Alitude sickness
/Accute Mountain Sickness
/FEELING CRAPPY AT THE TOP

Whilst preparing for the day hike up Mt Whitney I became quite fascinated (actually a little obsessed) with the notion of altitude sickness. I am from DownUnder after all – a ridiculously low and flat continent. The highest peak in Australia is Mt Kosciusko at a puny 7310ft (2228m) - not even close to our starting point. The Whitney Portal trailhead is at 8300ft. Even though Uluru - (or Ayers Rock) - is the second-largest monolith in the world (after Mount Augustus, also in Australia), it is only 986ft high. As aptly described by explorer Ernest Giles in 1872, it is a "remarkable pebble"… not a formidable mountain. What is more, my family history didn’t fill me with confidence - generations of lowland dwellers that have had no experience of high altitude at all. Was I destined to succumb to this scary phenomenon? I was somewhat relieved to read that susceptibility to altitude sickness is primarily related to an individual’s physiology (genetics). Apparently age, gender, physical fitness and previous altitude experience had little or no bearing on how an otherwise healthy individual is going to be affected by a sudden (one day) climb to 14,495 ft above sea level.

Altitude sickness is a general term that encompasses a spectrum of unpleasant symptoms that occur at high altitude. High altitude is generally defined as anything above 8,000ft (2,438m). From what I read, most of us would be expected to experience at least mild symptoms of altitude sickness ascending Mt Whitney in a day. These may include AMS symptoms including dizziness, headache, shortness of breath, nausea, vomiting, loss of appetite … feeling a bit “drunk” even. But altitude sickness includes not only AMS (acute mountain sickness) but also the more severe HAPE (high altitude pulmonary edema) and HACE (high altitude cerebral edema). Not only scary sounding but potentially deadly outcomes if not handled properly.

Altitude sickness occurs because the partial pressure (concentration) of oxygen decreases with altitude. Even though the barometric pressure decreases the air still contains 21% oxygen – it is just that there are fewer molecules each breath (hypoxia) and hence less oxygen reaches the blood (hypoxemia).

Only a small percentage of folks develop the more serious form of altitude sickness HAPE (high altitude pulmonary edema). HAPE however can strike even without being preceded by AMS. Experts think it is not even related. With HAPE, fluid leaks from within the pulmonary blood vessels into the lung tissue and accumulates. It is potentially nasty (life threatening in fact) and is known to afflict all types of individuals regardless of their level of physical fitness. In fact it is supposed to be more frequent in young fit climbers. Often it is mistaken for pneumonia.

HACE (high altitude cerebral edema) is also rare but it is the most severe/dangerous form of altitude sickness. As you might guess, it involves neurologic symptoms including altered levels of consciousness, speech abnormalities, severe headaches, loss of coordination (ataxia), hallucinations, and even seizures. Presumably these disorders are a result of low levels of oxygen in the blood but the exact nature of how and why they occur is not fully understood. With narrow trails, possible inclement weather (high winds etc), sheer drops on either side through the “windows” or “keyholes”, it would not be good to fall victim to these described conditions up there. With this in mind, Peggy and I devised our plan – stick together and no heroics (descend immediately if either one of us experiences altitude sickness). We would expect normal physiological changes such as shortness of breath, hyperventilating, increased urination and some discomfort (light-headedness or a bit of a headache/nausea etc) but beyond that we agreed to monitor ourselves (and each other) diligently and “be smart”.

Strange things happen to the body chemistry/physiology at altitude. We’re all trying to suck up more oxygen by hyperventilating but this increased breathing results in a reduction of CO2 in the blood (the metabolic waste product removed by the lungs). It is the CO2 that triggers the brain to remind you to breathe. If it is low, the drive to breathe is blunted. The lack of O2 is a much weaker signal. When you get up to high altitude you actually have to consciously remind yourself to “breathe”. Unless we were pretty dehydrated and not acclimatizing at all well, we were also peeing copiously. This can be attributed to the significant changes occurring to the body chemistry and fluid balance as a result of acclimatization. The “osmotic” regulator (detecting concentration in the blood) gets reset so that the blood is more concentrated. Exactly how and why is another area of uncertainty but it is possibly to increase the hematocrit as more RBC’s (red blood cells) may result in an increase in the oxygen carrying ability of the blood. The result is duiresis as the kidneys excrete more fluid (this may also work as a counteraction to edema).

Some Striders opted to take the prescription drug Acetazolamide (Diamox). This drug forces the kidneys to excrete bicarbonate (the base form of carbon dioxide) – which reacidifies the blood, balancing the effects of hyperventilation. This reacidification acts as a respiratory stimulant so in effect “accelerates: the acclimatization process. If ascending from sea level, it is recommended that individuals’ acclimatize by spending at least one night at intermediate altitude (under 8,000ft) and then allow one day for each 2000ft extra of altitude. Clearly we weren’t going to be able to follow these guidelines. We left the Bay Area on Friday morning, arrived at Mt Whitney Portal Friday evening (8,300ft) and set out early the next morning to climb over 6,000ft before lunch.

Our preventative plan was to be mindful of hydration before, during and after the hike. Water loss is a problem at high altitude. If you don’t hydrate adequately, any acclimatization process the body is able to go through is inhibited. We would also take care to keep our energy levels up with adequate calorie intake. Hydration and energy intake we both felt we were pretty much in tune with from our long runs.

Happily (this story does have a happy ending) everyone in both parties were able to ascend and summit Mt Whitney (and return to base of course) in a day. Each one of us had our own special, unique experience with the mountain and the altitude; we each have our own story to tell. For me personally, I fared well on the mountain and in retrospect needn’t have worried so much about the perils of altitude sickness. In the vernacular… it was “no worries” after all.

Penny