KORR MetaCheck 7100, Руководство пользователя, Страница: 8 / 48

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1.3 Theory of Operation
1.3.1 Metabolic Testing
Metabolism is the process of converting food into heat or energy. The rate
and efficiency with which the body converts food to energy is referred to as
the metabolic rate. The most direct method of measuring metabolic rate is to
directly measure the amount of heat produced by the body. This method is
referred to as direct calorimetry. Direct calorimetry is difficult and impractical,
as it requires a subject to be placed in a special insulated room where the
flow of heat into and out of the room is measured and controlled. A more
common method of metabolic rate measurement is indirect calorimetry. In
indirect calorimetry, the amount of oxygen consumed rather than the amount
of heat produced is measured. Every calorie consumed requires a fixed
amount of oxygen to be converted to energy. The rate at which oxygen is
used is directly proportional to the rate of caloric expenditure. In short,
measuring the rate of oxygen consumption is equivalent to measuring the
amount of calories being used. The MetaCheck™ is an indirect calorimeter
because it measures oxygen consumption and calculates energy expenditure.
1.3.2 Oxygen Consumption
The number of calories burned by the body is directly proportional to the
amount of oxygen consumed. The MetaCheck™ calculates oxygen
consumption by measuring the concentration of oxygen inhaled and
comparing it to the concentration of oxygen exhaled. Oxygen concentration is
measured during an automatic calibration cycle prior to each test to ensure
accuracy of the measurement. The MetaCheck™ also measures the
temperature, relative humidity, and barometric pressure to further improve the
accuracy of the calculations.
To measure oxygen consumption, all of the air exhaled by the user must pass
through the MetaCheck™. Two one-way valves are configured in the
disposable mouthpiece of the MetaBreather™ to ensure that only fresh air is
inhaled and all exhaled gas passes through the hose and into the
MetaCheck™. Because of the “one-way” valves in the MetaBreather™, the
user can never inhale gas from the hose or the MetaCheck™, thereby
eliminating the possibility of cross-contamination between users. It is
important to use a nose clip during a test so that no air escapes through the
nostrils and is not analyzed. Failure to use a nose clip would cause a lower
REE reading.