A New Promising Treatment Strategy for Carbon Monoxide Poisoning: High Flow Nasal Cannula Oxygen Therapy

Respiratory support in the emergency department: A systematic review and meta-analysis

BACKGROUND

An estimated 20% of emergency department (ED) patients require respiratory support (RS). Evidence suggests that nasal high flow (NHF) reduces RS need.

AIMS

This review compared NHF to conventional oxygen therapy (COT) or noninvasive ventilation (NIV) in adult ED patients.

METHOD

The systematic review (SR) and meta-analysis (MA) methods reflect the Cochrane Collaboration methodology. Six databases were searched for randomized controlled trials (RCTs) comparing NHF to COT or NIV use in the ED. Three summary estimates were reported: (1) need to escalate care, (2) mortality, and (3) adverse events (AEs).

RESULTS

This SR and MA included 18 RCTs (n = 1874 participants). Two of the five MA conclusions were statistically significant. Compared with COT, NHF reduced the risk of escalation by 45% (RR 0.55; 95% CI [0.33, 0.92], p = .02, NNT = 32); however, no statistically significant differences in risk of mortality (RR 1.02; 95% CI [0.68, 1.54]; p = .91) and AE (RR 0.98; 95% CI [0.61, 1.59]; p = .94) outcomes were found. Compared with NIV, NHF increased the risk of escalation by 60% (RR 1.60; 95% CI [1.10, 2.33]; p = .01); mortality risk was not statistically significant (RR 1.23, 95% CI [0.78, 1.95]; p = .37).

LINKING EVIDENCE TO ACTION

Evidence-based decision-making regarding RS in the ED is challenging. ED clinicians have at times had to rely on non-ED evidence to support their practice. Compared with COT, NHF was seen to be superior and reduced the risk of escalation. Conversely, for this same outcome, NIV was superior to NHF. However, substantial clinical heterogeneity was seen in the NIV delivered. Research considering NHF versus NIV is needed. COVID-19 has exposed the research gaps and slowed the progress of ED research.

Comparing high-flow nasal oxygen therapy and normobaric oxygen therapy on the treatment of carbon monoxide poisoning

AIM

We aimed to investigate whether there is a difference in the rate of decrease in carboxyhemoglobin (COHB) values between high-flow nasal oxygen (HFNO) and normobaric oxygen (NBO) therapy.

MATERIAL AND METHOD

This retrospective observational study included patients with carbon monoxide poisoning who were treated with HFNO or NBO (control group). All patients were started on NBO therapy with a non-rebreather face mask at a rate of 15 L/min. In the NBO group, NBO treatment was continued until the COHB value fell below 10%. In the HFNO group, as soon as the preparation of the HFNO device was completed, NBO treatment was terminated and HFNO treatment was started and continued until the COHB value fell below 10%. The primary outcome of the study was the difference between HFNO and NBO in terms of COHB half-life rates.

RESULTS

A total of 81 patients were included in the study, 44 in the HFNO group and 37 in the NBO group. The median of COHB t1/2 values between HFNO and the NBO treatment groups were 47.3 (IQR: 25-75%: 31.5-65.4) and 46 (IQR: 25-75%: 32.3-56.2), respectively, but this difference was not statistically significant (p = 0.81).

CONCLUSION

The results of this study suggest that HFNO treatment does not have a significant advantage over NBO treatment in the carbon monoxide elimination rate within the first 60 min of treatment.

Effects of hyperbaric oxygen on Notch signaling pathway after severe carbon monoxide poisoning in mice

Demyelination of the cerebral white matter is the most common pathological change after carbon monoxide (CO) poisoning. Notch signaling, the mechanism underlying the differentiation of astrocytes and oligodendrocytes, is critical to remyelination of the white matter after brain lesion. The purpose of this work was to determine the effects of hyperbaric oxygen (HBO) on Notch signaling pathway after CO poisoning for the explanation of the protective effects of HBO on CO-poisoning-related cerebral white matter demyelination. The male C57 BL/6 mice with severe CO poisoning were treated by HBO. And HBO therapy shortened the escape latency and improved the body mass after CO poisoning. HBO therapy also significantly suppressed protein and mRNA levels of Notch1 and Hes5 after CO poisoning. Our findings suggested that HBO could suppress the activation of Notch signaling pathway after CO poisoning, which is the mechanism underlying the neuroprotection of HBO on demyelination after severe CO poisoning.

Oxygenation Performance of Different Non-Invasive Devices for Treatment of Decompression Illness and Carbon Monoxide Poisoning

Study Objective: Application of high concentrations of oxygen to increase oxygen partial pressure (pO2) is the most important treatment for patients with carbon monoxide intoxication or divers with suspected decompression illness. The aim of this study was to evaluate the oxygenation performance of various non-invasive oxygen systems.

Methods: The effect of different oxygen systems on arterial pO2, pCO2 and pH and their subjective comfort was evaluated in 30 healthy participants. Eight devices were included: nasal cannula, non-rebreather mask, AirLife Open mask, Flow-Safe II CPAP device, SuperNO₂VA nasal PAP device, all operated with 15 L/min constant flow oxygen; nasal high-flow (50 L/min flow, 1.0 FiO2), non-invasive positive pressure ventilation (NPPV, 12 PEEP, 4 ASB, 1.0 FiO2) and a standard diving regulator (operated with pure oxygen).

Results: Diving regulator, SuperNO₂VA, nasal high-flow and NPPV achieved mean arterial pO2 concentrations between 538 and 556 mm Hg within 5 minutes. The AirLife Open mask, the nasal cannula and the non-rebreather mask achieved concentrations of 348–451 mm Hg and the Flow-Safe II device 270 mm Hg. Except for the AirLife open mask, pCO2 decreased and pH increased with all devices. The highest pH values were observed with NPPV, diving regulator, Flow-Safe II and nasal high-flow but apparent hyperventilation was uncommon. The AirLife Open and the non-rebreather mask were the most comfortable, the SuperNO₂VA and the nasal cannula the most uncomfortable devices.

Conclusion: A standard diving regulator and the SuperNO₂VA device were equally effective in providing highest physiologically possible pO2 as compared to nasal high-flow and NPPV.

German S3 Guideline: Oxygen Therapy in the Acute Care of Adult Patients

BACKGROUND

Oxygen (O2) is a drug with specific biochemical and physiological properties, a range of effective doses and may have side effects. In 2015, 14% of over 55,000 hospital patients in the UK were using oxygen. 42% of patients received this supplemental oxygen without a valid prescription. Health care professionals are frequently uncertain about the relevance of hypoxemia and have low awareness about the risks of hyperoxemia. Numerous randomized controlled trials about targets of oxygen therapy have been published in recent years. A national guideline is urgently needed.

METHODS

A national S3 guideline was developed and published within the Program for National Disease Management Guidelines (AWMF) with participation of 10 medical associations. A literature search was performed until February 1, 2021, to answer 10 key questions. The Oxford Centre for Evidence-Based Medicine (CEBM) System ("The Oxford 2011 Levels of Evidence") was used to classify types of studies in terms of validity. Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used for assessing the quality of evidence and for grading guideline recommendation, and a formal consensus-building process was performed.

RESULTS

The guideline includes 34 evidence-based recommendations about indications, prescription, monitoring and discontinuation of oxygen therapy in acute care. The main indication for O2 therapy is hypoxemia. In acute care both hypoxemia and hyperoxemia should be avoided. Hyperoxemia also seems to be associated with increased mortality, especially in patients with hypercapnia. The guideline provides recommended target oxygen saturation for acute medicine without differentiating between diagnoses. Target ranges for oxygen saturation are based depending on ventilation status risk for hypercapnia. The guideline provides an overview of available oxygen delivery systems and includes recommendations for their selection based on patient safety and comfort.

CONCLUSION

This is the first national guideline on the use of oxygen in acute care. It addresses health care professionals using oxygen in acute out-of-hospital and in-hospital settings.

[German S3 Guideline - Oxygen Therapy in the Acute Care of Adult Patients]

BACKGROUND

 Oxygen (O₂) is a drug with specific biochemical and physiologic properties, a range of effective doses and may have side effects. In 2015, 14 % of over 55 000 hospital patients in the UK were using oxygen. 42 % of patients received this supplemental oxygen without a valid prescription. Healthcare professionals are frequently uncertain about the relevance of hypoxemia and have low awareness about the risks of hyperoxemia. Numerous randomized controlled trials about targets of oxygen therapy have been published in recent years. A national guideline is urgently needed.

METHODS

 A S3-guideline was developed and published within the Program for National Disease Management Guidelines (AWMF) with participation of 10 medical associations. Literature search was performed until Feb 1st 2021 to answer 10 key questions. The Oxford Centre for Evidence-Based Medicine (CEBM) System ("The Oxford 2011 Levels of Evidence") was used to classify types of studies in terms of validity. Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used and for assessing the quality of evidence and for grading guideline recommendation and a formal consensus-building process was performed.

RESULTS

 The guideline includes 34 evidence-based recommendations about indications, prescription, monitoring and discontinuation of oxygen therapy in acute care. The main indication for O₂ therapy is hypoxemia. In acute care both hypoxemia and hyperoxemia should be avoided. Hyperoxemia also seems to be associated with increased mortality, especially in patients with hypercapnia. The guideline provides recommended target oxygen saturation for acute medicine without differentiating between diagnoses. Target ranges for oxygen saturation are depending on ventilation status risk for hypercapnia. The guideline provides an overview of available oxygen delivery systems and includes recommendations for their selection based on patient safety and comfort.

CONCLUSION

 This is the first national guideline on the use of oxygen in acute care. It addresses healthcare professionals using oxygen in acute out-of-hospital and in-hospital settings. The guideline will be valid for 3 years until June 30, 2024.

High flow nasal cannula for adult acute hypoxemic respiratory failure in the ED setting: A narrative review

Introduction

High flow nasal cannula (HFNC) is a noninvasive ventilation (NIV) system that has demonstrated promise in the emergency department (ED) setting.

Objective

This narrative review evaluates the utility of HFNC in adult patients with acute hypoxemic respiratory failure in the ED setting.

Discussion

HFNC provides warm (37 °C), humidified (100% relative humidity) oxygen at high flows with a reliable fraction of inspired oxygen (FiO₂). HFNC can improve oxygenation, reduce airway resistance, provide humidified flow that can flush anatomical dead space, and provide a low amount of positive end expiratory pressure. Recent literature has demonstrated efficacy in acute hypoxemic respiratory failure, including pneumonia, acute respiratory distress syndrome (ARDS), coronavirus disease 2019 (COVID-19), interstitial lung disease, immunocompromised states, the peri-intubation state, and palliative care, with reduced need for intubation, length of stay, and mortality in some of these conditions. Individual patient factors play an important role in infection control risks with respect to the use of HFNC in patients with COVID-19. Appropriate personal protective equipment, adherence to hand hygiene, surgical mask placement over the HFNC device, and environmental controls promoting adequate room ventilation are the foundation for protecting healthcare personnel. Frequent reassessment of the patient placed on HFNC is necessary; those with severe end organ dysfunction, thoracoabdominal asynchrony, significantly increased respiratory rate, poor oxygenation despite HFNC, and tachycardia are at increased risk of HFNC failure and need for further intervention.

Conclusions

HFNC demonstrates promise in several conditions requiring respiratory support. Further randomized trials are needed in the ED setting.

Treatment of carbon monoxide poisoning: high-flow nasal cannula versus non-rebreather face mask

OBJECTIVE

In this study, the aim was to compare the rate of decrease in carboxyhemoglobin (COHb) values at consecutive time points and calculate the half-life of COHb (COHb t½) in patients admitted to the emergency department (ED) with carbon monoxide (CO) poisoning and treated with either high flow nasal cannula oxygen therapy (HFNC) or non-rebreather face mask (NRFM).

METHODS

This retrospective, cohort study with historical controls was performed over a 2-year period and included adult patients with CO poisoning, whose COHb values were checked. The HFNC group consisted of patients admitted to the ED with CO poisoning when HFNC was available in the hospital, while the NRFM group consisted of patients who presented to the ED with CO poisoning before the availability of HFNC. The primary outcome of the study was to detect the COHb t½.

RESULTS

A total of 71 patients were enrolled in the study. While 35 patients received oxygen with NRFM, 36 patients received HFNC. The mean COHb t½ in the HFNC group was 41.1 min (95% CI: 31.0-58.4) and 64.0 min (95% CI: 43.5-114.4) in the NRFM group. We did not find a significant difference in the COHb t½ between the HFNC group and NRFM group (p = 0.099). COHb levels between treatment arms at serial time points showed a statistically significant difference at 60 min (p = 0.048). We compared the decay constant and half-life of COHb between groups according to gender. In both genders, COHb t½ was significantly different between groups, and COHb t½ was lower in the patients treated with HFNC.

CONCLUSION

HFNC was effective in reducing the half-life of COHb values in patients with carbon monoxide poisoning. Prospective studies to be conducted in larger groups are needed to fully understand the effect of HFNC on carbon monoxide poisoning.

Blood carboxyhemoglobin elimination curve, half-lifetime, and arterial-venous differences in acute phase of carbon monoxide poisoning in ovine smoke inhalation injury model

Smoke inhalation injury (SII) affects more than 50,000 people annually causing carbon monoxide (CO) poisoning. Although the increased blood level of carboxyhemoglobin (CO-Hb) is frequently used to confirm the diagnosis of SII, knowledge of its elimination in the acute phase is still limited. The aim of this study is to determine CO-Hb elimination rates and their differences in arterial (aCO-Hb) and mixed-venous (vCO-Hb) blood following severe SII in a clinically relevant ovine model. Forty-three chronically instrumented female sheep were subjected to SII (12 breaths, 4 sets) through tracheostomy tube under anesthesia and analgesia. After the SII, sheep were awakened and placed on a mechanical ventilator (FiO₂ = 1.0, tidal volume 12 mL/kg, and PEEP = 5cmH₂O) and monitored. Arterial and mixed-venous blood samples were withdrawn simultaneously for blood gas analysis at various time points to determine CO-HB half-lifetime and an elimination curve. The mean of highest aCO-Hb level during SII was 70.8 ± 13.9%. The aCO-Hb elimination curve showed an approximated exponential decay during the first 60 min. Per mixed linear regression model analysis, aCO-Hb significantly (p < 0.001) declined (4.3%/minute) with a decay constant lambda of 0.044. With this lambda, mean lifetime and half-lifetime of aCO-Hb were 22.7 and 15.7 min, respectively. The aCO-Hb was significantly lower compared to vCO-Hb at all-time points (0-180 min). To our knowledge, this is the first report describing CO-Hb elimination curve in the acute phase after severe SII in the clinically relevant ovine model. Our data shows that CO-Hb is decreasing in linear manner with supportive mechanical ventilation (0-60 min). The results may help to understand CO-Hb elimination curve in the acute phase and improvement of pre-hospital and initial clinical care in patients with CO poisoning.

S-100β in predicting the need of hyperbaric oxygen in CO-induced delayed neurological sequels

BACKGROUND

Delayed neurological sequels (DNS) have been described after carbon monoxide (CO) poisoning. There is a need to find a new prognostic marker to guide the use of hyperbaric oxygen (HBO) therapy.

AIM

To evaluate serum S-100β level in patients presenting with acute CO poisoning as an indicator of poisoning severity and predictor of DNS occurrence and HBO need in those patients.

METHODS

This prospective cohort study included patients with acute CO poisoning. On admission, carboxyhemoglobin (COHb) and S-100β levels were measured. Patients were followed up for 6 months for signs of DNS.

RESULTS

Out of 50 patients, 6 only developed DNS. The mean of S-100β levels was significantly higher in patients with severe poisoning and those with DNS. Receiver operating characteristic curve analysis revealed that S-100β had an area under the curve 0. 871; at a cutoff value ≥ 0.67 µg/L, its sensitivity and specificity were 100% and 77.3%, respectively. The sensitivity of S-100β was significantly higher than that of COHb, while its specificity and overall accuracy were significantly higher than those of HBO criteria.

CONCLUSION

Serum S-100β level on admission could be a marker of poisoning severity and a predictor of CO-induced DNS development that guides the use of HBO therapy.

Carbon Monoxide Poisoning Effectively Treated with High-flow Nasal Cannula

Carbon monoxide (CO) poisoning is typically treated by administration of oxygen via non-rebreather mask (NRB). High-flow nasal cannula (HFNC) is an alternative to NRB in a variety of disease states. We report a case of the novel use of HFNC in the treatment of acute CO poisoning. A 29-year-old man presented with a carboxyhemoglobin (COHb) level of 29.8%. He was treated with HFNC, and COHb levels declined to 5.4% in 230 minutes. Given several theoretical advantages of HFNC relative to NRB, HFNC is a potential option for use in the treatment of CO poisoning.

Effect of Hyperbaric Oxygen on Neurologic Sequelae and All-Cause Mortality in Patients with Carbon Monoxide Poisoning: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND Hyperbaric oxygen (HBO) is used in patients with carbon monoxide (CO) poisoning to prevent the occurrence of delayed neurological sequelae. However, inconsistent results were obtained regarding the treatment effects of HBO. Therefore, the current meta-analysis was conducted based on published randomized controlled trials (RCTs) to determine the effect of HBO on neurologic sequelae and all-cause mortality in patients with CO poisoning. MATERIAL AND METHODS Electronic databases MedLine, EmBase, and the Cochrane Library were searched for relevant RCTs from inception to March 1, 2019. The pooled relative risks (RRs) and weighted mean differences (WMDs) with corresponding 95% confidence intervals (CIs) were calculated to evaluate the outcomes by using a random-effects model. Sensitivity, subgroup, and publication bias analyses were also conducted. RESULTS Seven RCTs, including 9 cohorts and a total of 2023 patients with CO poisoning, were enrolled in this study. The summary results revealed that HBO showed an association with lower risk of memory impairment compared to patients receiving normobaric oxygen (NBO), whereas 2 sessions of HBO showed an association with higher risk of memory impairment compared to those who received 1 session of HBO. Moreover, HBO was associated with increased neuropsychologic scores of block design and trail making when compared with NBO. No other significant differences regarding the treatment effects of HBO were observed. CONCLUSIONS These results indicate that HBO therapy significantly reduces the risk of memory impairment compared to NBO, but 2 sessions of HBO might not be better for memory impairment than 1 session of HBO.