Traveling to elevations above 8,000 feet subjects the body to an environment where oxygen delivery becomes less efficient. Although the air still contains 21% oxygen, the decrease in atmospheric pressure reduces the overall amount of oxygen molecules available with each breath. This reduced availability can quickly lead to symptoms of altitude sickness. Understanding the underlying physiology and mastering paced breathing and acclimatization schedules are the most effective ways to manage this challenge and ensure a safer, more comfortable experience.
How Altitude Affects Oxygen Uptake
The primary challenge at high altitude is a drop in the atmospheric pressure pushing oxygen into the lungs and blood. At sea level, pressure is about 760 mmHg. As elevation increases, this pressure decreases significantly, falling by roughly 100 mmHg for every 3,300 feet (1,000 meters) of ascent up to about 10,000 feet. This drop directly reduces the partial pressure of inspired oxygen (\(P_I O_2\)), the driving force moving oxygen from the lung’s air sacs (alveoli) into the bloodstream.
A lower \(P_I O_2\) means less oxygen is diffused into the arterial blood, a state known as hypoxemia. The body attempts to compensate by increasing the depth and rate of breathing, the natural ventilatory response to hypoxia. This increased ventilation helps maintain blood oxygen saturation, but it requires conscious effort and cannot fully overcome the physical limitations of reduced pressure.
Immediate Techniques for Paced Breathing
Diaphragmatic Breathing
Improving immediate oxygen uptake requires deliberate control over the respiratory muscles and rhythm, moving beyond shallow, panic-induced breathing. Diaphragmatic breathing, also known as belly breathing, maximizes the volume of air exchanged in the lungs. Focus on inhaling deeply through the nose, allowing the abdomen to expand outward, and then slowly exhaling through the mouth, ensuring the chest remains relatively still. This deeper inhalation utilizes the full capacity of the lungs, delivering a greater volume of oxygen to the alveoli.
Pursed-Lip Breathing
Pursed-lip breathing involves inhaling slowly through the nose and then exhaling slowly through tightly pursed lips. This action creates a back-pressure in the airways, which helps to keep the smaller air passages open longer. The prolonged exhalation allows for more complete gas exchange and the efficient removal of carbon dioxide. Mountaineers find this particularly beneficial during periods of exertion.
Rest-Step Pacing
When moving, synchronize your breath with your steps to maintain a sustainable rhythm and prevent over-exertion, a method called rest-step pacing. A common pattern is to inhale over two to three steps and exhale over the next two to three steps, ensuring the exhalation is slightly longer than the inhalation. This deliberate pacing forces a slow, deep respiratory cycle that stabilizes the body’s oxygen demand and consumption.
Essential Preparation and Acclimatization Strategies
Acclimatization Schedule
The most effective strategy for breathing better is allowing sufficient time for the body to acclimatize. Avoid flying directly to a destination above 10,000 feet (3,048 meters). Once above this elevation, increase your sleeping altitude by no more than 1,000 to 1,600 feet (300 to 500 meters) per day. Incorporate a rest day every 3,000 feet (915 meters) of elevation gain to allow for biological adjustment.
A well-established method is the “climb high, sleep low” principle, which involves hiking to a higher elevation during the day and descending to a lower camp to sleep. Sleeping at a lower altitude provides a greater partial pressure of oxygen for the body’s recovery period overnight. This strategy stimulates the body’s natural adaptation mechanisms while allowing for better rest.
Hydration and Nutrition
Hydration and nutrition are important components of preparation, as fluid loss increases at altitude. Aim to drink at least three to four quarts of water daily, with the goal of producing clear urine, a reliable sign of adequate hydration. Consuming a diet rich in complex carbohydrates is recommended, as this macronutrient is more efficiently metabolized in a low-oxygen environment than fats or proteins.
Recognizing Signs of Severe Altitude Sickness
Paced breathing and gradual ascent can prevent most issues, but it is important to recognize when symptoms progress into signs of severe altitude illness. Acute Mountain Sickness (AMS) is the mildest form, presenting with symptoms similar to a hangover, such as headache, nausea, fatigue, and dizziness. If these symptoms appear, halt ascent, rest, and hydrate; never go higher until symptoms have fully resolved. Progression of symptoms can lead to two serious conditions: High Altitude Pulmonary Edema (HAPE) and High Altitude Cerebral Edema (HACE).
High Altitude Pulmonary Edema (HAPE)
HAPE involves fluid accumulation in the lungs. Symptoms include:
- Severe shortness of breath even while resting.
- A persistent, wet-sounding cough that may produce pink or frothy sputum.
- A feeling of tightness in the chest.
High Altitude Cerebral Edema (HACE)
HACE is swelling of the brain, indicated by a change in mental status, such as confusion, irrational behavior, or severe lack of coordination (ataxia). Ataxia can be tested by the inability to walk a straight line heel-to-toe.
Both HAPE and HACE require immediate, rapid descent of at least 1,000 to 2,000 feet (300 to 600 meters). Descent is the primary treatment. Ignoring these warnings and attempting to push through can result in a fatal outcome within hours.