Respiratory Mechanics Flashcards
How are respiratory mechanics performed outside of the body, to determine pressure/volume relationships?
Negative pressure is created in a container with the lung.
The change of the volume of the lung is calculated.
In respiratory mechanics, as the intrapleural pressure (pressure around the lung) becomes more negative, what happens?
Air flows into the lungs= lung volume increases.
Is the change in volume for a given change in pressure constant?
No.
The line produces is not straight.
How are pressure and volume related in respiratory mechanics?
At a low lung volume, it takes a big amount of pressure to get a small increase in volume.
Once a little bit of air enters the lungs, a little change in pressure produces a large change in volume.
Thus, it becomes easier to stretch the lungs.
When the lungs get close to TLC, what happens?
It becomes hard to stretch (inflate) again.
Thus, a large pressure change will only change the volume a little.
What is compliance of the lung?
How easy it is to stretch our lungs.
to calculate=
Change in volume/ change in pressure
What is the opposite of compliance?
Elasticity- ability to recoil
When is compliance the highest?
When we are in normal breathing range (normal Tidal Volume).
Thus, we dont have to work hard.
At either extreme of the pressure/volume relationship curve (sigmoidal), (very small lung volume or very big lung volume), what is compliance?
Compliance is low.
What does a high compliance mean?
Very stretchable and easy to inflate.
At birth, bb must inflate its lungs for the 1st time. What is the compliance of the lungs for the first breath and how hard does the bb have to work?
Very very low compliance bc lung volume is v low.
BB has to work v hard.
Do the lungs inflate and deflate the same?
No.
Thus, exhalation and inhalation is different.
What would happen if we inflated the lungs with saline (instead of air)?
Saline allows for high compliance due to there being no air/water surface, so there is no surface tension, allowing rapid intake of saline, exhale also occurs at the same place
What is the main reason the inhale and exhale graphs do not align (also know as hysteresis)?
- Due to surfactant molecules moving one way during inspiration and different during expiration /
- LaPlaces Law! (P=2T/Radius)
Why does the gap between the expiration and inspiration line (hysteresis)?
Surfactant= differences in surface tension
Surfactant is not evenly distributed on the alveolar surface, instead it is small droplets randomly positioned. So if the alveolar volume is small…?
the droplets are close together and pull apart during inspiration and fuse together during expiration
What is the SLIGHT hysteresis in the saline-filled curve due to?
Resistance caused by tissue sliding over one another. (ST)
When there is low compliance, there is ____ stretchability and _____ to inflate… vice versa for high compliance
low stretchability and hard to inflate high stretchability and easy to inflate with high compliance or high slope of deltaV/deltaP
What is the pressure/volume relationship for the lungs?
Looks like what we saw for INSPIRATION.
Normal resting point (without the rib cage) is low (because they want to collapse).
What is the normal resting point for lungs alone, which is VERY small, referred to as?
Minimal volume.
However, we do not usually see in person because the rib cage is attached.
The elastic recoil of the lungs and rib cage balance each other out at ______
FRC (functional residual capacity). – volume of hair present at the end of a passive expiration.
In this situation, airway pressure goes down to zero, due to elastic recoil of both even each other out.
With forced expiration, goes below FRC –> residiual volume
What will FEV1/FVC ratio look like for someone with an obstructive dz: emphysema or athasma?
It will take longer to get the air out of the lungs.
FVC is reduced because air is trapped in lungs.
FEV1 is even more reduced.
Thus, FEV1/FVC ratio is below ~70%
What represents the work done to stretch (elastic forces) the lungs/thorax?
0AECD0= work of breathing to overcome the elastic forces (compliance)
What area is the work required to overcome resistive forces?
ABCEA
Increase in airway resistance means it takes a greater pressure to generate flow into lungs. What do we have to change to change the amount of work being done to stretch the lungs/rib cage?
Change the compliance. Decrease in compliance = work harder to stretch lungs = increase in area (pneumonia, pneumonia, overwight all decrease compliance)
