Any unacclimatized traveler proceeding to a sleeping elevation of ≥8,000 ft (≈2,450 m)-and sometimes lower-is at risk for altitude illness. Children are as susceptible as adults people aged >50 years have slightly less risk. A traveler’s sex plays a minimal role, if any, in determining predisposition. Training or physical fitness do not affect risk. Susceptibility and resistance to altitude illness are, in part, genetically determined traits, but there are no simple screening tests to predict risk. These reasonable recommendations can still be too fast for some travelers and annoyingly slow for others. The Wilderness Medical Society recommends avoiding ascent to a sleeping elevation of ≥9,000 ft (≈2,750 m) in a single day ascending at a rate of no greater than 1,650 ft (≈500 m) per night in sleeping elevation once above 9,800 ft (≈3,000 m) and allowing an extra night to acclimatize for every 3,300 ft (≈1,000 m) of sleeping elevation gain. For example, acclimatizing for a minimum of 2–3 nights at 8,000–9,000 ft (≈2,450–≈2,750 m) before proceeding to a higher elevation is markedly protective against acute mountain sickness (AMS). Gradually ascending to elevation or staging the ascent provides crucial time for the body to adjust. Travelers can optimize acclimatization by adjusting their itineraries to avoid going “too high too fast” (see Box 4-08). In addition to preventing altitude illness, acclimatization improves sleep, increases comfort and sense of well-being, and improves submaximal endurance maximal exercise performance at high elevation will always be reduced compared to that at low elevation. Increased red cell production does not play a role in acute acclimatization, although a decrease in plasma volume over the first few days does increase hemoglobin concentration.Īltitude illness can develop before the acute acclimatization process is complete, but not afterwards. The acute phase is associated with a steady increase in ventilation, improved oxygenation, and changes in cerebral blood flow. Some acclimatization to high elevation continues for weeks to months, but the acute process, which occurs over the first 3–5 days following ascent, is crucial for travelers. The human body can adjust to moderate hypoxia at elevations ≤17,000 ft (≈5,200 m) but requires time to do so. Because of the key role of ventilation, travelers must avoid taking respiratory depressants at high elevations. Hypoxemia is greatest during sleep day trips to high-elevation destinations with an evening return to a lower elevation are much less stressful on the body. The magnitude and consequences of hypoxic stress depend on the elevation, rate of ascent, and duration of exposure host genetic factors may also contribute. At 10,000 ft (≈3,050 m), for example, the inspired PO2 is only 69% of that at sea level acute exposure to this reduced PO2 can lower arterial oxygen saturation to 88%–91%. The biggest concern, however, is hypoxia, due to the decreased partial pressure of oxygen (PO2). High-elevation environments expose travelers to cold, low humidity, increased ultraviolet radiation, and decreased air pressure, all of which can cause health problems.
Typical high-elevation travel destinations include Colorado ski resorts with lodgings at 8,000–10,000 ft (≈2,440–3,050 m) Cusco, Peru (11,000 ft ≈3,350 m) La Paz, Bolivia (12,000 ft ≈3,650 m) Lhasa, Tibet Autonomous Region (12,100 ft ≈3,700 m) Everest base camp, Nepal (17,700 ft ≈5,400 m) and Mount Kilimanjaro, Tanzania (19,341 ft ≈5,900 m). Preventing Severe Altitude Illness or Death.
Calling local 411 and/or national directory assistance (1.area code.555.Directory Assistance charges may appear on your bill when:.
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National Directory Assistance refers to a long distance directory assistance call placed to 1-AREA CODE-555-1212, where the area code dialed is not within your local calling area.Local Directory Assistance refers to a call placed to 411.Local Directory Assistance, National Directory Assistance and Call Completion charges vary by location. If the call is answered, you be charged for the call completion service and the directory assistance request.If the number is not answered or busy, you will only be billed for the directory assistance request.Call allowances not used within one billing period cannot be transferred to an additional billing period or to another account.ĭirectory Assistance Call Completion charges are as follows: Individuals with physical or visual disabilities and seniors may also be eligible for call allowances, depending on the state. Depending on your state, you may be eligible to receive a certain number of local directory assistance calls each month at no charge (“call allowances”).
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