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True tales of hypoxia

Mount Royal biology graduates contribute to high-level acute mountain sickness research

Words by associate professor of biology Sarah Hewitt, PhD

Photo of Britty Byman and Lindsay Boulet performing a echochardiography on Jordan Bird.

MRU recent graduate Britta Byman, left, watches as UBC Okanagan doctoral student (and also former MRU student) Lindsay Boulet, centre, performs echochardiography on MRU student, Jordan Bird.

At 4:30 a.m., my alarm started ringing in the darkness of the dorm room. I looked to see if my roommates, a researcher from Texas and MRU graduate Ali Skalk, were awake. I couldn't get up without disturbing them because we all had ECG electrodes stuck to our chests, with the leads attached to a computer in the centre of the room ― like a scene from a sci-fi movie. I pulled out my nasal cannula, removed the pulse oximeter I'd worn all night to track my blood oxygen levels, undid the tension strap from around my chest and pulled off the electrodes. It was time to get up.

A line of vivid red outlined the distant peaks of the California Sierras in the chilly pre-dawn sky outside the Barcroft Research Station. The station sits at 3,800 metres ― almost the same height as the highest point in the Canadian Rockies. In August, Associate Professor Trevor Day, PhD, led a team of 25 people from six different universities up to the station for 11 days to study the physiology underlying acute mountain sickness (AMS). Five recent MRU Bachelor of Science ― Health Science graduates were part of the team: Jordan Bird, Britta Byman, Brandon Pentz, Ali Skalk and Scott Thrall.

The students each did independent projects with Day and worked in his lab as research assistants over the summer to get the experience they needed to assist in the projects at Barcroft. The goal of the trip was to measure how the body responds to the stress of high altitude exposure and how those responses change as we acclimatize. Each student contributed to data collection for studies that will be published in scientific journals ― an experience that's relatively rare amongst undergraduates. This is no field school, it's the real deal as a research expedition.

Day describes himself as an integrative cardiorespiratory, cerebrovascular, and acid-base physiologist, and his work has received federal NSERC funding. He and his students are usually working in a lab in the B-wing, but this is his fifth field expedition to altitude, having previously taken students to Everest base camp.

Photo of the full team, which consisted of 25 people from six different universities.

The full team consisted of 25 people from six different universities.

For Skalk and Thrall, it was also a chance to see into their own future ― they both left the day after we returned to pursue master's degrees in respiratory physiology at the University of British Columbia Okanagan Campus and the University of Alberta, respectively.

"These students are people I'll be working with quite closely in the coming years," Thrall said, "so this is kind of my 'meet the family' experience!"

"We're nothing without our trainees," Day said. "Science is a team sport ― we need hands, we need help, we can't do all the instrumentation and data collection alone."

The data collection started the moment we arrived at the station.

Symptoms of acute mountain sickness (AMS) can start around 3,000 metres ― breathlessness, headaches, nausea, dizziness, confusion, and difficulty sleeping. Within hours of arriving at the lab, we were all experiencing AMS symptoms to some degree.

The symptoms peaked within the first three days. Almost everyone had a headache, one person felt nauseous, others described a mental fogginess like after waking from a nap. Some, however, reported no effects at all. This variability was one of the reasons for the trip ― to understand why AMS affects some people more than others.

Climbers and travellers going to altitude often use a subjective AMS scoring system, self-reporting how they feel and tallying their symptoms. But even we underestimated our symptoms at times ― such as scoring a headache as a 3/10 when it was actually much worse.

"People were sicker than they realized or admitted," said Day.

It's a common problem for someone who wants to keep going on their trek, or in the lab. So, to circumvent the subjective scores, we also took daily physiological measurements of breathing, oxygen, carbon dioxide and hemoglobin levels, as well as heart rate and blood pressure, to get an objective snapshot of how we were each acclimatizing to the low oxygen at the research station.

The kidneys, lungs, cardiovascular and nervous systems all respond to the changes in oxygen and carbon dioxide levels that occur at altitude. The team collected data for 12 studies that looked at how these systems interact and adapt when a person first arrives at altitude, and when they stay there for a period of time.

We slept in bunk-beds in dorms, some nights tethered to a central computer, 25 people sharing two bathrooms, together 24/7. With the exception of a couple of rest days, experiments ran full-tilt collecting data for 10 to 12 hours a day. A schedule, pinned to the wall in the kitchen, kept us on track as people shuffled between labs, often stealing a researcher from one lab to be a participant in another.

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Sarah Hewitt participating in in a study by University of Alberta researchers to the blood flow responses during a simulated fight-or-flight response at varying levels of oxygen.
Photo by Trevor Day

The MRU crew floated wherever they were needed, learning new techniques and helping out where they could. Suddenly, students I'd been teaching a few weeks earlier were sampling my blood, adjusting the Doppler ultrasound apparatus on my head, or wiping the drool from my chin after pulling out my mouthpiece.

"We're going to make you hypoxic now," I heard Day say to me. "Just breathe through it, it'll get easier in a few minutes."

Technically, I was already hypoxic at the research station, but they dialled back the oxygen coming through my mouthpiece even further to see how it would affect the blood flow to my brain.

In seconds, I felt an uncontrollable urge to gasp for air ― the chemosensors in my body telling me to breathe harder to get more oxygen. My heart hammered in my chest, and my breath came like I was sprinting a race. But I was in a chair, with eight cables connecting me to machines monitoring my vital signs. Eventually, the feeling dissolved into something almost relaxing, at least by comparison, as I reached a new steady-state.

The drive to breathe is a physiological response to not getting enough oxygen and is called the hypoxic ventilatory response, something both Day and I teach at MRU. But getting out of the classroom, beyond the theory, changed my perspective, and the students'.

"We get so wrapped up in textbooks," said Thrall, who graduated from MRU in spring 2019, "but that doesn't prepare you for sitting on top of a mountain. You feel your heart pounding, you're lightheaded, and you're gasping for breath … but it's exactly the way it's laid out in your books, and it brings it all together in a really interesting, comprehensive way."

Finding one single test that predicts how well you'll fare at altitude is a nice idea, but Day thinks it's unlikely, given the variability in how organ systems respond among individuals.

"You may just have to go to altitude to find out," he said.


Associate Professor Sarah Hewitt received her PhD in neuroscience from the Hotchkiss Brain Institute at the University of Calgary. She teaches neuroscience and physiology at MRU. She also travels the world to work with researchers in the field and photograph and write about what they do and how they do it. You can follow her science adventures here.


Oct. 16, 2019

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