26-year-old woman, 32-year-old man critically injured, taken to hospital, after their jeep becomes stranded at Kaena Point on Oahu.

Investigators believe carbon monoxide may have filled a stranded Jeep at Kaena Point Saturday afternoon, leaving the two people inside in critical condition. Honolulu police say several bystanders found the vehicle in about three feet of water with a 32-year-old man and a 26-year-old woman unconscious inside, possibly of carbon monoxide poisoning.

Police say the two weren’t stranded that long, and questions remain as to why the two never got out of the vehicle. With the Jeep trapped in mud and partially underwater, carbon monoxide would have quickly filled its cabin. Medical experts say in about 20 minutes, the odorless gas can knock two people in a car unconscious and permanent brain damage can occur.

“As more carbon monoxide displaces the life-giving oxygen, the carbon monoxide doesn’t enter the brain,” said Dr. Kalani Brady from the John A. Burns School of Medicine. “It doesn’t oxygenate the brain and the brain begins to die.”

Once enough of the gas enters the bloodstream, Dr. Brady says it can render you unconscious, although he points out that people normally feel the effects of carbon monoxide well before that. “It could take five to 10 minutes before someone begins to feel the dizziness, headache and sort of queasiness or nausea that is the sign of early monoxide poisoning,” he said.

In that case, it would have made sense for the victims to open the windows and they would have been fine. But it’s also possible that they were knocked out when the Jeep fell into the mud bog, so they never had a chance to react.

If rescuers were able to get to the victims in time, they can recover fully. “We displace (the carbon monoxide by having) patients breathe pure oxygen in the hospital and sometimes we even use hyperbaric oxygen, although usually pure 100 percent oxygen is sufficient,” Dr. Brady said.

For extra protection, there are portable carbon monoxide detectors that are sold online which are normally used by health care workers and emergency responders.

The state Dept. of Land and Natural Resources points out that the area where the Jeep was found is not a designated trail. A spokeswoman says 13 people were cited for violating such rules at Kaena Point last year.