L3 - measuring lung capacity

• Volume of air in the lungs:

  -total human lung capacity is about 5dm cubed (ranging from 3.5 to 6) depending on the age and fitness level of the individual

  -as we inhale and exhale, air loves in and out altering the air volume in our lungs. this allows air in our lungs to be refreshed and CO2 to be removed
• Tidal volume: volume of air moved in and out of the lungs with each breath when at rest
• Vital capacity: largest volume of air than can be moved into and out of the lungs in one breath
• Residual volume: volume of air always remaining in the lungs
• Inspiratory reserve volume: how much air can be breathed in over normal tidal volume when you take a deep breath
• Expiratory reserve volume: how much air can be breathed out over normal tidal volume
• Total lung capacity: total of vital capacity and residual volume
• People with larger lung volumes tend to be:

  -males

  -tall people

  -non smokers

  -professional athletes

  -people living at high altitudes
• People with smaller lung volumes tend to be:

  -females

  -shorter people

  -heavy smokers

  -non athletes

  -people living at low altitudes
• A spirometer is used to measure and record volumes of inspired and expired air. The graph produced is called a spirogram
• How a spirometer works:

  -subject breathes in and out of an airtight container, which involves a perspex lid floating on water and a a kymograph (pen on a revolving drum)

  -as the person breathes in and out, the lid moves up and down recording ‘up‘ and ‘down’ waves forming a spirogram

  -as the subject inhales, the volume of air decrease and the float drops down. as the person exhales, the air volume increases and the float moves up
• How a spirometer works:

  -chamber is filled with medical grade oxygen and the air passes through a canister of soda lime to absorb carbon dioxide

  -as oxygen is used up the ‘lid’ sinks, meaning the chamber is not the same height each time as the oxygen is used up

  -recording paper is calibrated for time and volume so that depth and frequency can be recorded. tidal volume of vital capacity can be recorded depending on how the subject breathes
• Safety aspects:

  -carbon dioxide levels can build up so soda lime is used to absorb it, this means total spirometer gas level will decrease, this carbon dioxide removal is equal to oxygen used so oxygen use can be calculated

  -mouthpiece should be disinfected

  -no asthma or respiratory problems

  -tight nose clip so accurate readings