21. 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 lung volume change is measured
As negative pressure around the lungs (intrapleural pressure) becomes more negative, what does air and volume in lungs do?
Air flows into lungs and lung volume increases
Change in volume is not equal to the change in pressure. It varies. At low(start of breath) and high lung volumes(TLC) in the lung, what pressure is needed to make a small change in volume?
you need a fairly large pressure change to make a small increase in volume at high and low volumes
What is the compliance of the lungs and how is it measured?
Compliance is the measure of stretchability of the lungs, and can be calculated by find the slope of the line (Change Volume/Change Pressure)
What is elastance of the lungs?
Opposite of compliance, instead of stretchability it is recoilability… 1/compliance
When is the compliance of the lungs highest during breathing?
During normal breathing range when there is the largest slope. We do not have to work heard to get a decent Vt
At either extreme-too small or too large volume, compliance will be?
low, meaning we have to work hard to inflate the lungs at low and high volume
What is compliance at birth and how much work needs to be done to get air into the lungs?
First breath, lung volume is v low, compliance is very low, meaning the effort to breath is very high (crying helps baby get past this step)
The lung does not deflate the same way it inflates. What occurs if we inflate 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! (2T/r=P)
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
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
The normal resting point of the lungs alone is quite small and known as the minimal volume(near 0) due to elastic recoil. The rib cage rests?
At a higher volume, where pressure is near 0cmH2O due to orientation of ribs, joints and muscles
When you put the lungs and rib cages alone, together, you get the entire system. These balance eachother at the ______, which means what?
The FRC, is where if you exhale normally, airway pressure goes down to zero, due to elastic recoil of both even eachother out. With forced expiration, goes below FRC to residiual volume
So for instance, if there is a pneumothorax, what would happen to the lungs and rib cage, separate?
Rib cage would increase in volume while the lungs would collapse and decrease in volume