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.
Altitude - Related Illnesses
Acute Mountain Sickness (AMS)
High Altitude Pulmonary Edema (HAPE)
High Altitude Cerebral Edema (HACE)
High Altitude Retinopathy
High Altitude Peripheral Edema
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")
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
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
Wall mounted oxygen in hotel in Lhasa, Tibet (altitude 13,000
feet)
Relationships of the Different
Forms of Altitude Illness
Altitude illness may be an interrelated spectrum :
AMS
HAPE
HACE
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)
Barometric pressure versus altitude
Arterial Blood Gas Values in Normal
Adults at Different Altitudes
Altitude
PaO2
O2 Saturation
PaCO2
(per cent)
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)
Relative hypoventilation
Sleep disordered breathing
s
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
Acute Mountain Sickness :
Symptoms
Headache
Nausea
Anorexia
Lassitude
"Like a hangover"
Insomnia
Decreased urination
Onset typically 8 to 24 hours after ascent
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)
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
Physiologic adaptation to altitude
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
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
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
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
High Altitude Pulmonary Edema in Longterm 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"
Abrupt ascent
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"
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
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
High Altitude Cerebral Edema :
Symptoms
Severe headache
Confusion
Agitation / irritability
Nausea / emesis
Ataxia
Hallucinations
 Seizures
Coma
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
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)
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
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)
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)
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
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
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
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")
Snow Blindness Symptoms & Signs
Eye pain
Gritty sensation of eyes
Light sensitivity
Tearing
Conjunctival injection
Chemosis
Eyelid swelling
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
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
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
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
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
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