Practical 7: Lung mechanics Flashcards
describe the structure of a spirometer
- has light metal triangular-shaped wedge inverted into a tank of water, which ‘traps’ a certain volume of air
- wide tubing with a mouthpiece connects the airways of the subject with the spirometer
What happens to the spirometer during breathing?
During expiration, the volume of air within it increases and the wedge rises
during inspiration, the volume of air within it decreases and the wedge falls
how are precise volume changes seen in this practical?
on powerlab
How do you set up the spirometer to the subject?
- place a clean, disposable mouthpiece inside the plastic mouthpiece
- use the handle on the wheel to move the disk to ‘subject to spirometer’
- fill the spirometer with air by raising the the wedge out of the water slowly
- once full, turn the wheel to ‘subject to atmosphere’ (the wedge will remain elevated)
- put nose clip on subject and connect them to the spirometer
- turn the wheel to ‘subject to spirometer’ - the wedge should start to fall as they breathe
How do you record vital capacity using the spirometer?
once the subject has reached a steady breathing rate, they should make a maximal inspiration followed by a maximal expiration (this is vital capacity). This doesn’t need to be hurried but should be as full/ complete as possible
return to normal breathing and repeat 2 more times
use powerlab to see vital capacity
How do you record Forced Vital Capacity using the spirometer?
set up the spirometer
ask subject to make a maximal inspiration then as fast and hard as they can breathe out
return to normal breathing and refill spirometer and do again 2 more times
How do you find FEV1 from forced vital capacity?
look at powerlab and see how much the volume changed in the first second
How is PEFR recorded?
the subject breathes out as fast as possible, starting with lungs fully inflated- only the peak airflow is recorded
