By Lin d sey B. Koe hle r an d N ata s ha G ardne r october 2009

Transcription

1 com october 2009

2 Low On O2 The ultimate guide to living at altitude. By Lindsey B. Koehler and Natasha Gardner Illustrations by Newhouse Design october com 95

3 O2 Do You Know Altitude? The truth, the fiction, and the theories behind living up high. It takes approximately three months for a new Denver resident coming from sea level to fully acclimatize to living at 5,280 feet. Almost 600,000 people live above 7,000 feet in Colorado. Doctors can prescribe Viagra a As the highest state in the Lower 48, Colorado sells altitude. It s what we ve got that others want which is why people come from all over to ski down our mountains, camp near our alpine lakes, and climb our fourteeners. Not that we blame them; we dig our state s Godgiven natural beauty and well-endowed topography, too. But here s the rub: There are risks associated with living, playing, or vacationing at altitude. Strange thing is, most people and way too many Coloradans don t realize just how much we re all affected by our extraordinarily thin air. Q&A How High is High Altitude? High Altitude 5,000 feet to 11,500 feet Very High Altitude 11,500 feet to 18,000 feet Extreme Altitude above 18,000 feet Why is there Less Oxygen at Altitude? The percentage of oxygen (21 percent) in the air is the same at all terrestrial altitudes, but because of the reduced air pressure at high elevations, the air you breathe contains fewer oxygen molecules in each breath. In Denver, there are 18 percent fewer oxygen molecules compared to sea level. At the summits of Colorado s famous fourteeners, the air has 42 percent less usable oxygen than at sea level. What is Hypoxia? Hypoxia is a Latin word that means low oxygen. In medical terms, it s a condition in which the body as a whole or a region of the body lacks the oxygen needed to function normally. Most physiologists say the effects of hypoxia begin around 5,000 feet above sea level com october 2009

4 drug known for its ability to increase blood flow elsewhere in the body to help prevent and/or treat high altitude pulmonary edema (HAPE). Some athletes are looking at Viagra as a potential way to improve exercise performance. Currently, the World Anti-Doping Agency is considering a ban of the drug. Contrary to popular belief, booze does not go farther at altitude. The effects of two cocktails at 10,000 feet are the same as they are at sea > > health Into Thin Air Demystifying Acute Mountain Sickness. What is AMS? A person has acute mountain sickness (AMS) if he has a headache plus at least one other symptom, such as nausea, fatigue, and dizziness, while at altitude. Researchers don t know exactly what causes AMS, but many believe that hypoxia (low oxygen) causes blood vessels in the brain to dilate in an attempt to get more oxygen. The process of dilation causes a headache in most people; the increased blood flow from the dilation also causes swelling in the brain, which may be worse in those that eventually come down with AMS. The brain swelling is thought to be the origin of the other AMS symptoms as well. How can I prevent AMS? A gradual ascent to higher altitudes is the key to thwarting AMS. Take your visiting flatlander family too high, too quick, and you re begging for someone to get sick. Instead of taking them to, say, Breckenridge (9,603 feet above sea level), have them spend their first night in Colorado at an intermediate altitude such as Denver (5,280 feet) or Idaho Springs (7,526 feet) before heading higher into the I-70 corridor. (Some Denver hotels, like the Hotel Teatro, even offer discounted acclimatization packages to get you to stay in Denver for a night before heading up the hill.) Beyond planning a deliberate rate of ascent, you ll want to keep your lowlanders hydrated forcing them to down 100 ounces of water a day will help with acclimatizing and help them avoid overexertion for the first 48 hours at altitude. (That means no crazy hiking at 9,600 feet, folks.) Also, remind your family to stay away from alcohol and sleeping pills in the benzodiazepine family (like Halcion and Restoril), as both suppress breathing and result in lower blood-oxygen levels. People who know they are susceptible to altitude sickness meaning they ve acquired it repeatedly can ask a doctor to prescribe Diamox. By increasing the amount of bicarbonate excreted in your urine, Diamox makes your blood become more acidic. Acidifying the blood stimulates breathing, which increases the amount of oxygen in the blood. Taken 24 hours before arrival at altitude and every 12 hours for the first two days at altitude, the drug can be up to 75 percent effective in preventing AMS, depending on dose, rate of ascent, and susceptibility. L O S S O F A P P E T I T E D I Z Z Y N E S S VOM I T I N G T R O U B L E S L E E P I N G FATI G U E N A U S E A How can I ID the symptoms of AMS? The Lake Louise Score is the gold standard for putting a numerical value on the severity of AMS symptoms, such as headache, gastrointestinal distress, and fatigue. A score of four or higher, and you ve got AMS. Download the Lake Louise Score sheet at H O S P I T A L I R R I T A B I L I T Y Classic AMS Symptoms Headache, dizziness, chills, nausea, vomiting, loss of appetite, trouble sleeping, fatigue, and irritability. How do I treat AMS? The best remedy is to descend to lower altitude. But if you can t go lower or simply want to tough out mild symptoms, the next best treatment is rest, liberal use of ibuprofen or acetaminophen, and time (AMS usually gets better within 24 to 48 hours). If you have AMS symptoms, do not go higher; if you, or someone in your party, is very sick, descend immediately. Of course, if you have access to bottled oxygen, sucking down those Os will decrease AMS symptoms quickly. october com 97

5 O2 level. However, the use of alcohol can increase the risk of acute mountain sickness. Colorado has long had one of the leanest populations in the nation. Some altitude researchers conclude that this may be because of our elevation not only is low oxygen a known appetite suppressant, but metabolism also increases tourism Slope Sick Calculating the cost of altitude illness. If your most vivid memory from your last getaway to a Colorado ski resort is downing Tylenol and curling up, fetal position style, in your slope-side condo, you re not alone. More than 20 percent of Colorado s ski resort visitors find themselves feeling a bit nauseated and it s not from the cafeteria s $8 bowl of chili. The culprit is, ironically, exactly what people come to Colorado for: the prized geography. With an average base-village elevation of nearly 9,000 feet, Colorado s resorts sell the legendary Rocky Mountain High. But while we all covet the spectacular terrain the altitude affords, the thin air takes its toll and it s a high price to pay. Colorado s high hills attract more than 25 million tourists annually. Of those, more than five million will feel altitude s effects: nausea, fatigue, headache, weakness, dizziness all of which lead the affected to reduce their activity level by a whopping 56 percent. Missing a meal, skipping a shopping trip, or passing up a day of skiing may not seem like a tragedy, but according to Telluride s Institute for Altitude Medicine (IFAM), acute mountain sickness costs the Colorado ski biz upward of $200 million each year. It s a problem that disproportionately affects Colorado s ski areas. Ever wonder why you don t hear about sickly skiers in the high mountains of Switzerland or Italy? Can t figure out why istockphoto.com by the numbers How High Do They Go? Arapahoe Basin 10,780 / 13,050 Aspen Highlands 8,040 / 11,675 Aspen Mountain 7,945 / 11,212 Breckenridge 9,600 / 12,998 Beaver Creek 8,100 / 11,440 Copper Mountain 9,712 / 12,313 Crested Butte 9,375 / 12,162 Eldora Echo Mountain 10,050 / 10,650 9,200 / 10,800 Keystone 9,300 / 12,408 Loveland Ski Area 10,600 / 13,010 Silverton 10,400 / 13,487 Monarch 10,790 / 11,961 Key Base altitude (in feet) / Peak altitude (in feet) Buttermilk 7,870 / 9,900 Durango Purgatory 8,793 / 10,822 Howelsen 6,696 / 7,136 Powderhorn 8,200 / 9, com october 2009

6 at altitude. A 2006 Harvard University longevity study puts seven high-country Colorado counties (Summit, Park, Eagle, Clear Creek, Gilpin, Jackson, and Grand) in the top 10 in the nation, with an average lifespan of 81.3 years. Although researchers are still studying this phenomenon, many surmise that altitude s effect on the human heart may have something to do with it. There is lower death from heart disease up here, says Dr. Peter > > nearby Park City has tall peaks and fewer issues? The answer lies not in the elevation of the highest ski lift (which is the Imperial Express SuperChair at Breckenridge, by the way), but in the altitude of the base village. Colorado s resorts, unlike most European ones, have very high-altitude villages. People don t typically get altitude sickness in Europe, says Dr. Peter Hackett, one of the world s leading experts in altitude medicine and the founder of IFAM. European base villages are tucked into lower-elevation valleys, which means people are sleeping at lower altitudes. And it s the sleeping altitude the elevation where your body spends the most time acclimatizing that often determines whether you will acquire acute mountain sickness. Anything higher than 8,000 feet could mean a very bad ski vacation; go even higher and your chances of illness increase exponentially. Of course, Colorado s ski resorts aren t exactly clamoring to get the word out on AMS after all, scaring off tourists never seems like a good business move. I understand the ski industry not wanting a headline that says Avoid Altitude Sickness, Dr. Hackett says, but it s irresponsible for ski areas to not talk about it. Resorts like Breckenridge and Vail have information about AMS on their Web sites, while others provide information when asked. Climb high, sleep low is a maxim used by experienced mountaineers, and it s a good guideline for travelers and even those from the comparably low altitude of Denver who know they are susceptible to altitude sickness. Not every resort offers base-village accommodations in which case it s a good idea to shack up at a much lower altitude. Before you, or your sea-level-dwelling friends, book your next Colorado ski vacation, take the numbers below into consideration. great outdoors Tent Sense Pack in these five important camping tips. Denverites often assume they can t get altitude sickness: We re all acclimatized, right? Actually, no. Our state of denial about AMS often catches up with us not when we re skiing but during the summer months when we re camping. Coloradans can easily get sick while camping because they ascend quickly in a car, exert themselves hiking all day, and then often sleep at very high elevations, says IFAM s Hackett. If you live in Denver and then camp at 11 or 12,000 feet, you open yourself up to the possibility of getting sick. Of course, there are a few ways to avoid the hassle altogether: >> Instead of driving to a high-altitude trailhead, park at a lower altitude and slowly hike up. Ski Cooper Telluride 10,500 / 11,700 8,750 / 12,570 Snowmass Vail 8,104 / 12,510 8,120 / 11,570 Steamboat 6,900 / 10,568 Winter Park/ Mary Jane 9,000 / 12,060 Wolf Creek 10,300 / 11,904 >> Pitch your tent at a lower altitude. You can always hike up high to see the sights, but following the climb high, sleep low mantra will ward off AMS. >> Start hydrating the night before. Ski Hesperus 8,200 / 8,880 SolVista 8,202 / 9,202 Sunlight 7,885 / 9,895 >> Carbo-load before and during your trip. Carbohydrates help your body transport oxygen through the bloodstream. >> Limit your fat and salt intake; these substances impede your already-compromised ability to supply your body with proper amounts of oxygen. Sources: Colorado Ski Country USA, Vail Resorts, Ski Hesperus october com 99

7 O2 Hackett. People living at altitude have more capillaries in their hearts. According to some studies, a twice-daily 100 mg dose of ginkgo biloba was effective in preventing acute mountain sickness when started five days before ascending to altitude. Even after acclimatization, athletes will never perform as well at physiology Got Oxygen? A low O 2 environment forces the body to tr y to adjust. Here s what happens when you head for the hills. DIAG NOSIS SWELLING F E V E R CAROT ID BODIES M U S C L E S B U R N I N G TIME LIGHTHEADED BRAIN COUGH THROAT RESPIRATION HEART RATE LUNGS HEART BLOOD KIDNEY STOMACH BONE MARROW NAUSEA SKIN I N F E C T I O N S OXYGEN Respiration At the first hint of hypoxia, or lack of oxygen, oxygen-sensing nerves in the neck tell the body to breathe faster and deeper, allowing increased oxygen intake. Hyperventilation means you re off-gassing carbon dioxide more quickly, too. The lower level of CO 2 can lead to a feeling of lightheadedness. Heart An increased heart rate, which you may be able to feel for the first day or two at altitude, speeds oxygenated blood to the tissues. People who are born and raised at altitude often have larger hearts with more blood vessels. Throat Many people who venture into the thin air complain about a dry, sometimes debilitating cough. The hacking may be caused by cold, dry air, but studies also have shown that receptors in the airways that incite cough may simply be more sensitive at altitude. Carotid Bodies Located where the carotid arteries split into the internal and external carotid arteries, these nerve bundles sense low oxygen in the blood and cause increased respiration. People com october 2009

8 altitude as they do at sea level because of the body s diminished ability to extract oxygen from the air and deliver it to the tissues. Go any higher than 5,000 feet and the maximum work you can do decreases by three percent for every 1,000 feet in elevation. Elevations in Colorado range from 3,350 feet in the Arkansas Valley to 14,440 atop Mt. Elbert. The state has an average elevation of 6,800 feet. Foods have high-altitude instructions because the > > who have had a carotid endarterectomy, a surgical procedure that removes plaque from the lining of the carotid artery, may have a decreased ability to acclimatize because of damage to the carotid bodies. Lungs Blood picks up oxygen as it flows through the lungs. In situations where a part of the lung isn t well-oxygenated (say, pneumonia), blood vessels in the less-oxygenated part of the lung constrict to allow more blood flow to areas where oxygen is available. At altitude, all areas of the lung can have reduced oxygenation; all of the blood vessels can tighten, which results in high blood pressure in the lung. That, in turn, may cause high altitude pulmonary edema (HAPE), a life-threatening condition in which fluid fills up air pockets in the lungs and prevents oxygen from getting into the blood. HAPE occurs in about one in every 10,000 Colorado skiers. Kidneys During hypoxia the kidneys release erythropoietin (EPO), a protein that stimulates red blood cell production. Also, typically noticeable on the second day at altitude, the kidneys react to lower CO 2 levels and the resulting alkaline blood by increasing urination. (Which is why you always feel like you have to pee just as you get on the chairlift.) Bone Marrow EPO produced in the kidneys tells the bone marrow to up the production of oxygen-carrying red blood cells. Blood Increased red blood cells deliver more oxygen to the tissues. Brain Some altitude researchers believe that mild swelling in the brain may be a root cause of acute mountain sickness (AMS, see page 97). One percent of people that ascend above 13,000 feet will experience a build-up of fluid on the brain (high altitude cerebral edema, or HACE); this condition is life-threatening and requires immediate descent to low altitude. Traveling to extreme altitude, like climbing Mt. Everest, can cause temporary decline in cognitive and speaking abilities. Muscles Muscles use oxygen and sugars to create energy. In situations where oxygen isn t readily available, energy is created using a process called anaerobic metabolism. The by-product of anaerobic metabolism is lactic acid, a substance that produces that burning sensation you feel in your thighs after only the second run of the day. Skin Increased stress hormones and lower oxygen levels in body tissues at altitude (starting around 14,000 feet) can delay wound healing. Even the smallest cut can take a long time to heal, and can become infected more easily. Wheeze Play Playing at Coors Field s milehigh elevation has its benefits (think: long, sailing home runs balls actually fly 10 percent farther at Coors Field than at any other ballpark in the country). But it can wreak havoc on cardio training. The Rockies played 81 games below Coors Field s elevation in the 2009 regular season, meaning that every time they hit the road their bodies adjust to lower elevations. When the team returns to Denver, players must reacclimatize, which prompts Rockies trainer Brian Jordan to cut back workouts by at least 25 percent when the team is at home. So much for home-field advantage. october com 101

9 O2 boiling point of water changes with altitude. As you go higher, the boiling temperature decreases. At sea level, the boiling point of water is 212. As a general rule, the boiling-point temperature decreases by 1 for every 540 feet of altitude gained. On top of 14,110-foot Pikes Peak, for example, the boiling point of water medicine Study Groups Colorado s cutting-edge research aims to lower the risk of altitude sickness. Higher education Dr. Robert Roach researches the effects of altitude at CU s Altitude Research Center in Aurora. In an unassuming white building on Aurora s Anschutz Medical Campus, researchers toil away in front of computers and charts and vials of unrecognizable substances, but these scientists look more like the high school soccer team than the math club. That s no coincidence: The researchers who work at the University of Colorado s Altitude Research Center (ARC) labor over their experiments because it s their job, but also because many of them have a personal interest in the results. Most of us are here because we figured out a way to combine our interests in science and outdoor recreation, says Jason Chapman, a former research associate at ARC and a regular marathoner. Plus, we get to use the information we learn here to help us perform better at altitude. The center, which has been around in various incarnations for more than 15 years, is one of the few research organizations of its kind in the world. With a mission to improve life through research on how hypoxia affects health and performance, ARC strives to generate science that will help both an experienced mountaineer climb higher without consequence and an oxygen-starved ICU patient heal more quickly. Dr. Robert Roach, ARC s research director and an avid mountain climber, has been consumed with the desire to allow people to have more fun at altitude for three decades. We want to be a place where people can bring their problems with altitude and hypoxia, he says, adding that the center offers workshops and seminars for the public as well as for health-care providers. But we also want to radically advance the field of high-altitude biology. That means conducting groundbreaking experiments things like determining whether intracranial pressure causes altitude headache, figuring out if there s a genetic susceptibility for altitude illness, and sussing out the basic mechanism behind acute mountain com october 2009 photograph by matthew staver

10 is 186. For an easy remedy, employ this formula: For every 1,000 feet above 2,000 feet in elevation, increase the cooking time by five percent. Altitude affects your exposure to the sun. The higher you go, the greater the risk of burn, because there is less atmosphere to filter UV radiation. For every 984 feet gained, the danger increases by about four percent. In Colorado, the incidence of melanoma (skin cancer) is 30 percent higher than the national > > sickness. On any given day at ARC you ll see research subjects furiously exercising in the hypobaric chamber, scientists peering at brain scans, and Roach and company pounding out grant proposals. Of course, ARC s crack team of scientists isn t the only Colorado-based group interested in altitude medicine. We re dedicated to research at ARC, says Roach, but Peter Hackett is the best person in the world for clinical work. So if you re in good shape but you still suck serious wind trying to climb Mt. Massive, your best bet for figuring out why you can t summit is Hackett. Considered one of the planet s foremost experts on altitude medicine, Hackett operates the Institute for Altitude Medicine (IFAM) in Telluride. IFAM, founded in 2007, has an affiliation with ARC but exists for a very different reason: Effective clinical consultations and treatment for altitude-related illness are not widely available. People come to me for a variety of reasons, says Hackett, but mostly it s, I had a problem on Everest last time and need to know why, or My blood pressure is simply too high at altitude, or I just can t catch my breath past a certain elevation. And, fortunately, almost all of these issues can be dealt with. It may not be surprising that Colorado fields a rather large brain trust of high-altitude researchers. After all, the state s mountainous backbone serves as a natural laboratory and a vast reservoir for anecdotal evidence. What is surprising, though, is how far-reaching the results of this clinical and laboratory research could one day be. If we can figure out what causes high-altitude headache, says Roach, we might be able to expand that research and help figure out what causes the common, everyday headache. Furthermore, if we can determine the basic mechanisms of hypoxia, we may come to a better understanding of diseases like stroke, which affect millions of Americans. homeland security The Unseen Enemy Why altitude research matters to the U.S. armed forces. Bullets, bombs, I.E.D.s these are the visible and tangible dangers of war. Soldiers know about them, fear them, and are on alert for them. But such ordnance is not the only threat that America s military forces encounter. Some hazards like altitude are much less perceptible and are often underestimated. It s been more than 100 years since any large battle has been fought on American soil; instead, our military men and women have found themselves in increasingly exotic and remote locations Vietnam, Kosovo, Afghanistan, Iraq facing extreme temperatures, uncharted waters, and high altitudes in unfamiliar terrain. In Afghanistan, our soldiers are pursuing a seasoned, acclimatized, and battle-hardened enemy on their home turf, said Dr. Michael Callahan, a program manager with Defense Advanced Research Projects Agency (DARPA), at a 2007 symposium in California. Our Army Rangers who train in the mountains of Georgia at elevations less than 4,000 feet must engage an enemy superbly conditioned to fighting on the 16,000-foot peaks of the Kashmir. And our soldiers must pursue the enemy while wearing 100- pound packs. It s a high-altitude recipe for insomnia, sluggish reaction times, debilitating headaches, and nausea not to mention more dire elevation-related conditions, like high altitude cerebral edema, that can rapidly lead to death. All of this poses a serious problem, and the Department of Defense wants a quick solution. Dr. Robert Roach, of CU s Altitude Research Center (ARC), hopes he ll be able to provide an answer soon. We had applied for a $9 million DARPA grant to study the genetic responses of people who are immune to getting altitude illness and then use that information to try to discover new drugs that would create the same type of response in lowlanders, he says. ARC didn t win that particular grant, but Roach plans to move forward with the research anyway. It would be a landmark genetic study that could prevent the U.S. armed forces from sending at-risk troops to elevations where acute mountain sickness, high altitude pulmonary edema, and high altitude cerebral edema are a distinct possibility. It would be great if we could create a test where all you d have to do is lick a test strip to see if you would get AMS, says Roach. october com 103

11 O2 average. Food companies, like mega-producer General Mills, must adjust the amount of air in their packaging so bags of Chex-Mix don t explode while going through the Eisenhower Tunnel. Local companies have the opposite problem. Udi s Foods uses a bigger package to ship its granola so the packages don t shrink shop talk The Tune-up Just like their drivers, cars need time to adjust to altitude. If you re driving up from sea level, it can take 35 to 40 days for your car s computers to adapt. But the mechanics at Addison Auto Repair and Body Shop in Denver warn that your ride can still feel the effects from a simple drive up to the Eisenhower Tunnel. Here s why. Engine Porsche or Prius, all cars will be less powerful we re talking at least 10 percent at altitude. With less oxygen in the air, engines suck in a smaller amount of fuel, which leads to a lack of giddyap. You can adjust the fuel injection, but you ll just be contributing to Denver s brown cloud with pollution by burning too much fuel. Tires With less air pressure in Denver, a perfectly inflated tire at a sealevel elevation will read higher at an elevation of 5,280 feet. You ll often need to add (yes, add) three or four more psi up to 36 pounds to keep that pesky tire pressure monitor from lighting up on your dashboard at altitude. Gas Ever notice that Colorado gas stations carry lower-octane fuel than elsewhere? Turns out the gas is basically the same as what you d get at zero feet, but the ignition point is different. With less oxygen at higher elevations, the gas burns at a lower pressure, earning it a lower-octane measurement. Our advice? If your car s manual asks for premium, it s not just a suggestion at altitude. Don t skimp on the octane you ll want to pay up at the pump rather than at the shop. Pint-Size Tykes More than nine percent of Colorado babies have low birth weights tipping the scales at an average of less than five pounds nine ounces. The thin air is to blame, says Dr. Vaughn Browne, a professor in the surgery division of emergency medicine at the University of Colorado at Boulder. A baby s weight decreases by 100 grams for every 3,280 feet gained in elevation. The long-term effects of low birth weight are not yet known, although researchers are looking at whether low birth weights could lead to disease later in life. For now, though, the Colorado Department of Public Health and Environment is more concerned with the unusually high number of Coloradans (one in four) who don t gain enough weight during pregnancy anywhere between 15 and 40 pounds is generally recommended to help keep their babies weights in the green zone. Coloradans are famously lean active lifestyle and altitude-induced high metabolism help which is great unless your offspring needs the added fat stores. So, moms-to-be, grab that pint of Cherry Garcia the baby needs those tasty and vital calories com october 2009

12 into hard bricks en route to Arizona. General Mills uses an altitude simulator a sort of foodie humidor to test how a product will hold up in high altitudes. It even ships a small amount of a product to different altitudes to test how the packaging and the food inside stands up to the pressure. Outdoor retailer REI sells more regular hydration packs in the mountain states (Colorado, Utah, and Montana) than anywhere else. The Cost of Air Three Colorado companies turn a profit on selling, well, next to nothing. first person Going Up! My journey to 16,000 feet above sea level. Product BetterThan- Air s O2go canister What It Does The size of a hairspray bottle, the disposable O2go holds around 150 breaths of 90 percent oxygen. Take five quick puffs at the top of a ski run, every 30 minutes, or whenever you start to feel the negative effects of altitude. Cost $38 $42 per canister Who Uses It Skiers, hikers, out-of-state wedding guests, conferencegoers Alpine Oxygen s Oxygen Concentrators Forget refills. Oxygen concentrator machines suck in air, isolating oxygen molecules and delivering 93 percent pure oxygen via a mask or nasal cannula. $105 per day rental Jazz Aspen Snowmass musicians, condo owners Colorado Altitude Training s Hypoxic Tent System com If you don t mind sleeping with a tent pitched around your bed, these altitude simulators separate oxygen and nitrogen, so you can sleep at Breck s altitude in Miami or vice versa. Starting at $3,900 Lance Armstrong, Shaquille O Neal, thoroughbred horses M y brain hurts. OK, not so much hurts as it feels like it s sloshing around in my head, periodically slamming into my skull. If even one glass of red wine had crossed my lips last night I would chalk up my symptoms to a nasty hangover. But this morning I didn t wake to find myself in last night s clothing, on top of the sheets, with my shoes still on. Instead, dressed in gym clothes, I m hugging a heating pad and praying that I don t puke on the cute lab tech who s taking my temperature. I m getting sick. Not flu sick or 24-hour-bug sick. Altitude sick. I ve been 16,000 feet above sea level for nearly four hours, and, although I m trying to tell myself I m just being a hypochondriac, I m feeling awful. Which is great because that s exactly what I was hoping for when I climbed into the altitude chamber, a 28-foot-by-10-foot, light blue hypobaric tank at the University of Colorado s Altitude Research Center (ARC). True, the view from ARC s chamber lacks the jaw-dropping scenery one might find atop Longs Peak. But what it lacks in beauty it makes up for in convenience. It took me less than 15 ear-popping minutes to scream up to 16,000 feet from Denver s 5,280 feet. Here, there s no weather to contend with. No twisted ankles on rock-strewn trails. No 35-pound packs to haul. Inside the chamber, the only battles to fight are with the nippy 60-degree air, the sub-10-percent humidity, and the dreaded stationary bike. Oh, and the ultra-low-oxygen environment. My normal resting heart rate hovers around 65 beats per minute. In Denver, my typical blood-oxygen saturation (the percentage of oxygen that s carried by my red blood cells) registers about 94 percent (it would be 100 percent at sea level). But at 16,000 feet there is 35 percent less oxygen than in Denver and I m feeling it. The pulse is the first thing to go. Nerve centers in my head and neck say something like Hello? Where in the hell is my oxygen? and ask the heart to pump harder. Simply sitting on a bench in the tank, my heart rate increases by 30 to 40 beats a minute; I can actually feel the pounding in my chest. Then we add exercise to the equation, and the numbers really get screwy. Twenty minutes into a ride on a stationary bike my heart rate spikes to 169 and my oxygen saturation plummets to 79 percent. Even in an easy gear, spinning away, my muscles burn as if I ve been downhill skiing for six hours. My appearance must be going downhill as well, because Dr. Jim Sederberg, my chamber buddy, asks if I m OK. When I nod a meek yes, he adds, Yeah, acute hypoxia with exercise is a real bitch. Indeed. LBK m october com 105