core prac 17

Question 1

How does a spirometer work?

Answer 1

• It’s a tank of water with an air-filled chamber suspended within it.
• Adding air to the chamber (expiring) makes the lid rise, removing air makes it fall (inhalation)
• Movements of air are recorded on a kymograph (pen writing on a rotating drum)

Question 2

What’s the method for the spirometer prac?

Answer 2

1. Canister containing soda lime is inserted between the mouthpiece and the floating chamber, this helps absorb the co2 that the subject exhales to prevent a toxic atmosphere being created within the tank.
2. After calibration the spirometer is filled with oxygen, a disinfected mouthpiece is added to the tube with the tap positioned so that the mouthpiece is connected to the outside air.
3. The subject puts a clip on their nose and the mouthpiece in their mouth.
4. Switch on the recording apparatus and at the end of an exhaled breath turn the tap so that the mouthpiece is connected to the spirometer chamber. The trace will move down as the person breathes in.
5. After breathing normally the subject should take as deep a breath as possible and then exhale as much air as possible before returning to normal breathing.

Question 3

Look at the pic of a spirometer trace on bookmark tabs, what are the labels A-F?

Answer 3

• A : tidal volume (the volume of air that’s inspired/expired per breath)
• B : Inspiratory reserve volume (the maximum volume of air that can be breathed in over and above normal inhalation)
• C : Expiratory reserve volume (The extra amount of air that can be forced out of the lungs over and above the normal tidal volume of air you breathe out)
• D : Residual volume (The volume of air that is left in the lungs when you have exhaled as hard as possible)
• E : Vital capacity (The maximum volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible intake of breath)
• F : total lung capacity (Sum of vital capacity and residual volume)