ALTITUDE ILLNESS

1. ALTITUDE ILLNESS • Setting • Acclimatization • Common Disorders • Emergency Care • Other Aspects Myron B. Allen Medicine Bow Nordic Ski Patrol allen@uwyo.edu

2. 1. SETTING The high mountain environment: • Cold: temperature drops 3.5 F / 1000 ft. • Dry: cold air holds less water vapor. • Rugged: • Increased sweating & ventilation. • Increased energy consumption. • Oxygen-poor: • Pressure (and PO2) drops 3.8% / 1000 ft. • O2 concentration stays constant, 21%.

3. Who’s vulnerable? 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.

4. 2. ACCLIMATIZATION Normal physiologic changes that start immediately and take 6 or more weeks to stabilize.

5. Increased heart rate • Increased hypoxic drive: faster, deeper breathing • Altitude diuresis (near-term increase in red blood cell concentration) • Long-term increase in red blood cell count (and blood viscosity) • Increased pulmonary artery pressure (opens capillaries in lungs) • Increases in blood O2 capacity, number of capillaries, size of mitochondria • Decreased aerobic performance

6. Other effects: • Periodic (Cheyne-Stokes) breathing at night • Poor sleep • Increased blood alkalinity (blowing off CO2) • Edema (leakage increases red blood cell concentration)

7. Adverse feedback loops: • Blood alkalinity suppresses hypoxic drive. • Taking sleeping pills or alcohol suppresses hypoxic drive • Edema can interfere with lung & brain function. • Diuresis can lead to dehydration. • Thick blood clots more easily (→ aspirin therapy?)

8. Techniques that promote acclimatization: • 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. • A person who’s not feeling well shouldn’t raise sleeping altitude at all. • Hydrate!

9. 3. COMMON DISORDERS All result from the effects of hypoxia & failure to acclimatize • Effects of mountain environment: • Hypothermia (& cold diuresis) • Rapid dehydration. • Metabolic stress • Chronic hypoxia • Edema • fills alveoli • irritates intracranial tissues • interferes with brain function Buckskin Mtn, CO

10. 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?

11. 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.

12. 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.

13. 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

14. HAPE and HACE are deadly within hours or minutes!

15. Diagnostics for immediate descent & evacuation: • Persistent ataxia • Cognitive deficits • Respiratory distress • Cyanosis • Persistent nausea & vomiting Do it while the patient can still help.

16. Summary • Mild AMS: Go no higher until symptoms resolve. • 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.

17. 5. OTHER ASPECTS Disorders with signs and symptoms similar to AMS • 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)

18. Drugs the patient may be taking • Acetazolamide (Diamox): sulfa drug, improves hypoxic drive. (It’s a diuretic & promotes excretion of bicarbonate to restore blood pH.) Promotes acclimatization. • Nifedipine (Procardia): prevents & treats HAPE by dilating pulmonary arteries. Lowers blood pressure & does not promote acclimatization. • Dexamethasone (Decadron): a steroid used to treat HACE. Does not help acclimatization. • Bronchodilators (Salmeterol and Albuterol): some evidence that they help alleviate HAPE.

19. QUESTIONS? “An Altitude Tutorial, ” International Society for Mountain Medicine, http://www.ismmed.org/np_altitude_tutorial.htm, accessed 18 July 2009