1. Altitude - Related Illnesses
Jim Holliman, M.D., F.A.C.E.P.
Professor of Military and Emergency Medicine
Uniformed Services University of the Health Sciences
Clinical Professor of Emergency Medicine
George Washington University
Bethesda, Maryland, U.S.A.

2. Altitude - Related Illnesses
Acute Mountain Sickness (AMS)
High Altitude Pulmonary Edema (HAPE)
High Altitude Cerebral Edema (HACE)
High Altitude Retinopathy
High Altitude Peripheral Edema

3. Acute Mountain Sickness : Incidence
Sudden ascent > 10,000 feet (3000 meters) : 30 %
Sudden ascent > 14,000 feet : 75 %
Report from Colorado ski resort : 12 %
Can occur in those with no prior problems with altitude exposure
Can recur (no consistent tolerance or "immunity")

4. Acute Mountain Sickness : Etiology
Typically occurs at altitude > 8000 feet
Rarely occurs at altitude 6000 to 8000 feet
No predeliction based on gender
More likely if :
Rapid ascent
Lack of acclimatization

5. Situations Predisposing to Possible Acute Mountain Sickness
Prolonged non-pressurized aircraft or balloon flight
Colorado or Utah ski resorts
Base altitude for most is about 8000 feet
Yellowstone National Park
base altitude 7000 to 7500 feet
Medellin and Bogota, Colombia
base altitude > 9000 feet

6. Wall mounted oxygen in hotel in Lhasa, Tibet (altitude 13,000 feet)

7. Relationships of the Different Forms of Altitude Illness
Altitude illness may be an interrelated spectrum :
AMS HAPE
HACE

8. Acute Mountain Sickness : Pathophysiology
Much individual variation in susceptibility
Basically due to hypobaric hypoxia of altitude
Also involves tendency for fluid retention (effect of antidiuretic hormone)

9. Barometric pressure versus altitude

10. Arterial Blood Gas Values in Normal Adults at Different Altitudes
PaO2
O2 Saturation
(per cent)
PaCO2
Sea Level
90 to 95 96 40
5000 feet
75 to 81 95
32 to 33
7500 feet
69 to 74
92 to 93
31 to 33
15,000 feet
48 to 53 86 25
20,000 feet
37 to 45 76 20
25,000 feet
32 to 39 68 13
29,029 feet *
26 to 33 58
9.5 to 13
* (the top of Mt. Everest)

11. Relative hypoventilation
Sleep disordered breathing s

12. Acute Mountain Sickness : Exacerbating Factors
Sudden ascent
Exertion soon after arrival
Alcohol intake
Sedatives (sleeping pills)
Narcotics
Note : youth and / or prior conditioning are NOT uniformly protective

13. Acute Mountain Sickness : Symptoms
Headache
Nausea
Anorexia
Lassitude
"Like a hangover"
Insomnia
Decreased urination
Onset typically 8 to 24 hours after ascent

14. Acute Mountain Sickness : Differential Diagnosis
Dehydration
Hypothermia
Exhaustion
Respiratory infection
Hyperventilation syndrome
Psychiatric disorders
Drug intoxication
Carbon monoxide poisoning (as from tent heaters or stoves)

15. Acute Mountain Sickness : Prophylaxis
Acclimatization
Staging of ascent
Delaying exertion
Medication choices :
Acetazolamide (Diamox) 250 mg PO bid or tid
Dexamethasone (Decadron) 4 mg PO tid or qid
Should start either med 24 hours prior to ascent

16. Physiologic adaptation to altitude

18. Acute Mountain Sickness : Treatment of the Established Syndrome
Usually resolves in 1 to 3 days even without Rx or descent
Sx will improve however with descent
If severe Sx, start acetazolamide 250 mg PO bid or tid, or dexamethasone 4 mg PO tid to qid
Resting is the most important treatment

19. Progression of Acute Mountain Sickness
If ascent is continued or accelerated by a patient with untreated AMS, HAPE or HACE may occur and death may result

20. High Altitude Pulmonary Edema (HAPE)
Is a non-cardiogenic pulmonary edema related to altitudinal hypoxia
Can be fatal if patient is unable to descend
Occurs in 1 to 2 % of patients quickly ascending to > 12,000 feet
Can occur even in well fit and acclimatized individuals

21. High Altitude Pulmonary Edema : Onset
Usually begins 24 to 72 hours after arrival at altitude
Can occur, but uncommon, at altitude 8000 to 12,000 feet
Onset usually at night

22. High Altitude Pulmonary Edema in Long-term Mountain Residents
H.A.P.E. has been reported in patients acclimatized to high altitude who went to low altitude for > 10 days, & then returned to high altitude
Termed "reentry pulmonary edema"

23. Abrupt ascent

24. High Altitude Pulmonary Edema : Symptoms
Usual sequence :
Cough dyspnea at rest achy chest pain progressive cough progressive rales frothy sputum hemoptysis frank respiratory failure
Chest X-ray appearance is variable :
Patchy infiltrates (often right > left)
If severe, may be bilateral "whiteout"

25. High Altitude Pulmonary Edema : Treatment
Most important : Rapid descent : at least 2000 feet
High flow O2 ; CPAP mask if available
Have patient avoid exertion on descent (other people should carry him / her)
Can give acetazolamide or dexamethasone but these do not help much or obviate the need for descent
Can try bag pressure chamber if available but still need descent

26. High Altitude Cerebral Edema (HACE)
Less common than HAPE
Possibly a malignant form of AMS
Can be fatal or result in permanent neurologic disability (stroke-like syndromes)
Onset is gradual : usually over 2 to 3 days

27. High Altitude Cerebral Edema : Symptoms
Severe headache
Confusion
Agitation / irritability
Nausea / emesis
Ataxia
Hallucinations
Seizures
Coma

28. High Altitude Cerebral Edema : Field Treatment
ONLY effective treatment is descent : at least 3000 feet
Rx adjuncts :
High flow O2 / hyperventilation
Dexamethasone / acetazolamide
Furosemide / mannitol
Benzodiazepines / diphenylhydantoin if seizures occur
Avoid exertion during descent
Hyperbaric bag if available

29. In-Hospital Treatment of Suspected HAPE or HACE
Airway / breathing / circulation
High flow oxygen +/- intubation & hyperventilation
Chest X-ray
IV dexamethasone & acetazolamide
Check ABG & carboxyhemoglobin
Consider tox & drug screen
Head CT if abnormal mental status
Admit to ICU
Consider hyperbaric O2 Rx (call nearest chamber)

30. High Altitude Retinal Hemorrhage
Incidence is 20 to 40 % above 14,000 feet
Usually does not affect vision (unless macular bleed)
Usually asymptomatic
Diabetics at higher risk
Usually no Rx or descent needed

33. High Altitude Peripheral Edema
Shows as edema of :
Face
Eyelids
Hands
Feet
Lower legs
No Rx usually needed (can use diuretic effect of acetazolamide if patient uncomfortable)

34. Miscellaneous Altitude Related Medical Problems
Tendency to venous thrombosis & pulmonary emboli (partly due to polycythemia of altitude exposure)
Immune suppression
probably related to tissue hypoxia
wounds slower to heal & more likely to get infected
wound infections can show antibiotic resistance
High Altitude Flatus Expulsion (HAFE)
Reference : Auerbach & Geehr, 1989, pg. 25
No serious sequelae noted to date
"Snow Blindness" (ultraviolet light exposure)

35. Preexisting Illnesses Aggravated by High Altitude
C.O.P.D.
Coronary artery disease
Peripheral vascular disease
Hypertension
Variable worsening in some patients
Sickle cell disease
Pregnancy
Preeclampsia, but not other complications of pregnancy, is more common at altitude

36. Skin Problems Related to High Altitude Exposure
Shorter time for sunburn to occur to exposed skin
Tendency to drying ; thereby more risk of chilblains or pernio
Slower wound healing & higher wound infection rate ; prevention of even minor skin injuries (especially friction blisters) is therefore important

37. Altitude Illnesses : Summary Best treatment is prevention :
Acclimatization / staging ascent
Avoiding alcohol & sedatives
Medication prophylaxis
If symptoms suggest HAPE or HACE :
start oxygen
arrange immediate assisted descent
definitive followup care in a medical facility after descent, even if symptoms abate

38. Ultraviolet Light Keratitis ("Snow Blindness")
UV radiation increases 4 % for every 300 meters increase in altitude
Cornea absorbs UVB (below 300 nm)
Lens cataracts can result from chronic exposure to UV radiation > 300 nm
High exposure levels can cause corneal burn in < 1 hour
Symptoms usually take 6 to 12 hours to develop (same as for "welders' arc keratitis")

39. Snow Blindness Symptoms & Signs
Eye pain
Gritty sensation of eyes
Light sensitivity
Tearing
Conjunctival injection
Chemosis
Eyelid swelling

40. Snow Blindness : Treatment Remove contact lenses
Topical anesthetic : single dose only
Tetracaine or proparacaine
Repetitive use may damage cornea
Ophthalmic antibiotic ointment
Erythromycin, gentamicin, or sulfacetamide
Eye patch for 12 to 24 hours
Most should heal in < 24 hours
May need oral narcotics for pain

41. Snow Blindness : Prevention
Should choose sunglass lenses that are rated to transmit < 10 % of UVB
Side shields or full goggles needed to prevent exposure from side bounce
Sunglasses should always be secured with a neck loop when mountain climbing
If sunglasses are lost, makeshift protective shields can be made by cutting thin slits in pieces of cardboard

42. Snow Avalanches : Medical Relevance
About 100,000 release annually in U.S.
About 100 of these cause injury, death, or major property damage
About 140 people in U.S. are caught each year
Reported average of 12 major injuries & 17 deaths annually
Persons at risk include skiers, snowmobilers, highway plow operators, and forest rangers & game wardens

44. Physical Characteristics of Avalanches
Typical velocities are 50 to 100 miles per hour
Can be as fast as 200 miles per hour
Can generate impact pressures > 150 lbs/square inch (can destroy even concrete structures)
Occur with greatest frequency on slopes of 30 to 45 degrees

45. Causes of Death from Avalanches
Direct impact trauma of snow blocks or ice
Indirect trauma of hitting against objects such as trees or rocks
Hypoxia from encasement in snow
Hypothermia
Restrictive chest compression

46. Prevention of Death or Injury from Avalanches
Have group spread out when approaching or crossing avalanche terrain
Have rescue poles, colored cords, & avalanche rescue beacons or transceivers ready
Always try to escape an avalanche to the side (not downhill away from the avalanche)
If caught & tumbled, keep your hands up near your face