Acute Mountain Sickness: Scientists Laid Low by a High Adventure

No one promised it would be a dream weekend.

The idea hatched by 10 friends and colleagues from San Diego was to work all day Friday, drive most of the night, sleep a few hours in a motel, rise before dawn, drive straight up a mountain and become violently sick.

It worked like a charm.

They arrived in Bishop long after midnight. The motel had mishandled the booking, so they slept four to a room. Up at 5 a.m., there was no time for a real breakfast. They headed up White Mountain on a bellyful of doughnuts.

By 8,000 feet, they were still feeling chipper. But at 12,000, one man was too addled to pitch his own tent. With a splitting headache and no appetite, he lumbered into his sleeping bag and lay there for the next 24 hours, groaning.

The cook had fallen into a trance over the rice and vegetables. Another woman had developed a “blinding” headache. When they reached 13,500 feet the next day, she collapsed on the ground--nauseated, vomiting, unable to move.

All in all, they pronounced the weekend a great success.

The purpose of the trip, led by a neurologist at Scripps Clinic and Research Foundation in La Jolla, was to study acute mountain sickness, a condition believed to afflict perhaps a third of all people who travel to altitudes above 8,000 to 10,000 feet.

Specifically, the Scripps project aimed to test the theory that the symptoms are caused at least in part by dilation of arteries in the brain. The test used a new device capable of measuring through the skull the speed at which blood is traveling.

The results, which the Scripps researchers intend to publish, showed clear increases in cerebral blood flow. The researchers say they were also able to trace those increases to dilation of blood vessels in the brain.

Acute mountain sickness and responses to altitude are attracting increasing attention as people resort to hiking, climbing and skiing for recreation. Currently, 44 million people worldwide are believed each year to experience altitudes over 8,000 feet.

Some scientists also study acute mountain sickness for what it reveals about medical conditions that deprive people of oxygen, like lung and heart disease. They use acute mountain sickness to study how oxygen deprivation affects the functioning of the brain.

The military, too, is interested in the effects of “going to altitude”--that is, going above 8,000 feet--because many mountainous areas worldwide are of strategic importance to the United States and troops might one day be forced to fight at high altitudes.

But many details of the condition remain poorly understood.

It is not known why certain people are susceptible, even though the condition was documented centuries ago by the Conquistadors and even Marco Polo. Nor is it known why people become sick at widely varying altitudes.

One researcher said 25% to 30% of all mountain climbers seem to suffer from some symptoms. Some speculate that perhaps 60% of all climbing accidents stem from the loss of judgment that comes with mountain sickness.

They said as many as 1% of all climbers go on from mountain sickness to experience cerebral and pulmonary edema--a swelling condition that causes respiratory and brain problems and can be fatal.

A milder form of brain swelling appears to be the cause of mountain sickness, researchers seem to agree. But it is unclear whether the swelling comes from increased blood flow or a build-up of fluid caused by cells malfunctioning from lack of oxygen.

It may come from both.

“One of the last and greatest frontiers in altitude medicine is the brain and why it malfunctions at altitude,” said Dr. Allan Hamilton, who does altitude research for the U.S. Army in Natick, Mass. “That and lung problems are the No. 1 issues that stop people from going to heights and kill people when they go up too fast.”

The condition may also have economic significance.

Dr. Charles Houston, a retired professor of medicine and environmental health at the University of Vermont, participated five years ago in a study that found that 17% of all tourists at eight Colorado resorts experienced some symptoms of mountain sickness.

Assuming that those symptoms were sufficient to deter those tourists from spending just $10 on food or drink, Houston concluded that symptoms of acute mountain sickness cost Colorado resorts about $50 million a year.

So experiments are being conducted worldwide in which scientists and volunteers “go to altitude”--climbing Mt. Everest, the Himalayas, Mt. McKinley and Pikes Peak, and spending weeks on the ground in so-called hyperbaric chambers that simulate the same experience.

Some of the participants are scientists with a professional interest. Others are soldiers or recreational climbers interested in performance “at altitude.” Even when aware of the misery of acute mountain sickness, researchers say, people almost invariably volunteer.

‘Beat People Away’

“In fact, I had to beat people away,” said Dr. Shirley Otis, head of the division of neurology at Scripps and an organizer of the September trip. “All these people are scientists and it’s always fun to combine something scientific with something you enjoy.”

Otis’ team of 10 doctors and medical specialists set off from Scripps Sept. 11 and spent a near-sleepless night on the road and in Bishop, deliberately fatiguing themselves in order to exacerbate their susceptibility to sickness.

The next morning, they headed up White Mountain, chosen for its 14,500-foot height and its access road, for transporting people and equipment. They drove straight up to 8,000 feet, avoiding the acclimatization that reduces or even prevents sickness.

At 8,000 feet, they tested one another’s vital signs and coordination, using a series of tests like those given to a person suspected of drunken driving. There were also tests involving arithmetic, repetitions and stating one’s address.

They also tested one another using so-called transcranial Doppler monitoring, done by a portable machine that Otis has helped develop in the cerebral blood flow lab at Scripps. Using ultrasound, the machine traced the speed of blood flow in each participant’s brain.

Finally, they inhaled carbon dioxide to see whether blood vessel dilation was the cause of increased flow. If no increased dilation occurred in response to carbon dioxide (which causes dilation), they would know the altitude had already caused maximum dilation.

Irritable and Angry

At 12,000 feet, Otis developed a headache so severe it became impossible to think. Trying to pitch two tents, she became irritable and angry, slow and short of breath. Everything about the tents seemed unfamiliar.

“I remember sitting down and saying, ‘When I get back, I’m throwing this tent out,’ ” recalled Otis, 51, who has climbed to 19,000 feet in the Himalayas. “ . . . I knew I had the headache and some symptoms, but I didn’t catch on. I really felt it was the tent.”

Alan Roberts, 58, was even sicker.

“I crawled in my tent and basically lay there moaning,” he said in an interview last week. He could neither eat nor go to the bathroom nor roll over. He had a terrible headache--and a bitter memory of a bout with mountain sickness years earlier.

“I began to think more about how bad it was and how sorry I was that I had gone,” said Roberts. “I certainly at no time thought myself in danger. I just could hardly wait to get down. But I couldn’t figure out how we were going to be able to do that, either.”

The next morning, the other nine began hiking higher. But at 13,500 feet, Otis and another woman, age 62, became unable to go on. When Otis collapsed on the barren earth and began vomiting, the group decided it was time for the only true antidote: Descent.

“Otis was totally incapacitated,” said Mary Rossman, the technical director of Scripps’s vascular lab. “She was lying on the ground. You know, she is a take-charge lady. I knew that she should get down.”

Nevertheless, the group went through the tests they had already done at sea level, 8,000 and 12,000 feet. The process took nearly twice as long. Although the other seven participants weren’t sick, some were functioning slowly and had mild headaches.

The hourlong descent by car, however, proved a well-known point.

“It was just the most dramatic thing,” said Otis. “If you could have seen how we looked--pale, pasty, acutely ill. By the time we got down, we were thirsty and hungry. The headache had gone. We were a little unsteady, but that went away.”

Pizza and Beer

Nine of the 10 headed out for beer and pizza: Quick salt, electrolytes and fluid. Roberts, however, went back to the motel and crawled into bed.

Back at Scripps, the group has now completed analyzing its data.

According to Otis, they found increased blood flow in everyone as they ascended. They also found a progressive decrease in responsiveness to carbon dioxide, suggesting the increased blood flow resulted from blood vessel dilation.

“We wanted to prove or disprove the hypothesis that acute mountain sickness is due to a vascular cause,” namely dilation, said Otis. “ . . . I think (the findings) give credibility to those who have been saying this is what it is due to.”

Otis and other researchers interested in responses to altitude said there are several theories about what causes the symptoms of mountain sickness--theories that might be complementary, not mutually exclusive.

Some suggest the swelling and symptoms are caused less by increased blood flow than by cells malfunctioning from lack of oxygen. That malfunction might lead cells to accumulate excess water if their natural pumping system is out of whack.

Retired professor Houston from Vermont, who has studied altitude acclimatization on Everest, said he thinks most people believe the “fundamental defect” is an abnormality in “the sodium-potassium pump.”

He said lack of oxygen easily deranges the delicate balance of sodium and potassium in cells, causing an excessive accumulation of sodium. Water enters the cells and they swell, causing what Houston said is believed to be the basis of acute mountain sickness.

Extensive Studies

Yet the cause of the swelling could be both fluid and increased blood flow: “Like most things in life, it’s probably a little bit of both,” said Houston.

“It’s probably one of the most complicated pure physiologic areas you can delve into,” said Robert Roache, assistant director of the Denali Medical Research Project on Mt. McKinley in Alaska. “Because of the way the brain and lungs interact.”

Otis now hopes to do more extensive studies using a hyperbaric chamber owned by the U.S. Navy. Researchers use the device to simulate the experience of high altitude, sucking air out of the locked chamber and altering the barometric pressure.

Once again, Otis will be recruiting volunteers.

“I’m kind of interested in how I would respond if she asked me,” said Alan Roberts thoughtfully. “I haven’t ruled it out.”