Human Body Ability to Adapt

Introduction
The human body has the ability to adapt to extreme environment. The body has the capacity to make adjustment on the blood chemical composition, breathing rate, and red blood cell production in response to changes in the availability of oxygen. In aviation, there is a high-demand on the compensation capabilities of the body. Flights involve significant changes in the environment. This includes low atmospheric pressure, changes in the temperature, and movement in the three dimensions. Human is naturally a terrestrial dwelling organism. The human body has limitation in response to a life on land. The advanced technology to the modern world enables engineers to design highly versatile aircrafts. These aircrafts can operate in environment beyond the ability of human to adapt. Humans require physical aid to manage the aircrafts effectively.
The atmosphere
The atmosphere comprises a mixture of gases. The primary compositions of the atmosphere are nitrogen and oxygen. Nitrogen and oxygen comprise approximately 80% and 20% of the atmosphere.
The other gases are found in low concentrations and have no bodily function. The basic challenge to flight is the physical property of the atmosphere. The pressure of the atmosphere decreases with increase in altitude. The temperature changes drastically with the change in altitude (Schierholz, 2010).
The atmosphere support life only at the lower levels. The human body has the ability to adapt in the lower levels. This includes 12,500-feet and below. At this level, only minor effects are possible. This includes trapped gas problems, shortness of breath. Headaches, dizziness, and fatigue may occur if exposure is for a long period. At the range of 12,500 to 50,000 feet, the lack of oxygen in the body causes hypoxia, decompression sickness, and other physiological problems. A majority of commercial flights are in this range. Above 50,000 feet, the environment is hostile to the human body. Exposure at this level may cause the body fluids to boil. There is need for a pressurized cabin above 10,000 feet. Above 50,000 feet, the aircraft requires thrusters (Ira, Kathy, 1995).
Circulation and respiration
The flight environment affects the human body in many ways. The areas mostly affected are circulation and respiration. It is important for one to be familiar with the responses and limitations of these systems to the changing pressure, temperature, and motion. Respiration involves the absorption of oxygen from the environment and the expulsion of carbon dioxide from an organisms body. The absorption of oxygen into the blood from the air in the air sacs depends on the pressure of the gas. The absorption of oxygen internally, from the blood to the cells also depends on pressure. The higher the pressure the low the absorption rate and vice versa is true (Laker, 2012).
The circulation system transports blood throughout the body. The blood carries oxygen, food, and water to the cells. It also removes metabolic waste materials from the cells. The blood also regulates body temperature. Oxygen is transported in the blood by red blood cells. Red blood cells have hemoglobin. Hemoglobin contains iron to facilitate biding the oxygen. The relationship between the hemoglobin and oxygen is not linear, however; oxygen dissociates at low pressure (Ira, Kathy, 1995).
Hypoxia
When there is insufficient oxygen in the blood, cells, and tissues, an individual suffers from hypoxia. Hypoxia occurs when the oxygen deficiency is sufficient to impair normal functioning. There are four major types of hypoxia. These include Hypemic Hypoxia, Hypoxic Hypoxia, Stagnant Hypoxia, and Histotoxic Hypoxia. These variants of hypoxia affect the lungs, blood, blood transport, and cell respectively. Some of the causes of hypoxia include low cabin pressure, G force along the Z-axis, presence of carbon monoxide or cyanide in the air, or the presence of alcohol and narcotics in the blood system (Laker, 2012).
Some of the signs of hypoxia include lethargy, bluing of the skin, poor coordination, executing poor judgment, and rapid breathing. Some of the symptoms include fatigue, nausea, euphoria, hot, cold flashes, and headaches. To treat hypoxia one must immediately use supplementary oxygen. The percentage of the oxygen is 100%. It is essential to act fast, especially when flying in high altitudes because the time of useful consciousness (TUC) decreases with altitude. To prevent against hypoxia fly at altitude where supplementary oxygen is not required (10,000-feet and below), pressurize the cabin, and follow the flight regulations (Schierholz, 2010).
Hyperventilation
A normal healthy person breath at a rate of 12 to 16 cycles per second. At this rate, the person inhales sufficient oxygen to meet the body demand and exhale the excess carbon dioxide in the blood. The breathing rate of a person is controlled chemically, physically, and emotionally. Physical control involves the voluntary contraction and relaxation of chest muscles. Chemical control involves the detection of carbon dioxide levels in the brain and adjustments to meet normal levels. Emotional control involves the hormone adrenaline. Adrenaline is a hormone produced to increase body alertness in the face of danger (Ira, Kathy, 1995).
Anxiety and fear cause adrenaline production. When adrenaline is produced, and there is no physical activity to use the excess oxygen, the individual is said to be hyperventilating. Hyperventilation reduces carbon dioxide levels in the blood. This reduces the levels of carbonic acid in the blood. This results in the blood becoming alkaline. Alkaline blood reacts with nerve endings to cause tingling. The brain also responds by reducing blood flow to avert damage. The result is blurry vision, dizziness, and muscle spasm. This impairs the pilots capacity to fly the aircraft. To treat hyperventilation, one must regulate the breathing rate voluntarily (Schierholz, 2010).
Trapped gas
The expansion and compression of gases is dependent on the environmental pressure. When descent or ascent occurs at a high rate there is a chance the air in the body does not have sufficient time to escape. The body parts affected includes the ear, lungs, sinuses, gastro-intestinal, and the teeth. The gases in the organs escape through openings found on the body. Closed or reduced openings result in the trapping of the air. As the flight rises the gas change in volume because of pressure change, which results in pain. Some of the symptoms of trapped gas include progressive pain in the ears, pain under the cheekbone and under the eyebrows, pain in the abdominal area, and toothache. Some of the remedies include leveling off from descent or ascent, and, ear-nose clearing maneuvers, such as swallowing, yawning, and jaw jut. If the symptoms persist, land soonest, and seek medical help (Laker, 2012).
Altitude induced decompression sickness
Decompression sickness (DCS) results from exposure to low pressure. This may occur in an aircraft with an unpressurized cabin or if depressurization occurs. These results to nitrogen dissolved in body fluids turning into gas. The most common areas where the air bubbles form are the joints. DCS may also affect the neurological system. This manifests as headaches and poor vision. When the pilot experience DCS, immediate use of 100% oxygen is the best remedy. The pilot must level off and if necessary return to the initial altitude. Some activities, such as scuba diving increases the probability of DCS, especially when flying in an unpressurized cabin (Ira, Kathy, 1995).
The pressurization of the cabin is a safe way to escape the dangers associated with high altitude flying. There is, however, the constant danger of losing pressure. When depressurization occurs immediately, the dangers occur in the aircraft immediately. If the depressurization is low, the dangers can sneak in and rob the pilot good judgment and essential reaction time. The pilot should always be on the lookout for the symptoms and signs of this high altitude flying (Schierholz, 2010).
 References
Ira J. Blumen, Kathy J. Rinnert. (1995). Altitude physiology and the stresses of flight. Air Medical Journal, Volume 14, Issue 2, Pages 87-100, ISSN 1067-991X.
Laker, M. (2012). SPECIFIC PHOBIA: FLIGHT. Activitas Nervosa Superior, 54(3), 108-117.
Schierholz, Elizabeth. (2010). Flight Physiology: Science of Air Travel With Neonatal Transport Considerations. Advances in Neonatal Care. Issue: Volume 10(4), August 2010, p 196199