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Concepts in Human Factors Engineering (Part 6 of 11)

Concepts in Human Factors Engineering (6): The Oxygen Machine

by Dennis R Andrews PhD, PSP, CECD

By Dennis R Andrews PhD, PSP, CECD (ExpertPages member profile page)

The oxygen machine refers to the respiratory system such as the lungs and adjacent tissue. The oxygen drawn into the lungs is used for metabolism and upon exhaling discharges harmful byproducts. Oxygen is necessary to circulate through the blood and arrive at starving muscles when strained such as during work. The byproduct carbon dioxide is harmful and must be expelled from the body. Also dispelled is excessive heat and water. Oxygen is transported by the transportation system of the body namely the blood.

Concepts in Human Factors Engineering is a series containing eleven articles:
  1. An Overview of Anthropomorphic Data Gathering
  2. The Fragile Skeletal System
  3. The Energy Force of Our Frame
  4. The Message Delivery System
  5. The Body as a Machine
  6. The Oxygen Machine
  7. The Body’s Transportation System
  8. Human Body Energy
  9. A Hot Workplace
  10. The Rhythm of Working
  11. The Bionic Worker of the Future
The lungs contain small sacks known as alveoli, which transfer the oxygen to the blood. The respiratory system is sometimes thought of as a tree, due to the branching out of the bronchea. The air sacs exchange oxygen and carbon dioxide between the blood and air. The surface area, which conducts the exchange, is approximately 70 to 90 m square which is considerably large and therefore very efficient.

When a person suffers from a respiratory problem the lungs may be coated in fluid, which prevents efficient exchange to take place. If the necessary exchange does not occur the person will become easily exhausted or to the point of critically not supplying the body with needed oxygen as well as expelling carbon dioxide. The muscles and rib cage act as bellows forcing air in and out of the lungs. This is the reason people who are caught in a rush to exit such as in a fire may actually suffocate at the door because their chest movement is restricted.

The pumping action of the chest forcing air in and out of the lungs increases substantially during heavy work from a rest position. Resistance of the airflow comes from the airway and coefficient of friction of the tissue. Obviously the less friction the more air and the quicker the lungs fill with air. Heat loss of the body plays an important role especially during periods of exposure. The human body must maintain a specific core temperature and may allow the outer extremities to cool in an effort to maintain temperature for the vital organs. The opposite is also true in that to maintain a core temperature excess heat must be disposed of. The environment plays an important part in determining the amount of heat loss or gain of the body. Obviously in a warm climate the air temperature inhaled may be near the core temperature. In this circumstance the body must work harder to expel the heated air and find ways to bring the core temperature down. In a cold climate the reverse is true the body may steal valuable heat from the extremities to prevent damage to the organs or brain.

An athlete who has trained for many years has lung volume of between seven and eight liters. Untrained persons and women will have volumes 60 to 80 percent of the athletes and 10 percent less than male peers, respectively.

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