My Most Unusual Case: Asphyxiation by Cake: An Interesting Case of Dyspnea
A 58-year-old man experiences shortness of breath, lightheadedness, and nausea immediately after getting into a rental vehicle.
The normal concentration of CO2 in the atmosphere is approximately 0.04% (396 ppm). The Occupational Safety and Health Administration (OSHA) has set a maximum safe exposure level of CO2 at 0.5% (5,000 ppm) over an 8-hour day.3 Concentrations as low as 1% (10,000 ppm) may cause drowsiness. Exposure to concentrations of 7% to 10% for several minutes to an hour results in headache, tachycardia, dyspnea, and hyperventilation. At levels of 10% to 15%, dizziness, severe muscle twitching, and loss of consciousness can occur after only a few minutes. Death occurs within minutes at concentrations greater than 30%.2
Carbon dioxide also acts as a potent cerebral vasodilator, which may explain symptoms such as headache and dizziness.2 The severity of symptoms is dependent on the concentration of CO2, the length of the exposure, and the underlying health of the patient. Elevated concentrations of CO2 can occur in areas where there is limited or poor ventilation, such as in a mine (where it is known as blackdamp, stythe, or choke damp),4 submarine, grain silo, or a sealed building without mechanical ventilation.
Other Case Presentations
Similar cases as the one presented in this article have been described in the literature. In one such case, following Hurricane Ivan, a 34-year-old-man placed four 25-pound blocks of dry ice wrapped in paper in the front seat of his truck with the windows closed.5 After driving less than one quarter of a mile, he developed dyspnea and telephoned for help before losing consciousness. Fortunately, he was found in time and recovered soon after the doors to his truck were opened.5
In another case, a 59-year-old man entered a walk-in freezer that contained dry ice wrapped loosely in plastic. He was found inside the freezer 20 minutes later in cardiac arrest; resuscitation efforts were unsuccessful. Investigation of the freezer found the initial O2 concentration to be 13% (normal level, 20.93%) and an estimated CO2 level of 40%.5
Similarly, a 35-year-old woman was inadvertently locked in a bank vault while storing receipts. In a bid for help, she pulled the fire alarm, which triggered a CO2-based fire-extinguishing system. The fire department responded and found the woman dead in the vault 30 minutes later. The cause of death was labeled as CO2 intoxication.6
Natural Phenomenon
Differential Diagnosis
When CO2 toxicity is suspected, other conditions should be considered as there may be more than one process involved. For example, other causes of coma or dyspnea should be investigated, including trauma, hypoglycemia, CO, methemoglobinemia, or other metabolic processes. In addition, a patient may have a pre-existing condition, such as a trauma or an altered mental status due to drugs or alcohol, all of which can increase his or her susceptibility to the effects of CO2.
Evaluation and Treatment
Useful laboratory testing includes arterial blood gas, venous co-oximetry for carboxyhemoglobin, chemistry panels, ethanol testing, and radiographs or computed tomography scanning, as indicated.
Initial management of suspected CO2 toxicity includes first removing the patient from the source of the gas. Rescuers must exercise caution so as to prevent a mass casualty incident. Once out of the dangerous environment, as long as the patient is conscious and spontaneously breathing, supportive measures are generally all that are necessary. Oxygen should be applied, after which the spontaneously breathing patient without underlying lung disease should rapidly return to normal. If there is marked decrease in mental status or poor respiratory drive despite O2 administration, intubation with mechanical ventilation may be required. A higher than normal RR will help remove excessive CO2 if mechanical ventilation is required. If a respiratory acidosis is present, intravenous sodium bicarbonate should be avoided as this may increase the level of serum CO2. Intravenous fluids and other supportive measures, including treatment for any concurrent conditions, may be indicated.
Dr Schreckengaust is an emergency physician in the department of emergency medicine at Camp Lejune, North Carolina. Dr Lang is an assistant professor in the department of emergency medicine at Eastern Virginia Medical School, Norfolk; and a physician at Emergency Physicians of Tidewater, Norfolk, Virginia. Dr Counselman is the distinguished professor and chairman of the department of emergency medicine at Eastern Virginia Medical School, Norfolk; and a physician at Emergency Physicians of Tidewater, Norfolk, Virginia. He is also the associate editor in chief of EMERGENCY MEDICINE editorial board.
