lung ventilation Flashcards
what is meant by ventilation?
air moving in and out due to the thorax resulting in pressure changes
what is the diaphragm?
broad muscle below the thorax
what is the pleural cavity?
contains membrane which surrounds the lungs
summarise ‘inspiration’
- diaphragm contracts and lowers
- external intercostal muscles move ribs up and out as they contract
- internal intercostal muscles relax
- volume of thorax increases and pressure decreases
- pressure is lower than in the atmosphere so air moves in
- requires energy
summarise ‘expiration’
- diaphragm relaxes and moves up
- external intercostal muscles relax, ribs move down and in
- elastic fibres recoil
- volume decreases and pressure increases
- air moves out
- doesn’t require energy
define ‘tidal volume’
the volume of air in and out with one resting breath
define ‘vital capacity’
volume of air in when deepest exhale and deepest inhale
define ‘inspiration reserve volume’
maximum volume of air breathed in over and above a normal inhale
define ‘expiratory reserve volume’
extra air forced out over and above a normal exhale
define ‘residual volume’
volume of air left in lungs after maximum exhale
define ‘total lung capacity’
vital capacity and residual volume
define ‘ventilation rate’
tidal volume x breathing rate
what is a spirometer?
A machine that can give readings of tidal volume, vital capacity, breathing rate and oxygen uptake
Describe how a spirometer works.
- has an oxygen filled chamber with a moveable lid
- the person breaths through a mouth piece connected to the oxygen chamber
as person breathes in and out, the lid of the chamber moves up and down - these movements are recorded by a pen attached to the lid of the chamber-it writes on a rotating drum creating a spirometer trace
- the soda lime in the tube the person breathes in and out of absorbs carbon dioxide
Why does the total volume of gas in the chamber decrease over time?
-air breathed out is mix of oxygen and carbon dioxide, and carbon dioxide is absorbed by the soda lime so there’s only oxygen in the chamber the subject breathes from. Decreasing total volume
