Lesson 5: Respiratory Mechanics and Compliance Flashcards
what generates inspiratory air flow?
the relationship among all the four pressure
(KEY)
- however, you also need to have a difference between atmospheric pressure and alveolar pressure (KEY)
we we inspire, does alveolar increase or decrease? why?
decrease, the space is getting bigger in the alveoli
- so then, now atmospheric pressure is higher and air goes from high pressure to low pressure so we inhale
negative flow represents?
inspiration
positive flow represents?
expiration
when we inhale, what happens to our pleural pressure?
decreases because the space in the lung is getting bigger
what does the recoil (transpulmonary) pressure do to the lungs/alveoli?
when expiration happens, it decompresses the lungs/alveoli which will higher the pressure because now there is less space. this is why air moves out. atmospheric would then have lower pressure. gradient = high –> low
what starts inspiration?
muscular contraction
what happens directly after inspiration?
there is a short static phase where there is no air flow because the alveolar and atmospheric pressure are equalized
why is negative pleural pressure key?
it helps keep the lung properly inflated and from the chest wall flailing out. (-4 pleural pressure at the end of an expiration before inspiration)
what is pneumothorax?
a collapsed lunge
- a fully recoiled/uninflated lung
what happens in pneumothorax?
it is an abnormal condition of air entering the pleural space
- the pleural and alveolar pressure both equal atmospheric so a pressure gradient no longer exists across either lung wall or the chest wall
- with no opposing negative pleural pressure to keep it inflated, the lung collapses to its unstretched size
ESSENTIALLY: the plural space is negative pressure in a resting state at the end of an expiration so the gaining of pressure is what causes pneumothorax. If it becomes positive that means that it is no longer holding the chest wall in, and the lung wall will fall out.
what is the pleural pressure in a resting state/at the end of an expiration?
negative
when we breathe all the way out, what happens to pleural pressure?
it gets positive and deflates our lung
can we fully deflate our lungs?
no, there is always a residual volume of air so we can’t fully collapse our lung
three possible scenarios for pneumothorax and lung collapse?
- traumatic pneumothorax (puncture wound in chest wall)
- collapsed lung
- spontaneous pneumothorax (hole in lung)
what is the only way that we can deflate our lung fully?
if there is some kind of puncture or there is some event where the pleural space is exposed to either the chest wall or the airway
what are possible ways that the pleural and alveolar pressures can equalize with the atmospheric pressure?
- from an external issue (through the chest wall connection) like a puncture
- when there is a puncture, the air tight sack will become exposed and it will naturally follow pressure gradients and everything will then be equal (pneumothorax)
can you survive if one lung collapses?
yes, it is just uncomfortable
during ______________, negative intrapleural and alveolar pressure are required to move air into the lungs. _______________ muscles generate the forces required to change volume and pressure and generate flow.
inspiration, inspiratory
during __________(at rest), the recoil pressure moves air out of the lung once the inspiratory muscles relax (ie, passive expiration).
expiration
what is required to empty the lungs?
use of expiratory muscles are required to increase intrapleural and alveolar pressure (active expiration)
what is compliance in a respiratory setting?
for a given level of respiratory effort or pressure change how much air do we move?
- how much pressure generation or drops in intrapleural pressure or increases in transpulmonary pressure is required to move air
what does a highly compliant lung mean?
not a lot of pressure, not a lot of effort to move a lot of air
what does a poorly compliant lung mean?
lots of effort to move little air
what does compliance refer to?
how much effort is required to stretch or distend the lungs/change the size of the lungs (inflate/deflate)
what can decrease the compliance of lungs?
factors such as pulmonary fibrosis bc the lung will get stiff and harder to inflate
what shape is important when talking about compliance on the pressure-volume graph?
(two curves/inflections/ ‘S’) sigmoidal shape of the pressure-volume curve of the respiratory system
as we expand the chest, is it a one-to-one ratio all the way across from the bottom of the lung all the way to the top of pressure and volume?
it is not a one-to-one ration all the way across from the bottom of the lung all the way to the top. so when you take a breath, all the way up, the pressure doesn’t go up with volume in a one-to-one ration
- this is because of the sigmoid relationship and elastic nature of the lung
when does the elastic nature of the lungs really flex the muscle and heart?
when its completely deflated and completely inflated
(when its the hardest to breathe)
if a lung is stiff, will it be hard to inflate?
yes
what is the equation for lung compliance?
the change in volume / given change in pressure (specifically recoil pressure)
what do you need to do if you need to create more pressure in the lungs?
diaphragm needs to work harder
is compliance the same everywhere in the lung?
no, that is why there is a sigmoid relationship
