Inca Trail to Machu Picchu

Altitude sickness - inca trail

Acute Mountain Sickness on the Inca Trail to Machu Picchu in Peru

How your body reacts ?

The higher altitute you reach, the more your body has to adapt. Here's what happens - from the inside out. No matter where you travel on our planet, the concentration of oxygen in the air remains a steady 21 percent. At sea level, the weight of the atmosphere compresses a huge amount of oxygen molecules into any given volume. The higher you trek, however, the less overhanging atmosphere there is to do this compaction. The result: Air becomes increasingly less dense. Atop Warmiwañusca on the Inca Trail, the absolute number of oxygen molecules per lungful is aproximate 49 percent the number at sea level. On Everest, it's an inadequate 33 percent. But even though the human body hates being deprived of its favorite gas, we've evolved clearly to face this circumstances.

BREATHING

Rapid-fire breathing brings more oxygen into your system, but it also causes you to blow of CO2 faster than normal. This lowers CO2 levels in the bloodstream - which, over time, can leave you feeling light-headed and actually decrease ventilation, upping the odds of altitude sickness.

SPEECH

A warning sign of deterioration: intermittent subtle slurring of speech, with the pronunciation of the letters P, T and K shortening so they're indistinguishable from B, D and G - an effect that has also been found in patients suffering from Parkinson's.

NECK

As blood-oxygen saturation drops, sensors called caratoid bodies, along with central receptors in the brain stem, detect the threatening condition and sound an alarm.

LUNG SACKS

The enhanced ventilatory response inflates additional lung sacks - or alveoil - deep inside and opens extra pulmonary capillaries you normally don't need to use.

CIRCULATION

Blood distribution patterns shift throughout the body; More blood is routed from the periphery and shunted to vital organs - the same basic process seen in hypothermia.

BLOOD

Increased hematocrit - a measure of red cell count and size - bumps up oxygen-carrying capacity, but it also makes blood thicker, harder to pump, and more prone to the clotting problems that can trigger heart attacks.

BONE MARROW

EPO signals your bone marrow to start making new red cells, a process that can take up to a month. Because of this, people who live at high altitude tend to have significantly higher hematocrits.

EYES

Reduced blood flow through the retinas can cause visual disturbances, from changes in color perception to reduced sensitivity to light and dark.

BRAIN

Performance on cognitive tests - pattern recognition, short-term memory, and the like - initially declines, but rebounds within a week or so as the body becomes acclimatized. Edema in the brain can cause side effects that progress from severe headache and loss of coordination to impaired judgement and eventually coma.

HEART

The heart contracts more often, more forcefully, to increase total blood flow. Your lungs and cardiovascular system begin processing greater volumes of thin air in order to extract the same absolute amount of oxygen.

PULMONARY ARTERY

Blood pressure rises especially on the right side of the heart chich supplies blood via the pulmonary arteryto the lungs. this enhances gas exchange - but if the pressure gets too high, the smaller tributary vessels interlacing the alveoil can begin to leak like soaker-style garden hoses, leading to fluid buildup and HAPE.

MUSCLES

Hemoglobin carries oxygen in the blood, and a similar protein, myoglobin, delivers oxygen within muscle cells themselves. One study suggests myoglobin levels slowly increase the longer you spend at altitude - though it may take weeks or months.

DIAPHRAGM AND RIBS

Nerves relay the emergency alert to your diaphragm and ribcage intercostal muscles, causing you to breathe more deeply and more often - something called enhanced ventilatory response.

KIDNEYS

Within minutes of hypoxia, your kidneys begin releasing erythropoitin (EPO), which stimulates blood production. They also react to plummeting blood CO2 levels in a complicated cascade that triggers increased urination - chich removes liquid from your blood, concentrating red blood cells. Good news: more oxygen uptake. Bad news: Your blood is "sludgier" and requires more power to pump.

Trekking Peru