Mt. Whitney Portal Store & Hostel Forums General Mt. Whitney Portal Store Message Board Another Thread On Altitude

Since this thread ( http://tinyurl.com/jcm5l ) seems to have been locked, I'll start a new one (that will hopefully get some replies )

I've been "playing" with a pulse oximeter for the past couple of months. It seems to have raised a few more questions:

1. Are the finger models considered accurate?

2. Is there a correlation between a reading and the symptoms of AMS?

3. Are wild (10-15%) fluctuations normal while at rest?

4. Will conditioning impact the reading?

The reason that I ask is I thought I seemed to have a few things figured out, but that doesn't seem to be the case:

- When traveling from sea level to about 11,500', the readings would drop into the low to mid 80's and I would start to feel a mild headache.

- This was contradicted by my last "Around Whitney" trip, where I had a reading of 82 when I returned to the Crabtree Meadows junction. (I left the meter in the pack, so I didn't get a summit reading.) In spite of this "low" reading, I felt great and had no problem getting down from the summit in a little over 4 hours at the end of a trip that included nearly 22 hours of walking/climbing over 2 days and one evening up to UBSL.

My answers to your questions are:

1. They can be very accurate to measure the blood O2 saturation in your fingertip, but this depends on a number of factors, including which unit you use.

2. Not necessarily (as you have seen from your own experience). All peripheral O2 saturation (what this fingertip probe measures) tells you is what is going on at that part of you body at that moment in time. FOr example, I've seen O2 sats in the 90's above 20,000 when resting in the tent, but it drops to low 80's or below when the same person is climbing hard at the same altitude. Most people are feeling some altitude effects at that elevation. Also, different organs (particularly including the brain) have different priorities for blood flow, so you can get very different O2 sat readings in different parts of the body.

3. Shouldn't be varying that much over a short amount of time (like minutes).

4. Yes.

Hmmm... I'd caution against using one as the sole source of determining your AMS. Perhaps use it in conjunction with something else -- llike your own assessment of yourself, which is very very difficult, I know. But here's why...

1. It seems finger temperature affects the reading. While trekking and climbing in Nepal, an ER doctor had one and was taking a lot of readings. My finger went from 72 to 87 within 10 minutes. Why? When I arrived at camp, my finger was cold. After warming it up and drinking some hot liquids, ...I was "deemed" ok. At 72, that's pretty bad... but I wasn't feeling any headaches or anything.

2. Psychological affects. The ER doctor was on a guided team with other clients in her economic category -- No. 9 guy at Microsoft, investment banker, etc.. Anyway, she was taking numerous data of them all and they all knew their reading all the time... It was cold up there... and so their reading was low. Whether this affected their ability to climb higher or not, I don' know. But I would imagine that my 72 reading would have freaked me out.

I wish there was something good to use to assess AMS level... or the threat of AMS.

Taking the measurement in bright sunlight might cause an error.

Normal constriction of the blood vessels in your extremeties because of cold might cause an error.

In general, your body is always adjusting the blood flow to its various parts by constricting or dilating blood vessels, depending on the situation. These pulse oximeters were initially meant for patients in hospitals. Not sure what other errors might be incurred by hikers in the great outdoors.

The researchers who took a survey in July at Portal which included a pulse oximeter on the finger might know more about its limitations and proper use.

i am a paramedic and all this is interesting and a cool toy but one thing you learn and need to rember is with AMS and any medical condition is you don"t treat the machine you treat the patient if you feel sick you probly have AMS weather your sat is 70 or 100 and thease can be wrong cold fingers will change it sun all kinds of things the pulse ox tells how much of your hemoglobin is oxygenated not how much is in each cell if you have a low Hg you could be transporting less oxygen with a high sat then someone with a high hemoglobin and lower sat could be moving as much oxygen throughtout their body anyway my porint is if you feel sick it is probly AMS and go down even if you sat says 100 but it is a cool toy have fun all talk later

Richard, you can indeed see fluctuations at rest. Just simply looking at your number be a bit low is enough to consciously or subconsciously stimulate you to breathe more and raise your 02sat 5%.

Now for 10-15 % that's a bunch. But I did this experiment with my pulse ox (SportStat) sitting here right now in front of the computer at sea level.
no big inhale - just hold breath:
start sat 98
15 sec sat 98
30 sec sat 95. uncomfortable- had to breathe
45 sec sat 87 nadir and then recovered.
so my "sensors" telling me to breathe recognized the drop was just starting. Obviously it kept falling for a while until I had enough breaths to recuperate.

Also, here's a real life set of numbers to show how the 02sat may vary depending on what your definition of rest is:
setting: 20K summit, back to 17K camp, push hard.
on arrival: sat 71%, pulse 130. guzzle 4 pints tea
30 min rest: sat 79, pulse 105
60 min rest: sat 86, pulse 100

hope this helps. Harvey

PS: going to 11,500 ft and measuring at rest should not be "low to mid 80s" but upper 80s. Wonder if this and your 10-15% fluctuations mean that your machine is "off" ????

Cool thread, I didn't even know something like that existed. I'm afraid I can't add any info, but I do have a couple of questions.

Is there a rough, informal way to estimate O2 saturation (or lack thereof)? I know it would be somewhat subjective, but even a rough estimation tool would be fun.

For example, as I was nearing the summit on Whitney, I found my balance was just slightly impaired and I felt a very slight dizziness. I was pressing a fast (for me) pace, and the symptoms vanished immediately when I stopped, and did not recur when I began heading down. I attributed this the the decreased oxygen consumption, but that was just a guess.

Also, just in case someone here knows, is there some rough ratio of oxygen consumption based on the grade of the trail? In other words, if a person is heading up a 10% grade, how would that impact the amount of oxygen needed as compared to a level area? How would going downhill affect it? I ask because I found that my usual, pace turned into something of an exhausted stagger towards the top, but it felt easy to run on the way down. I knew the amount of oxygen would be less going down, but the drop off is precipitous. My pulse drops by about 35% - that's a tremendous difference.

Is that a nonsense question, or is there any info on such a thing?

z

yep, lots easier going down.

hmmm, rule of thumb.....

even after acclimatization, a person can only optimize to a submaximal level of physical performance compared to sea level. You can never do as much as you can at sea level. At 14,000, you can, at best and after acclimatization, be only 75%.

Harvey.

Having watched Sherpas at 17,000 and up, I would disagree that "you can, at best and after acclimatization, be only 75%." Sherpas carry multiple heavy loads (around 80% of their body weight) up very steep technical slopes at high altitude and look to be working at 100% to me. Can we attain that level of performance after a few days of acclimating? doubtful.

Yes, amazing isn't it? I have travelled with porters carrying all day long a load that I could not even get off the ground. Then again, if I wasn't sitting behind a desk and at sea level, but instead had lived at altitude all my life and carrying loads, then I might be able to.

So the comment on submaximal performance must be taken in the context of high altitude, and comparing the porters to themselves at sea level, not to me/us. That's the proper comparison. The human machine at altitude can never do as much as it can at sea level. Neither can any oxygen-
breathing machine, including cars on Pikes Peak.

As for short term climbing rates, Hultgren's text (High Altitude Medicine) says that "although acclimatized climbers may be able to maintain a climbing pace with an altitude gain of 2,000 to 3,000 feet per hour up to 15,000 feet, at higher elevations the maximum rate of climb decreases sharply......at 24,000 feet may be only 500 feet per hour...at higher elevations the rates may be even slower" Harvey

I agree that there is some altitude above which no-one, including Sherpas, can perform well. However, I don't think that is true at lower altitudes. What is the evidence that Sherpas can operate better at sea level than at 10,000 feet? I actually do not believe that is the case. Their oxygen association/dissociation curve will shift back to (our) "normal", their hematocrit will drop, etc. and their performace will be about the same. Sort of a 'reverse acclimization'.

One indication that performance at altitude can equal that on the ground is that Olympic records have been set at high altitude venues (like Mexico City) beating those set at sea level.

Cars are the wrong analogy, as they don't adjust their machinery the way that humans do (yes, I know that mixture and timing change, but that is very different from increasing the number of red blood cells).

Agreed, cars and people engines are different, but both burn oxygen, that was the comparison, and the higher one goes up the weaker the engine in both.

Agreed, high altitude Sherpas or porters cannot necessarily perform better at sea level than 10,000. But....the comparison I gave was for more significant altitude. The quote from Hultgren I gave for performance was for above 15,000. The other quote from a lesser source that performance might be 75% at 14,000 does sound pessimistic, although perhaps it was not after "full" acclimatization which takes 6 weeks.

Mexico City: 10% slower times only for distance running longer than 1500 meters in the 1955 Pan American Games compared to comparable sea level meets. Whether that figure held up in later Olympics I don't have a reference, but it's "only" at 7300 feet.

Here's another angle. Hultgrens' book also says something about VO2max. This may be a partial surrogate for performance, although clearly not the only factor as,for example, Rheinhold Messner did not have a high one. Hultgren states "upon arrival at altitude VO2 max is decreased proportional to the altitude, being about 20% lower at 14,000 feet....note that even when maximum acclimatization has occurred, maximum performance still remains below sea level values."

Measuring people performance day after day when cold, tired, load-carrying, etc is much more complex. For the sake of this thread's original question.... measuring O2sat or fancier high-altitude lab VO2max will not answer all the questions ,as others have stated here.

Enjoying the discussion. Just ask me instead about brains at high altitude! Thanks, Harvey

There has been a lot of work on athletic performance at altitude. Performance in events like distance decreases markedly, even at altitudes as "low" as 5000'.

The times in the distance events at the 1968 Mexico City Olympics were awful, as expected. Ditto for other events held at relatively high altitude. There were numerous world records in Mexiso City in the sprints and jumps, due to the decreased air resistance. Some of those records lasted anomalously long because of the advantage vs. sea level. the crossover occurs at around 800m, which is the distance at which aerobic and anerobic processes contribute about equally.

Altitude is detrimental to aerobic endurance.

Actually, not all engines perform more poorly with increasing altitude. Jet engines get much more efficient as they go higher (up to a point, ~40,000 feet?).

I'm curious to hear what you have to say about brains. A buddy of mine did retinal exams climbing Everest and found the backs of people's eyes (which are arguably the front of the brain) to be a bloody mess.

Altitude is detrimental to aerobic endurance.

I like that, Alan. Succinct.

Jet engines are automatically turbocharged, so that doesn't count.

The FAA recommends that pilots in unpressurized planes (usually general aviation civilian pilots) use oxygen above 10,000 ft day, and 5,000 ft night. Only 5,000 ft!

The reason has to do with the retina being very sensitive. Loss of color vision and other important pilot stuff, like depth perception. The eye is an extension of the brain.

Really high altitude causes retinal hemorrhages.

Altitude is detrimental to aerobic endurance... and.... other physical abilities. Harvey

PS. Had fun with study on Brains and Video Games at High Altitude.
<a href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=11199536&query_hl=5&itool=pubmed_docsum" target=_new>Entrez PubMed</a>

> Had fun with study on Brains and Video Games at High Altitude.

So where is the text to the study???

sorry, Pub Med doesn't have it any more.
Here's the text and references.

Lankford HV. Brains and Video Games at High Altitude.
Wilderness and Environmental Medicine
11(4): 290-292, 2000.

Brains and Video Games at High Altitude

The central nervous system has a high demand for oxygen and is therefore physiologically vulnerable to even modest degrees of hypoxia. Because the cerebral cortex is more vulnerable than lower centers, the earliest abnormalities due to hypoxia involve higher cortical functions. Reported here for the first time is a study about deterioration of a specific psychomotor speed skill at high altitude, adding to the knowledge from other altitude and hypobaric chamber tests.

Acute Mountain Sickness (AMS) develops and mental abilities decline above 2,400m (8,000ft). Aircraft cabins are pressurized to maintain levels below this threshold. Coning of attention, lowering of arousal state, loss of short term memory, mental incoordination, and loss of reaction time are all typical effects of even mild hypoxia and only partially relieved by acclimatization. Poor decision-making will leave both pilot and climber on the mountain. (1,2,3) High Altitude Pulmonary Edema (HAPE) and High Altitude Cerebral Edema (HACE) are later but often fatal complications at altitude. More common and more insidious are the early effects of hypoxia on psychomotor skills and judgement, both of which are important in the thin air of mountaineering.

From Houston’s (2) and Hultgren's (3) encyclopedic reviews of high altitude, hypobaric chamber tests show that the earliest features of hypoxia include impairments of night vision at only 1,500m (5,000ft), other visual skills and memory above 2,400m (8,000ft), code tasks above 3,000m (10,000ft), and conceptual reasoning above 3,600m (12,000ft). During Operation Everest II, skill studies using the Tower task, addition, map compass, and computer interaction showed a decrease in performance, especially speed, above a simulated altitude of 4,500m (15,000ft). The Tower task is described as requiring the ability to visualize anticipated movements of puzzle blocks, to foresee the consequences of block movements under consideration, and to relate intended actions to consequences learned previously. (2,3) Computer device interaction, in part, tests the reaction time for a human-machine complex, conventionally divided into phases of perception, evaluation, decision, action, and response. (1)

Rather than perform these tests in the lab, we tested in the field, combining aspects of the Tower task and computer interaction by using a simple handheld video game system to demonstrate a hypoxia-induced deterioration in brain function while operating an electronic device at high altitude. The program we chose used spatial orientation and manipulation of geometric figures akin to the Tower task. It had been used in earlier studies, but only at sea level, to evaluate performance, visuospatial, cerebral glucose metabolism, and electroencephalographic effects. (4,5,6) It was easily learned and reflexive, yet our speed skills deteriorated at 5,900m (19,500ft). Performance of novel or more complex challenges using more brain power was, by extension, also abnormal.

The setting was 6,962m (22,841ft) Cerro Aconcagua, the highest mountain in Argentina and the Western Hemisphere. We went in February, the end of the austral summer. The 1998 season was plagued by a persistent El Niño-fed low pressure system over the region, generating daily storms, reducing the overall summit success rate to just 10%, and contributing to between nine (7) and fifteen (8) deaths. During our stay, an American man with HAPE was evacuated from 5,200m (17,400 ft), a British woman with HACE was evacuated from 5,900m (19,500ft), and a Polish man died on the summit, 6,962m (22,841ft). (7)

Study methodology included the use of two electronic devices. Daily oxygen saturation measurements were made using a handheld pulse oximeter (model 8500M, Nonin) upon awakening but before leaving our self-enclosed passive heating devices. There was significant operator effect, as much as +5%, after seeing ones own frightening degree of hypoxia from the combined effects of altitude and sleep-induced hypoventilation. Cognitive abilities were tested using a video game system (model Gameboy, Nintendo). We competed daily with the Tetris game program at level 9, the most challenging preset speed. The goal was to best the previous day's record of lines. Study subject 1 was RS, a 32 year old priest and native of Poland. RS had had an episode on Denali suggesting HAPE. Study subject 2 was HL, a 47 year old endocrinologist native of flatland Virginia.

Our findings revealed that oxygen saturation (SaO2) fell in an expected, non-linear fashion, falling only slightly initially, but more rapidly as altitude increased. For example, sea level SaO2 was 98% and only a slightly lower 94% at the 2,720m (8,924ft) trailhead. Adding another similar increment in height by going to 5,900m (19,500ft) resulted in a much lower SaO2 of 63%. After further acclimatization at this height, SaO2s rose to a more tolerable 70%.

Figure 1 shows results of cognitive studies on the Gameboy. The number of Tetris lines completed at preset speed level 9 improved with daily practice. The maximum was 97 lines by Subject 2, versus 94 lines obtained by his opponent. This steadily improving level of accomplishment occurred by the time we reached 5,200m (17,100ft). Above this altitude, performance at speed level 9 was non-existent for both subjects. Lack of concentration, slower reflexes and bad headaches at high camp 5,900m (19,500ft) suggested evidence of cerebral dysfunction. Going higher toward the summit was deemed proof by those not in the business. However, residual self-preservatory brainstem function was intact, allowing independent decisions to turn around, rescue another climber, and descend when confronted by storm above 6,700m (22,000ft). (7)

Discussion

As a major consumer of oxygen the brain is affected early by altitude, leading to errors in judgement, compounding what may already be a desperate situation. Hypoxia alone or in combination with other altitude complications may be fatal. AMS occurs in unacclimatized individuals at altitudes above 2,400m (8,000ft)

The classic symptoms are headache, nausea, anorexia, fatigue, insomnia, disturbed sleep, lightheadedness, dyspnea on exertion, cough, and edema. By the time most climbers reach 5,500m (18,000ft) they are partially acclimatized but have decrements in somatic workload, complex mental task performance, short term memory, and judgement. At higher altitudes and longer stays, further difficulties are largely due to deterioration of physiologic function, eventually outstripping acclimatization. HACE lies at the far end of the continuum beyond altitude headaches and high altitude encephalopathy. Headache and lassitude may herald in a fulminant clinical picture dominated by confusion, hallucination, inappropriateness, and ataxia, the latter a pathognomonic sign. Deterioration is rapid and progressive with a very high mortality rate. Victims of AMS, HAPE, and HACE are best treated with descent, descent, descent (10) but combinations of acetazolamide, dexamethasone, nifedipine, and oxygen are useful . Risk-reduction by acclimatization and the recognition of altitude illnesses is a better choice. (2, 3, 9, 10)

In addition to hypobaric chamber tests, studies of brain function made in field conditions of military, mining, tourism, and mountaineering situations have revealed abnormalities of arithmetic tests, visual and verbal memory, writing, comprehension, bright light after-images, card sorting, learning rate, reflexes, finger-tapping speed, verbal expression, and more. (2,3) These effects are only partially corrected with acclimatization, and are especially significant above 5,200m (17,000ft) where atmospheric pressure is about half that at sea level. Our high altitude video game results are now added to the list. Upon descent, some minor neurological deficiencies may linger after uncomplicated sojourns, but significant loss of intellectual function is disputed. (2,3).

Errors of cognition and judgment, such as in the environment we faced above 6,700m (22,000ft), may cause as many deaths as more obvious factors. Recognizing this mental decline can be difficult. With HAPE, where a low oximeter reading may not be predictive, at least a slower climbing rate may be a recognized clue. With HACE, no early test is predictive either, but the clues of subtle personality changes, mild confusion, and general lassitude are even more easily overlooked. Our loss of video game speed performance at high altitude was because of hypoxia and not HACE, but nonetheless it simply illustrates the problem. Our lack of interest, lack of concentration, slower reflexes, and slower decision-making was not life-threatening at the time, but with a longer stay might have been so on the mountain, or even in the tent. Ours was a pilot study with the limitations inherent in a small sample. Therefore, we challenge other mountaineers to duplicate or exceed our high altitude video game performance.

References

1. Harding RM, Mills FJ. Aviation Medicine 3rd Ed. London. BMJ Publishing, 1993.
2. Houston C. Going Higher. Oxygen, Man, and Mountains, 4th Ed. Seattle. The Mountaineers, 1998.
3. Hultgren HN. High Altitude Medicine. Stanford. Hultgren Publications, 1997.
4. Haier RJ, Siegel BV Jr, MacLachlan A et al. Regional Glucose Metabolic Changes after Learning a Complex Visuospatial/Motor Task: A Positron Emission Tomographic Study. Brain Res 1992;570(1-2): 134-143.
5. Laczika K, Staudinger T, Locker GJ et al. Tetris and Physician’s Performance State. Lancet 1995; 346(8973):516.
6. Trimmel M, Huber R. After-Effects of Human-Computer Interaction Indicated by P300 of the Event-Related Brain Potential. Ergonomics 1998;41(5): 649-55.
7. Lankford HV. Aconcagua: Life at 22,000 Feet. South American Explorer 1998;54: 12-24.
8. McClannan K. Climbs and Expeditions:Argentina. American Alpine Journal 1999;41(73): 325-326.
9. Hackett P. Mountain Sickness. Golden, Colorado. American Alpine Club, 1993
10. Houston C. High Altitude: Sickness and Wellness. Merrillville, Indiana. ICS Books, 1993.

Harvey, Thanks for the abstract.
"During Operation Everest II, skill studies using the Tower task, addition, map compass, and computer interaction showed a decrease in performance, especially speed, above a simulated altitude of 4,500m (15,000ft)."

Does this mean that reduced brain function from hypoxia is not a problem for Whitney?

Nope. Problems can arise at any altitude. Many people have reduced brain function at sea level!

Seriously, the Tower Task and computer interaction quote (for above 15,000) was enclosed to legitimize our comparable Gameboy usage where our mental performance of that specific skill changed (stopped) at 19,500.

Brain function begins subtle deterioration at sub-Whitney altitudes. "hypobaric chamber tests show that the earliest features of hypoxia include impairments of night vision at only 1,500m (5,000ft), other visual skills and memory above 2,400m (8,000ft), code tasks above 3,000m (10,000ft), and conceptual reasoning above 3,600m (12,000ft)."

These are subtle and not noticed by the Whitney hiker. But people do notice lightheadedness, eh? However, a Whitney hiker with serious AMS, HAPE or HACE, would have significant deficits in mental and physical function.

Harvey

"Brain function begins subtle deterioration at sub-Whitney altitudes. ... These are subtle and not noticed by the Whitney hiker."

The diminished mental capacity from hypoxia due to high altitude might be exacerbated by the oxygen demands of heavy exertion while hiking. Some of the oxygen that is needed by the brain is used up by muscles. This may have contributed to some questionable judgements I've read about on this message board like "walking into lightning" and summit fever. On occasion I haven't felt too sharp myself up there.

Bob