![]() Ĭerebral autoregulation is a process in which the brain works to maintain a constant and steady supply of nutrients and oxygen despite changes in cerebral perfusion pressure. Patients with chronic hypercapnia may not experience alterations in consciousness until PaCO2 exceeds 90 mmHg. Normal individuals do not experience alterations in consciousness until PaCO2 greater than75 mmHg. Patient baseline PaCO2 is important to consider in the development of CO2 narcosis. There is a hypothesis that there are increased levels of glutamine and gamma-aminobutyric acid(GABA) and decreased glutamate levels. The current belief is that hypercapnia changes neurotransmitter levels involved with consciousness. It is more likely that this group only partially contributes to hypercapnia and is not commonly the primary cause but can occur in conditions that increase metabolic rate, sepsis, thyrotoxicosis, or fever.Įnvironmental exposure to areas rich in carbon dioxide, such as volcanoes or geothermal activity, puts patients at risk for carbon dioxide poisoning.Īnother unique situation to consider is oxygen-induced hypercapnia, which presents in some patients with COPD when given supplemental oxygen. The third group is anything that increases CO2 production. A large pulmonary embolism can also cause significant dead space. This condition can be due to pulmonary capillary compression (positive pressure ventilation) or the destruction of pulmonary capillaries (pulmonary vasculitides, COPD, asthma, interstitial lung disease). The second group is anything that increases physiologic dead space (part of the lung that does not participate in gas exchange) this is ventilation without perfusion. Deformity of the thoracic cage can impact tidal volumes, therefore decreasing minute ventilation. Notable etiologies include Guillain-Barre, myasthenia gravis, amyotrophic lateral sclerosis, myositis, multiple sclerosis, phrenic nerve injury, tetanus, botulism, organophosphates, and ciguatera. Decreased respiratory neuromuscular function can decrease minute ventilation. Although the medulla functions to control the respiratory drive, many peripheral nerves and respiratory muscles are needed to perform respirations. Notable etiologies include overdose of sedative medications (narcotics, benzodiazepines, tricyclic antidepressants, etc.), stroke, and hypothermia. Anything that affects the central respiratory center can affect the minute ventilation. The central respiratory center in the medulla takes feedback from multiple inputs and integrates them into a respiratory drive, which functions to control our minute ventilation. The first group is anything that causes decreased minute ventilation (respiratory rate x tidal volume). The etiology can be extensive, but it can be helpful to divide the potential causes into three groups: decreased minute ventilation, increased physiologic dead space, increased carbon dioxide production. The proximate cause of death in all cases was attributed to CO(2) intoxication, based on the scene findings, the reconstructed sequence of events, the autopsy, and results of toxicological studies.Overall, the driving mechanism of CO2 narcosis is acute hypercapnia. The rapid increase in CO(2) concentration would render a victim helpless, with no time to wake and defend themselves, or others. Inhalation of pure CO(2) ensured their rapid unconsciousness due to hypercapnia and severe anoxia. ![]() ![]() It is hypothesized that the husband placed an inhalation mask over the mouths and noses of his wife and children while they were sleeping. ![]() ![]() Two synthetic inhalation face masks and tubing were also found, which tested positive for the DNA of all four deceased family members. The container was almost empty and according to the label had been sold as a CO(2)-fertilizer for aquarium plants. A 500 g single-use CO(2) cylinder was standing on the floor. The police found the wife and two sons lying in their beds and the husband in a supine position on the floor with a plastic bag over his head tied loosely around his neck with a rope. The bodies were those of a father (a 69-year-old business consultant), his wife (aged 26-years), and two sons (aged 3 and 6 years, respectively). Four bodies were discovered in an apartment in midsummer 2012 in Berlin, Germany. This report demonstrates how carbon dioxide (CO(2)) may be a potent weapon in murder-suicide, where the death scene offers virtually no clues as to the lethal modality and the autopsy findings are nonspecific. ![]()
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