Elevation describes the vertical distance of a location above a fixed reference point. Understanding its effects on the human body is essential for human activities, including travel and health.
Understanding Elevation Measurement
Elevation is precisely defined as the height of a point on the Earth’s surface relative to a consistent reference level. The universally accepted benchmark for this measurement is mean sea level (MSL), which represents the average height of the ocean’s surface over a long period. This average accounts for variations caused by tides and waves, providing a stable baseline for global measurements.
Measuring elevation involves several methods, each with varying degrees of precision and application. Modern approaches frequently utilize Global Positioning Systems (GPS), which provide highly accurate three-dimensional positions. Additionally, altimeters, which measure atmospheric pressure changes, are commonly used.
Classifying High Elevation
For the human body, elevation is categorized into specific ranges that indicate increasing physiological impact due to decreasing atmospheric pressure and oxygen availability. These classifications are widely used in medical and physiological contexts to assess potential health risks.
Moderate altitude typically spans from 1,500 to 2,500 meters (approximately 4,900 to 8,000 feet) above sea level. While many individuals experience minimal effects within this range, some might notice slight changes in breathing during physical exertion. Beyond this, high altitude is considered to be between 2,500 and 3,500 meters (around 8,000 to 11,500 feet). At these heights, physiological responses become more pronounced, and the body begins to adjust to the reduced oxygen.
Ascending further, very high altitude ranges from 3,500 to 5,500 meters (roughly 11,500 to 18,000 feet). The effects of thinner air are distinctly noticeable at these elevations, posing more significant challenges for the human body. Lastly, extreme altitude encompasses any elevation above 5,500 meters (over 18,000 feet). Survival at extreme altitudes for extended periods is not possible without supplemental oxygen, as the atmospheric conditions are severely hypoxic.
Human Response to Elevation
The primary reason these elevation classifications are significant for human physiology is the decrease in atmospheric pressure as altitude increases. This reduction in pressure means that even though the percentage of oxygen in the air remains constant (around 21%), the partial pressure of oxygen, which drives oxygen into the bloodstream, significantly drops. This phenomenon, known as hypoxia, challenges the body’s ability to oxygenate its tissues.
To cope with reduced oxygen, the human body initiates a process called acclimatization. This involves a series of physiological adjustments, such as an increased breathing rate to take in more air and an elevated heart rate to circulate oxygen more rapidly. Over time, the body also produces more red blood cells, which are responsible for carrying oxygen, to enhance its oxygen-carrying capacity. However, rapid ascent to higher elevations without sufficient time for acclimatization can lead to altitude sickness, a general term for various conditions caused by the body’s struggle to adapt to low oxygen environments.