At higher concentrations (>5%), it causes the development of hypercapnia and respiratory acidosis. CO 2 toxicity in humansĬarbon dioxide at low concentration has little, if any, toxicological effects. These findings show that the cause of death in breathing high concentrations of CO 2 is not the hypoxia but the intoxication of carbon dioxide. After a few minutes of apnea, circulatory arrest was seen. In higher concentrations of CO 2, unconsciousness occurred almost instantaneously and respiratory movement ceased in 1 min. After 30–90 min, the respiratory center was depressed, and hypotension occurred gradually or suddenly from reduced cardiac output, leading to an apnea and eventually to circulatory arrest. It is believed that the initial BP depression with the decreased heart rate is due to the direct depressant effect of CO 2 upon the heart and that the return of blood pressure to its original level was due to the rapid rise of PaCO 2. The heart rate slowed slightly just after the gas mixture inhalation. The blood pressure (BP) decreased transiently during the increased respiratory movement and then rose again and maintained the original level for a while. Hill and Flack showed that CO 2 concentrations up to 35% have an exciting effect upon both circulation and respiration, but those beyond 35% are depressant upon them. Tests performed on mongrel dogs show the physiological effect of carbon dioxide on the body: after inhalation of a 50% CO 2 and 50% air mixture, respiratory movement increased for about 2 min, and then, it decreased for 30–90 min. In the end, a total of 19 articles were evaluated to be relevant to this topic and included in this review. For all of the articles, an unanimous consensus among the authors was reached whether to include or exclude. Each article was independently evaluated by two of the authors. Studies related to decompression sickness were excluded. Articles were included based on their focus on medical or physiological effects of carbon dioxide. MethodsĪ literature review was performed where articles were sought in MEDLINE medical database via PubMed using the search terms: “dry ice poisoning,” “carbon dioxide poisoning,” “CO 2 poisoning,” “carbon dioxide intoxication,” and “CO 2 intoxication.” The references of the articles that were found were further evaluated to incorporate as much of the available literature as possible. We performed this literature review to understand the contribution of CO 2 specifically to “confined space hypoxic syndrome,” and wanted to make physicians more aware of the condition. Massive geothermal emissions have also been described as a possible cause of CO 2 intoxications, though in these cases, a relation with other toxic gasses inhaled might not be excluded. Dry ice intoxication might be accidental or deliberately as several suicide cases have been described. Dry ice undergoes sublimation (direct conversion from a solid state into a gas), and if it is warmed rapidly, large amounts of CO 2 are generated, which is especially dangerous in closed environments. Other causes of carbon dioxide intoxication have been identified as well, such as dry ice. At high concentrations, it has been showed to cause unconsciousness almost instantaneously and respiratory arrest within 1 min. Ĭarbon dioxide does not only cause asphyxiation by hypoxia but also acts as a toxicant. Unfortunately, the number of killed rescuers has risen to two thirds of those deaths. A recent study of the Occupational Safety and Health Administration (OSHA) in 2015 still estimated the number of deaths involving confined spaces to be around 90 per year. Studies conducted in the 1980s showed that there were 89 deaths per year in the USA alone, during work in confined spaces 22% occur during rescue efforts. The term “confined space hypoxic syndrome” has been proposed to describe confined space accidents occurring in water meter pits, tanks, holds of ships, mines, underground storage bins, and so forth, resulting from oxygen-deficient atmospheres. These characteristics explain why enclosed environments are vulnerable for CO 2 buildup, displacing oxygen from the area. It is a colorless, odorless, and nonflammable gas that accumulates near the ground (CO 2 is 1.5 times heavier than air). In normal room air, carbon dioxide percentages are very low (around 0.04%). Carbon dioxide (CO 2) is a product of combustion, fermentation, and respiration.
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