Unintentional carbon monoxide poisoning inside a motor-vehicle

After performing Hajj, 1415, a family of 3 men and 6 women, aged between 21 and 70, returned home to Al Quwayiyah, Riyadh Region in a 1991 Toyota Landcruiser. For the entire trip, two men sat in the front seat, one man and three women sat in the middle seat, and three women sat on the floor in the back where the seat had been removed. The air conditioner was off and all windows closed. After five hours of driving, they stopped to sleep in the desert. One woman in the back had developed a mild headache, but it had resolved when she woke up.

After driving for one hour in the morning, the group stopped for gasoline. The driver left the engine running, the windows closed and the air conditioner off. All 3 men left the car for more than 20 minutes to buy food. All six women stayed in the car. The woman in the back who had suffered from a headache the previous day was apparently asleep on the floor. She did not eat. After driving for 45 minutes, a second woman sitting on the floor in the back, fainted. They stopped and revived the woman who had fainted. The third woman in the back felt dizzy and unsteady on her feet. They checked on the first woman, whom they thought was merely asleep, and could not revive her. They took her 3 km to the nearest hospital where she was pronounced dead. The woman, who fainted was admitted to the ICU for observation. The other passengers were not admitted. The five surviving women said that after leaving the gasoline station they had headaches and nausea, while the men developed only mild headaches.

The woman who died was 35 years old. She had no prior history of chronic illness and until the headaches began had not complained of any symptoms on the journey. None of the passengers smoke.

The death and symptoms in the other travelers suggest carbon monoxide (CO) poisoning. However, CO poisoning wasn't originally suspected at the hospital and arterial blood gases and carboxyhemoglobin were not evaluated.

When the team inspected the car, they found two holes in the floor for the bolts that should attach the back seat to the floor. Both holes were covered by a bed sheet. The woman who had first become unconscious and subsequently died had been sitting directly over the one hole and the woman who fainted had been sitting over the other hole. The hole under the dead woman was directly above the exhaust pipe of the car that had a 10cm crack immediately opposite the hole. In addition, the rubber seal on the rear door was broken. The test of the exhaust showed that the CO level was 6.4%, which exceeds the normal upper levels (4.6%).

CO is an odorless and invisible gas with an affinity for hemoglobin over 240 times that of 02. CO exposure results in elevated carboxyhemoglobin concentration in the blood and a decreased capacity to transport 02 to tissue. The resultant anoxia of vital tissues (brain and heart) is responsible for life-threatening manifestations. Mild manifestations include headache, nausea, dimness of vision and fainting. Severe manifestations include coma, convulsions, myocardial ischemia (ECG changes), and death.

The nearly simultaneous presentation of headache in all nine persons confined in a closed vehicle with a faulty exhaust system and with fainting, dizziness and unconsciousness in three of them, suggests that this outbreak was due to CO poisoning. The most severe manifestations and earlier onset corresponds to the closest and most direct exposure to exhaust gasses (the two women sitting over the holes). While the car was in motion, airflow probably forced the exhaust gases away from the holes. Parking the car at the gasoline station probably allowed more exhaust gases to enter.

Exposure to CO, and thereafter CO poisoning, increased generally with the growth of the use of the new products of the modern world. CO exposure comes from three sources[1] 1) CO in the surrounding environment produced mainly by the automobile, from domestic charcoal burning and space heaters, 2) occupational exposure and 3) cigarette, cigar and pipe smoke in confined places.

In the United States, the unintentional deaths due to CO poisoning result mainly from exposure to motor-vehicle exhaust and occurs more often during the cold months of the year.[2] In Saudi Arabia, CO poisoning is not reportable, but emergency rooms in the hospitals often receive cases in winter due to exposure to burning charcoal smoke in closed places.

This report should alert physicians, especially in the health centers and hospitals serving towns adjacent to highways. They should keep CO poisoning in mind if they receive patients with headache, fainting, dizziness, dim vision or unconsciousness while riding in cars. 100% 02 therapy should be started immediately, if CO poisoning is suspected.[3] People need to be warned to maintain correctly the exhaust systems of their vehicles.