Spirometry & Ventilation Flashcards
What is a spirometer, and what 2 things is it used to measure?
Is a pulmonary function test (PFT) and is used to measure 2 assets relating to inhalation and exhalation of air:
- volume
- speed (flow)
Inspiratory reverse volume
Max vol of air you can breathe in over and above a normal inhalation
Tidal volume
The vol of air that moves in and out of your lungs with each resting breath
Residual volume
The vol of air left in your lungs, when you have exhaled as hard as possible (this cannot be measured directly).
Inspiratory capacity
The total/ maximum amount of air that can be inspired (breathed in).
Vital capacity
The vol of air breathed in, when the strongest exhalation is followed by the deepest possible intake of breath.
Expiratory reverse volume
The extra volume of air you can force out of your lungs, over and above the normal tidal vol of air you breathe out.
Total lung capacity
Sum of the vital capacity and the residual volume.
Explain the 4 stages of inhalation in the human lungs
Anatomical change: Diaphragm contracts (flattens/ moves down). External intercostal muscles contract (rib cage moves up and out).
Volume change: As a result this increases the vol of the thorax (thoracic cavity).
Pressure change: Decreases the pressure within the thoracic cavity below atmospheric pressure (now a pressure gradient).
Air movement: Air rushes in, down the pressure gradient.
Explain the 4 stages of exhalation in the human lungs
Anatomical change: Diaphragm relaxes (arching back to normal bent position). External intercostal muscles relax and the rib cage moves down and in.
Volume change: As a result decreases the vol of the thorax
Pressure change: This increases the pressure within the thoracic cavity above atmospheric pressure (pressure gradient).
Air movement: Air rushes out, down the pressure gradient
