Measuring lung capacity

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  • Created by: Steff06
  • Created on: 15-02-16 16:35
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  • Measuring lung capacity
    • Breathing:
      • Breathing gets oxygen-rich air into the lungs and removes carbon dioxide-rich air out of the lungs.
      • Controlled by the diaphragm and intercostal muscles contracting and relaxing.
    • Measuring different volumes of air:
      • TIDAL volume = Volume of air  moved in + out of the lungs with each breath when at rest.
        • Approximately 0.5dm3 and provides body with enough oxygen for resting needs whilst removing enough CO2 to a safe level.
      • VITAL CAPACITY = Largest volume of air that can be moved in and out of lungs in one breath. 5dm3.
        • Varies between men and women. Also varies with age and size. Regular exercise increases vital capacity.
      • RESIDUAL VOLUME = Volume of air that always remains in the lungs, even after the biggest possible exhalation. 1.5dm3
      • DEAD SPACE = The air in the bronchioles, trachea and bronchi. There is no gas exchange between this air and the blood.
      • INSPIRATORY RESERVE VOLUME = How much more air can be breathed in (inspired) over and above normal tidal volume when you take a bid deep breath. Call on this reserve when exercising.
      • EXPIRATORY RESERVE = How much more air can be breathed out (expired) over and above the amount that is breathed in a tidal volume breath.
    • Spirometer and lung volume:
      • Spirometer = chamber filled with oxygen that floats on a tank of water. Person breathes from a disposable mouth piece attached to a tube connected to the chamber of medical-grade oxygen.
      • Breathing in takes oxygen from the chamber, which then sink down. Breathing out pushes air into the chamber which then floats up. Movements recorded on a datalogger so a spirometer trace can be produced.
      • The person breathing in and out of the spirometer can be asked to breathe normally at rest, take deep breaths or to exercise so different patterns of breathing can be shown.
    • Measuring oxygen uptake:
      • If a person breathes in and out of a spirometer for a period of time, levels of carbon dioxide will increase dangerously.
        • To avoid this, soda lime is used to absorb the CO2 that is exhaled so the total volume of gas in the spirometer will go down.
      • Volume of CO2 breathed out = volume of oxygen breathed in, so as the CO2 is removed, the total reduction is equal to the volume of oxygen used up by the person breathing.


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