A number of popular tourist destinations in Costa Rica are at high enough elevations that Acute Mountain Sickness and Altitude Sickness are a concern.  Some are even high enough that potentially fatal High Altitude Pulmonary Edema and High Altitude Cerebral Edema are possible.

There’s no reason to panic if you notice that Volcán Irazú is on your tour itinerary and listed as a “Very High Altitude”.  People who are at elevation for short periods of time experience what are described as hangover-like symptoms and simply returning to lower elevation relieves them.  If you’re planning an extended trek in Chirripó National Park or a stay at one of the Biological Stations around Cerro de la Muerte you should probably educate yourself about altitude related illnesses.

High Elevation Tourist Destinations in Costa Rica

Very High Altitude (above ~3,500 meters—11,000 feet)

If you plan to visit (especially overnight) any of these locations altitude sickness is a likely explanation for a headache and flu-like symptoms, and life threatening edemas are possible (though unlikely).

• Cerro Chirripó—the highest point in Costa Rica and about 10% of climbers are likely to experience an altitude related illness. The refugio is above 10,000 feet and sleeping at altitude can increase the likelihood of symptoms.
• Volcán Irazú—at over 11,000 feet Volcán Irazú is the highest point in Costa Rica you can easily drive to and reaching a high elevation quickly is an important risk factor of altitude related illness.
• Cerro de la Muerte—with area trails and peaks over 11,000 feet and the highway around 10,000 the Cerro de la Muerte region is particularly problematic because you can drive to the top.  One major factors in the likelihood of altitude related illness is how quickly you change elevations.
• Volcán Turrialba—at 10,922 feet Turrialba isn’t technically “Very High Altitude”, but close enough that if you climb it you should be aware of the possibility of Acute Mountain Sickness and Altitude Sickness.

High Altitude (2,500 to 3,500 meters—8,000 to 11,000 feet)

Around one out of twenty people that travel from sea level to these elevations experience mild symptoms of altitude sickness.

• Volcán Poás—at 8,872 feet Poás is significantly lower than the other drive up volcano (Irazú) but it’s still not unusual to experience an altitude induced headache.
• Volcán Barva—under 10,000 feet so it’s unlikely that if you’re just hiking through altitude related illness probably won’t be a major issue, but if you stay in the backcountry camping area it becomes more likely.

Moderately High Altitude (1,500 to 2,500 meters—5,000 to 8,000 feet)

Unless you’re particularly susceptible, altitude is probably not a factor in your headache or hangover-like symptoms at these elevations.

• Braulio Carrillo National Park—on the Guápiles Highway between San José and the Caribbean Coast.
• Cartago—slightly below the moderately high altitude limit, but a good place to acclimate for a few days.
• Monteverde—most of the reserve is above 1,500 meters, but most of the lodging in the region is slightly below the moderately high altitude limit.
• Varablanca—on the road from Alajuela or Heredia to San Miguel.
• Zarcero—on the road from Naranjo (Pan American Highway) to San Carlos and La Fortuna Arenal.

Altitude Illness Symptoms

Normal physiologic responses in every person who goes to altitude.  These are not indicators of altitude related illnesses and are listed here so you don’t mistakenly think someone has an altitude illness.

• Hyperventilation (breathing faster, deeper, or both)
• Shortness of breath during exertion
• Changed breathing pattern at night
• Awakening frequently at night
• Increased urination

Symptoms of altitude related illnesses
These illnesses occur at high-altitude, even mild symptoms are unlikely below 2,500 meters (8,000 feet), and the more severe forms are uncommon below 3,000 meters.

Acute Mountain Sickness (AMS)

• Many sufferers say it feels like a severe hangover
• Headache—cause by a slight swelling of the brain in response to lower oxygen availability in the bloodstream.
• Loss of appetite, nausea, or vomiting
• Fatigue or weakness
• Dizziness or light-headedness
• Difficulty sleeping

High Altitude Cerebral Edema (HACE) is the extreme form of Acute Mountain Sickness and can be fatal in a matter of hours.  Any of the above symptoms in extreme forms or the addition of

• Loss of mental acuity—the inability to perform simple logical or math tasks.
• Loss of memory
• Loss of coordination—the person may appear drunk or the symptoms may be more subtle.  A simple test is to have the person walk a straight line.  If they do a balancing act or fall, HACE is a probability.

High Altitude Pulmonary Edema (HAPE) may occur without the classic symptoms of Acute Mountain Sickness.

• Usually occurs on the second night after an ascent, and is more frequent in young, fit climbers or trekkers.
• Extreme fatigue
• Breathlessness at rest
• Fast, shallow breathing
• Cough, possibly with frothy or pink sputum
• Gurgling or rattling breaths
• Chest tightness, fullness, or congestion
• Blue or gray lips or fingernails
• Drowsiness

Prevention and Treatment

The Golden Rules for safe exploration at high altitude

• If you feel unwell at high altitude it is altitude illness until proven otherwise.
• Never go any higher if you have symptoms of Acute Mountain Sickness.
• If you are getting worse go down.

Prevention

• Acclimate—if you are headed to high altitude spend a night or two at an intermediate elevation first.
• Sleep low—the altitude you sleep at is a much more critical factor than any high elevation you pass over during the day.
• Respiratory depression is undesirable and (the slowing down of breathing) may be caused by alcohol, sleeping pills or narcotic pain medications in more than modest doses.

Treatment

• Follow the Golden Rules
• The best treatment for any form of altitude sickness is to move to a lower elevation.
• Administer oxygen—it’s exceedingly unlikely that you’re carrying a bottle of oxygen but if you’ve got it use it.
• Other treatments including medication and hyperbaric therapy are described in the International Society for Mountain Medicine’s (ISMM) excellent tutorial on Altitude Sickness designed for the non-physician.