Breathing and spirometre Flashcards
Why do we breathe?
To refresh air at alveoli for steep concentration gradient for efficient gas exchange
What muscles control breathing?
- External Intercostal muscles contract pushing ribs up and out (volume + pressure impacted)
- Intercostal muscles push more air out after exhaling (FORCED EXHALATION)
What is VENTILATION?
Essentially breathing (air in + out) caused by changes in pressure in the thoracic cavity
Inhale and exhale
What is Inhalation (inspiration)
- external intercostal muscles contract pushing ribs up and out
- diaphragm also contracts
- lungs increase in size so volume increases so pressure decreases
- air moves in down concentration gradient
- active process
What is exhalation?
- diaphragm and external intercostal muscles relax
ribs move down and in - volume of lungs decreased so pressure increases
- air is pushed out of lungs as greater Pa in lungs than atmosphere
- passive process
How does forced exhalation occur?
- intercostal muscles contract
- ribs move down and in further
- diaphragm further relaxed
and abdominal muscles contract - for decreases volume for inc Pa
What is a spirometre?
device to measure and record volumes air inspired and expired over time
the paper trace is known as spirograph
How does spirograph work?
when inspire oxygen is being used so trace goes down
expire trace climbs
expire - inspire = vol of single breath
there is always some air in lungs so alveoli stay open
- trace lower over time as oxygen used by body
Precautions when using spirometre?
- healthy subject
- subject wears nose peg
- soda lime to absorb co2 exhaled
- no leaks to avoid inaccurate result
- dont overfill water chamber
what is breathing rate?
breaths per min
- up and down on graph
how to calc o2 uptake
drop volume o2 over time
- change / time
how to calc pulmonary respiration
tidal vol x breathing rate
tidal volume is?
-air in and out in one breath
-height of single trace eg just up
expiratory vs inspiratory reserve volume
expiratory is max force out after
inspiratory is max inspired above tidal inspiration
