Download High-Altitude Pulmonary Edema

ALTITUDE ILLNESS
1.
2.
3.
4.
5.
Setting
Acclimatization
Common Disorders
Emergency Care
Other Aspects
Myron B. Allen
Medicine Bow Nordic Ski Patrol
[email protected]
1. SETTING
The high mountain environment:
1. Cold: temperature drops 3.5 F / 1000 ft.
2. Dry: cold air holds less water vapor.
3. Rugged:
• Increased sweating & ventilation.
• Increased energy consumption.
4. Oxygen-poor:
• Pressure (and PO2) drops 3.8% / 1000 ft.
• O2 concentration stays constant, 21%.
Who’s vulnerable?
1.
2.
3.
4.
Visitors from sea level at altitudes > 7,000 ft
Most people at altitudes > 12,000 ft
People with compromised respiratory systems
Young people (anecdotal)
CAVEATS:
•
•
•
Aerobic fitness does not confer immunity
An individual’s response to altitude can
vary from one trip to another
People born at altitude can become
susceptible after a few weeks at sea level.
2. ACCLIMATIZATION
Normal physiologic changes that start
immediately and take 6 or more weeks to
stabilize.
1. Increased heart rate
2. Increased hypoxic drive: faster, deeper
breathing
3. Altitude diuresis (near-term increase in red
blood cell concentration)
4. Long-term increase in red blood cell count
(and blood viscosity)
5. Increased pulmonary artery pressure (opens
capillaries in lungs)
6. Increases in blood O2 capacity, number of
capillaries, size of mitochondria
7. Decreased aerobic performance
Other effects:
• Periodic (Cheyne-Stokes) breathing at night
• Poor sleep
• Increased blood alkalinity (blowing off CO2)
• Edema (leakage increases red blood cell
concentration)
Adverse feedback loops:
1. Blood alkalinity suppresses hypoxic drive.
2. Taking sleeping pills or alcohol suppresses
hypoxic drive
3. Edema can interfere with lung & brain function.
4. Diuresis can lead to dehydration.
5. Thick blood clots more easily (→ aspirin therapy?)
Techniques that promote acclimatization:
1.
2.
3.
4.
Sleep at < 8,000 ft before going above 10,000 ft.
Moderate exertion for first 2 days at altitude.
Climb high, sleep low.
Above 10,000 ft, raise sleeping elevation ≤ 1000
ft/day.
5. A person who’s not feeling well shouldn’t raise
sleeping altitude at all.
6. Hydrate!
3. COMMON DISORDERS
All result from the effects of hypoxia & failure to
acclimatize
Effects of mountain environment:
Buckskin Mtn, CO
• Hypothermia (& cold diuresis)
• Rapid dehydration.
• Metabolic stress
• Chronic hypoxia
• Edema
 fills alveoli
 irritates intracranial tissues
 interferes with brain function
Acute Mountain Sickness (AMS)
Signs & symptoms:
• Headache that responds to aspirin, etc.
• At least one of the following:
 Nausea or vomiting
 Loss of appetite
 Difficulty sleeping or Cheyne-Stokes breathing
 Fatigue
 Dizziness
Remember edema?
HAPE:
High-Altitude Pulmonary Edema
• Coughing, respiratory distress, rales
• Cyanosis
• Pink sputum
HACE:
High-Altitude Cerebral Edema
• Severe headache, despite analgesics
• Ataxia: failing the tandem gait test
• Confusion, stupor, coma
• Paralysis, blindness, convulsions
HAFE:
High-Altitude Flatus Expulsion
• Serious morale problem on extended trips.
• Epidemic among ski patrollers.
4. EMERGENCY CARE
Stable AMS:
•
•
•
•
•
Rest. Monitor closely. Often
resolves in a day or so.
Hydrate.
Aspirin, ibuprofen, acetamenophen,
naproxen may help patients who
tolerate them.
Don’t go higher until signs &
symptoms resolve.
If they get worse, descend below
last symptom-free altitude.
HAPE, HACE, or deteriorating AMS:
1. Descend immediately .*
• at least 2000 ft
• below last symptom-free altitude
• preferably below 10,000 ft
• Don’t wait until morning!
2. Give O2 if available, but don’t wait for it.
3. Drug therapy is no substitute for descent.
*Few places in the lower 48 are too
remote from AMS-free elevations
HAPE and HACE are deadly
within hours or minutes!
Diagnostics for immediate descent &
evacuation:
1.
2.
3.
4.
5.
Persistent ataxia
Cognitive deficits
Respiratory distress
Cyanosis
Persistent nausea &
vomiting
Do it while the patient
can still help.
1. Mild AMS: Go no higher
until symptoms resolve.
Summary
2. HAPE, HACE, or
deteriorating AMS: Descend
immediately.
3. Acclimatization and early
intervention are simple and
unheroic. But when the
problem becomes severe,
field treatment can be
difficult or impossible.
5. OTHER ASPECTS
Disorders with signs and symptoms similar to AMS
1.
2.
3.
4.
5.
6.
7.
Hangover (treat as for AMS)
Exhaustion (treat as for AMS)
Pneumonia (look for yellow sputum, fever)
Other infection (AMS rarely causes fever)
Asthma (try patient’s inhaler)
Hypoglycemia (ask about diabetes)
CO poisoning (patient history is critical)
Drugs the patient may be taking
1. Acetazolamide (Diamox): sulfa drug, improves
hypoxic drive. (It’s a diuretic & promotes excretion
of bicarbonate to restore blood pH.) Promotes
acclimatization.
2. Nifedipine (Procardia): prevents & treats HAPE
by dilating pulmonary arteries. Lowers blood
pressure & does not promote acclimatization.
3. Dexamethasone (Decadron): a steroid used to
treat HACE. Does not help acclimatization.
4. Bronchodilators (Salmeterol and Albuterol):
some evidence that they help alleviate HAPE.
QUESTIONS?
“An Altitude Tutorial, ” International Society for Mountain Medicine,
http://www.ismmed.org/np_altitude_tutorial.htm, accessed 18 July 2009