Carbon monoxide poisoning

Carbon Monoxide as a Potential Therapeutic Agent: A Molecular Analysis of Its Safety Profiles

Carbon monoxide (CO) is endogenously produced in mammals, with blood concentrations in the high micromolar range in the hemoglobin-bound form. Further, CO has shown therapeutic effects in various animal models. Despite its reputation as a poisonous gas at high concentrations, we show that CO should have a wide enough safety margin for therapeutic applications. The analysis considers a large number of factors including levels of endogenous CO, its safety margin in comparison to commonly encountered biomolecules or drugs, anticipated enhanced safety profiles when delivered via a noninhalation mode, and the large amount of safety data from human clinical trials. It should be emphasized that having a wide enough safety margin for therapeutic use does not mean that it is benign or safe to the general public, even at low doses. We defer the latter to public health experts. Importantly, this Perspective is written for drug discovery professionals and not the general public.

Understanding the CO capture reaction through electronic structure analysis of four-membered-ring group-13/N- and B/group-15-based Lewis acid-base pairs

Incomplete combustion yields a significant byproduct, known for its high toxicity to humans: gas phase carbon monoxide (CO). This study utilized several advanced theoretical methods to examine the factors contributing to the activation energy involved in CO capture by a frustrated Lewis pair (FLP) and to forecast the potential success of the CO capture reaction. The current theoretical findings indicate that among the four-membered-ring Group-13/N-FLP and B/Group-15-FLP molecules, only the B/N-based FLP-type molecule effectively captures CO, considering both thermodynamics and kinetics. According to the results obtained through energy decomposition analysis-natural orbitals for chemical valence (EDA-NOCV), it can be concluded that the donor-acceptor (singlet-singlet) model, rather than the electron-sharing (triplet-triplet) model, effectively characterizes the electronic structures in the CO trapping reaction involving four-membered-ring G13/G15-FLPs. Theoretical findings, derived from EDA-NOCV and frontier molecular orbital theory, demonstrate that the CO capture reaction by G13/G15-FLP involves two distinct bonding interactions. The first interaction is characterized by FLP-to-CO forward bonding, with the lone pair of G15 (G13/G15-FLP) donating to the empty p-π* orbital of carbon (CO), which predominates. The second interaction involves CO-to-FLP backward bonding, where the empty σ* orbital of G13 (G13/G15-FLP) accepts the lone pair of carbon (CO), albeit to a lesser extent. In summary, our theoretical findings indicate that the G13-C and G15-C bonds in the G15/G15-TS species with a four-membered ring can be classified as two dative single bonds. The importance of the interaction between Lewis bases and CO surpasses that of the interaction between Lewis acids and CO. Theoretical evidences in this study demonstrate a linear connection between the G13-G15 bond length within the four-membered-ring G13/G15-FLP and the activation barrier linked to CO capture. The activation strain model analysis in this study suggests that the activation energy required for bond formation primarily depends on the geometric deformation energy of G13/G15-FLP in capturing CO. Our DFT investigation shows that Hammond's postulate is obeyed by the CO catching reaction of the four-membered-ring G13/N-FLP, meaning that an earlier transition state is associated with a lower activation barrier, but not with the CO catching reaction of the four-membered-ring B/G15-FLP.

Neurotoxicology: a clinical systems-based review

Neurological disease caused by toxins is widespread but under-recognised. Despite increasing public interest and a growing number of novel potential neurotoxins, diagnosis of neurotoxic disease is often delayed or missed, resulting in poorer patient outcomes. This article discusses neurotoxic syndromes using a systems-based approach, focusing on environmental and occupational agents. We do not discuss recreational drugs, pharmaceutical agents or developmental neurotoxins in detail. We aim to provide neurologists with a working understanding of the scenarios in which a clinical presentation may be due to a neurotoxin and how to approach confirmation of the diagnosis.

Binding of Carbon Monoxide to Hemoglobin in an Oxygen Environment: Force Field Development for Molecular Dynamics

Carbon monoxide (CO) is a byproduct of the incomplete combustion of carbon-based fuels, such as wood, coal, gasoline, or natural gas. As incomplete combustion in a fire accident or in an engine, massively produced CO leads to a serious life threat because CO competes with oxygen (O2) binding to hemoglobin and makes people suffer from hypoxia. Although there is hyperbaric O2 therapy for patients with CO poisoning, the nanoscale mechanism of CO dissociation in the O2-rich environment is not completely understood. In this study, we construct the classical force field parameters compatible with the CHARMM for simulating the coordination interactions between hemoglobin, CO, and O2, and use the force field to reveal the impact of O2 on the binding strength between hemoglobin and CO. Density functional theory and Car-Parrinello molecular dynamics simulations are used to obtain the bond energy and equilibrium geometry, and we used machine learning enabled via a feedforward neural network model to obtain the classical force field parameters. We used steered molecular dynamics simulations with a force field to characterize the mechanical strength of the hemoglobin-CO bond before rupture under different simulated O2-rich environments. The results show that as O2 approaches the Fe2+ of heme at a distance smaller than ∼2.8 Å, the coordination bond between CO and Fe2+ is reduced to 50% bond strength in terms of the peak force observed in the rupture process. This weakening effect is also shown by the free energy landscape measured by our metadynamics simulation. Our work suggests that the O2-rich environment around the hemoglobin-CO bond effectively weakens the bonding, so that designing of O2 delivery vector to the site is helpful for alleviating CO binding, which may shed light on de novo drug design for CO poisoning.

Effects of acute carbon monoxide poisoning on liver damage and comparisons of related oxygen therapies in a rat model

Acute carbon monoxide (CO) poisoning may cause liver damage and liver dysfunction. Therefore, in this study, we aimed to compare the efficiency of normobaric oxygen (NBO) and high-flow nasal cannula oxygen (HFNCO) treatments on liver injury. For that purpose, 28 male Wistar albino rats were divided into four groups (Control, CO, CO + NBO, and CO + HFNCO). The control group was allowed to breath room air for 30 min. Acute CO poisoning in CO, CO + NBO, CO + HFNCO was induced by CO exposure for 30 min. Thereafter, NBO group received 100% NBO with reservoir mask for 30 min. HFNCO group received high-flow oxygen through nasal cannula for 30 min. At the end of the experiment, all animals were sacrificed by cardiac puncture under anesthesia. Serum liver function tests were measured. Liver tissue total antioxidant status (TAS), total oxidant status (TOS), and oxidative stress index (OSI) levels, tissue histomorphology and immunoexpression levels of Bax, Caspase 3, TNF-α, IL-1β, and NF-κB were also examined. Our observations indicated that acute CO poisoning caused significant increases in blood COHb, serum aminotransferase (AST), alanine aminotransferase (ALT0, alkaline phosphatase (ALP), total protein, albumin, and globulin levels but a decrease in albumin to globulin ratio (all, p < 0.05). Furthermore, acute CO poisoning significantly increased the OSI value, and the immunoexpresssion of Bax, Caspase 3, TNF-α, IL-1β, and NF-κB in liver tissue (all, p < 0.05). These pathological changes in serum and liver tissue were alleviated through both of the treatment methods. In conclusion, both the NBO and HFNCO treatments were beneficial to alleviate the acute CO poisoning associated with liver injury and dysfunction.

Pathological alterations and COHb evaluations as tools for investigating fire-related deaths in veterinary forensic pathology

Fire-related deaths are usually a consequence of carbon monoxide (CO) poisoning or shock from thermal injuries. In humans, high levels of carboxyhemoglobin (COHb) concentrations in the blood can support a diagnosis of CO poisoning. In veterinary medicine, few studies investigated the pathological changes and blood COHb% in fire victims, and no data are available on post-mortem changes in blood gas composition due to fire. This study aims to investigate the pathological changes and COHb levels in both animal victims of fire and cadavers experimentally exposed to fire. For this purpose, dogs were selected and subdivided into three groups. Group A comprised 9 adult dogs, and Group B comprised 7 puppies that died under fire-related conditions. Group C was represented by 4 dog cadavers experimentally exposed to heat and smoke. A complete macroscopic, histological, and COHb evaluation were performed on each animal. Animals in Groups A and B showed cherry-red discoloration, thermal-injuries and soot deposits along the respiratory tract. Animals in Group C showed thermal injuries and soot deposits limited to the upper respiratory tract. The mean COHb% values in cadavers in Group C were lower than those observed in the other groups but higher compared to the values detected before the heat and smoke treatment. These findings suggest that both pathological changes and COHb analysis are valid tools for investigating fire-related deaths in dogs. However, the increase of COHb levels in cadavers exposed post-mortem to heat and smoke highlights how the COHb analysis should always be evaluated together with macroscopical and microscopical findings to avoid significant misjudgments in investigating fire-related fatalities in veterinary forensic practice.

Carbon monoxide poisoning with hippocampi lesions on MRI: cases report and literature review

BACKGROUND

Carbon monoxide (CO) poisoning is now one of the leading causes of poisoning-related mortality worldwide. The central nervous system is the most vulnerable structure in acute CO poisoning. MRI is of great significance in the diagnosis and prognosis of CO toxic encephalopathy. The imaging features of CO poisoning are diverse. We report atypical hippocampal lesions observed on MRI in four patients after acute CO exposure.

CASE PRESENTATIONS

We report four patients who presented to the emergency department with loss of consciousness. The diagnosis of CO poisoning was confirmed on the basis of their detailed history, physical examination and laboratory tests. Brain MRI in all of these patients revealed abnormal signal intensity in hippocampi bilaterally. They all received hyperbaric oxygen therapy. The prognosis of all four patients was poor.

CONCLUSION

Hippocampi, as a relatively rare lesion on MRI of CO poisoning, is of important significance both in the early and delayed stages of acute CO poisoning. In this article, we summarize the case reports of hippocampal lesions on MRI in patients with CO poisoning in recent years, in order to provide reference for the diagnosis and prognosis of CO poisoning.

Carbon Monoxide Poisoning: From Occupational Health to Emergency Medicine

Carbon monoxide poisoning remains a leading cause of accidental poisoning worldwide (both at home and at work), and it is also a cause of suicidal poisoning. Such poisoning can arise following prolonged exposure to low levels of CO or following brief exposure to high concentrations of the gas. In fact, despite exposure limits, high safety standards, and the availability of CO alarms, nearly 50,000 people in the United States visit the emergency department each year due to poisoning. Additionally, CO poisoning in the United States causes up to 500 deaths each year. Despite the widespread nature of this form of poisoning, known about for centuries and whose damage mechanisms have been recognized (or rather hypothesized about) since the 1800s, early recognition, especially of late complications, and treatment remain a medical challenge. A well-designed therapeutic diagnostic process is necessary so that indication for hyperbaric or normobaric therapy is correctly made and so that patients are followed up even after acute exposure to diagnose late complications early. Furthermore, it is necessary to consider that in the setting of emergency medicine, CO poisoning can be part of a differential diagnosis along with other more frequent conditions, making its recognition difficult. The last thirty years have been marked by a significant increase in knowledge regarding the toxicity of CO, as well as its functioning and its importance at physiological concentrations in mammalian systems. This review, taking into account the significant progress made in recent years, aims to reconsider the pathogenicity of CO, which is not trivially just poisonous to tissues. A revision of the paradigm, especially as regards treatment and sequelae, appears necessary, and new studies should focus on this new point of view.

Structure-Photoreactivity Relationship Study of Substituted 3-Hydroxyflavones and 3-Hydroxyflavothiones for Improving Carbon Monoxide Photorelease

Carbon monoxide (CO) is notorious for its toxic effects but is also recognized as a gasotransmitter with considerable therapeutic potential. Due to the inherent challenges in its delivery, the utilization of organic CO photoreleasing molecules (photoCORMs) represents an interesting alternative to CO administration characterized by high spatial and temporal precision of release. This paper focused on the design, synthesis, and photophysical and photochemical studies of 20 3-hydroxyflavone (flavonol) and 3-hydroxyflavothione derivatives as photoCORMs. Newly synthesized compounds bearing various electron-donating and electron-withdrawing groups show bathochromically shifted absorption maxima and considerably enhanced CO release yields compared to the parent unsubstituted flavonol, exceeding 0.8 equiv of released CO in derivatives exhibiting excited states with a charge-transfer character. Until now, such outcomes have been limited to flavonol derivatives possessing a π-extended aromatic system. In addition, thione analogs of flavonols, 3-hydroxyflavothiones, show substantial bathochromic shifts of their absorption maxima and enhanced photosensitivity but provide lower yields of CO formation. Our study elucidates in detail the mechanism of CO photorelease from flavonols and flavothiones, utilizing steady-state and time-resolved spectroscopies and photoproduct analyses, with a particular emphasis on unraveling the structure-photoreactivity relationship and understanding competing side processes.

Assessment of emissions and potential occupational exposure to carbon monoxide during biowaste composting

To date, only a few studies focused on the carbon monoxide (CO) production during waste composting; all targeted on CO inside piles. Here, the CO net emissions from compost piles and the assessment of worker's occupational risk of exposure to CO at large-scale composting plants are shown for the first time. CO net emissions were measured at two plants processing green waste, sewage sludge, or undersize fraction of municipal solid waste. Effects of the location of piles (hermetised hall vs. open yard) and turning (before vs. after) were studied. Higher CO net emission rates were observed from piles located in a closed hall. The average CO flux before turning was 23.25 and 0.60 mg‧m-2‧h-1 for hermetised and open piles, respectively, while after- 69.38 and 5.11 mg‧m-2‧h-1. The maximum CO net emissions occurred after the compost was turned (1.7x to 13.7x higher than before turning). The top sections of hermetised piles had greater CO emissions compared to sides. Additionally, 5% of measurement points of hermetised piles switched to 'CO sinks'. The 1-h concentration in hermetised composting hall can reach max. ~50 mg CO∙m-3 before turning, and >115 mg CO∙m-3 after, exceeding the WHO thresholds for a 1-h and 15-min exposures, respectively.

Correlation between Carboxyhemoglobin Levels Measured by Blood Gas Analysis and by Multiwave Pulse Oximetry

Carbon monoxide (CO) poisoning is difficult to diagnose owing to its nonspecific symptoms. Multiwave pulse oximetry can be used to quickly screen patients for CO poisoning. However, few studies have analyzed patients with CO poisoning who presented to the emergency department (ED). The primary aim of our study was to determine the correlation between COHb levels measured in blood gas analysis and COHb levels measured in multiwave pulse oximetry. Secondary aims were the sensitivity and specificity of the COHb level cutoff value using multiwave pulse oximetry to predict a 25% COHb level in blood gas analysis. This single-center retrospective observational study included patients with CO poisoning who visited the ED of a university-affiliated hospital in Seoul, Korea between July 2021 and June 2023. COHb poisoning was determined using blood gas analysis and multiwave pulse oximetry. The correlation of COHb levels between the two tests was evaluated using correlation analysis. The area under the receiver operating characteristic curve (AUC) of multiwave pulse oximetry was calculated to predict COHb levels from the blood gas analysis. The optimal cutoff values, sensitivity, and specificity of COHb were determined. A total of 224 patients who had COHb levels measured using both multiwave pulse oximetry and blood gas analysis were included in the analysis. In the correlation analysis, COHb showed a high positive correlation with COHb measured using blood gas analysis (Spearman correlation coefficient = 0.86, p < 0.001). The AUC of COHb measured by multiwave pulse oximetry to predict 25% of the COHb level (which can be an indication of hyperbaric oxygen treatment) measured by blood gas analysis was 0.916. When the COHb levels measured with multiwave pulse oximetry were 20% the sensitivity was 81% and the specificity was 83%, and when the COHb levels were 25% the sensitivity was 50% and the specificity was 95%. The COHb value measured using multiwave pulse oximetry blood gas analysis showed a high correlation. However, additional research using large-scale studies is required for validation.

Correlation between Time to Hyperbaric Oxygen Therapy and Delayed Neurological Sequelae in Acute Carbon Monoxide Poisoning Patients

Carbon monoxide (CO) is one of the most common causes of intoxication. Delayed neurologic sequelae (DNS) have a major impact on prognosis of CO poisoning patients. Hyperbaric oxygen therapy (HBOT) is widely used to treat DNS. However, there is no consensus regarding the optimal timing of HBOT. This prospective study enrolled patients who visited the hospital from November 2019 to October 2022. The cutoff value for the latency to HBOT after CO exposure was determined, and the area under the receiver operating characteristic curve (AUC) was estimated. In total, 167 patients were divided into non-DNS and DNS groups. The initial Glasgow Coma Scale (GCS) score, CO exposure time, latency to HBOT after CO exposure, median length of hospital stay (p < 0.001) and creatine kinase (p = 0.016) showed significant differences. A GCS score ≤ 9 had an odds ratio (OR) of 5.059 (95% confidence interval [CI]: 1.602-15.976, p = 0.006), and latency to HBOT after CO exposure ≥ 200 min had an OR of 18.971 (95% CI: 4.310-83.508, p < 0.001). The AUC was 0.8235 (95% CI: 0.7504-0.8966). A GCS score ≤ 9 and latency to HBOT ≥ 200 min may be significant risk factors for DNS.

Toxic gas sensing performance of arsenene functionalized by single atoms (Ag, Au): a DFT study

The detection and removal of toxic gases from the air are imminent tasks owing to their hazards to the environment and human health. Based on DFT calculations with VdW correction, adsorption configurations, adsorption energies, and electronic properties were compared for the adsorption of toxic gas molecules (CO, NO, NO2, SO2, NH3 and H2S) on pure arsenene (p-arsenene) and Ag/Au-doped arsenene (Ag/Au-arsenene). Our calculations show that all molecules considered to chemisorb on Ag/Au-arsenene and the substitution of noble metal, particularly Ag, could remarkably enhance the interactions and charge transfer between the gas molecules and Ag/Au-arsenene. Thus, Ag/Au-arsenene is expected to show higher sensitivity in detecting CO, NO, NO2, SO2, NH3 and H2S molecules than p-arsenene. Furthermore, the changes in the vibrational frequencies of gas molecules and the work functions of Ag/Au-arsenene substrates upon adsorption are shown to be closely related to the adsorption energies and charge transfer between the molecules and Ag/Au-arsenene, which is dependent on the molecules. Therefore, Ag/Au-arsenene-based gas sensors are expected to show good selectivity of molecules. The analysis of theoretical recovery time suggested that Ag-arsenene shows high reusability while detecting H2S, CO, and NO, whereas Au-arsenene has high selectivity to sensing NO at room temperature. With the increase in work temperature and decrease in recovery times, Ag/Au-arsenene could be used to detect NH3 and NO2 from factory emission and automobile exhaust with quite good reusability. The above results indicated that Ag/Au-arsenene shows good performance in toxic gas sensing with high sensitivity, selectivity, and reusability at different temperatures.

Experimental study on the purification capacity of potted plants on low-concentration carbon monoxide in indoor environment

Indoor low-concentration carbon monoxide (CO) exposure is widespread worldwide, and potted plants may be a potential means for CO purification. The objective is to evaluate common indoor plants' CO purification and tolerance capacities. Epipremnum aureum (Linden ex André) G.S.Bunting, Chlorophytum comosum (Thunb.) Jacques, Spathiphyllum kochii Engl. & K.Krause, and Sansevieria trifasciata Hort. ex Prain with similar sizes were tested in the glass chamber with initial CO concentrations of 10, 25, 50, 100, 200, and 400 ppm, respectively. (1) The CO purification capacity of the four potted plants is ranked as Epipremnum aureum (Linden ex André) G.S.Bunting > Chlorophytum comosum (Thunb.) Jacques > Spathiphyllum kochii Engl. & K.Krause > Sansevieria trifasciata Hort. ex Prain. Under the purification effect of each plant, the CO concentration in the chamber decreases linearly and significantly (p < 0.05), and within a specific time period, the time-weighted average (TWA) CO concentrations can be reduced to below the corresponding permissible exposure limits specified by some countries and organizations. (2) With the increase of the stomatal number of each plant and the increase in CO concentration, the hourly and cumulative absorbed CO of each plant increase linearly and significantly (p < 0.05). (3) With the increase in CO concentration, the CO purification efficiency of each plant decreases exponentially and significantly (p < 0.05). (4) When the CO concentration was ≤ 50 ppm, all plants could effectively purify CO without damage. When the CO concentration was in the range of 100 ~ 400 ppm, within 2 weeks after the 48-h experiment, the leaf tips of Chlorophytum comosum (Thunb.) Jacques and Epipremnum aureum (Linden ex André) G.S.Bunting were damaged one after another, and the damaged leaf area increased with the increase of CO concentration. However, each plant as a whole still survived. This study demonstrated that different species of potted plants can effectively absorb low concentrations of CO to varying degrees, but higher concentrations of CO will damage the survival of specific species of potted plants.

Carbon monoxide and prognosis in smokers hospitalised with acute cardiac events: a multicentre, prospective cohort study

Background

Smoking cigarettes produces carbon monoxide (CO), which can reduce the oxygen-carrying capacity of the blood. We aimed to determine whether elevated expiratory CO levels would be associated with a worse prognosis in smokers presenting with acute cardiac events.

Methods

From 7 to 22 April 2021, expiratory CO levels were measured in a prospective registry including all consecutive patients admitted for acute cardiac event in 39 centres throughout France. The primary outcome was 1-year all-cause death. Initial in-hospital major adverse cardiac events (MAE; death, resuscitated cardiac arrest and cardiogenic shock) were also analysed. The study was registered at ClinicalTrials.gov (NCT05063097).

Findings

Among 1379 patients (63 ± 15 years, 70% men), 368 (27%) were active smokers. Expiratory CO levels were significantly raised in active smokers compared to non-smokers. A CO level >11 parts per million (ppm) found in 94 (25.5%) smokers was associated with a significant increase in death (14.9% for CO > 11 ppm vs. 2.9% for CO ≤ 11 ppm; p < 0.001). Similar results were found after adjustment for comorbidities (hazard ratio [HR] [95% confidence interval (CI)]): 5.92 [2.43-14.38]) or parameters of in-hospital severity (HR 6.09, 95% CI [2.51-14.80]) and propensity score matching (HR 7.46, 95% CI [1.70-32.8]). CO > 11 ppm was associated with a significant increase in MAE in smokers during initial hospitalisation after adjustment for comorbidities (odds ratio [OR] 15.75, 95% CI [5.56-44.60]) or parameters of in-hospital severity (OR 10.67, 95% CI [4.06-28.04]). In the overall population, CO > 11 ppm but not smoking was associated with an increased rate of all-cause death (HR 4.03, 95% CI [2.33-6.98] and 1.66 [0.96-2.85] respectively).

Interpretation

Elevated CO level is independently associated with a 6-fold increase in 1-year death and 10-fold in-hospital MAE in smokers hospitalized for acute cardiac events.

Funding

Grant from Fondation Coeur & Recherche.

The diagnostic accuracy of carbon monoxide pulse oximetry in adults with suspected acute carbon monoxide poisoning: a systematic review and meta-analysis

Introduction

Acute carbon monoxide poisoning (COP) is one of the leading causes of intoxication among patients presenting to the emergency department (ED). COP symptoms are not always specific and may vary from mild to critical. In the last few years, COHb pulse oximeters have been developed and applied to the setting of suspected COP. The aim of this systematic review is to assess the diagnostic accuracy of CO pulse oximetry (SpCO) with carboxyhemoglobin (COHb) levels measured by blood gas analysis, used as a reference standard, in patients with suspected COP.

Methods

We developed our search strategy according to the PICOS framework, population, index/intervention, comparison, outcome, and study, considering the diagnostic accuracy of SpCO compared to COHb levels measured by blood gas analysis, used as a reference standard, in patients with suspected COP enrolled in cross-sectional studies in English. The search was performed on MEDLINE/PubMed and EMBASE in February 2022. Quality assessment was performed using the QUADAS-2 methodology. A COHb cutoff of 10% was chosen to test the sensitivity and specificity of the index test. A bivariate model was used to perform the meta-analysis. The protocol was registered on PROSPERO (CRD42022359144).

Results

A total of six studies (1734 patients) were included. The pooled sensitivity of the test was 0.65 (95% CI 0.44-0.81), and the pooled specificity was 0.93 (95% CI 0.83-0.98). The pooled LR+ was 9.4 (95% CI 4.4 to 20.1), and the pooled LR- was 0.38 (95% CI 0.24 to 0.62).

Conclusion

Our results show that SpCO cannot be used as a screening tool for COP in the ED due to its low sensitivity. Because of its high LR+, it would be interesting to evaluate, if SpCO could have a role in the prehospital setting as a tool to quickly identify COP patients and prioritize their transport to specialized hospitals on larger samples with a prospective design.

Predicting acute brain lesions on magnetic resonance imaging in acute carbon monoxide poisoning: a multicenter prospective observational study

An acute brain lesion (ABL) identified by brain magnetic resonance imaging (MRI) after acute carbon monoxide (CO) poisoning is a strong prognostic factor for the development of delayed neuropsychiatric syndrome (DNS). This study aimed to identify predictors of ABLs on MRI in patients with acute CO poisoning. This was a multicenter prospective registry-based observational study conducted at two tertiary hospitals. A total of 1,034 patients were included. Multivariable logistic regression analysis showed that loss of consciousness (LOC) (adjusted odds ratio [aOR] 2.68, 95% Confidence Interval [CI]: 1.49-5.06), Glasgow Coma Scale (GCS) score < 9 (aOR 2.41, 95% CI: 1.49-3.91), troponin-I (TnI) (aOR 1.22, 95% CI: 1.08-1.41), CO exposure duration (aOR 1.09, 95% CI: 1.05-1.13), and white blood cell (WBC) (aOR 1.05, 95% CI: 1.01-1.09) were independent predictors of ABLs on MRI. LOC, GCS score, TnI, CO exposure duration, and WBC count can be useful predictors of ABLs on MRI in patients with acute CO poisoning, helping clinicians decide the need for an MRI scan or transfer the patient to an appropriate institution for MRI or hyperbaric oxygen therapy.

Delayed neuropsychiatric sequelae due to long-term effects of carbon monoxide poisoning in Ethiopia: A case report

Background

One emergency that occurs frequently and has high morbidity is carbon monoxide poisoning. After a time of lucidity, some victims who recover from the incident of acute carbon monoxide exposure may later suffer delayed neuropsychiatric sequelae (DNS), which can include cognitive impairments, a wide range of neurological abnormalities, and affective disorders. Below, we report the first documented incident of DNS after carbon monoxide poisoning in Ethiopia.

Case presentation

A 40-year-old male patient who developed a coma after he was exposed to burning charcoal in a closed room was admitted to Debre Tabor Comprehensive Specialized Hospital in the northwest region of Ethiopia. He stayed for 12 days during his first admission and was discharged with improvement. One month after discharge, he developed delayed neuropsychiatric sequelae, which manifested as bizarre behavior, being unable to walk unsupported, loss of concentration, and failure to control urine and feces. Brain MRI showed bilateral periventricular and frontoparietal deep white matter subcortical abnormal T1 and T2 prolongation with no restriction of diffusivity, possibly due to demyelinating disorders. He was managed with fluid therapy, benzhexol, risperidone, and rehabilitation therapy. He stayed for two weeks in our hospital and was discharged with improvement.

Conclusion

Despite the paucity of delayed neuropsychiatric sequelae from carbon monoxide poisoning, physicians should be highly suspicious in the right situations. The precise mechanisms of delayed toxic effects, prevention measures, and treatment modalities have not yet been determined; therefore, more research and attention are required.

Diagnostic accuracy of carboxyhemoglobin saturation with pulse CO-oximetry in patients with carbon monoxide poisoning

Objective

Carboxyhemoglobin saturation (SpCO)with pulse CO-oximetry is an alternative method in CO poisoning; however, the correlation of it with blood carboxyhemoglobin level (COHb) is still debated.The study aimed to evaluate the correlation between SpCO and venous COHb level and factors associated with the diagnostic accuracy of SpCO.

Material and methods

SpCO and venous COHb levels of patients with CO poisoning, according to a COHb level was 3%, were evaluated. The sensitivity, specificity, 95% CI (confidence interval), and the cut-off value of SpCO were calculated using ROC analysis at a 10% threshold for COHb. Agreement levels were calculated with Bland-Altman analysis. Risk factors affecting diagnostic accuracy were analyzed using logistic regression analysis.

Results

If the 10% threshold of COHb was accepted as the diagnostic threshold for CO poisoning, the sensitivity and specificity of SpCO were 98.4% and 100% (95% CI: 0.996-1.000) at the 6.85 cut-off point of SpCO. The scatter plot of COHb and SpCO showed a strong positive relationship at values of presentation and discharge (r = .979, p<0.001; r = .969, p<0.001). With a bias of 3.1% for the mean difference between-COHb and SpCO, the limits of agreement from Bland- Altman analysis were -0.7 to 7.1. For the 10% threshold, age and male gender have significantly increased false negativity rates (B = .074, p = 0.010, and B = 0.252, p = 0.011, respectively).

Conclusion

SpCO is a reliable method with high sensitivity and specificity; therefore, a lower cut-off points of SpCO compared to COHb level may be accepted to diagnose and follow-up CO poisoning.

The Clinical Association between Carbon Monoxide Poisoning and Myocardial Injury as Measured by Elevated Troponin I Levels

Carbon monoxide (CO) poisoning accounts for over 50,000 estimated emergency room visits and approximately 1200 deaths per year in the US. Despite the high prevalence, there is a paucity of data looking at the association between laboratory biomarkers and clinical outcomes. Our study investigates the association between myocardial injury as assessed by increased troponin levels and its effect on in-hospital outcomes in CO poisoning. A total of 900 sequential charts of patients presenting with CO poisoning between 1 January 2012, and 31 August 2019, at our tertiary center with regional hyperbaric chamber and burn unit, were reviewed. Of the 900, a total of 488 patients had elevated carboxyhemoglobin levels. Of these 488 patients, 119 (24.4%) also had blood troponin levels measured. Patients were stratified based on the presence or absence of myocardial injury as evidenced by highly sensitive serum troponin I (TnI) level > 0.5 ng/mL to determine if a correlation exists relating to myocardial injury and risk of major adverse events. Mean age was 51.2 years, 58.8% were males, 35.3% were non-White, and 10.1% were intentional CO poisonings. Comorbidities included hypertension: 37%, diabetes: 21%, smoking: 21%, hyperlipidemia: 17.6%, coronary artery disease: 11.8%, asthma: 5.9%, heart failure: 5%, atrial fibrillation: 4.2%, and chronic obstructive pulmonary disease: 4.2%. Myocardial injury occurred in 22 patients (18.5%) and was associated with increased likelihood of requiring intensive care admission (54.5% vs. 20.6%, p = 0.002) and intubation (40.9% vs. 14.4%, p = 0.008). TnI elevation was associated with higher in-hospital mortality (p = 0.008, OR 21.3) compared to patients without TnI elevation. Older age was independently associated with increased in-hospital mortality (p = 0.03, OR 1.08). When controlling for age, in-hospital mortality remained statistically significant (p = 0.01, OR 21.37). No significant difference was found with respect to age, comorbidities, gender, race, ethnicity, or hospital length of stay in patients with and without myocardial injury. Myocardial injury induced by CO exposure occurs frequently and adversely affects clinical outcomes. Further research is needed to help guide physicians in the management of CO poisoning and associated myocardial injury to improve patient outcomes.

Involvement of the Superior Colliculus in SIDS Pathogenesis

The aim of this study was to investigate the involvement of the mesencephalic superior colliculus (SC) in the pathogenetic mechanism of SIDS, a syndrome frequently ascribed to arousal failure from sleep. We analyzed the brains of 44 infants who died suddenly within the first 7 months of life, among which were 26 infants with SIDS and 18 controls. In-depth neuropathological investigations of serial sections of the midbrain showed the SC layered cytoarchitectural organization already well known in animals, as made up of seven distinct layers, but so far never highlighted in humans, albeit with some differences. In 69% of SIDS cases but never in the controls, we observed alterations of the laminar arrangement of the SC deep layers (precisely, an increased number of polygonal cells invading the superficial layers and an increased presence of intensely stained myelinated fibers). Since it has been demonstrated in experimental studies that the deep layers of the SC exert motor control including that of the head, their developmental disorder could lead to the failure of newborns who are in a prone position to resume regular breathing by moving their heads in the sleep-arousal phase. The SC anomalies highlighted here represent a new step in understanding the pathogenetic process that leads to SIDS.

Clinical and Laboratory Characteristics Predicting the Severity of Carbon Monoxide Poisoning in Children: A Single-Center Retrospective Study

OBJECTIVES

Carbon monoxide poisoning (COP) is extremely common throughout the world. The purpose of this study was to assess the demographic, clinical, and laboratory characteristics predicting the severity COP in children.

METHODS

The study included 380 children diagnosed with COP between January 2017 and January 2021 and 380 healthy controls. Carbon monoxide poisoning was diagnosed based on the medical history and a carboxyhemoglobin (COHb) level of more than 5%. The patients were classified as mild (COHb 10%), moderate (COHb 10%-25%), or severely (COHb > 25%) poisoned.

RESULTS

The mean age of the severe group was 8.60 ± 6.30, for the moderate group was 9.50 ± 5.81, for the mild group was 8.79 ± 5.94, and for the control group was 8.95 ± 5.98. The most common place of exposure was at home and all cases were affected accidentally. The coal stove was the most common source of exposure, followed by natural gas. The most common symptoms were nausea/vomiting, vertigo, and headache. Neurologic symptoms such as syncope, confusion, dyspnea, and seizures were more common in the severe group. A total of 91.3% of the children had hyperbaric oxygen therapy, 3.8% were intubated, and 3.8% were transferred to intensive care in the severe group, whereas no death or sequela was observed. Mean platelet volume and red cell distribution width had the highest area under the curve in the receiver operating characteristic analysis (0.659; 0.379). A positive and low statistically significant relationship was found between COHb levels and troponin and lactate levels in the severe group ( P < 0.05).

CONCLUSIONS

Carbon monoxide poisoning progressed more severely in children presented with neurological symptoms and have elevated red cell distribution width and mean platelet volume. Even in severe COP cases, satisfactory results have been obtained with early and appropriate treatment.

Atypical Presentation of Carbon Monoxide Poisoning With Aphasia

We present a patient with carbon monoxide poisoning with a single focal neurological deficit. The patient was found by emergency medical services (EMS) to be resting in his truck with a generator running nearby. On arrival, the patient was hemodynamically stable. The patient was aphasic but did not exhibit any other focal or lateralizing deficits. He was able to communicate by writing clearly and coherently on a sheet of paper. His initial carboxyhemoglobin was 29%, confirming the diagnosis of carbon monoxide poisoning. He was treated with 100% O₂ via a non-rebreather mask and regained his speech during his ED (emergency department) course. The patient was ultimately hospitalized for continued oxygen treatment and serial examinations. This case highlights the varied presenting symptoms of carbon monoxide poisoning as well as the importance of including a broad differential diagnosis while working up patients with a focal neurologic deficit.

Rational design of trimetallic AgPt-Fe3O4 nanozyme for catalyst poisoning-mediated CO colorimetric detection

Carbon monoxide (CO) is not only a highly poisonous gas that brings great health risk, but also a significant signaling molecule in body. However, it is still challengeable for development of alternative colorimetric probes to traditional organic chromophores for simple, sensitive and convenient CO sensing. Here, for the first time, we rationally design a novel hydrophilic AgPt-Fe₃O₄ nanozyme with a unique heterodimeric nanostructure for colorimetric sensing of CO based on the excellent peroxidase-like catalytic activity as well as highly poisonous effect of CO on the nanozyme's catalytic activity. Both experimental evidence and theoretical calculations reveal the trimetallic AgPt-Fe₃O₄ nanozyme is susceptible to poisoning with the strongest affinity towards CO compared to individual Fe₃O₄ or Ag-Fe₃O₄, which is attributed to the adequate exposure of the active metallic sites and efficient interfacial synergy of unique heterodimeric nanostructure. Accordingly, a novel nanozyme-based colorimetric strategy is developed for CO detection with a low detection limit of 5.6 ppb in solution. Furthermore, the probe can be prepared as very convenient test strips and integrated with the portable smartphone platforms for detecting CO gas samples with a low detection limit of 8.9 ppm. Overall, our work proposes guidelines for the rational design of metallic heterogeneous nanostructure to expand the analytical application of nanozyme.

Early gray matter atrophy and neurological deficits in patients with carbon monoxide poisoning

PURPOSE

To investigate early neurological deficits-related change patterns in gray matter (GM) volume in patients with carbon monoxide poisoning (COP) and GM volume differences between patients with and without delayed neurological sequelae (DNS) and those with and without T2 hyperintense lesions after COP.

METHODS

Forty-one COP patients (24 patients with DNS) and 36 sex- and age-matched healthy controls (HC) were enrolled in this study. The neurological assessments were administered within 24 h after MRI scans. Voxel-based morphometry analysis was used to detect regional GM volume change.

RESULTS

The COP group had statistically significant GM atrophy in the bilateral prefrontal and temporal lobes, anterior cingulate (ACC), thalamus, posterior cerebellum, and right hippocampus compared to the HC group. Atrophy in the left medial orbital superior frontal gyrus (SFG), bilateral ACC, and bilateral thalamus were related to lower Mini-Mental State Examination (MMSE) scores and higher Unified Parkinson's Disease Rating Scale subsection III and neuro-psychiatric inventory scores. Atrophy in the hippocampus and posterior cerebellum were also related to decrease MMSE scores. The DNS subgroup had greater GM atrophy in the limbic system than the non-DNS subgroup. Compared to the subgroup without T2 hyperintense lesions, greater GM atrophy in the limbic system, motor and visual cortex, and default network was observed in the subgroup with T2 hyperintense lesions.

CONCLUSION

GM atrophy in the medial orbital SFG, ACC, thalamus, hippocampus, and posterior cerebellum is associated with early neurological deficits in patients with COP. Greater atrophy occurred in patients with DNS and those with T2 hyperintense lesions.

Dexamethasone therapy prevents delayed neuropsychiatric sequelae after carbon monoxide poisoning: a prospective registry-based study

BACKGROUND

Delayed neuropsychiatric sequelae are major complications of carbon monoxide poisoning; carbon monoxide triggers brain oxidation and inflammation. Corticosteroids such as dexamethasone modulate neurological damage after carbon monoxide poisoning through anti-inflammatory actions and immune response inhibition. However, it is not known whether corticosteroids prevent delayed neuropsychiatric sequelae. We thus studied whether dexamethasone reduced the incidence of delayed neuropsychiatric sequelae.

METHODS

This registry-based study enrolled patients with carbon monoxide poisoning treated in a Korean tertiary care hospital from March 1^st, 2020 to November 30^th, 2021. Data of patients were prospectively collected during the study period, and retrospectively analyzed. One group received intravenous dexamethasone. We performed multivariable logistic regression analysis to identify factors associated with delayed neuropsychiatric sequelae.

RESULTS

A total of 128 patients were enrolled, of which 99 patients received dexamethasone therapy and 29 patients did not. The incidences of delayed neuropsychiatric sequelae in the dexamethasone and non-dexamethasone groups were 16.2% and 37.9%, respectively. Multivariable logistic regression analysis revealed that dexamethasone use (odds ratio = 0.122, 95% confidence interval 0.031-0.489) and a higher Glasgow Coma Scale (odds ratio = 0.818, 95% confidence interval 0.682-0.981) was associated with a lower incidence of delayed neuropsychiatric sequelae.

CONCLUSION

Early dexamethasone treatment was significantly associated with a decreased incidence of delayed neuropsychiatric sequelae. A higher Glasgow Coma Scale at presentation also was associated with a lower incidence of delayed neuropsychiatric sequelae.

An urgent health problem of indoor air pollution: results from a 15-years carbon monoxide poisoning observed study in Jinan City

Carbon monoxide (CO) poisoning is a public health concern in developing countries especially in China with a high disease burden. We aimed to focus on non-occupational CO poisoning caused by household coal heating secular trends based on registry data in Jinan, China, and we aim to provide further evidence and suggestions for public health policy. We analyzed the occurrence and development trend and assess the spatial-temporal epidemiological characteristics of non-occupational CO poisoning caused by household coal heating in Jinan between 2007 and 2021. Among total of 6588 CO poisoning, 5616 cases (85.25%) and 180 deaths caused by household coal heating was identified during study period. The cumulative incidence rate was 5.78 per 100,000 person-years and the mortality rate was 0.19 per 100,000 person-years. The incidence in urban areas (6.55 per 100,000 person-years) was higher than rural areas (5.04 per 100,000 person-years), and there was a statistical difference between urban and rural (P < 0.001) (P < 0.001). The poisoning time point mainly occurs in the sleep stage. In Jinan, socioeconomic status, accessibility to health services and rural status are determinants for CO poisoning incidence and mortality. Implementation of urban and rural central heating renovation is an effective way to further reduce the disease burden of CO poisoning in the future.

Retrospective Evaluation of Characteristics of Patients with Burn Injuries Treated at the Largest Reference Hospital in Brazil

Burn injuries are a significant cause of morbidity and mortality in the Brazilian population. We conducted this study in a tertiary hospital in Brazil to discover the epidemiological characteristics of patients with burn injuries. We conducted a cohort review of patients admitted to the burn unit of our institute during a 5-year period. For each patient, we collected data that included age, gender, total percentage of burned body surface area, burn location, burn mode, and burn cause. We analyzed the data using the R programming language. We included a total of 496 patients in our study. The mean age of the patients was 28 ± 14.7 years. The median length of hospital stay was 2 weeks. We found a significant correlation between the total percentage of burned body surface area and the length of hospitalization (p < .001) and the length of hospitalization in the intensive care unit (p < .001). A total of 427 patients (86%) were discharged from the hospital after successful treatment. In contrast, 43 patients (8.67%) died. The mortality rate was highest in patients who had more than 70% of their total body surface area burned. The average length of hospitalization aligned with global and national statistics presented in the literature. The main causes of the burn injuries were thermal (e.g., fire, hot liquids). We found inhalation injuries present in more than one third of the patients who were hospitalized in the intensive care unit with thermal burns.

Toxicological Emergencies

Poisoning, drug overdose, and adverse drug effects continue to be a common encounter, especially in the intensive care unit (ICU). Patients are often critically ill or have a potential to rapidly deteriorate and warrant ICU admission. Adults suffering from overdoses rarely give a complete and accurate description of the quantity or type of medications ingested. In most adult cases, multiple substances are involved. A tentative diagnosis in most overdose and poisoning cases can be made by physical examination and simple laboratory tests (electrolyte panel, creatinine, serum osmolarity, urinalysis, etc). Supportive care, with particular attention to airway management, oxygenation, and circulation, is the mainstay of treatment. Basic treatment principles include limiting the amount of toxin absorbed, enhancing the elimination of ingested toxin, and preventing the conversion of non-toxic compounds to toxic metabolites. Drugs or poisons, where specific antidotes or effective therapies exist (especially acetaminophen, salicylates, methanol, ethylene glycol, and digitalis), should be aggressively sought and treated after initial stabilization has been accomplished. For those drugs or poisons where specific quantitative tests are available, levels should be obtained before treatment and may be repeated as clinically indicated.

An artificial intelligence algorithm for analyzing globus pallidus necrosis after carbon monoxide intoxication

Globus pallidus necrosis (GPN) is one of typical neurological imaging features in patients with carbon monoxide (CO) poisoning. Current clinical guideline recommends neurological imaging examination for CO-intoxicated patients with conscious disturbance rather than routine screening, which may lead to undiagnosed GPN. We aimed to develop an artificial intelligence algorithm for predicting GPN in CO intoxication patients. We included CO intoxication patients with neurological images between 2000 and 2019 in Chang Gung Memorial Hospital. We collected 41 clinical and laboratory parameters on the first day of admission for algorithm development. We used fivefold cross validation and applied several machine learning algorithms. Random forest classifier (RFC) provided the best predictive performance in our cohort. Among the 261 patients with CO intoxication, 52 patients presented with GPN. The artificial intelligence algorithm using the RFC-based AI model achieved an accuracy = 79.2 ± 2.6%, sensitivity = 77.7%, precision score = 81.9 ± 3.4%, and F1 score = 73.2 ± 1.8%. The area under receiver operating characteristic was approximately 0.64. Top five weighted variables were Platelet count, carboxyhemoglobin, Glasgow Coma scale, creatinine, and hemoglobin. Our RFC-based algorithm is the first to predict GPN in patients with CO intoxication and provides fair predictive ability. Further studies are needed to validate our findings.

Magnetic resonance imaging for predicting delayed neurologic sequelae caused by carbon monoxide poisoning: A systematic review and meta-analysis

BACKGROUND

This study summarized and analyzed the prognostic value of magnetic resonance imaging (MRI) for delayed neurologic sequelae (DNS) caused by carbon monoxide (CO) poisoning.

METHODS

PubMed, China National Knowledge Infrastructure, and Wanfang Database were searched to identify relevant articles from their inception to October 30, 2022. The pooled sensitivity and specificity were estimated to investigate MRI for predicting DNS.

RESULTS

6 studies comprising 635 participants were identified as eligible for the present analysis. The pooled sensitivity and specificity of MRI were 0.72 (95% CI: 0.62-0.81) and 0.80 (95% CI: 0.71-0.86), respectively. The findings of sensitivity analyses proved that the overall results were robust, and no publication bias was detected (P = .49).

CONCLUSION

Based on current evidence, MRI may be useful in determining DNS caused by acute CO poisoning.

Prospective Study Investigating Change in Carboxyhemoglobin Blood Level During Operative Hysteroscopy

STUDY OBJECTIVES

To evaluate whether the use of radiofrequency energy during resectoscopy leads to increases in patient blood levels of carboxyhemoglobin (COHb) and investigate procedural variables associated with these elevations.

DESIGN

A prospective cross-sectional study of 40 subjects undergoing a hysteroscopic procedure using bipolar radiofrequency energy.

SETTING, PATIENTS, AND INTERVENTIONS

The study was conducted at an ambulatory surgery center. Procedures for uterine leiomyoma, septa, products of conception, or a combination of these pathologies were included. We measured blood COHb levels before and immediately after the surgery. Abnormal postoperative COHb level was defined as an increase of plasma COHb ≥3.0%. All patients with abnormal postoperative levels were contacted and screened for carbon monoxide toxicity symptoms. Summary statistics included frequency for categorical variables and averages for continuous variables. p values were reported without modification.

MEASUREMENTS AND MAIN RESULTS

A total of 17.5% of subjects met the criteria for abnormal postoperative COHb levels. None of these subjects reported symptoms of carbon monoxide toxicity. One subject with an elevated postoperative COHb level had intraoperative hemodynamic changes possibly related to COHb elevation. An abnormal postoperative COHb level was associated with a higher fluid deficit (p = .024) and greater myoma volume (p = .04).

CONCLUSION

This study demonstrates that systemic absorption of carbon monoxide is a reproducible phenomenon in hysteroscopic resections using bipolar diathermy. Greater absorption is associated with a higher fluid deficit and greater myoma volume. Although none of the subjects with an abnormal increase screened positive for symptoms in the postoperative setting and only 1 experienced hemodynamic changes intraoperatively, our study looked at a healthy and young patient population. More research is needed on the safety of this COHb exposure in patients with medical comorbidities. Special consideration should be given to the possibility of carbon monoxide absorption and the uncertain long-term effects when planning extensive hysteroscopic resections.

Examination of central nervous system by functional observation battery after massive intravenous infusion of carbon monoxide-bound and oxygen-bound hemoglobin vesicles in rats

Carbon monoxide (CO) is known as a toxic gas inducing "CO poisoning", which acutely affects the central nervous system (CNS) and which persistently affects brain functions depending on the exposure time and CO concentration. By contrast, in pathological rodent models, intravenous infusion of CO-bound hemoglobin vesicles (CO-HbV) has shown various beneficial effects such as anti-oxidative and anti-inflammatory reactions. This study assessed effects of CO-HbV infusion on CNS using a functional observation battery, sensory reflexes, grip strength, and landing foot splay measurements. The test fluids were CO-HbV and O₂-bound HbV (O₂-HbV) suspended in saline ([Hb] ​= ​10 ​g/dL), and saline alone for comparison. The rats received either 16 or 32 ​mL/kg of fluid intravenously at 1.5 ​mL/min/kg. Observations were made before infusion, and at 5 ​min, 4, 8, 24, 48 and 72 ​h after infusion. Massive doses of 16 and 32 ​mL/kg respectively corresponded to about 29 and 57% of the whole circulating blood volume (56 ​mL/kg). No toxicological effect was observed in any measurement item for any group in comparison to the control saline infusion group. Histopathological examination of hippocampal tissue at 14 days after infusion showed the number of necrotic cells to be minimal. Results obtained from rats in this experiment suggest that the massive intravenous infusion of CO-HbV yields beneficial anti-oxidative and anti-inflammatory effects without showing CO-poisoning-related symptoms of CNS damage.

Fe@χ3-borophene as a promising catalyst for CO oxidation reaction: A first-principles study

A novel single-atom catalyst of Fe adsorbed on χ₃-borophene has been proposed as a potential catalyst for CO oxidation reaction (COOR). Quantitative pictures have been provided of both the stability of Fe@χ₃-borophene and various kinetic reaction pathways using first-principles calculations. Strong adsorption energy of -3.19 eV and large diffusion potential of 3.51 eV indicates that Fe@χ₃-borophene is highly stable. By exploring reaction mechanisms for COOR, both Eley-Ridel (E-R) and trimolecule E-R (TER) were identified as possible reaction paths. Low reaction barriers with 0.49 eV of E-R and 0.57 eV of TER suggest that Fe@χ₃-borophene is a very promising catalyst for COOR. Charge transfer between the χ₃-borophene and CO, O₂ and CO₂ gas molecules plays a key role in lowering the energy barrier during the reactions. Our results propose that Fe@χ₃-borophene can be a good candidate of single-atom catalyst for COOR with both high stability and catalytic activity.

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.

Residential Fuel Transition and Fuel Interchangeability in Current Self-Aspirating Combustion Applications: Historical Development and Future Expectations

To reduce greenhouse gases and air pollutants, new technologies are emerging to reduce fossil fuel usage and to adopt more renewable energy sources. As the major aspects of fuel consumption, power generation, transportation, and industrial applications have been given significant attention. The past few decades witnessed astonishing technological advancement in these energy sectors. In contrast, the residential sector has had relatively little attention despite its significant utilization of fuels for a much longer period. However, almost every energy transition in human history was initiated by the residential sector. For example, the transition from fuelwood to cheap coal in the 1700s first took place in residential houses due to urbanization and industrialization. The present review demonstrates the energy transitions in the residential sector during the past two centuries while portending an upcoming energy transition and future energy structure for the residential sector. The feasibility of the 100% electrification of residential buildings is discussed based on current residential appliance adoption, and the analysis indicates a hybrid residential energy structure is preferred over depending on a single energy source. Technical considerations and suggestions are given to help incorporate more renewable energy into the residential fuel supply system. Finally, it is observed that, compared to the numerous regulations on large energy-consumption aspects, standards for residential appliances are scarce. Therefore, it is concluded that establishing appropriate testing methods is a critical enabling step to facilitate the adoption of renewable fuels in future appliances.

Care of the Critically Injured Burn Patient

Care of the critically injured burn patient presents unique challenges to the intensivist. Certified burn centers are rare and geographically sparse, necessitating that much of the initial management of patients with severe burn injuries must happen in the pre-burn center setting.1 Severe burn injuries often lead to a wide range of complications that extend beyond the loss of skin integrity and require specialized care. As such, medical intensivists are often called upon to stabilize these critically injured patients. This focused review outlines the clinical care of these medically complex patients, including airway management, post-burn complications, volume resuscitation, nutrition, and end-of-life care.

The Legacy of the TTASAAN Report-Premature Conclusions and Forgotten Promises: A Review of Policy and Practice Part I

Brain perfusion single photon emission computed tomography (SPECT) scans were initially developed in 1970's. A key radiopharmaceutical, hexamethylpropyleneamine oxime (HMPAO), was originally approved in 1988, but was unstable. As a result, the quality of SPECT images varied greatly based on technique until 1993, when a method of stabilizing HMPAO was developed. In addition, most SPECT perfusion studies pre-1996 were performed on single-head gamma cameras. In 1996, the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology (TTASAAN) issued a report regarding the use of SPECT in the evaluation of neurological disorders. Although the TTASAAN report was published in January 1996, it was approved for publication in October 1994. Consequently, the reported brain SPECT studies relied upon to derive the conclusions of the TTASAAN report largely pre-date the introduction of stabilized HMPAO. While only 12% of the studies on traumatic brain injury (TBI) in the TTASAAN report utilized stable tracers and multi-head cameras, 69 subsequent studies with more than 23,000 subjects describe the utility of perfusion SPECT scans in the evaluation of TBI. Similarly, dementia SPECT imaging has improved. Modern SPECT utilizing multi-headed gamma cameras and quantitative analysis has a sensitivity of 86% and a specificity of 89% for the diagnosis of mild to moderate Alzheimer's disease-comparable to fluorodeoxyglucose positron emission tomography. Advances also have occurred in seizure neuroimaging. Lastly, developments in SPECT imaging of neurotoxicity and neuropsychiatric disorders have been striking. At the 25-year anniversary of the publication of the TTASAAN report, it is time to re-examine the utility of perfusion SPECT brain imaging. Herein, we review studies cited by the TTASAAN report vs. current brain SPECT imaging research literature for the major indications addressed in the report, as well as for emerging indications. In Part II, we elaborate technical aspects of SPECT neuroimaging and discuss scan interpretation for the clinician.

A case of extreme carboxyhaemoglominemia due to vaping

Acute carbon monoxide (CO) poisoning is known to cause neurological, metabolic and cardiorespiratory sequalae. However, data on chronic CO exposure are scant, particularly in the context of vaping, which recent literature suggests may be a greater source of CO than tobacco cigarette smoking. During a series of admissions at the time of vaping, our patient repeatedly presented with significant CO poisoning and developed pulmonary arterial hypertension with resultant high‐output right heart failure. On each occasion, our patient's levels of carboxyhaemoglobin were both higher and took longer to resolve than 12 smokers who underwent arterial blood gas testing at two time points. Our observation may reveal an association between vaping, chronic carboxyhaemoglobinemia and the development of cardiorespiratory disease. Thus, further studies into the safety of vaping and chronic CO exposure are urged.

Harmful Effect of Intrauterine Smoke Exposure on Neuronal Control of "Fetal Breathing System" in Stillbirths

This article is aimed to contribute to the current knowledge on the role of toxic substances such as nicotine on sudden intrauterine unexplained deaths’ (SIUDS’) pathogenetic mechanisms. The in-depth histopathological examination of the autonomic nervous system in wide groups of victims of SIUDS (47 cases) and controls (20 cases), with both smoking and no-smoking mothers, highlighted the frequent presence of the hypodevelopment of brainstem structures checking the vital functions. In particular, the hypoplasia of the pontine parafacial nucleus together with hypoplastic lungs for gestational age were observed in SIUDS cases with mothers who smoked cigarettes, including electronic ones. The results allow us to assume that the products of cigarette smoke during pregnancy can easily cross the placental barrier, thus entering the fetal circulation and damaging the most sensitive organs, such as lungs and brain. In a non-negligible percentage of SIUDS, the mothers did not smoke. Furthermore, based on previous and ongoing studies conducted through analytical procedures and the use of scanning electron microscopy, the authors envisage the involvement of toxic nanoparticles (such as agricultural pesticides and nanomaterials increasingly used in biomedicine, bioscience and biotechnology) in the death pathogenesis, with similar mechanisms to those of nicotine.

Therapeutic potential of carbon monoxide in hypertension-induced vascular smooth muscle cell damage revisited: from physiology and pharmacology

As a chronic and progressive disorder, hypertension remains to be a serious public health problem around the world. Among the different types of hypertension, pulmonary arterial hypertension (PAH) is a devastating disease associated with pulmonary arteriole remodeling, right ventricular failure and death. The contemporary management of systemic hypertension and PAH has substantially grown since more therapeutic targets and/or agents have been developed. Evolving treatment strategies targeting the vascular remodeling lead to improving outcomes in patients with hypertension, nevertheless, significant advancement opportunities for developing better antihypertensive drugs remain. Carbon monoxide (CO), an active endogenous gasotransmitter along with hydrogen sulfide (H₂S) and nitric oxide (NO), is primarily generated by heme oxygenase (HO). Cumulative evidence suggests that CO is considered as an important signaling molecule under both physiological and pathological conditions. Studies have shown that CO confers a number of biological and pharmacological properties, especially its involvement in the pathological process and treatment of hypertension-related vascular remodeling. This review will critically outline the roles of CO in hypertension-associated vascular remodeling and discuss the underlying mechanisms for the protective effects of CO against hypertension and vascular remodeling. In addition, we will propose the challenges and perspectives of CO in hypertensive vascular remodeling. It is expected that a comprehensive understanding of CO in the vasculature might be essential to translate CO to be a novel pharmacological agent for hypertension-induced vascular remodeling.

Pediatric Carbon Monoxide Poisoning: Effects of Hyperbaric Oxygen Therapy on Thiol/Disulfide Balance

OBJECTIVES

Carbon monoxide (CO) poisoning remains the foremost cause of poisoning worldwide. This study aimed to investigate the effects of hyperbaric oxygen therapy (HBOT) and normobaric oxygen therapy (NBOT) on thiol/disulfide homeostasis in children with CO intoxication.

METHODS

Eighty-one children aged 0 to 18 years with CO intoxication were included in this cross-sectional study. No changes were made in the routine clinical evaluation and treatment practices of the patients. Thirty-two children who received HBOT and 49 children who received NBOT were compared for serum native thiol, disulfide, and total thiol levels, as well as for the changes in disulfide/native thiol, disulfide/total thiol, and native thiol/total thiol ratios before and after treatment.

RESULTS

Antioxidant levels, such as native thiol and total thiol, were significantly decreased in patients who received HBOT and increased in those who received NBOT (P = 0.02 and P = 0.01, respectively). There was no statistically significant difference between the 2 groups concerning the change of native thiol/total thiol ratios (P = 0.07). In addition, there was no significant difference regarding changes in disulfide, disulfide/native thiol, and disulfide/total thiol levels before and after treatment (P = 0.39, P = 0.07, and P = 0.07, respectively).

CONCLUSIONS

Although thiol-disulfide balance is maintained in patients treated with HBOT, antioxidant levels decrease significantly compared with NBOT. Despite efficiency of HBOT in CO intoxication, oxidative stress and reperfusion injury due to hyperoxygenation should be considered in the treatment of HBOT.

Impact of Hyperbaric Oxygen Therapy on Cognitive Functions: a Systematic Review

Hyperbaric oxygen therapy (HBOT) is a modality of treatment in which patients inhale 100% oxygen inside a hyperbaric chamber pressurised to greater than 1 atmosphere. The aim of this review is to discuss neuropsychological findings in various neurological disorders treated with HBOT and to open new perspectives for therapeutic improvement. A literature search was conducted in the MEDLINE (via PubMed) database from the inception up 10 May 2020. Eligibility criteria included original articles published in English. Case studies were excluded. Full-text articles were obtained from the selected studies and were reviewed on the following inclusion criteria (1) performed cognitive processes assessment (2) performed HBOT with described protocol. Two neuropsychologists independently reviewed titles, abstracts, full texts and extracted data. The initial search retrieved 1024 articles, and a total of 42 studies were finally included after applying inclusion and exclusion criteria. The search yielded controversial results with regard to the efficiency of HBOT in various neurological conditions with cognitive disturbance outcome. To the best of our knowledge this is the first state-of-the art, systematic review in the field. More objective and precise neuropsychological assessment methods are needed to exact evaluation of the efficacy of HBOT for neuropsychological deficits. Future studies should widen the assessment of HBOT effects on different cognitive domains because most of the existing studies have focussed on a single process. Finally, there is a need for further longitudinal studies.

Evaluation of Data Sources for Carbon Monoxide Poisoning Surveillance in New York City

CONTEXT

Carbon monoxide (CO) exposure can be life-threatening. Suspected and confirmed cases of CO poisoning warranting health care in New York City (NYC) are reportable to the NYC Poison Control Center (PCC).

OBJECTIVES

We evaluated 4 hospital-based sources of CO surveillance data to identify ways to improve data capture and reporting.

DESIGN

Suspected and confirmed CO poisoning records from October 2015 through December 2016 were collected from the NYC emergency department (ED) syndromic surveillance system, New York State Statewide Planning and Research Cooperative System (SPARCS) ED billing data, NYC PCC calls made from hospitals, and the Electronic Clinical Laboratory Reporting System (ECLRS). Syndromic and SPARCS records were person- and visit-matched. SPARCS and ECLRS records were also matched to PCC records on combinations of name, demographic characteristics, and visit information.

SETTING

Hospitals in NYC.

PARTICIPANTS

Individuals who visited NYC hospitals for CO-related health effects.

MAIN OUTCOME MEASURES

We assessed the validity of syndromic data, with SPARCS records as the gold standard. We matched SPARCS and ECLRS records to PCC records to analyze reporting rates by case characteristics.

RESULTS

The sensitivity of syndromic surveillance was 60% (225 true-positives detected among 372 visit-matched SPARCS cases), and positive predictive value was 46%. Syndromic records often missed CO flags because of a nonspecific or absent International Classification of Diseases code in the diagnosis field. Only 15% of 428 SPARCS records (total includes 56 records not visit-matched to syndromic) and 16% of 199 ECLRS records were reported to PCC, with male sex and younger age associated with higher reporting.

CONCLUSIONS

Mandatory reporting makes PCC useful for tracking CO poisoning in NYC, but incomplete reporting and challenges in distinguishing between confirmed and suspected cases limit its utility. Simultaneous tracking of the systems we evaluated can best reveal surveillance patterns.

Acute carbon monoxide poisoning in Shandong, China: an observational study

Background

Carbon monoxide (CO) poisoning remains a major cause of accidental injuries and multiple studies have indicated that CO is also associated with significantly severe or long-term toxicity to the central nervous system. Given that CO poisoning causes serious morbidity and mortality, a better understanding of epidemiological features and clinical characteristics of acute CO poisoning in China is crucial.

Methods

We collected the clinical data of acute CO poisoning in patients between November 2019 and April 2020 across Shandong province, China and analyzed its characteristics focusing on the weekly amount and the severity of the confirmed cases.

Results

A total number of 21,088 acute CO poisoning cases were diagnosed. The overall incidence of acute CO poisoning was approximately 0.021%. On severity rankings, 63% of confirmed cases (n = 13,378) were mild, 27% (n = 5635) were moderate, and 10% (n = 2075) were severe. Interestingly, the coastal cities had more confirmed cases than the inland/suburban areas in Shandong. Meanwhile, the number of confirmed cases was negatively correlated with the local mean daily temperature (P = 0.0167).

Conclusions

Mild acute CO poisoning cases accounted for the majority of all confirmed cases during the winter of 2019. In Shandong province, which is located in east China, residents of the coastal cities are more susceptible to CO poisoning than residents of inland cities.