Dispatches from the roof of the world
Dispatch #25 May 4, 2012
Mayo Puts Us to the Test
Andy Bardon
Emily Harrington tests her lung capacity for physiologist Bryan Taylor of the Mayo Clinic.

Our expedition has more goals than just reaching the summit of Everest.

One priority is to help study the connection between high altitude acclimatization and one of the most common diseases in America, heart failure. Conducting the research is acclaimed scientist Dr. Bruce Johnson, who is here at Base Camp with four crack research scientists from the Mayo Clinic’s Human Integrative and Environmental Physiology Lab—Amine Issa, Doug Summerfield, Bryan Taylor and Alex Kasak.

“We have data that show many heart failure patients get constrictions in the lungs,” says Johnson, “which is similar, if controversial, to what happens to climbers at altitude.” Heart failure patients often have pulmonary congestion; essentially, their lungs fill with fluid. Climbers who are well-acclimatized have lungs that successfully balance pulmonary fluids. Johnson and the team want to understand the mechanisms that facilitate this process.

Another similarity between high altitude climbers and heart failure patients is that they both chronically hyperventilate. “This may cause the brain to inhibit breathing,” says Johnson, “in some cases triggering sleep apnea.” Why and how this happens is another subject of scrutiny. To gather heart and lung function data, everyone being tested has tiny computers, smaller than the smallest cell phone, taped to our chests. This multi-thousand-dollar device is wired to two electrodes attached just below our nipples. A high resolution accelerometer and miniature electrocardiogram, this machine measures heart rate and the interbeat interval, taking 400 readings per second. When a human hikes to high altitude, heart rate variability is one measure of stress on the system.

Andy Bardon
Mark gets a blood test.

The Mayo team is also performing a series of tests on themselves and on us. We are weighed every day and we all take the same self-examination test each morning: How are you sleeping, how are you eating, do you have a headache? Yesterday and today we all went through a tailored physiological and psychological lab protocol. Blood was taken, fat was pinched with calipers, and a jelly-smeared chest ultrasound was performed. Next, biting down on a hard tube connected to a monitor, we forcefully inhaled and exhaled several times. This measured lung size and airway function, as well as provided an estimate of lung fluid. We also blew into a nitric oxide detector the size of a cantaloupe, which can help determine lung health. Following these tests, we moved to another dome tent where our cognitive skills (or degeneration thereof) were measured with computer games similar to those once given to astronauts. In one, you stab a plastic pen on the screen whenever and wherever a square appears—this is to measure hand-eye coordination. In another you match the color of a word (for instance, the word “red” printed in the color green) with the name of the color—not the word—right below. Then we do a hand strength test (who has the crusher handshake?) to show maximum grip as well as a three-minute endurance trial. Finally, we performed a step test, jumping up and down on a small stool like Jane Fonda with ever-increasing rapidity—this measures the efficiency of the lungs.

Last night we were all fitted with larger computers: iPhone-size devices strapped to our chests. With wires running to electrodes attached to our foreheads and forefingers, we looked like modern-day Frankensteins. These gadgets measure and correlate sleep patterns in the brain with respiration rate, heart rate, and arterial oxygen saturation, all of which combined give an assessment of sleep quality. We also each downed a $1,300 cocktail of isotope-marked water, that when collected as urine samples over the course of the expedition, will give a good measure of energy expenditure. “Our goal is to learn as much as we can about the physiology of the cardiopulmonary system under extreme stress,” summarizes Johnson, “and then apply these findings to treating heart failure patients.”

To learn more about the Mayo Clinic's work on Everest, visit their Advancing the Science blog.

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