Carbon dioxide poisoning: a literature review of an often forgotten cause of intoxication in the emergency department

An introduction to environmental neurotoxicology: Lessons from a clinical perspective

In 1992, the Committee on Neurotoxicology and Models for Assessing Risk of the National Academy of Sciences in Washington DC focused with a scientific perspective on the identification of substances with neurotoxic potential, studies of exposed populations, risk assessment, and biologic markers of disease. This Committee recommended: "all physicians should be trained to take a thorough occupational-exposure history and to be aware of other possible sources of toxic exposure". Although convened after several outbreaks of neurotoxic syndromes, clinical neurological considerations were lacking. After defining keys words, namely Environment, Neurotoxicology and Neurotoxicants, we present some demonstrative cases; e.g., the Epidemic Neuropathy in Cuba, Minamata disease, ALS/PDC on Guam, and the ALS hot spot in the French Alps. Always with a clinical and practical approach, we will then review the milieux that contain and convey potential neurotoxicants, the different exposure routes and the clinical presentations. Drawing lessons from clinical cases, we offer some thoughts concerning the future of Environmental Neurotoxicology (ENT). Pointing notably to the diffuse chemical contamination of ecosystems and living beings, including Homo sapiens, we question the real impact of agents with neurotoxic potential on the human brain, considering the effects, for example, of air pollution, endocrine disruptors and nanoparticles. Concern is expressed over the lack of knowledge of the non-monotonic kinetics of many of these chemicals, the major concern being related to mixtures and low-dose exposures, as well as the delayed appearance in clinical expression of prevalent neurodegenerative diseases.

Biogas Upgrading Using a Single-Membrane System: A Review

In recent years, the use of biogas as a natural gas substitute has gained great attention. Typically, in addition to methane (CH4), biogas contains carbon dioxide (CO2), as well as small amounts of impurities, e.g., hydrogen sulfide (H2S), nitrogen (N2), oxygen (O2) and volatile organic compounds (VOCs). One of the latest trends in biogas purification is the application of membrane processes. However, literature reports are ambiguous regarding the specific requirement for biogas pretreatment prior to its upgrading using membranes. Therefore, the main aim of the present study was to comprehensively examine and discuss the most recent achievements in the use of single-membrane separation units for biogas upgrading. Performing a literature review allowed to indicate that, in recent years, considerable progress has been made on the use of polymeric membranes for this purpose. For instance, it has been documented that the application of thin-film composite (TFC) membranes with a swollen polyamide (PA) layer ensures the successful upgrading of raw biogas and eliminates the need for its pretreatment. The importance of the performed literature review is the inference drawn that biogas enrichment performed in a single step allows to obtain upgraded biogas that could be employed for household uses. Nevertheless, this solution may not be sufficient for obtaining high-purity gas at high recovery efficiency. Hence, in order to obtain biogas that could be used for applications designed for natural gas, a membrane cascade may be required. Moreover, it has been documented that a significant number of experimental studies have been focused on the upgrading of synthetic biogas; meanwhile, the data on the raw biogas are very limited. In addition, it has been noted that, although ceramic membranes demonstrate several advantages, experimental studies on their applications in single-membrane systems have been neglected. Summarizing the literature data, it can be concluded that, in order to thoroughly evaluate the presented issue, the long-term experimental studies on the upgrading of raw biogas with the use of polymeric and ceramic membranes in pilot-scale systems are required. The presented literature review has practical implications as it would be beneficial in supporting the development of membrane processes used for biogas upgrading.

Tracheal injury diagnosed by a sudden increase in end-tidal carbon dioxide levels during mediastinoscopic subtotal esophagectomy: a case report

BACKGROUND

Mediastinoscopic surgery for esophageal cancer facilitates early postoperative recovery. However, it can occasionally cause serious complications. Here, we present the case of a patient with a tracheal injury diagnosed by a sudden increase in end-tidal carbon dioxide (EtCO2) during mediastinoscopic subtotal esophagectomy.

CASE PRESENTATION

A 52-year-old man diagnosed with esophageal cancer was scheduled to undergo mediastinoscopic subtotal esophagectomy. During the mediastinoscopic procedure, the EtCO2 level suddenly increased above 200 mmHg, and the blood pressure dropped below 80 mmHg. We immediately asked the operator to stop insufflation and found a tracheal injury on the right side of the trachea near the carina by bronchoscopy. The endotracheal tube was replaced with a double-lumen tube, and the trachea was repaired via right thoracotomy. There were no further intraoperative complications. After surgery, the patient was extubated and admitted to the intensive care unit.

CONCLUSIONS

Monitoring EtCO2 levels and close communication with the operator is important for safely managing sudden tracheal injury during mediastinoscopic esophagectomy.

Synthesis and performance analysis of zeolitic imidazolate frameworks for CO2 sensing applications

In this paper, we investigate the potential use of Zeolitic Imidazolate Frameworks (ZIF-8) as a sensing material for CO2 detection. Three synthesis techniques are considered for the preparation of ZIF-8, namely room temperature, microwave-assisted, and ball milling. The latter is a green and facile alternative for synthesis with its solvent-free, room-temperature operation. In addition, ball milling produces ZIF-8 samples with superior CO2 adsorption and detection characteristics, as concluded from fluorescence measurements. Characterization tests including X-ray diffraction (XRD), Fourier transform infrared (FTIR), Thermogravimetric analysis (TGA), Field emission scanning electron microscopy (FE-SEM) and Energy-dispersive X-ray spectroscopy (EDS) are conducted to inspect the structural morphology, the thermal stability, and elements content of the ZIF-8 samples obtained from the different aforementioned synthesis techniques. The characterization tests revealed the appearance of a new phase of ZIF-8 which is ZIF-L when deploying the ball milling technique with different structure, morphology, response to CO2 exposure and thermal stability when compared to its counterparts. Fluorescence measurements are carried out to evaluate the limit of detection (LOD), selectivity, and recyclability of the different ZIF-8 samples. The LOD of the ZIF-8 sample synthesized based on ball milling synthesis technique is 815.2 ppm, while LODs of the samples obtained from microwave and room temperature-based synthesis techniques are 1780.6 ppm and 723.8 ppm, respectively. This indicates that the room temperature and ball milling produced MOFs have comparable LODs. However, the room temperature procedure requires the use of a harmful solvent. The range of LOD demonstrates the suitable use of ZIF-8 for indoor air quality monitoring and other industrial applications.

Are slaughterhouse-obtained livers suitable for use in ex vivo perfusion research?

OBJECTIVES

The success of the ex vivo machine perfusion of pig livers used for preclinical research depends on organ quality and availability. In this study, we investigated whether livers obtained from slaughterhouses are suitable and equivalent to livers obtained from laboratory pigs.

METHODS

Livers were obtained from slaughterhouse pigs stunned by electrocution or CO2 inhalation and from laboratory pigs. For the latter group, 45 minutes of warm ischemia was mimicked for a subgroup, ensuring a valid comparison with slaughterhouse-derived livers.

RESULTS

Livers from CO2-stunned pigs showed lower indocyanine green clearance and bile production, higher blood lactate and potassium concentrations, and higher alanine aminotransferase activities than electrically stunned pigs. Furthermore, livers from electrically stunned pigs, and livers from laboratory pigs, subjected or not to warm ischemia, showed similar performance in terms of perfusion and metabolism.

CONCLUSION

For an ex vivo liver model generated using slaughterhouse pigs, electrical stunning is preferable to CO2 stunning. Livers from electrically stunned slaughterhouse pigs performed similarly to laboratory pig livers. These findings support the use of livers from electrically stunned slaughterhouse pigs, which may therefore provide an alternative to livers obtained from laboratory pigs, consistent with the principle of the 3Rs.

CO2 Stunning in Pigs: Physiological Deviations at Onset of Excitatory Behaviour

Stunning by carbon dioxide (CO₂) inhalation is controversial because it is associated with vigorous movements and behaviours which may or may not be conscious reactions. Furthermore, it is unknown whether some behaviours might indicate the transition into unconsciousness. Our study objective was to investigate the loss of consciousness during CO₂ stunning by linking physiological variables (in particular pH, PaO₂ and PaCO₂) to the onset of observed behaviours. A total of 11 cross-bred pigs were studied. A tracheostomy tube, venous and arterial cannulae were placed under sevoflurane anaesthesia. After recovery from this, and a "wash out" period of at least 30 min, arterial blood samples were taken (and baseline values established) before 90-95% CO₂ in medical air was administered through the tracheostomy tube. Subsequent behaviours were video-recorded and key physiological variables were evaluated using an anaesthetic monitor and the frequent sampling of arterial blood (albeit with inconsistent inter-sample intervals). After the study, behaviours were classified in an ethogram. At the onset of behaviours categorised as "vigorous movement extremities", "opisthotonos" and "agonal gasping" pH values (range) were: 6.74-7.34; 6.66-6.96 and 6.65-6.87, while PaCO₂ (kPa) was 4.6-42.2, 24.4-51.4 and 29.1-47.6. Based upon these values, we conclude that the pigs were probably unconscious at the onset of "opisthotonos" and "agonal gasping", but some were probably conscious at the onset of "vigorous movements".

Lessons Learned: Asphyxiation Hazard Associated with Dry Ice

Dry ice is widely used in the chemistry research settings as an excellent coolant. Herein, we report a case study of a graduate student researcher who lost consciousness while retrieving 180 lbs of dry ice from a deep dry ice container. We share the details of the incident and the lessons learned from it to promote safer handling of dry ice in these situations.

Experimental studies of carbon dioxide concentration in the space under the face mask protecting against Covid-19 - Pilot studies

Masks are the primary tool used to prevent the spread of COVID-19 in the current pandemic. The use of masks may result in some discomfort, which may be caused by the accumulation of carbon dioxide in the inner space of the mask. This paper presents tests of carbon dioxide concentration in the inner space of the mask during work at a computer, for various flat and convex masks. Five different masks were used in the tests. Convex masks showed a greater accumulation of carbon dioxide than flat masks. The concentration of carbon dioxide was also higher for masks made of more layers. The dependence of the average values of carbon dioxide concentrations under the masks for selected people depending on the BMI and the type of mask was determined, as well as the measurements of carbon dioxide concentrations without the mask. An increase in carbon dioxide concentration was observed with increasing BMI. The development of effective self-defense tools against the virus, including masks, is essential to contain the spread of COVID-19.

Estudio teórico de la oxidación de CO con O2 usando catalizadores de Au-Pd y Au-Pt

En el presente estudio se realizaron cálculos con base en la Teoría del Funcional de la Densidad Electrónica (DFT) con la aproximación B3PW91/LANL2DZ para optimizar los sistemas monometálicos y bimetálicos Au9, Au8Pd, Au8Pt, AuPd8, AuPt8, Pd9 y Pt9. Los materiales fueron teóricamente evaluados como catalizadores para la oxidación de monóxido de carbono (CO) y se determinó el sistema más favorable para la adsorción de esta molécula. La sustitución de átomos de Pt y Pd por átomos de Au en los nonámeros generó un cambio en la estructura tridimensional del sistema. El análisis de reactividad global mostró que el clúster más reactivo es 𝑃𝑡9, seguido por 𝐴𝑢𝑃𝑡8. Los índices de Fukui identificaron los sitios más susceptibles para un ataque nucleofílico de ambos clústeres. La adsorción de CO generó una cascada de oxidación que liberó ~4,5 eV, indicando que la reacción es altamente exotérmica y exergónica. Los clústeres 𝐴𝑢𝑃𝑡8 y 𝑃𝑡9 mostraron los valores más bajos de energía de activación de la etapa determinante del mecanismo. En general, la sustitución de un átomo de platino (o paladio) por un átomo de oro no afecta la reactividad de los nonámeros y, por tanto, se infiere que el clúster 𝐴𝑢𝑃𝑡8 podría ser un catalizador promisorio en la oxidación de CO.

The health consequences of greenhouse gas emissions: a potential pathway

Excessive greenhouse gas emissions might be the major culprit for environmental degradation, which have direct and indirect adverse impacts in various ways. As the largest emitter of carbon emissions, China suffered great harm from climate change during the past 40 years. Therefore, it becomes necessary to study the impact of carbon emissions on health issues and their potential mechanism. Using the panel data from 30 provinces in China between 2002 and 2017, this study employes and extends the Stochastic Impacts by Regression on Population, Affluence, and Technology (STIRPAT) model and mediating effect model to analyze the direct and indirect effects of carbon emissions. The main results are as follows: (1) Carbon emissions has a certain negative impact on public health, which would increase with the rise of temperature. (2) The increase in carbon emissions has a more significant negative effect on health with the average temperature exceeding 17.75 °C, indicating that the temperature has a threshold effect. (3) The potential health risks become higher with the development of urbanization, but there is no obvious spillover effect in the health consequences. The results remain robust after controlling other factors. This study supplements the literature of climate governance and human health, potentially contributing to the next stage of high-quality and sustainable development.

Air Quality Monitoring During High-Level Biocontainment Ground Transport: Observations From Two Operational Exercises

OBJECTIVE

Stretcher transport isolators provide mobile, high-level biocontainment outside the hospital for patients with highly infectious diseases, such as Ebola virus disease. Air quality within this confined space may pose human health risks.

METHODS

Ambient air temperature, relative humidity, and CO₂ concentration were monitored within an isolator during 2 operational exercises with healthy volunteers, including a ground transport exercise of approximately 257 miles. In addition, failure of the blower unit providing ambient air to the isolator was simulated. A simple compartmental model was developed to predict CO₂ and H₂O concentrations within the isolator.

RESULTS

In both exercises, CO₂ and H₂O concentrations were elevated inside the isolator, reaching steady-state values of 4434 ± 1013 ppm CO₂ and 22 ± 2 mbar H₂O in the first exercise and 3038 ± 269 ppm CO₂ and 20 ± 1 mbar H₂O in the second exercise. When blower failure was simulated, CO₂ concentration exceeded 10 000 ppm within 8 minutes. A simple compartmental model predicted CO₂ and H₂O concentrations by accounting for human emissions and blower air exchange.

CONCLUSIONS

Attention to air quality within stretcher transport isolators (including adequate ventilation to prevent accumulation of CO₂ and other bioeffluents) is needed to optimize patient safety.

Effect of Wearing Surgical Face Masks on Gas Detection from Respiration Using Photoacoustic Spectroscopy

Wearing surgical face masks is among the measures taken to mitigate coronavirus disease (COVID-19) transmission and deaths. Lately, concern was expressed about the possibility that gases from respiration could build up in the mask over time, causing medical issues related to the respiratory system. In this research study, the carbon dioxide concentration and ethylene in the breathing zone were measured before and immediately after wearing surgical face masks using the photoacoustic spectroscopy method. From the determinations of this study, the C₂H₄ was established to be increased by 1.5% after one hour of wearing the surgical face mask, while CO₂ was established to be at a higher concentration of 1.2% after one hour of wearing the surgical face mask, when the values were correlated with the baseline (control).

Novel Solventless Extraction Technique to Preserve Cannabinoid and Terpenoid Profiles of Fresh Cannabis Inflorescence

Despite its use by humans for thousands of years, the technology of cannabis usage and extraction is still evolving. Given that the primary pharmacological compounds of interest are cannabinoid and terpenoids found in greatest abundance in capitate glandular trichomes of unfertilized female inflorescences, it is surprising that older techniques of hashish making have received less technological advancement. The purpose of this study was to employ organically grown cannabis and to isolate pure trichomes from freshly picked flowers via exposure to vapor from solid CO2, commonly known as "dry ice", followed by their isolation via sifting through a 150 µ screens while maintaining the cold chain. Biochemical analysis was undertaken on fresh flower, frozen-sifted flower by-products, treated trichomes (Kryo-Kief™), dried flower, dried sifted flower by-product and dried kief. The dry ice process successfully concentrated cannabinoid content as high as 60.7%, with corresponding concentration and preservation of monoterpenoids encountered in fresh flower that are usually lost during the conventional cannabis drying and curing process. The resulting dried sifted flower by-product after dry ice processing remains a usable commodity. This approach may be of interest to pharmaceutical companies and supplement producers pursuing cannabis-based medicine development with an eye toward full synergy of ingredients harnessing the entourage effect.

Recent Insights into the Measurement of Carbon Dioxide Concentrations for Clinical Practice in Respiratory Medicine

In the field of respiratory clinical practice, the importance of measuring carbon dioxide (CO2) concentrations cannot be overemphasized. Within the body, assessment of the arterial partial pressure of CO2 (PaCO2) has been the gold standard for many decades. Non-invasive assessments are usually predicated on the measurement of CO2 concentrations in the air, usually using an infrared analyzer, and these data are clearly important regarding climate changes as well as regulations of air quality in buildings to ascertain adequate ventilation. Measurements of CO2 production with oxygen consumption yield important indices such as the respiratory quotient and estimates of energy expenditure, which may be used for further investigation in the various fields of metabolism, obesity, sleep disorders, and lifestyle-related issues. Measures of PaCO2 are nowadays performed using the Severinghaus electrode in arterial blood or in arterialized capillary blood, while the same electrode system has been modified to enable relatively accurate non-invasive monitoring of the transcutaneous partial pressure of CO2 (PtcCO2). PtcCO2 monitoring during sleep can be helpful for evaluating sleep apnea syndrome, particularly in children. End-tidal PCO2 is inferior to PtcCO2 as far as accuracy, but it provides breath-by-breath estimates of respiratory gas exchange, while PtcCO2 reflects temporal trends in alveolar ventilation. The frequency of monitoring end-tidal PCO2 has markedly increased in light of its multiple applications (e.g., verify endotracheal intubation, anesthesia or mechanical ventilation, exercise testing, respiratory patterning during sleep, etc.).

Indoor Air Quality Improvement Using Nature-Based Solutions: Design Proposals to Greener Cities

Low indoor air quality is an increasingly important problem due to the spread of urbanization. Because people spend most of their time inside, poor indoor air quality causes serious human health issues, resulting in significant economic losses. In this work, the current state of affairs is presented and analyzed, focusing on the current problems and the available solutions to improve the quality of indoor air, and the use of nature-based solutions. These involve the cultivation of microalgae in closed photobioreactors. In these systems, photosynthetic organisms can capture CO₂ and other pollutants generated in indoor environments, which they use to grow and develop biomass. Several possible layouts for the implementation of microalgae-based indoor air cleaning systems are presented, taking into account the systems that are currently available at a commercial scale. A critical analysis of the microalgae indoor purification systems is presented, highlighting their advantages and disadvantages, and suggesting potential improvements and future lines of research and development in the area.

Unveiling the sensory and interneuronal pathways of the neuroendocrine connectome in Drosophila

Neuroendocrine systems in animals maintain organismal homeostasis and regulate stress response. Although a great deal of work has been done on the neuropeptides and hormones that are released and act on target organs in the periphery, the synaptic inputs onto these neuroendocrine outputs in the brain are less well understood. Here, we use the transmission electron microscopy reconstruction of a whole central nervous system in the Drosophila larva to elucidate the sensory pathways and the interneurons that provide synaptic input to the neurosecretory cells projecting to the endocrine organs. Predicted by network modeling, we also identify a new carbon dioxide-responsive network that acts on a specific set of neurosecretory cells and that includes those expressing corazonin (Crz) and diuretic hormone 44 (Dh44) neuropeptides. Our analysis reveals a neuronal network architecture for combinatorial action based on sensory and interneuronal pathways that converge onto distinct combinations of neuroendocrine outputs.

A phase I, nonrandomized controlled trial demonstrating the novel technique of cytoreductive surgery and hyperthermic intraperitoneal chemotherapy utilizing warm humidified carbon dioxide insufflation

AIM

The aim of this work was to report on the safety and feasibility of warm humidified CO₂ (WHCO₂ ) insufflation during cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC).

METHOD

Ten consecutive patients with histologically confirmed peritoneal cancer were enrolled in this phase I pilot nonrandomized controlled trial. They were alternately assigned to CRS and HIPEC with WHCO₂ versus standard procedure. WHCO₂ was delivered at 10 L/min, a pressure of 4.5 bar, 37ºC and 98% relative humidity during CRS using the HumiGard^TM system. HIPEC was performed with an open abdomen using the Coliseum technique at 42ºC for 60 min. All patients were admitted to the intensive care unit and commenced on total parenteral nutrition postoperatively. Surface and core temperatures were measured every 30 min using an infrared camera and nasopharyngeal probe, respectively. Clinicopathological, intra- and postoperative details were collated between groups, and median surface and core temperatures were statistically compared.

RESULTS

Surface and core temperatures were generally higher in the WHCO₂ group. Core temperature at 120 and 180 min was significantly higher in the WHCO₂ versus the non-WHCO₂ group (p = 0.028 and 0.008, respectively). There was a significant linear relationship between core and surface temperature at 30, 60, 90, 120, 150 and 180 min (p = 0.033, 0.004, 0.007, 0.021, 0.009 and 0.006, respectively). The peritoneal cancer index was lower but the estimated blood loss was higher in the non-WHCO₂ than the WHCO₂ group.

CONCLUSION

WHCO₂ in CRS and HIPEC appears to be safe and feasible. An appropriately powered phase II trial will be required to determine if WHCO₂ is associated with improved intra- and postoperative outcomes.

Takotsubo Cardiomyopathy Caused by Carbon Dioxide Intoxication

A 49-year-old man transferred to our hospital for dyspnea that developed while transporting significant loads of dry ice, which may have caused potential carbon dioxide intoxication. On admission, he presented hyperventilation and disorientation. Transthoracic echocardiography showed the reduced motion of the anterior wall of the left ventricle with decreased left ventricular ejection fraction. The patient underwent coronary angiography, which did not show apparent coronary arterial stenosis. The electrocardiogram revealed T-wave change and echocardiography results showed the subsided changes on the third hospital day. He was discharged without any symptoms on the fourth hospital day. Our case demonstrates the potential association between carbon dioxide intoxication and Takotsubo cardiomyopathy. Our experience may inform emergency physicians in formulating diagnostic/therapeutic approaches for similar patients experiencing cardiac failure following carbon dioxide intoxication.

Synthesis and characterization of hexagonal boron nitride used for comparison of removal of anionic and cationic hazardous azo-dye: kinetics and equilibrium studies

The purpose of this study was to compare the adsorption behavior of cationic and anionic dyes onto a hexagonal boron nitride (hBN) nanostructure that was rich in a negative charge. Herein, the hBN nanostructure was synthesized using boric acid as a precursor material. The characteristic peaks of the hBN nanostructure were performed using Fourier transform infrared (FT-IR) and Raman spectroscopies. The morphology and the particle size of hBN nanostructure were determined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). During the studies, various essential adsorption parameters were investigated, such as the initial dye concentration, pH of the dye solution, adsorbent dose, and contact time. Under optimal conditions, the removal of 42.6% Metanil yellow (MY) and 90% Victoria blue B (VBB) from aqueous solution was performed using a 10-mg hBN nanostructure. Furthermore, the equilibrium studies showed that the Freundlich isotherm model fitted well for the removal of MY. However, the Langmuir isotherm model fitted well for the removal of VBB. Moreover, according to the results obtained from the kinetic studies, while the first-order kinetic model was suited for the adsorption of the MY, the second-order kinetic model was found to well fit for the adsorption of VBB.

Hypothesis: Potentially Systemic Impacts of Elevated CO2 on the Human Proteome and Health

Uniform CO₂ during human evolution (180 to 280 ppm) resulted, because of the role of the CO₂-bicarbonate buffer in regulating pH, in rather constant pH (7.35 to 7.45) in human fluids, cells and tissues, determining, in turn, the narrow pH range for optimal functioning of the human proteome. Herein, we hypothesize that chronic exposure to elevated pCO₂ with increasing atmospheric CO₂ (>400 ppm), and extended time spent in confined, crowded indoor atmospheres (pCO₂ up to 5,000 ppm) with urban lifestyles, may be an important, largely overlooked driver of change in human proteome performance. The reduced pH (downregulated from 0.1 to 0.4 units below the optimum pH) of extant humans chronically exposed to elevated CO₂ is likely to lead to proteome malfunction. This malfunction is due to protein misfolding, aggregation, charge distribution, and altered interaction with other molecules (e.g., nucleic acids, metals, proteins, and drugs). Such alterations would have systemic effects that help explain the prevalence of syndromes (obesity, diabetes, respiratory diseases, osteoporosis, cancer, and neurological disorders) characteristic of the modern lifestyle. Chronic exposure to elevated CO₂ poses risks to human health that are too serious to be ignored and require testing with fit-for-purpose equipment and protocols along with indoor carbon capture technologies to bring CO₂ levels down to approach levels (180–280 ppm) under which the human proteome evolved.

Cryopreservation without dry ice-induced acidification during sample transport

Dry ice (solid CO₂) remains highly useful when temperature-sensitive biological samples need to be cryogenically transported. CO₂ released during the sublimation of dry ice can diffuse through gas permeable receptacle material or any defective seals resulting in potential sample acidification and compromised integrity. In addition, the quality of cryopreservation can be undermined once the dry ice is exhausted. The dry ice carrier design described here has been demonstrated to prevent sublimated CO₂ from reaching the samples while maintaining storage temperature below -60 °C for 19 h. It is also equipped with microcontroller-based temperature monitoring for traceability and CO₂ gas monitoring for safety.

Case of cardiac arrest due to carbon dioxide poisoning following an explosion of a carbon dioxide tank

Carbon dioxide is widely used for a variety of purposes. As it is a normal constituent of air, the public generally regards it as safe. Although low concentrations of carbon dioxide are not harmful to human beings, high concentrations are toxic, and can cause serious harm, including cardiac arrest. Only a limited number of cases of carbon dioxide intoxication have been reported in Korea, and they have all been mild, with no cases of cardiac arrest following acute exposure to high concentrations of carbon dioxide, reported previously. We describe a case of carbon dioxide poisoning following an explosion of a carbon dioxide tank, which led to cardiac arrest in a 66-year-old patient. This cardiac arrest could have been avoided if the patient was fully aware of the hazardous effects and serious consequences of exposure to high concentrations of carbon dioxide.

Welfare Impact of Carbon Dioxide Euthanasia on Laboratory Mice and Rats: A Systematic Review

Background: There has been increased concern about the suitability of CO2 as a method for euthanasia of laboratory mice and rats, including the potential discomfort, pain or distress that animals may experience prior to loss of consciousness; time to loss of consciousness; best methods for use of CO2; and the availability of better alternatives. These discussions have been useful in providing new information, but have resulted in significant confusion regarding the acceptability of CO2 for rodent euthanasia. In some cases, researchers and veterinarians have become uncertain as to which techniques to recommend or use for euthanasia of laboratory mice and rats. Methods: The International Association of Colleges of Laboratory Animal Medicine (IACLAM) convened a taskforce to examine the evidence for adverse welfare indicators in laboratory rats and mice undergoing CO2 euthanasia using a SYRCLE-registered systematic review protocol. Of 3,772 papers identified through a database search (PubMed, Web of Science, CAB Direct, Agricola, and grey literature) from 1900 to 2017, 37 studies were identified for detailed review (some including more than one species or age group), including 15 in adult mice, 21 in adult rats, and 5 in neonates of both species. Experiments or reports were excluded if they only assessed parameters other than those directly affecting animal welfare during CO2 induction and/or euthanasia. Results: Study design and outcome measures were highly variable and there was an unclear to high risk of bias in many of the published studies. Changes in the outcome measures evaluated were inconsistent or poorly differentiated. It is likely that repeated exposures to carbon dioxide inhalation are aversive to adult rats and mice, based on avoidance behavior studies; however, this effect is largely indistinguishable from aversion induced by repeated exposures to other inhalant anesthetic gasses. Conclusion: There is insufficient evidence to permit an unbiased assessment of the effect of CO2 inhalation during euthanasia on welfare indicators in laboratory mice and rats. Additional well-designed, unbiased, and adequately powered studies are needed to accurately assess the welfare of laboratory mice and rats undergoing euthanasia via CO2 gas.

Low-Temperature Carbon Dioxide Gas Sensor Based on Yolk-Shell Ceria Nanospheres

Monitoring carbon dioxide (CO₂) levels is extremely important in a wide range of applications. Although metal oxide-based chemoresistive sensors have emerged as a promising approach for CO₂ detection, the development of efficient CO₂ sensors at low temperature remains a challenge. Herein, we report a low-temperature hollow nanostructured CeO₂-based sensor for CO₂ detection. We monitor the changes in the electrical resistance after CO₂ pulses in a relative humidity of 70% and show the high performance of the sensor at 100 °C. The yolk-shell nanospheres have not only 2 times higher sensitivity but also significantly increased stability and reversibility, faster response times, and greater CO₂ adsorption capacity than commercial ceria nanoparticles. The improvements in the CO₂ sensing performance are attributed to hollow and porous structure of the yolk-shell nanoparticles, allowing for enhanced gas diffusion and high specific surface area. We present an easy strategy to enhance the electrical and sensing properties of metal oxides at a low operating temperature that is desirable for practical applications of CO₂ sensors.

Beyond the burn: Studies on the physiological effects of flamethrowers during World War II

Flamethrowers are widely considered one of warfare's most controversial weapons and are capable of inflicting gruesome physical injuries and intense psychological trauma. Despite being the last of the major combatants in World War II (WWII) to develop them, the United States military quickly became the most frequent and adept operator of portable flamethrowers. This gave the U.S. military ample opportunity to observe the effects of flamethrowers on enemy soldiers. However, while most people in modern times would consider immolation by flamethrower to be an unnecessarily painful and inhumane way to inflict casualties, immolation was, at one point during World War II (WWII), referred to as "mercy killing" by the U.S. Chemical Warfare Service (CWS). This mischaracterization arose from a series of first-hand accounts describing what were believed to be quick, painless, and unmarred deaths, as well as from a poor and incomplete understanding of flamethrower lethality. As a result, indirect mechanisms such as hypoxia and carbon monoxide poisoning were generally absent from accounts of the flamethrower's fatal effects. It was not until several years after flamethrowers were introduced to the frontlines that the CWS and National Defense Research Committee (NDRC) conducted a series of tests to better understand the physiological and toxicological effects of flamethrowers. This article examines how the initial absence of scientific data on the physiologic effects of flamethrowers led to an inaccurate understanding of their lethality, and bizarre claims that one of history's most horrific instruments of war was considered one of the more "humane" weapons on the battlefield.

Genetic Algorithm Design of MOF-based Gas Sensor Arrays for CO2-in-Air Sensing

Gas sensor arrays, also known as electronic noses, leverage a diverse set of materials to identify the components of complex gas mixtures. Metal-organic frameworks (MOFs) have emerged as promising materials for electronic noses due to their high-surface areas and chemical as well as structural tunability. Using our recently reported genetic algorithm design approach, we examined a set of 50 MOFs and searched through over 1.125 × 1015 unique array combinations to identify optimal arrays for the detection of CO2 in air. We found that despite individual MOFs having lower selectivity for O2 or N2 relative to CO2, intelligently selecting the right combinations of MOFs enables accurate prediction of the concentrations of all components in the mixture (i.e., CO2, O2, N2). We also analyzed the physical properties of the elements in the arrays to develop an intuition for improving array design. Notably, we found that an array whose MOFs have diversity in their volumetric surface areas has improved sensing. Consistent with this observation, we found that the best arrays consistently had greater structural diversity (e.g., pore sizes, void fractions, and surface areas) than the worst arrays.

Regenerative water purification for space applications: Needs, challenges, and technologies towards 'closing the loop'

Human missions to establish surface habitats on the Moon and Mars are planned in the coming decades. Extraplanetary surface habitat life support systems (LSS) will require new capabilities to withstand anticipated unique, harsh conditions. In order to provide safe, habitable environments for the crew, water purification systems that are robust and reliable must be in place. These water purification systems will be required to treat all sources of water in order to achieve the necessary levels of recovery needed to sustain life over the long-duration missions. Current water recovery and purification systems aboard the International Space Station (ISS) are only partially closed, requiring external inputs and resupply. Furthermore, organic wastes, such as fecal and food wastes, are currently discarded and not recycled. For long-duration missions and habitats, this is not a viable approach. The inability to recycle organic wastes represents a lost opportunity to recover critical elements (e.g., C, H, O, N, P) for subsequent food production, water purification, and atmospheric regeneration. On Earth, a variety of technologies are available to meet terrestrial wastewater treatment needs; however, these systems are rarely completely closed-loop, due to lack of economic drivers, legacy infrastructure, and the (perceived) abundance of resources on Earth. Extraplanetary LSS provides a game-changing opportunity to incentivize the development of completely closed-loop systems. Candidate technologies may be biological, physical, or chemical, with associated advantages and disadvantages. This paper presents a survey of potential technologies, along with their inputs, outputs and requirements, which may be suitable for next-generation regenerative water purification in space. With this information, particular technologies can be down-selected for subsystem integration testing and optimization. In order for future space colonies to have closed-loop systems which minimize consumable inputs and maximize recovery, strategic implementation of a variety of complementary subsystems is needed.

Estimation of time to compromised tenability in fires: is it time to change paradigms?

The ISO standard 13571 estimates the time to the compromised tenability of people in enclosed fires. This is understood as the time which must be available for the structural design to pass an evacuation, or an escape paradigm for the evacuation of burning buildings. As with all emergency response planning values, such once-in-a-lifetime events cannot readily be validated side-by-side. Consequently, risk assessors must refer to animal-based reference data fitting the scenario of concern closely. The analysis detailed in this paper used the concentration × time (Cxt)-matrix of point of departures (PODs) from rats acutely exposed to carbon monoxide (CO), which is amongst the most abundant toxic fire gases. The objective of the analysis was to clarify whether the time- and effect-adjusted nonlethal threshold concentration LCt₀₁ × 1/3 from acute rat inhalation studies is suited to model thresholds characterizing any 'impairment of escape' in humans. Modeled outcomes are compared with published reference data from human volunteers exposed at the similar C × t's of CO at 800 ppm × 1-h and 100 ppm × 8-h. These exposure durations match the maximum escape duration of 1-h considered in the ISO standard 13571 and standards enforcing occupational exposure limits of 8-h duration. The reference PODs indicative of 'impairment of escape' in healthy adults relied on C × t's below those eliciting any loss of motor function or psychoneurological functions. The comparison of the LCt₀₁ × 1/3 based modeled outcomes from rats match favorably with the effect-based PODs from humans. Consistent with published evidence from humans, carboxyhemoglobin (COHb) saturation-a biomarker of exposure rather than of effect-failed to reliably predict effect-based outcomes. Unlike the LCt₀₁ × 1/3 threshold approach, the COHb-based median approach used by ISO TS 13571 is inconsistent with human evidence and both over- and under-estimates the CO-related potency for causing incapacitation at non-toxic and critically-toxic C × 's, respectively. In summary, it seems timely that the ISO TS 13571 standard pays attention to scientific progress in relevant toxicity information and refinements to scientific methods shown to adequately predict human risks.

A comprehensive investigation on the thermal and toxic hazards of large format lithium-ion batteries with LiFePO4 cathode

Toxic gases released from lithium-ion battery (LIB) fires pose a very large threat to human health, yet they are poorly studied, and the knowledge of LIB fire toxicity is limited. In this paper, the thermal and toxic hazards resulting from the thermally-induced failure of a 68 Ah pouch LIB are systematically investigated by means of the Fourier transform infrared spectroscopy (FTIR) and 1/2 ISO full scale test room. The LIBs with higher state of charge (SOC) are found to have greater fire risks in terms of their burning behavior, normalized heat release rate, and fire radiation, as well as the concentration of toxic gases. Specifically, the thermal hazards are evaluated by combining the effects of convective and radiative heat. The major toxic gases detected from the online analysis are CO, HF, SO₂, NO₂, NO and HCl. Furthermore, Fractional Effective Dose (FED) and Fractional Effective Concentration (FEC) models are used to quantitatively assess the overall gas toxicity. Results show that the effects of irritant gases are much more significant than those of asphyxiant gases. HF and SO₂ have much greater toxicity than the other fire gases. The maximum FEC value is approaching the critical threshold in such fire scenarios.

Elevated Environmental Carbon Dioxide Exposure Confounding Physiologic Events in Aviators?

INTRODUCTION

Physiological events (PEs) are a growing problem for US military aviation with detrimental risks to safety and mission readiness. Seeking causative factors is, therefore, of high importance. There is no evidence to date associating carbon dioxide (CO2) pre-flight exposure and decompression sickness (DCS) in aviators.

MATERIALS AND METHODS

This study is a case series of six aviators with PE after being exposed to a rapid decompression event (RDE) with symptoms consistent with type II DCS. The analysis includes retrospective review of flight and environmental data to further assess a possible link between CO2 levels and altitude physiologic events (PEs). IRB approval was obtained for this study.

RESULTS

This case series presents six aviators with PE after being exposed to a rapid decompression event (RDE) with symptoms consistent with type II DCS. Another three aviators were also exposed to a RDE, but remained asymptomatic. All events involved tactical jet aircraft flying at an average of 35,600' Mean Sea Level (MSL) when a RDE occurred, Retrospective reviews led to the discovery that the affected individuals were exposed, pre-flight, to poor indoor air quality demonstrated by elevated levels of measured CO2.

CONCLUSION

PEs are a growing safety concern for the aviation community in the military. As such, increasing measures are taken to ensure safety of flight and completion of the mission. To date, there is no correlation of CO2 exposure and altitude DCS. While elevated CO2 levels cannot be conclusively implicated as causative, this case series suggests a potential role of CO2 in altitude DCS through CO2 direct involvement with emboli gas composition, as well as pro-inflammatory cascade. Aviators exposed to elevated CO2 in poorly ventilated rooms developed PE symptoms consistent with DCS, while at the same command, aviators that were exposed to a well ventilated room did not. This report is far from an answer, but does demonstrate an interesting case series that draws some questions about CO2's role in these aviator's DCS experience. Other explanations are plausible, including the accurate diagnosis of DCS, health variables amongst the aviators, and differences in aircraft and On-Board Oxygen Generation Systems (OBOGS). For a better understanding, the role of environmental CO2 and pre-flight exposure as a risk of DCS should be reviewed.

Solid State Electronic Sensors for Detection of Carbon Dioxide

Detection of carbon dioxide (CO₂) is very important for environmental, health, safety and space applications. We have studied novel multiwall carbon nanotubes (MWCNTs) and an iron oxide (Fe₂O₃) nanocomposite based chemiresistive sensor for detection of CO₂ at room temperature. The sensor has been miniaturized to a chip size (1 cm × 2 cm). Good sensing performance was observed with a wide detection range of CO₂ concentrations (100–6000 ppm). Structural properties of the sensing materials were characterized using Field-Emission Scanning Electron Microscopy, Fourier-Transform Infrared and Raman spectroscopies. The greatly improved sensitivity of the composite materials to CO₂ can be attributed to the formation of a depletion layer at the p-n junction in an MWCNT/iron oxide heterostructure, and new CO₂ gas molecules adhere to the high surface area of MWCNTs due to the concentration gradient. The test results showed that the CO₂ sensor possesses fast response, compact size, ultra-low power consumption, high sensitivity and wide dynamic detection range.

A Fatal Case of Gas Intoxication in Silage Pit

Fatalities due to gas intoxication are rare in routine forensic casework. The most common gas is carbon monoxide, with other gases (ammonia, methane, propane and butane, carbon dioxide, hydrogen sulfide) encountered only very rarely. In this report, we describe the accidental death of two maintenance workers who were found in the silage pit at a biogas plant. The autopsy revealed signs of asphyxia in both the deceased. Analysis of the gaseous mixtures in the tank using an infrared gas analyzer showed slightly elevated concentrations of carbon dioxide. Toxicological examination of the blood of both the deceased using gas chromatography with a flame ionization detector, spectrophotometry and liquid chromatography-mass spectrometry did not detect any toxicologically significant substance that would explain the sudden collapse. Both the autopsy and the toxicology analyses suggest CO₂ intoxication as the most likely cause for the collapse of the two men, which then led to sudden asphyxia.