My Most Unusual Case: Asphyxiation by Cake: An Interesting Case of Dyspnea

Case

A 58-year-old man presented to the ED via emergency medical services (EMS) with shortness of breath, lightheadedness, and nausea. Upon arrival to the ED, most of his symptoms had resolved. The patient reported that he had taken a 2-hour flight into town the previous day and had spent an uneventful evening at a local hotel. He said that he began experiencing shortness of breath and lightheadedness soon after entering his rental vehicle an hour prior to presentation, explaining that he felt as if he “could not get any air.”

The patient’s vital signs at examination were: oral temperature, 97.5^oF; pulse, 62 beats/minute; respiratory rate (RR), 18 breaths/minute; and blood pressure, 133/83 mm Hg. Oxygen (O₂) saturation was 100% on room air. He was alert and oriented, in no distress, easily conversational, and without diaphoresis. The lungs were clear to auscultation bilaterally, and there was no calf swelling, tenderness, or palpable cords. The remainder of the physical examination was completely normal.

Ancillary studies revealed a normal chest X-ray. An electrocardiogram demonstrated sinus bradycardia with a rate of 56, but no evidence of ischemia or right heart strain. A complete blood count, troponin I, D-dimer, and creatine phosphokinase (CPK) with MB fraction levels were all within normal limits. A serum chemistry panel was also within normal limits, except for a serum glucose level of 181 mg/dL. Venous co-oximetry showed a carboxyhemoglobin level of 0.0, and methemoglobin level of 0.5 gm% (normal range, 0.4-1.5).

Since both the patient and hotel clerk’s symptoms started when each was in the rental car, the patient was questioned about the vehicle and its contents. The car was a late model rental in good condition per report. The patient informed the treating EP that he worked as a decorative cake salesman and had brought cake samples with him to display at a trade show. He further stated that he had left these samples in the car overnight, packed in dry ice.

Upon learning this information, EMS was contacted and instructed to return to the hotel and rental vehicle. The hotel room was noted to have normal levels of O₂ and carbon monoxide (CO) on measurement. Investigation of the car revealed normal levels of CO, but O₂ levels too low to read on the sensor. The emergency team concluded that the dry ice (the solid form of carbon dioxide [CO₂]), sublimed to CO₂ gas overnight. This displaced the O₂ in the vehicle, resulting in severe hypoxia and the symptoms of both the patient and hotel clerk.

The patient was initially placed on 15 L of O₂ via a nonrebreather mask, but he was switched to 2 L of O₂ via nasal cannula shortly afterward. He was observed for a total of 4 hours after arrival; as he remained symptom-free, he was discharged home. The EP was not able to obtain postdischarge follow up information.

Discussion

Carbon dioxide primarily acts as a simple asphyxiant, but it also dissolves in serum as carbonic acid, resulting in a metabolic acidosis. Carbon dioxide is a prevalent gas that is part of everyday life, from an agent in fire extinguishers and carbonation in beverages to byproducts of cellular metabolism. Similar to CO, it is a colorless and odorless gas. Carbon dioxide is commonly used in the food industry as dry ice to keep items cold. In its solid state, CO₂ can cause severe frostbite with direct contact, similar to a burn. However, when dry ice is warmed and sublimated to a gaseous state, large amounts of CO₂ are generated, and this heavy gas can accumulate and displace air (ie, atmospheric O₂), especially in confined spaces. In low concentrations, gaseous CO₂ appears to have minimal toxicological effects, but at higher concentrations it can cause tachycardia, tachypnea, dyspnea, visual disturbances, arrhythmias, impaired levels of consciousness, and even death.

Carbon dioxide primarily acts as a simple asphyxiant, but it also dissolves in serum as carbonic acid, resulting in a metabolic acidosis. Compensation for this acidosis is accomplished by an increased RR (ie, respiratory alkalosis), which further worsens the intake of CO₂.^1,2