-venous oxygen content difference. Data were available in 24 subjects (males = 10), with median age 8.3 years (0.8-17.6 years), weight 23.3 kg (7.5-95 kg), and body surface area 0.9 m² (0.4-2.0 m²). In hyperoxia compared with room air, we measured decreased VO₂ (154 ± 38 to 136 ± 34 ml/min/m², p = 0.007), heart rate (91 [Formula: see text] 20 to 83 [Formula: see text] 21 beats/minute, p=0.005), mean pulmonary artery pressure (41 [Formula: see text] 16 to 35 [Formula: see text] 14 mmHg, p=0.024), CI (3.6 [Formula: see text] 0.8 to 3.3 [Formula: see text] 0.9 L/min/m², p = 0.03), pulmonary vascular resistance (9 [Formula: see text] 6 to 7 [Formula: see text] 3 WU m², p = 0.029), increased mean aortic (61 [Formula: see text] 11 to 67 [Formula: see text] 11 mmHg, p = 0.005), pulmonary artery wedge pressures (11 [Formula: see text] 8 to 13 [Formula: see text] 9 mmHg, p = 0.006), and systemic vascular resistance (12 [Formula: see text] 6 to 20 [Formula: see text] 7 WU m², p=0.001). Hyperoxia decreased VO₂ and CI and caused pulmonary vasodilation and systemic vasoconstriction in children with PH. The assumption that VO₂ remains unchanged in hyperoxia may be incorrect and, if the Fick equation is used, may lead to an overestimation of pulmonary blood flow and underestimation of PVRI.

Proteomic analysis of mitochondrial proteins in the guinea pig heart following long-term normobaric hyperoxia

Normobaric hyperoxia is applied for the treatment of a wide variety of diseases and clinical conditions related to ischemia or hypoxia, but it can increase the risk of tissue damage and its efficiency is controversial. In the present study, we analyzed cardiac mitochondrial proteome derived from guinea pigs after 60 h exposure to 100% molecular oxygen (NBO) or O₂ enriched with oxygen cation (NBO+). Two-dimensional gel electrophoresis followed by MALDI-TOF/TOF mass spectrometry identified twenty-two different proteins (among them ten nonmitochondrial) that were overexpressed in NBO and/or NBO+ group. Identified proteins were mainly involved in cellular energy metabolism (tricarboxylic acid cycle, oxidative phosphorylation, glycolysis), cardioprotection against stress, control of mitochondrial function, muscle contraction, and oxygen transport. These findings support the viewpoint that hyperoxia is associated with cellular stress and suggest complex adaptive responses which probably contribute to maintain or improve intracellular ATP levels and contractile function of cardiomyocytes. In addition, the results suggest that hyperoxia-induced cellular stress may be partially attenuated by utilization of NBO+ treatment.

The 2017 International Joint Working Group recommendations of the Indian College of Cardiology, the Academic College of Emergency Experts, and INDUSEM on the management of low-risk chest pain in emergency departments across India

There have been no published recommendations for the management of low-risk chest pain in emergency departments (EDs) across India. This is despite the fact that chest pain continues to be one of the most common presenting complaints in EDs. Risk stratification of patients utilizing an accelerated diagnostic protocol has been shown to decrease hospitalizations by approximately 40% with a low 30-day risk of major adverse cardiac events. The experts group of academic leaders from the Indian College of Cardiology and Academic College of Emergency Experts in India partnered with academic experts in emergency medicine and cardiology from leading institutions in the UK and USA collaborated to study the scientific evidence and make recommendations to guide emergency physicians working in EDs across India.

2016: emergency medical services annotated literature in review

In the daily practice of emergency medicine, physicians constantly interact with components of emergency medical services systems. The provision of high-quality care in the prehospital setting requires emergency physicians to remain abreast of recent literature that may inform the care of patients prior to their arrival at the emergency department. This literature review will examine some recent trends in the prehospital literature. In addition, the review will highlight important areas of clinical practice which represent some of the many intersections between emergency medicine and emergency medical services such as cardiac arrest and airway management.

Fiber-optic fluorescence-quenching oxygen partial pressure sensor using platinum octaethylporphyrin

The development and bench testing of a fiber-optic oxygen sensor is described. The sensor is designed for measurement of tissue oxygen levels in the mucosa of the digestive tract. The materials and construction are optimized for insertion through the mouth for measurement in the lower esophagus. An oxygen-sensitive fluorescence-quenching film was applied as a solution of platinum octaethylporphyrin (PtOEP) poly(ethyl methacrylate) (PEMA) and dichloromethane and dip coated onto the distal tip of the fiber. The sensor was tested by comparing relative fluorescence when immersed in liquid water at 37°C, at a range of partial pressures (0-101 kPa). Maximum relative fluorescence at most oxygen concentrations was seen when the PtOEP concentration was 0.1  g.L^-1, four layers of coating solution were applied, and a fiber core radius of 600 μm was selected, giving a Stern-Volmer constant of 0.129  kPa^-1. The performance of the sensor is suitable for many in vivo applications, particularly mucosal measurements. It has sufficient sensitivity, is sterilizable, and is sufficiently flexible and robust for insertion via the mouth without damage to the probe or risk of harm to the patient.

Cardiac catheterization in children with pulmonary hypertensive vascular disease: consensus statement from the Pulmonary Vascular Research Institute, Pediatric and Congenital Heart Disease Task Forces

Cardiac catheterization is important in the diagnosis and risk stratification of pulmonary hypertensive vascular disease (PHVD) in children. Acute vasoreactivity testing provides key information about management, prognosis, therapeutic strategies, and efficacy. Data obtained at cardiac catheterization continue to play an important role in determining the surgical options for children with congenital heart disease and clinical evidence of increased pulmonary vascular resistance. The Pediatric and Congenital Heart Disease Task Forces of the Pulmonary Vascular Research Institute met to develop a consensus statement regarding indications for, conduct of, acute vasoreactivity testing with, and pitfalls and risks of cardiac catheterization in children with PHVD. This document contains the essentials of those discussions to provide a rationale for the hemodynamic assessment by cardiac catheterization of children with PHVD.

Oxigenoterapia inalatória em idosos internados em um hospital público

Resumo Objetivos: Descrever as características da oxigenoterapia inalatória (OI) utilizada em idosos internados no setor de clínica médica de um hospital público brasileiro, bem como verificar o conhecimento dos acompanhantes sobre esta terapia. Método: Estudo observacional, transversal e descritivo. A amostra foi composta por 52 idosos internados no setor de clínica médica de um hospital público de Minas Gerais por dois meses. As características da aplicação da OI, os aspectos sociodemográficos e características gerais de saúde do grupo foram avaliados pela análise dos prontuários, prescrições médicas e observação in loco. O conhecimento dos acompanhantes sobre a OI foi avaliado por meio de entrevista estruturada. A análise estatística contemplou análises univariadas exploratórias, com frequências das variáveis categóricas e estatísticas descritivas das variáveis contínuas. Resultados: Houve predomínio do sexo feminino (53,8%); idade média 75 anos; baixa escolaridade (dois anos) e renda per capita (entre um e três salários mínimos); situação conjugal casado (42,2%); não tabagistas (48,1%); 67,3% não estavam em ventilação mecânica anterior e 61,5% estavam em tratamento fisioterapêutico. A principal evolução foi alta sem OI (53,8%). O cateter nasal foi o dispositivo mais utilizado (51,9%); 42,0% das prescrições não foram documentadas; a monitorização esteve presente em 76,9%; 81,8% dos acompanhantes não sabiam o que era o dispositivo da OI e 27,0% relataram ter alterado o dispositivo de oferta de oxigênio. Conclusão: Este estudo mostrou características relevantes da aplicação da OI em idosos internados em um hospital público, demonstrando a necessidade de padronização das indicações, prescrições e monitorização dos idosos em OI, com medidas para a educação da equipe de saúde e acompanhantes.

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.

Implementation of a titrated oxygen protocol in the out-of-hospital setting

Oxygen is one of the most frequently-used therapeutic agents in medicine and the most commonly administered drug by prehospital personnel. There is increasing evidence of harm with too much supplemental oxygen in certain conditions, including stroke, chronic obstructive pulmonary disease (COPD), neonatal resuscitations, and in postresuscitation care. Recent guidelines published by the British Thoracic Society (BTS) advocate titrated oxygen therapy, but these guidelines have not been widely adapted in the out-of-hospital setting where high-flow oxygen is the standard. This report is a description of the implementation of a titrated oxygen protocol in a large urban-suburban Emergency Medical Services (EMS) system and a discussion of the practical application of this out-of-hospital protocol.

DETermination of the role of OXygen in suspected Acute Myocardial Infarction trial

BACKGROUND

The use of supplemental oxygen in the setting of suspected acute myocardial infarction (AMI) is recommended in international treatment guidelines and established in prehospital and hospital clinical routine throughout the world. However, to date there is no conclusive evidence from adequately designed and powered trials supporting this practice. Existing data are conflicting and fail to clarify the role of supplemental oxygen in AMI.

METHODS

A total of 6,600 normoxemic (oxygen saturation [SpO2] ≥90%) patients with suspected AMI will be randomly assigned to either supplemental oxygen 6 L/min delivered by Oxymask (MedCore Sweden AB, Kista, Sweden) for 6 to 12 hours in the treatment group or room air in the control group. Patient inclusion and randomization will take place at first medical contact, either before hospital admission or at the emergency department. The Swedish Web-system for Enhancement and Development of Evidence-based care in Heart disease Evaluated According to Recommended Therapies registry will be used for online randomization, allowing inclusion of a broad population of all-comers. Follow-up will be carried out in nationwide health registries and Swedish Web-system for Enhancement and Development of Evidence-based care in Heart disease Evaluated According to Recommended Therapies. The primary objective is to evaluate whether oxygen reduces 1-year all-cause mortality. Secondary end points include 30-day mortality, major adverse cardiac events, and health economy. Prespecified subgroups include patients with confirmed AMI and certain risk groups. In a 3-month pilot study, the study concept was found to be safe and feasible.

CONCLUSION

The need to clarify the uncertainty of the role of supplemental oxygen therapy in the setting of suspected AMI is urgent. The DETO2X-AMI trial is designed and powered to address this important issue and may have a direct impact on future recommendations.