To The Limit

Simon Fraser University Group Investigates How The Body Responds To Extreme Environments

By Emily Marshall

As the near record snowpack melts and the long winter fades to a vague memory, hikers across the Pacific Northwest have been dusting off their hiking boots for a summer in the mountains. Some of these hikers, like myself, will break out their crampons and spend some of their time high above sea level tackling peaks still blanketed in snow. While the mountains of the Pacific Northwest aren't exactly the Himalayas, they aren't to be trifled with either. Even experienced trekkers can encounter symptoms of altitude sickness on our mountains, and who will be affected and who won't is unpredictable.

The human body is capable of tremendous feats. People climb to the summit of Mount Everest (29,029 feet), where there is only a third of the oxygen available to breathe as at sea level. Many Ethiopians live at elevations over 7,900 feet, and those making homes in Cuzco, Peru are at over 10,000 feet. We dive, breathing gas mixtures, to depths of 750 feet, where the pressure is 25 times that on the surface. We live in the desert, where temperatures regularly soar to well over 110 F. How the body copes with and adapts to extreme environments like these are some of the topics of interest for the Environmental Physiology Unit (EPU) at Simon Fraser University (SFU) in British Columbia.

The potential applications of research done at the EPU are broad, and assistant professor Matthew White takes full advantage of the EPU facilities. His main research focus is human temperature regulation and control of breathing, but his lab also studies survival in many other extreme situations. One of these is safety and survival in cold offshore and maritime environments like those encountered by high-latitude fishermen and ocean helicopter crash victims, and the EPU facilities are being used to test the effectiveness of survival suits donned by those unfortunate enough to take a dip in frigid waters. Other lab projects examine HAZMAT suit performance in hot, humid conditions and the effects of cold temperatures on cognition.

The EPU is capable of simulating extremely extreme conditions, but much of the current research is under conditions we the public are more likely to encounter when hiking or skiing in the Rocky Mountains or even at Whistler, B.C. (over 7,000 feet). High altitude technically begins around 8,000 feet. Most people can tolerate altitudes up to around 8,000 feet without experiencing the telltale headache and nausea that are harbingers of altitude sickness, but they may notice some weakness and shortness of breath even at lower altitudes. On my last trip to Denver (just over 5,000 feet), I decided to put away my running shoes after I felt like I'd run a marathon after jogging up a flight of stairs. While this might be a minor annoyance for me, more of an armchair enthusiast than a serious athlete, for hard-core competitors the effects of altitude can be quite detrimental. Getting to the final altitude slowly, or acclimatizing, can help prevent or alleviate the problems of altitude sickness by giving the body time to adapt, but the core issue of less oxygen to breathe remains constant.

The concentration of oxygen at sea level is about 21 percent. As altitude increases, the percentage remains constant, but the number of oxygen molecules per breath is reduced due to the lower barometric pressure. Triggers in the brain tell the body to increase breathing rate and depth to compensate for the decreased oxygen coming in; the huffing and puffing you feel hiking around Mount Rainer might not mean you're out of shape, but that your body is working harder to get enough oxygen. Over time, more red blood cells are produced to increase oxygen carrying capacity to tissues. This increase in red blood cells is one reason many endurance athletes live or train at altitude; when they return to sea level they have increased oxygen carrying capacity and an edge over their lowland competitors.

The addition of cold temperatures throws a further difficulty in the way of high-altitude athletes like alpine ski racers, who compete in thin skinsuits. The body responds to cold conditions by decreasing circulation to the extremities in order to keep the core body temperature steady. The effects of this double-whammy of low oxygen and low temperature are not well understood, but they are one of White's main research targets. He notes that, "Low barometric pressure and extreme cold in high-altitude environments combine to reduce oxygen supply and muscle strength,” and goes on to mention that there haven't been many in-depth studies of the combined effect of cold temperatures and high altitudes on athletes.

White has a long history at SFU, having been an undergraduate and then graduate student in the School of Kinesiology. Once a competitive alpine ski racer, it was his experience competing in frigid temperatures and high altitudes that drove his interest in environmental physiology. After a brief stint at Memorial University in Newfoundland, White returned to his alma mater in 2003. He's excited because the EPU facilities allow him to conduct experiments in controlled extreme environments as well as collaborate with industry groups and other environmental physiologists who study topics related to increased athletic performance. White hopes the EPU can, "help researchers design equipment, clothing and exercise regimes that help athletes adapt quickly to challenging competitive environments.”

While White's focus is on the effects of relatively transient exposure to extreme environments, his colleague Victoria Claydon uses the EPU to study how long-term high-altitude dwellers have adapted to their low pressure and low oxygen environments. These conditions normally impair cardiovascular function, but some populations that have lived in high regions for generations have biologically adapted to breathe as easily at 8,000 feet or 12,000 feet as Seattleites do at sea level. High-altitude dwellers in Ethiopia rarely encounter altitude illnesses linked to oxygen deprivation like we might if we visited their homes without acclimatization.

Claydon's research has shown that the high-altitude Ethiopians have a higher-than-normal level of carbon dioxide in their blood and altered control of brain blood flow, and these two factors act increase blood supply and oxygen delivery. Their bodies have become more efficient at utilizing the oxygen available, allowing them to live comfortably where others might be gasping for breath. Understanding how human physiology changes in low oxygen conditions like those encountered by people living at high altitudes may be applicable to understanding what happens to heart attack and stroke victims, who also encounter hypoxia.

The world-class EPU, part of the SFU School of Kinesiology in Burnaby, B.C., started in the 1980s and is the only facility of its kind at a Canadian academic institution. The main facility contains a combination high pressure, or hyperbaric, and low pressure, or hypobaric, chamber system. The pressure chambers allow researchers to simulate situations as varied as dives to depths of 1,000 feet in seawater or altitudes equivalent to the atmospheric pressure on Mars, which is comparable to that found 100,000 feet above the Earth. One lower lock in the pressure chamber can be filled with water, making it a wet pot, for dive or altitude simulations, and the other two locks in the chamber can be depressurized by vacuum pumps for low-pressure flight simulations. Because people in high and low pressure situations aren't likely to be at ambient Burnaby temperatures, water temperatures in the wet pot can be controlled from +2C, just above freezing, to +50C, or 122F.

The EPU also contains a walk-in climate chamber for simulating high and low temperature and humidity conditions. The room holds both a bicycle ergometer and a treadmill, as well as equipment for monitoring cardiovascular and metabolic responses, which allow researchers to examine the effects of temperature and humidity on athletic performance. The conditions in the room can range from -26C to +50C, with a humidity range of 10 to 95 percent.

Emily Marshall is a graduate student in microbiology at the University of Washington.

Images:

Top: Summer beckons hikers to picturesque Mount Rainer. Photo: Emily Marshall

Bottom: The EPU hypobaric chamber and its wet pot can simulate dives up to 1,000 feet at temperatures ranging from just above freezing to 122F [MW1]and contains an underwater ergometer to measure work output during underwater swimming under varying conditions. Photo: Duncan Milne