Expeditions by Janet Belarmino

Palawan  Is land  hopping  from  El Nido  to  Coron  &  Himalayan Expeditions

Belarmino Ventures-

How can I optimize my health at altitude?

High Altitude Medicine.com

Definition of High Altitude

- High Altitude: 1500 - 3500 m (5000 - 11500 ft)
- Very High Altitude: 3500 - 5500 m (11500 - 18000 ft)
- Extreme Altitude: above 5500 m

Whether trekkiing in Nepal, doing high altitude mountaneering,  altitude acclimatization is the key to avoiding altitude sickness and improving altitude performance. The following are ways to optimize your adjustment to altitude and improve your chances of not getting altitude illness.

  • Slow ascent to altitude is the key to acclimatizing well. Alm ost anyone can get altitude illness if they go too high, too quickly. Because of the individual differences, a preventive rate of ascent for one person may be too slow or fast for another.
  • An overnight stay at an intermediate altitude such as Denver (5280 ft) or preferably a bit higher prior to further ascent into the mountains is very helpful. If traveling to Telluride, overnighting in Ridgway, Ouray, Placerville or Durango would be helpful, especially if the destination is Mountain Village.
  • Staying hydrated is important as it aids your body in acclimatizing.
  • Avoid use of alcohol or sleeping agents of the benzodiazepine family, since they both suppress breathing and result in lower blood oxygen. Other sleeping pills like Ambien or Lunesta do not affect breathing at high altitude and are safe. Avoid over-exertion for 1-2 days after arrival to altitude.
  • Acetazolamide (Diamox®) taken 24 hours prior to arrival to altitude and the first 2 days at altitude is 75% effective in preventing AMS. It speeds up the acclimatization process in the body, stimulates breathing, raises blood oxygen and increases urination.
  • Gingko biloba, according to some studies was effective in preventing AMS when started 5 days prior to ascending to altitude, at a dose of 100 mg twice a day.
  • Avoiding exposure to viral illness such as coughs and colds will improve your chances of staying healthy. When traveling consider wearing a mask if exposed to someone with a severe cough. Use proper hand washing and good hygiene to avoid transferring germs.


Altitude Myths Myth # 1 - Don't drink caffeine at altitude.

We don't know where this false assumption came from, but likely from the fact that caffeine is a mild diuretic (makes you pee). The concern is that it could dehydrate you and contribute to altitude sickness. This concern is unfounded unless you drink pots of black sludge coffee a day and little else. In reality, caffeine stimulates your brain, kidneys and breathing, all of which are helpful at altitude. And for those people who drink several caffeinated beverages a day, stopping abruptly can cause a profound headache. See Dr. Hackett's article on caffeine and altitude.

Myth #2 - Diamox masks symptoms of altitude sickness.

Taking Diamox to prevent AMS will not mask symptoms. It works on the same pathway that your own body uses to help you acclimatize. It is a carbonic anhydrase inhibitor which makes you urinate a base chemical called bicarbonate. This makes your blood more acidic and therefore stimulates breathing thereby taking in more oxygen. It speeds up your natural process of acclimatization and if you stop taking it you will not have rebound symptoms. It is one of the main medicines doctors use to prevent and treat acute mountain sickness (AMS).

Myth #3 - Physical fitness protects against altitude sickness.

Physical fitness offers no protection from altitude illness. In fact, many young fit athletes drive themselves too hard at altitude prior to acclimatizing thinking they can push through the discomfort. They ignore signs of altitude illness thinking it can't affect them because they are fit and healthy. Everyone, regardless of fitness, is susceptible to AMS.

Myth #4 - Drinking extra water will protect you from altitude illness.

Staying hydrated is important at altitude. Symptoms of dehydration are similar to AMS. In reality you only need an additional liter to a liter and a half of water at altitude. Too much water is harmful and can dilute your body's sodium levels (hyponatremia) causing weakness, confusion, seizures, and coma. A good rule of thumb to assess for hydration is to check your urine. Clear urine indicates adequate hydration, dark urine suggest dehydration and the need to drink more water.

Myth # 5 - Children are more susceptible to altitude illness.

Several studies have shown that children have similar rates of altitude illness as adults. No evidence exist that children are more susceptible to the altitude. If your child is otherwise healthy and the basic rules of acclimatization are followed they will likely do well at altitude. Children do get altitude illness and the main challenge in those very young is that they can't communicate their headache and other symptoms. Excessive crying in a baby the first 1-2 days at altitude could be altitude illness. Children with AMS bounce back quickly with treatment as do most adults.

Altitude Physiology

Normal Physiology

Normal Symptoms at Altitude
Hyperventilation/dyspnea on exertion (NO dyspnea at rest)
Increased urination
Awaken many times at night (sometimes to urinate)
Periodic breathing at night

Periodic Breathing

Periodic breathing is a normal phenomenon at altitude, and is most prominent during sleep. It is characterized by periods of hyperpnea followed by apnea. Apneic duration is commonly 3-10 seconds, but may be up to 15 seconds. It occurs in everyone above their personal altitude "threshold". It may lessen slightly with acclimatization, but does not resolve until descent. It becomes more pronounced with ascent, but is not associated with altitude illness. It may result in panic in the trekker who wakes up either during the breath-holding phase ("I've stopped breathing!") or with the post-apneic gasp ("I'm short of breath, I've got pulmonary edema!"). Reassurance is helpful.

Acetazolamide (Diamox®) 125 mg po about one hour before bedtime reduces or eliminates periodic breathing. If needed, this should be continued until the patient has descended below the threshold elevation where periodic breathing became troublesome.

Insomnia at altitude is not necessarily caused by periodic breathing, but is thought to be secondary to cerebral hypoxia. Thus the respiratory stimulant acetazolamide is the sleeping tablet of choice.

Benzodiazepines are controversial; one small study has shown that temazepam improved sleep quality but caused a small decrease in mean oxygenation in unacclimatized healthy climbers; in well-acclimatized climbers the mean sleep oxygenation was slightly increased. I believe benzodiazepines should be avoided in persons with symptoms of AMS.

Edema of Altitude

Peripheral edemaand facial edema are relatively common. If seen as an isolated finding without other symptoms of AMS it is not considered AMS, and is not a contraindication to ascent. It is likely to worsen with ascent, and is more common in women than men. It resolves rapidly with descent. Treatment, if necessary, is symptomatic with either acetazolamide or low doses of oral furosemide

Acute Mountain Sickness (AMS)

A spectrum of illness from mild to severe (HACE), AMS is common - the presence of moderate AMS (Lake Louise score of 4 or greater) is seen in approximately 25% of trekkers ascending to over 5000 m (16,500 ft) (personal study, unpublished). Under most circumstances, AMS is self-limiting, resolving in 24-48 hours.

At altitudes over 2400m / 8000 ft, the diagnosis of AMS is based on a headache plus at least one of the following symptoms:

GI upset (loss of appetite, nausea, vomiting)
insomnia (more than just the usual frequent waking)

The ascent history is an important part of managing AMS. At what elevation has the patient slept during their ascent? Did s/he fly in to a high airstrip, or walk in from low elevation? Trekkers on their way to Everest who fly into a high airstrip (Lukla 2850 m/9400 ft) have twice the incidence of AMS as trekkers who walk in from the lowlands (Jiri 1900 m/6300 ft). Has s/he exceeded the "standard" 300 m (1000 ft) sleeping elevation gain per night? By how much? At what elevation were symptoms first experienced? How many days ago was that? Has this patient ascended so rapidly that you should be expecting deterioration?

Denial is extremely common. I have seen many trekkers with obvious AMS who discount their headache as "sinus", in the absence of any other symptoms or physical findings of sinusitis; or trekkers who have walked for 8 hours uphill with a backpack, yet somehow believe that it is normal that they are not hungry. People who are on the "trip of a lifetime" to see Everest (or for that matter, any other destination) have a great deal invested emotionally in remaining well enough to achieve their goal (which may require staying on an unreasonable schedule). Many people fear being left behind, or holding up the group, and some cultures have such a strong group identity that it is common for members of the group to hide (or at least not reveal) their symptoms to the group, until they become so ill that it is unmistakable. Serious altitude illness (HACE, HAPE) is more common in trekkers in an organized group, possibly due to this group dynamic.

Dehydration is a common cause of non-AMS headaches, and there are many other potential causes as well. You can perform a diagnostic/therapeutic trial by having someone with a headache drink a liter of fluid and take a mild pain-reliever (aspirin, acetaminophen(paracetamol), ibuprofen). If the headache resolves completely, it's not likely to be AMS.

Once patients are completely symptom-free they have acclimatized, and continued ascent is acceptable.

AMS Medications


Acetazolamide 125 mg po q 12 hours, no further ascent until well. It has been shown to accelerate acclimatization; as the patient acclimatizes symptoms will resolve. It does not cover up any symptoms: if a patient feels well on acetazolamide s/he is well; it does not protect against worsening illness if ascending with symptoms.

Acetazolamide is a respiratory stimulant at altitude, and improves oxygenation. It is useful against Periodic Breathing.

Acetazolamide is a sulfonamide derivative, and should not be used in Sulfa-allergic patients.

Intermittent paresthesias in lips, hands, feet are common and irritating, and are dose-related. They are benign and resolve when the medication is stopped. Taste alterations and tinnitus may also occur. I have seen two cases of blurred vision (severe) occuring after a single dose of acetazolamide at altitude; in each case this resolved after several days off the medication. Acetazolamide can be stopped after clinical recovery from AMS, there is no risk of rebound from this.

If it is to be used prophylactically, 125 mg twice a day starting 24 hours before ascent, and discontinuing after the second or third night at the maximum altitude (or with descent if that occurs earlier). Sustained release acetazolamide, 500 mg, is also available and may be taken once per day instead of the shorter acting form (I have found side effects to be higher with this form).


Dexamethasone 4 mg po/IM q 6 hours x 2 doses. No further ascent until well and at least 18 hours after last dose. I believe that it treats the pathology, but this is controversial. Persons taking dexamethasone (or any other oral steroid) should not ascend until they have demonstrated wellness off the steroid. Dexamethasone should never be taken during ascent; it is well documented to suppress AMS, and does not improve acclimatization. Severe rebound AMS can occur if the medication is abruptly discontinued.

I have completed a preliminary study at Pheriche which shows that dexamethasone is at least equivalent to the Gamow® Bag in efficacy of treating moderate AMS (Lake Louise scores of 4 or greater) (Parker 1995)

Ginko biloba

Limited studies have been performed, but the results look very promising for prophylaxis of AMS (see the Hot Topics section). 120 mg po BID starting 5 days before ascent, and continuing at altitude.

AMS treatment options:
Pro rapid recovery: patients generally improve during descent, recover totally within several hours.
Con loss of "progress" toward trek goal; descent may be difficult in bad weather or at night; personnel to accompany patient.
Rest at same elevation
Pro as with rest alone, plus acclimatization is accelerated, recovery likely within 12-24 hours.
Con recovery may take 12-24 hours
Rest plus dexamethasone
Pro as with rest alone, recovery of even moderately severe AMS in 2-6 hours. Recovery is essentially as rapid as with descent, without the walk.
Con potential for steroid side effects, although in extensive use I have never seen this.
Rest plus acetazolamide & dexamethasone
Pro as with rest alone, plus acceleration of acclimatization and resolution of pathology.
Con ummm... Can't think of any significant ones not covered above. This is what I choose to do when I get AMS.
Oxygen or hyperbaric treatment
Pro Oxygen 4 l/m, or simulated descent in a hyperbaric bag works as well as descent in the short term, without the walk.
Con Not generally used as oxygen tanks are expensive and heavy, and hyperbaric bags are very expensive and labor-intensive; these are usually reserved for more serious illness. Treatment for 2 hours with either will resolve symptoms in most patients, but I have seen rebound illness in patients with moderately severe AMS (Lake Louise score > 8)

I use an AMS worksheet to help in scoring severity of illness and tracking treatment progress. There is also an AMS worksheet with phonetic Nepali translations, to help evaluate porters in your group, if you will be trekking in Nepal.

High Altitude Cerebral Edema (HACE)

High Altitude Cerebral Edema (HACE) is the severe end of AMS: AMS is believed to be subclinical HACE. According to the Lake Louise Consensus, in the context of a recent ascent, patients with HACE will have symptoms of AMS plus either gait ataxia or mental status changes, or will have both gait ataxia and mental status changes regardless of AMS symptoms. One must often rely on gait ataxia alone as language barriers may preclude an adequate mental status exam. I use a simple tandem-gait test, asking the patient to walk heel-toe along a straight line. This is demonstrable to the patient even in the face of a total language barrier. On even ground, without huge climbing boots or a backpack on, they should be able to perform this test without difficulty. If they struggle to stay on the line, fall off it, or are unable to walk without assistance, they fail and are presumed to have HACE. Subtle gait ataxia (balancing to stay on the line in heel-toe walking) may be present in severe AMS without frank cerebral edema being present, but as a rule significant ataxia means HACE. Interestingly, HACE does not affect finger-nose tests for ataxia.
I have not yet seen a case of HACE in which the patient didn't ascend with AMS symptoms, and believe that HACE is nearly always preventable (two exceptions: HACE secondary to severe HAPE, and HACE in climbers trapped high by deteriorating weather and sickened by dropping barometric pressure). Denial is extremely common.

HACE Treatment Protocols

Dr. Peter Hackett likes to say that there are three treatments for HACE: descent, descent, and descent. The need for descent is of utmost urgency. Immediate descent should be made to the last elevation that the patient awoke symptom-free. If uncertain at what altitude the patient developed symptoms, I would suggest descent to at least the altitude of two nights before - remember that it is almost certain that s/he had symptoms of AMS the day before developing HACE. Untreated HACE can result in death in hours, though some patients have had recorded survival after days in a coma at altitude. HACE frequently occurs at night; the moment it is recognized is the moment to start organizing flashlights, guides, porters, etc. for the descent. Speed is of the essence, delay may take a slightly confused, slightly ataxic patient to a condition of being comatose or unable to walk at all. DO NOT DELAY DESCENT - Trekkers have died in Namche Bazaar (3440 m, 11,300 ft) with HACE, waiting for a helicopter.

Unfortunately descent is not always possible, due to weather, terrain or patient condition. The following treatment options may be used in conjunction with descent, if descent is impossible or will be delayed, or to improve a patient to the point where s/he can more easily be evacuated.

Dexamethasone 8 mg IM STAT then 4 mg IM/po q 6 hours.
Hyperbaric Treatment
Simulated descent in a portable hyperbaric chamber can produce dramatic improvements. Patients are treated in one hour segments, removing them from the bag and reevaluating at the end of each hour. Studies have shown 4-6 hours total treatment to be optimal for HACE.
Oxygen, if available, can be lifesaving and should be used at 4 l/m for 4-6 hours.

I use dexamethasone plus the Gamow® Bag (a portable fabric hyperbaric chamber) for patients with HACE, and have had good results with this combination.

As in AMS, patients may reascend if they fully recover. Unfortunately, although mental status changes usually resolve fairly quickly (in hours with dexamethasone+hyperbaric treatment, overnight with descent), it is common for some ataxia to persist for days or weeks. In this case, reascent would clearly be inadvisable. Recovery is usually complete. It is extremely rare for patients with HACE to experience persistent neurologic deficits, though this has been reported.

High Altitude Pulmonary Edema (HAPE)

The pathophysiology is completely different from AMS/HACE; it is thought to be due to patchy hypoxic vasoconstriction in the pulmonary vascular bed, shunting blood flow through a limited number of vessels, resulting in a high pressure vascular leak. Pulmonary hypertension is universally present.

According to the Lake Louise Consensus, in the context of a recent ascent, patients with HAPE will have some combination of the following:

Symptoms - At least two of the following:
dyspnea at rest
weakness or decreased exercise performance
chest tightness or congestion

Signs - At least two of the following:
crackles or wheezing in at least one lung field
central cyanosis

Diagnosis has been revolutionized by the advent of relatively inexpensive hand-held pulse oximeters: Sa02 will be inappropriately low. "Normal" is clearly going to be altitude-dependant. For example, Sa02 is 80-86% in healthy individuals at 4200 m; values as low as 75% may occur in asymptomatic non-acclimatized individuals. Values significantly below this at elevations below 5500 m are usually diagnostic of HAPE. Sa02s of 50-60% are common in HAPE at this elevation, and I have seen saturations in the low 30s.

Patients with evolving HAPE may have normal saturations at rest. Always try to provoke desaturation in patients suspected of having HAPE, but who have a normal Sa02, with a simple exercise test: have them walk about 100 m on level ground, at a reasonable pace (enough to get out of breath). Persons with simple fatigue or High Altitude Bronchitis will not desaturate.

Patients will often be breathless, with rattling/gurgling respirations; they may be coughing up white or pink foamy sputum; they are frequently unable to lie flat. Crackles are heard first in the right middle lobe, but may be absent in up to 30% of cases of HAPE. Note that crackles may be present in up to 30% of cases of simple AMS, so they are not diagnostic. The onset of HAPE is frequently at night. Fever is common, and resolves with treatment. In part because of the fever, there have been many deaths due to HAPE being misdiagnosed and mistreated as pneumonia.

AMS/HACE may be present also, but otherwise the prodrome may be very subtle: fatigue out of proportion to exertion, dyspnea on exertion progressing to dyspnea at rest, a nonproductive cough. Someone who takes six hours to walk what takes everyone else two hours is likely to be in trouble, especially if they've been able to keep up previously. Severe fatigue or exercise intolerance is nearly universally present, and may be the most reliable hallmark of HAPE.

In my experience, the most frequent combination of diagnostic signs and symptoms is cough and fatigue plus either pulmonary crackles and desaturation or tachycardia and desaturation. Dyspnea and tachypnea are both surprisingly uncommon.
 Chest Xray
1 - Mild
Dyspnea on exertion
dry cough
fatigue while moving uphill
HR (rest) < 90-100
RR (rest) <20
dusky nailbeds or
exertional desaturation
localized crackles,if any
Minor exudate involving less than 25% of one lung field
2 - Moderate
Dyspnea at rest
fatigue on level walking
raspy cough
HR 90-110
RR 16-30
cyanotic nail beds
crackles present
Some infiltrate involving 50% of one lung or smaller area of both lungs
3 - Severe
Dyspnea at rest
extreme weakness
productive cough
HR > 110
RR > 30
facial & nailbed cyanosis
Bilateral crackles
blood-tinged sputum
Bilateral infiltrates > 50% of each lung

HAPE Treatment Protocols

As in HACE, the preferred treatment is descent, descent, descent. These patients may need to be carried, simply because they won't have the energy to walk, and exertion raises pulmonary artery pressure (PAP), worsening the illness. DESCENT IS URGENT, as HAPE may deteriorate quickly and death can occur in a few hours. Cold also increases PAP and it is imperative to keep HAPE patients as warm as possible.

Despite prompt and proper treatment, some HAPE victims will still die from the illness; this has been estimated at 10-15%, but in my experience is probably not that high.

Nifedipine 10 mg chew + 10 mg swallow stat, then either 10 mg po q 4 hours or an equivalent time-release dose. If the patient is comatose, pierce the nifedipine capsule and squirt the liquid into their mouth.

Nifedipine is thought to work by pulmonary vasodilation, resolving the pulmonary hypertension responsible for the high pressure leak in the lungs. Oxygen saturations generally improve modestly after administration of nifedipine. Some authors advocate nifedipine alone for HAPE, but I have had poor success with this in other than mild cases, and usually use this as an adjunct to descent or hyperbaric treatment.

Despite the potential risk of hypotension, after treating many cases of HAPE I have not seen this. HAPE patients seem to be universally slightly hypertensive, and tolerate the sublingual nifedipine quite well.

Hyperbaric Treatment
Simulated descent in a hyperbaric bag can produce dramatic improvements. Treat patients in one hour segments, removing them from the bag and re-evaluating at the end of each hour. Studies have shown 2-4 hours total treatment to be optimal for HAPE (Taber 1990). You may need to arrange for some way to tilt the bag if the patient is unable to tolerate lying flat, but generally once the bag is inflated patients find breathing so much easier that they tolerate being supine.

Oxygen, if available, is lifesaving and should be used at 4 l/m for 4-6 hours, or as needed to keep SaO2 at 99-100%.

Bedrest & Oxygen
This is an acceptable alternative to descent in the patient with mild HAPE. Strict bedrest is important, as any exertion (even walking) can worsen the illness.

In the 1960's, Singh et al. had good success using furosemide 80 mg q 12 hr to treat HAPE, but there have been no further studies to replicate their work.

HAPE Prophylaxis

Certainly the most important method is a slow ascent, however, climbers or trekkers with a history of recurrent episodes of HAPE may wish to consider prophylaxis. Nifedipine 20 mg slow release po q 8 hrs has been shown to be effective at preventing HAPE in these individuals (Bärtsch 1991). These persons should always carry nifedipine when at altitude, and be instructed on its use with the first signs of HAPE.

Approach to the Comatose Patient

It is not uncommon in the Himalaya to be consulted on a trekker who is found in the morning in a comatose state. Clearly the history will be limited to the ascent profile and second-hand information on whether the patient appeared ill the day prior. Evaluate respiratory status, measure arterial oxygen saturation with a pulse oximeter, and perform a quick neurological exam for any obvious focal deficits.

It may be clear whether or not the patient has HAPE, but often HACE cannot be ruled out as a cause of the coma. HACE is commonly seen with severe HAPE, presumably due to the severely decreased PaO2 (equivalent to an ascent to a much higher altitude). The patient is treated for both HACE and HAPE as follows: Dexamethasone 8 mg IM, nifedipine 10-20 mg sublingual, oxygen at 4 l/m, and hyperbaric treatment for 1 hour. Usually, at the end of this hour the patient is alert and a more thorough history and exam are obtained. Further treatment is then carried out according to the protocols previously described. Consider non-altitude causes of coma in patients with focal neurologic deficits, or who don't get better with the above treatment. Stroke is uncommon but can occur in persons who seem to have little in the way of risk factors. Clinically unsuspected brain tumors may also present at altitude with neurological signs.



Prevention is the key to avoiding frostbite. Here are some important reminders:

- Stay well hydrated and well fed to enable your body to generate heat!

- Avoid alcohol, which can impair your sensation (and judgment!)

- Avoid smoking, which will constrict your blood flow

- Don’t climb/trek under extreme weather conditions (wind, very cold)

- Avoid tight fitted clothing, no wrinkles in the socks

- If your clothing/socks/gloves get wet from snow/rain or perspiration, DRY them quickly – including boot insoles

- Wear mittens rather than gloves in extreme cold and a liner glove underneath if you need quick temporary access to fingers (e.g. photography)

- Never ignore numbness – as an old professor once told me – “if you feel your fingers and toes getting numb and you ignore it, that numbness might be the last thing you ever feel!” Numbness is a sign that you may be getting into trouble. If it doesn’t resolve by increasing activity, you need to get somewhere to take off your gloves/boots and rewarm yourself.

- Avoid rubbing frostbitten areas – beating on them only increases the chance of injury and doesn’t help them rewarm faster.

- IF you or your buddy has frostbite, get somewhere warm, but only rewarm the injured area if there is no chance it will refreeze

– keep the area padded and protected against further heat loss. The quickest way to rewarm is to submerge in warm water (~104F, or the warmth of a hot tub, test the water first with a thermometer or an uninjured body part – a frozen hand can’t determine if the water is too hot!)


Hypothermia can kill in mere minutes. Cold temperature, but also strong wind causes the body to rapidly lose heat. You start to shiver in order to maintain body heat from the rapid muscular shaking. If your body temperature drops to 35C/95F, you may get dizzy and disoriented, then the shivering stops. The body now maintains temperature only around the important organs; heart, brain and lungs and shuts down blood circulation to the arms and legs. Your pulse becomes weak and slow. Your blood vessels widen. Now, you feel hot and want to remove your clothes, finally slipping into unconsciousness. Eventually, your heartbeat stops.

Full blown Hypothermia will not be improved by additional clothing since clothing doesn’t generate heat. In difficult climbing situations, you need to put hot water bottles in your armpits, to your crotch and/or stomach – or you can strip and get into a sleeping bag - together with another undressed person, to warm up by the others body heat (yeah, yeah - keep your dirty imagination to yourself!).

Otherwise - keep moving until at safety. In 1998, a climber died of hypothermia on the North Side. All that was found left of him was his clothing neatly folded below the summit. This is quite typical of the condition. Confused, the brain tries to bring some order in the situation, thus folding the clothes.

Again, prevention is key! Here are some tips:

- Stay well nourished to help your body produce heat and shiver effectively when needed.
- Stay well hydrated and well rested.
- Change wet inner garments promptly
- INSULATE! (head and neck are key!) – great materials include Gore-Tex, Thinsulate, Flectalon

- Follow the C-O-L-D clothing principle:

- Clean
- Open – when exercising to reduce sweating/wetness
- Loose/Layers – to retain heat
- Dry – to limit conductive heat loss 

Eye concerns at altitude

The following is edited from “The Eye in the Wilderness” in Wilderness Medicine (Auerbach, ed Mosby publ)  by Capt Frank Butler, Jr. MD

High-Altitude Retinal Hemorrhage
There are many reports of retinal hemorrhages in mountain climbers. These have been described as high-altitude retinal hemorrhages (HARH) or as part of the more inclusive term altitude retinopathy. Some researchers have reported an incidence of HARH of 29% in climbers on a Mt. Everest expedition at altitudes ranging from 5300 to 8200 m (17,385 to 26,896 feet,) and others found that 56% of their subjects had HARH at an altitude of 5360 m (17,581 feet.) HARH has been discovered in 4% of 140 trekkers examined at 4243 m (13,917 feet) at Pheriche in the Himalayas. Scientists have also found a significant correlation of retinal hemorrhages with symptoms of acute mountain sickness (AMS). Differences in incidence of HARH for exposures at similar altitudes may be due to differences in time at altitude before examination, acclimatization schedule, exercise levels, examination techniques, and the presence of concurrent conditions that may predispose to HARH.

Although HARHs are often not associated with acute visual symptoms, they may result in a loss of visual acuity or paracentral scotomas. There is a reported case in which further ascent after the development of HARH resulted in additional lesions. HARH that results in decreased visual acuity should be a contraindication to further ascent. Some experts recommend that evacuation of individuals with decreases in visual function resulting from HARH (in the absence of high-altitude cerebral edema [HACE] or high-altitude pulmonary edema [HAPE] ) be considered nonemergent unless reexamination indicates a progressive deterioration of vision or increasingly severe retinopathy. HARH resolves over a period of 2 to 8 weeks after the altitude exposure is terminated. Recognizing advancing grades of HARH may allow physicians to recommend initiating treatment with oxygen, steroids, diuretics, and immediate descent to prevent HAR progression, macular involvement, or potentially fatal HACE. High altitude retinopathy is both a significant component of and a predictor of progressive altitude illness.

Contact Lenses in Mountaineering
Contact lenses may be used successfully at high altitude, but use at altitude during trekking or mountaineering entails several considerations beyond those encountered in normal use. In general, overnight use of extended-wear contact lenses is not recommended because of the associated increased rate of microbial keratitis. Even soft contact lenses decrease the oxygen available to the cornea. Lid closure during sleep further accentuates corneal hypoxia. Removing contact lenses at night, however, presents logistical problems in the mountaineering setting. Practicing acceptable lens hygiene during an expedition is difficult. The mountaineer who leaves contact lenses in a case filled with liquid solution in the tent outside of his or her sleeping bag at night may awaken to find the solution and lenses frozen solid. Lastly, wearing contact lenses can make eyes more sensitive to glare.

Guidelines for military personnel using contact lenses in austere environments have been developed and apply to the expedition setting:
1. Disposable extended-wear lenses may be left in the eye for up to 1 week. If the wearer is still in the field at the end of this period, the lenses should be removed and discarded. After an overnight period without lenses, new lenses may be inserted, with strict attention to contact lens hygiene.
2. Contact lens wearers should always have backup glasses available for use in the wilderness in case a lens is lost or becomes painful.
3. Individuals who wear contact lenses on expeditions should carry both fluoroquinolone eye drops and contact lens rewetting solution. Both types of drops may freeze if not protected from the cold.
4. Contact lens wearers often note that their eyes become dry. This discomfort may be alleviated with contact lens rewetting drops.
5. Contact lens wearers often note increased sensitivity to sunlight. Individuals who wear contact lenses in the field during daylight hours should carry sunglasses.

Continuous wearing of disposable contact lenses for a week, followed by discarding of the lenses and insertion of fresh lenses after an overnight period without a lens, is a controversial approach to contact lens wear in an expedition setting. Whether or not the reduction in lens handling offsets the increased risk of microbial keratitis resulting from overnight wear is not known. The decision to wear contact lenses while mountaineering should be made carefully in consultation with a personal ophthalmologist or optometrist. Microbial keratitis (corneal ulcers) can pose a significant threat to vision under the best of circumstances. Should this disorder occur with a 7- to 10-day delay to definitive ophthalmologic care, the danger of permanent loss of vision is great. Any eye pain that occurs in contacts lens wearers in the wilderness should be attended to urgently. Contact lenses that block out harmful UV rays are now available (Accuvue, Precision UV), but sunglasses are still a good idea both to help protect the eyes from drying wind effects and the eyelids from UV exposure even if contacts are worn. Considering all the potential problems, a good pair of prescription glacier glasses or laser refractive surgery might be a more reasonable alternative than contact lenses as a long-term solution to the refractive needs of mountaineers.

Refractive Changes at Altitude after Refractive Surgery
An acute hyperopic shift in persons who have had radial keratotomy (RK) and then experience an altitude exposure has been reported in past years, and has been observed at altitudes as low as 2744 m (9000 feet). A dramatic example of this phenomenon was that experienced by Dr. Beck Weathers in the Everest tragedy of May 1996 in which eight climbers also lost their lives. Dr. Weathers had undergone bilateral RK years before the expedition. He noted a decrease in vision, which started early during his ascent. Author Jon Krakauer recalls that “. . . as he was ascending from Camp Three to Camp Four, Beck later confessed to me, ‘my vision had gotten so bad that I couldn’t see more than a few feet.“ This decrease in vision forced Dr. Weathers to abandon his quest for the summit shortly after leaving Camp Four and nearly resulted in his death. Another report describes two expert climbers who experienced hyperopic shifts of three diopters or more during altitude exposures of 5000 m (16,400 feet) or higher on Mt. McKinley and Mt. Everest. One report noted no refractive change after 6 hours in post-RK eyes at a simulated altitude of 3659 m, suggesting that the hyperopic shift requires more than 6 hours to develop. Further studies at 4299 m (14,100 feet) on Pike’s Peak revealed that: (1) subjects who had undergone RK demonstrated a progressive hyperopic shift associated with flattened keratometry findings during a 72-hour exposure; (2) control eyes and eyes that had undergone laser refractive surgery (photorefractive keratectomy [PRK]) experienced no change in their refractive state; (3) peripheral corneal thickening was seen on pachymetry in all three groups; and (4) refraction, keratometry, and pachymetry all returned to baseline after return to sea level. There is strong evidence that the effect of altitude exposures on post-RK eyes is caused by hypoxia rather than by hypobarism and that breathing a normoxic inspired gas mix will not protect against the development of hypoxic corneal changes.

There is compelling evidence for myopic mountaineers that PRK instead of RK is their refractive surgical procedure of choice. Individuals who have undergone RK and plan to undertake an altitude exposure of 2744 m (9000 feet) or higher while mountaineering should bring multiple spectacles with increasing plus lens power.

The most commonly performed laser refractive surgery at present is laser in-situ keratomileusis (LASIK). Several studies observed climbers having undergone LASIK and the authors’ conclusion was that LASIK may be a good choice for individuals involved in high altitude activities, but those achieving extreme altitudes of 7927 m (26,000 ft) and above should be aware of possible fluctuation of vision. Data suggest that a small refractive shift in the myopic direction may be present at extreme altitudes. Climbers who do not ascend beyond moderate altitudes should not experience a post-LASIK refractive shift.


Snow blindness

Snow blindness, or solar/ultraviolet keratitis is an excruciatingly painful state that comes from the sun burning the covering of your eye -- the cornea. And it happens, very commonly if you don’t wear sunglasses, or if you don’t wear appropriate sunglasses in any bright light situation – especially easy to encounter at altitude.

A sunny day on fresh snow can be beautiful, but incapacitating if you’re not protected. Keep in mind that the brightness can exceed 10-15 times the amount of light that is safe and comfortable for your eyes to accommodate.

Sometimes, when climbing on oxygen, the warm and moist breathing air will escape your oxygen mask upwards and sometimes clog up your goggles, especially upon climbing down. Your choice will then be to climb "blindfolded" or remove the glasses. You might choose to pull your glasses a bit out from your face, allowing the warm air to pass them. The suns rays will now be able to burn your eyes at the unprotected sides. An anti-fog lens cleaner may help in this situation.

If the weather is overcast you might be tempted to remove the glasses altogether. Yet the rays are just as harmful when cloudy, and the following morning you’ll be sorry. After 8 years of climbing it finally happened to us. It took only a short time without goggles at our summit descent (shooting film), we noticed nothing, and in the morning we were a mess.

Here are some guidelines to use when choosing a good trekking/mountaineering pair of sunglasses:

- 99-100% UV absorption
- Polycarbonate or CR-39 lens (lighter, more comfortable than glass)
- 5-10% visible light transmittance
- Large lenses that fit close to the face
- Wraparound or side shielded to prevent incidental light exposure

Diarrhea is the number one medical complaint of travelers in the first 2 weeks away from home. It is prevalent in countries with underdeveloped water purification and sanitation systems, and it attacks nearly everyone who visits the Khumbu for any amount of time. BUT it is preventable if you are careful and practice good hygiene.

When you're sliding into first and you feel a something burst

Bacterial infection is only one cause of diarrhea. Viruses, protozoa, certain medications, food intolerances, allergies are among the myriad other causes of this ailment. This important to remember, because there is no one pill that takes care of all of them. And if you indiscriminately take antibiotics (which only work on bacteria), you can actually make any of the other causes of diarrhea even worse by knocking out all of your body’s natural “good” bacteria. Diarrhea is a complicated problem, and if it persists for days or is associated with bleeding, fainting, severe dehydration, high fevers, severe pain, you should see a doctor for professional evaluation and treatment.

When you're sliding into second and you feel something beckon

Some people take prophylactic (preventative) medication to prevent diarrhea, but this may be a very risky practice. The potential side effects from some of these medications range from slightly annoying to deadly, not to mention the alteration of your natural bacterial flora and potential development of antibiotic resistance. You should make the decision to take prophylactic medications with your personal physician. I don’t advise it in most situations.

When you're sliding into third and you and you feel a little. . .

For climbers with diarrhea on Everest, higher camps provide even more hostile situations; stripping in the icefall or while roped at the Lhotse wall is inevitable at times, and memorable always. In 1997, a climber fell and was killed while doing his thing at C3. Always be carefully roped when leaving tent at C3, even for very short distances!

Diarrhea causes dehydration and disturbance of the mineral balance in your body. Drink plenty and add electrolyte supplement (ORS packets are widely available in Nepal.)

When you're sliding into home and you feel a burst of . . .

Since diarrhea is such a pain on Everest, sometimes you will have to take aids like Imodium to halt it. You should be careful with these aids though. If you have a bacterial infection, diarrhea is your body’s way of getting rid of the bad bacteria. Use Imodium or the equivalent only when you really have to.

Again, prevention is key:

- WASH YOUR HANDS after using the toilet and before eating.
- Treat your water with a good filter or by boiling or by using iodine – and don’t slip up!
- Avoid raw food. Boil first or wash and peel before eating.
- Avoid unpasteurized dairy products.
- Avoid drinking products with ice that is made from untreated water.

For more up to date information about treatment of diarrhea in Nepal, follow the link to diarrhea discussion on the CIVEC website, www.ciwec-clinic.com

Khumbu cough

The relative humidity at high altitude is extraordinarily low, and almost invariably irritates the respiratory tract. The result is the infamous “Khumbu cough”, which can be serious enough to cause a person to cough hard enough to break a rib.

The best way to prevent it is to wear a mask that heats and moisturizes the air you breathe. A balaclava worn especially at night may be helpful. Many climbers use masks that can be found in cross-country ski stores. These masks have a metallic net inserted in a lightweight plastic or cloth shell and were originally developed for the Finnish Olympic ski team.

Carbon Monoxide poisoning

Carbon monoxide (CO) poisoning within tents and snow caves is a real and probably overlooked problem. It is potentially an even greater problem at altitude because of the multiplicity of risk factors for CO toxicity. Despite multiple anecdotal reports of climbers perishing from CO poisoning on Himalayan peaks circulating in climbing circles, the danger does not appear to be widely recognized.

Diagnosing CO poisoning in the early stages may be difficult because of the nonspecific nature of symptoms and (at altitude) their similarity to AMS. The masking of symptoms when subjects are sedentary exacerbates the problem, and these are likely to be the occasions when individuals are subjected to the highest CO levels, such as resting and cooking in tents for hours during inclement weather. All attempts must be made to prevent CO concentration from reaching dangerous levels; safety can be enhanced by the use of small portable CO detectors.

Summary of risk factors (and proposed precautions) for carbon monoxide poisoning in tents:

-- Cooking (Avoid prolonged simmering, keep stove highly pressurized, use white pure fuels, use small diameter pans, use maximal blue flame and avoid low flames)

-- Yellow flame (Turn stove off, repressurize, relight, maximize tent ventilation for a few minutes)

-- Inadequate tent ventilation (Ventilation area at least 50cm2, CO egress port as high as possible, O2 ingress port as low as possible, higher risk in zero wind conditions)

-- Insidious onset of symptoms if sedentary (beware headache and fast heart rate, make regular trips outside to unmask symptoms, ventilate tent at regular intervals, ventilation does not have to be continuous)

-- Dehydration (stay well hydrated)

-- Snow holes tend to be worse than tents (beware of all of the above)

-- Hyperventilation (more exposure to CO)

-- High altitude

-- Tent icing and snow cover (makes tent less porous -- keep cleaned to allow air flow)


This is a very common complaint at altitude. I have found that visitors to the Khumbu end up drinking much more tea than they usually do at home. The usual tea brewed in this area is black tea that contains lots of tannin, which is abrasive and irritating to the stomach.

I encourage you to drink herbal tea (which also eliminates the diuretic effects of caffeine) – many of my patients have had complete resolution of their heartburn when they gave up drinking so much of the local tea. Antacids may be helpful, and many find relieve with OTC ranitidine...


Although there are a variety of altitude hazards to your health and many ways to prevent and cure - especially by knowledge and good commonsense - there is one single important health tip that can help you avoid all sorts of health problems…..it can completely alter your performance in trekking/climbing as well as your ability to acclimatize and deal with altitude. It is very simple yet crucial – it is the drinking of water.

Simple as that. Drink. Drink, Drink! Staying hydrated equips you to acclimatize, exercise better, fight off hypothermia and frostbite, constipation, diarrhea….so plan to drink a minimum of 3 liters per day at rest, add more as needed for exertion and other losses (eg if you are working hard and sweating you may need up to 8 liters, or if you are ill with vomiting or diarrhea and losing lots of fluids, you will need to replace those losses too.) One or two hours before trekking/climbing, try to drink 1-2 liters to “fill your tank” -- some find that they continue to drink more while active if they use an easily accessible hydration hose system (an example of a commercial system – Camelback – these prevent the hassle of reaching for a bottle – the hose is right next to your mouth!)

The best way to check that you are well hydrated is to check your urine. You need to drink until it’s clear and straw colored. Deep yellow/amber urine color usually means you are concentrating and need more water. If you aren’t waking up at least once at night to urinate at altitude, you probably aren’t drinking enough.

Finally - remember that coffee, tea and chocolate contain caffeine, which is a diuretic and won’t do the work well. Count in only 50% liquid value with these.

Sleeping Pills

Almost everyone has trouble sleeping at high altitude (see the section on altitude acclimatization for further explanation.) Most sleeping pills, however, can be dangerous and actually predispose you to altitude sickness.

If you’re acclimatizing, acetazolamide can help a lot with the periodic breathing that disturbs sleep. Melatonin is an OTC sleep aid that helps many and has no contraindications at altitude. One prescription sleep aid that has shown NOT to disturb breathing at sleep is zoldipem; you may want to discuss taking this medication with your personal physician. Any other hypnotics/tranquilizers should probably not be used at altitude.

What's in a Good Medical Kit?

You need to plan ahead to organize your personal medical equipment for a rigorous high altitude expedition – whether you’re climbing or trekking, dedicate some forethought to researching the local risks, potential disease exposures, and typical injuries you may encounter. No matter how much equipment you decide to bring, you cannot possibly prepare for every eventuality.

So, what should you take? Minimalists might say, "nothing but a triangular bandage and Swiss army knife," and others might assemble a collection that would stagger a porter. Remember, overly bulky kits are often left behind.

The contents of a kit depend on many on many factors:

- Environmental extremes
- Endemic diseases (i.e. rabies, malaria, etc)
- Your medical expertise
- Length of trip
- Availability of rescue (i.e. helicopter)
- Distance from definitive medical care

Make sure that your vaccinations are up to date several months before travel. Visit your doctor or local health department for advice, but also do the homework on your own – access the CDC website for up to date information on recommended vaccinations for your destination. - www.cdc.gov

Personal Medical Kits

Each expedition member should carry his/her own personal kit; consider including these basic (but VERY IMPORTANT!) items:

- Non-narcotic pain relievers (acetaminophen or paracetamol, ibuprofen)
- Anti-inflammatories (ibuprofen)
- Throat lozenges
- Sunscreen and lip protection
- Minor wound care supplies:

- betadine or iodine type disinfectant solution
- bandaids
- moleskin or favorite blister remedy
- tape
- nonstick bandages
- antibiotic ointment

- Insect repellent if you travel through warmer climates en route
- Malaria prophylaxis prescription medications (if risk exists during your travel to altitude)
- Anti-diarrheal medication (loperamide is good)
- Antacids
- Anti-oxidant vitamins
- ORS (oral rehydration solution) – available in small packets to be reconstituted with water, provides electrolytes for replacing losses from vomiting/diarrhea
- Personal medications (for pre-existing problems)
- For women, supplies for menstrual flow

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