The cold at 14,000 feet is part of the science.

So are the rarefied air, the 50-mile-an-hour winds, and the altitude sickness. That’s why a Mayo Clinic research team spent several weeks on Argentina’s Mount Aconcagua. At 22,841 feet in the Andes, the mountain is the Western Hemisphere’s highest point and the second highest outside of central and southern Asia.

Bruce Johnson, Ph.D., Mayo Clinic physiologist, and colleague Paul Anderson, M.D., a federal researcher, braved the weather as they took vital signs, pulmonary and cardiac readings on the volunteers who became a mobile clinical trial. The goal was to study the effects of altitude as part of Mayo’s new Extreme Medicine and Physiology Program. The study focus is the ultra-healthy: athletes and explorers, their performance under extreme conditions, and why they handle adversities as well as they do.

“I’ve always been interested in athletes because they are the elites of the elite,” says Dr. Johnson. What accounts for their abilities has always been controversial. Is it the lungs, the heart, the muscles, the blood vessels? What is it that limits people from participating in high-level athletic events?”

Dr. Johnson has worked with the U.S. Department of Defense to study the impacts of high-altitude troop deployment, including a recent National Science Foundation project in Antarctica, the highest, driest and coldest continent on Earth. He also has been studying heart failure patients, many reporting shortness of breath, with a focus on the connection of lungs and muscles in heart disease. Heart failure affects about 5 million Americans. Some 550,000 patients are newly diagnosed each year. Heart failure is the leading cause of hospitalization in people older than 65.

Thus, the Mayo team went to the mountain to expand knowledge of how the heart and lungs adapt or maladapt under a range of stress factors. Besides the proven hands-on value of physical examination, they tested technologies for collecting data by telemetry, especially distance monitoring.

“The ultimate goal is to have a real-time wireless transmission attached to the people we are working with so we can actually see the physiology happening,” Dr. Johnson says. For this project, data collection was done at real time, but stored, transferred to laptops and transmitted to computers back at Mayo Clinic.

The Medical Marvel

To find extreme athletes willing to participate, Dr. Johnson turned to the National Geographic Society. One name quickly rose to the top: endurance runner Diane Van Deren.

Why Van Deren?

She already is a marvel. A former professional tennis player, Van Deren, then pregnant with her third child, was diagnosed with epilepsy. She experienced 10 years of debilitating seizures, and then underwent brain surgery to remove part of her right temporal lobe. The seizures disappeared and she resumed her athletic career. In 2008, she won the Yukon Arctic Ultra 300, a three-hundred-mile marathon, pulling a sled, in frigid conditions. Last year, she became the first woman to complete the longer, 430-mile journey.

“Diane is really amazing for a lot of reasons,” Dr. Johnson says. “One, she had her own medical issue, and, second, she is pushing the age of 50 and seems to be getting stronger, more competitive and is entering events that most of us couldn’t even conceive of training for, let alone competing in. She has the drive, the will that goes beyond normal.”

At Mayo Clinic, Dr. Johnson’s team put Van Deren in the lab for three days in December to study her physiology at baseline. Her heart rate during sustained activity proved to be phenomenal. Dr. Johnson told The New York Times that those initial tests found Van Deren’s peak aerobic capacity well above most 20-year-olds.

Van Deren and Guillermo “Willie” Benegas, an internationally renowned mountain-climbing guide, both sponsored by The North Face equipment manufacturer, were wired with a range of monitors.

The mission had two parts. One was to slowly walk to the top as a group of 22, to acclimatize and acquire baseline data on physiological changes that occurred. Second, Van Deren and Benegas would attempt a second ascent, running along a route never used before. However, blizzard conditions with 50 mph winds and temperatures falling to minus 20 degrees Fahrenheit at altitudes above the 14,000-foot base camp, forced a prudent cancellation of the second ascent.

“You never know what will happen in field research,” says Dr. Anderson, who normally works in Alaska. “Ultimately, no matter what you encounter, you end up learning things you never anticipated.”

The Science of Heights

At high altitudes, physiological changes occur mostly because of changes in oxygen. As the air thins, oxygen declines, creating a condition known as hypoxia. That is similar to what occurs in heart failure as the body’s ability to use oxygen — the heart-lungs connection — is compromised.

At high altitudes, illness is not uncommon, and death is possible. Climbers often face acute mountain sickness, in which the body adapts too slowly to decreasing oxygen. It begins with headache, nausea, fatigue and dizziness. There is high-altitude cerebral edema, in which the brain swells. A person becomes confused. Climbers often are schooled in its symptoms so they can assess if a fellow climber may be suffering from it. It can be deadly within hours. The lungs issue is high-altitude pulmonary edema, in which fluid enters the lungs as the result of the constriction of blood vessels caused by lack of oxygen.

“Breathing increases to try to increase oxygen in the blood, but it still drops off because of the air pressure,” Dr. Johnson says. “The body adapts as blood cells increase and alter their affinity to grab oxygen better and unload it to the tissues. But this can take time. Some people do it well, while others struggle. Why? Part of our research is to understand the mechanisms involved in high-altitude illnesses, especially as they develop above 14,000 feet. What we learn from healthy people adapting or maladapting to high altitude provides important information that can be translated to the heart failure population in the hospital with pulmonary edema.”

Dr. Johnson believes that hypoxia drives many pathways of heart failure due to their poor cardiac output and reduced tissue perfusion. In addition, “people with lung disease develop arterial hypoxia. People who snore at night experience dips of oxygen all night long,” he says. “This may drive high blood pressure and may affect blood-sugar regulation, so there are a lot of conditions that have overlapping issues.”

Testing the Telemetry

On the mountain, Van Deren wore a small, tea bag-sized harness on the middle of her chest. A small device within measured her respiratory and heart rates, the time between heartbeats (R-R interval) and oxygen saturation. A swallowed pill gave Mayo researchers access to Van Deren’s core temperature; however, this approach was meant to capture data during her canceled speed ascent.

An MP3 player-sized device was strapped to an arm to measure her steps and metabolic rate (accelerometer and galvanometer). At night, another device was used to carefully monitor her oxygen saturation and heart rate, determining if Van Deren was developing periodic breathing, a condition that is common at such altitudes. Overnight stops (climb high, sleep low) are vital for climbers to fully acclimate to increasing altitude.

Yet another portable device (housed in a small backpack) measured exhaled gasses, which allowed monitoring of oxygen consumption, carbon-dioxide production, ventilation and respiratory timing variables. Data were collected intermittently, especially at the higher altitudes where such records are rare, Dr. Johnson says.

“We’ve also worked with a neuropsychologist to perform some cognitive tests with Diane and the rest of us while on the mountain,” he says. “Hypoxia affects our ability to think, and affects us all differently. These are tests that we administer to each other.” Researchers also planned to assess changes in cognitive abilities with a 15-minute exercise created by NASA that can be completed on a laptop.

Outcomes

On February 9, 2010, members of the ascent team reached the summit of Mount Aconcagua. Not everyone got to the summit, and experiences differed among those who did. Those differences and the associated data will provide starting points for new inquiries.

Discoveries

• A wealth of physiology data – Ten climbers were monitored for the entire ascent ranging from 20-year-olds to Hector D’Amico, senior editor of La Nacion, who is in his sixth decade. The findings are being analyzed at Mayo Clinic.
• Technology information – Pushing their devices to the limit, the team returned with concrete information for each manufacturer on how to make products simpler, more robust and easier to use.
• Unknown data – The team discovered 20 years of store-housed surveillance data on Mount Aconcagua illnesses that has never been analyzed. Investigators will be working to better understand the types of high altitude illnesses most common on Aconcagua.

New Questions

• Moderate movement at new altitude levels help maintain or improve blood oxygenation levels, but excessive activity often caused a drop-off. Why?
• High levels of oxygenation don’t necessarily result in better acclimatization and fewer symptoms in individuals.
• Why did some climbers adjust better than others to new altitudes?
• Some members had significant and rapid weight loss, while others maintained weight relatively well. This seemed to be a muscle wasting condition. Perhaps this also follows mechanisms like those found in patient groups.
• What role does “fitness” play in the ability to adapt to high altitude vs one’s average metabolic rate during the climb?

Insights

• It is hard to be scientists and collect data when one is cold, ill from the altitude, and confined to the limits of a small tent.
• Investigators should arrive earlier and acclimatize before research subjects.
• Mules are invaluable platforms for “advancing” 21st century technology.
• Explorers and athletes are willing and interested participants; their curiosity and drive extends to science.
• Mountains and weather are experimental variables, so plan for delays.

In the near future, Dr. Johnson and his Mayo colleagues hope to apply newer technology that will allow real-time transmission of data directly to Mayo computers for instantaneous monitoring.

“Why some people keep striving amid life’s traumas and others don’t is a perplexing issue,” he says. “Psychologists at Mayo have told me that a significant number of young people give up on physical activity in their early teens. With our society increasing in weight and size, we need to understand what motivates people and keeps them hopeful and motivated. What keeps them striving is one thing. Secondly, there are physiological mechanisms involved in adaption. At high altitudes where people are adapting to the chronic hypoxia, I think we will learn about people who have a well-designed persistence for adaptation.”

The research also is pushing technology onward. He says that frail and elderly people may be among the first to benefit. “If we can monitor and do a good job in extreme environments, we ought to be able to do it just as well in patient populations that are in metropolitan areas.”

In June, Dr. Johnson’s team will work with another athlete — very likely using wireless data transmission — as South African outdoors adventurer Mike Horn attempts a never-before summit attempt in the Himalayas.

“The long-term goal is to dissect the unique abilities of extreme athletes, better understand mechanisms of human disease, and monitor humans real time in all environments,” he says.

— Jim Barlow, March 2010