Lecture 12 Flashcards
Exam 2 content
What is the FRC of a person standing up?
3L
What is the FRC of a supine person?
about 2L
What is basic spirometry and what does it measure? What doesn’t it measure?
An instrument that measures how the lung volume is changing as someone is breathing. It measures IRV, Vt, ERV and vital capacity. Anything with RV (FRC, TLC) it cannot measure because you can’t get that air out of the lungs.
What is advanced spirometry and what does it measure?
It is spirometry that uses an indicator gas. This can estimate RV by taking the FRC - ERV.
What is an example of a obstructive lung disease? What does this do to our pulmonary compliance and how does it affect VC?
Emphysema. This is a high compliance disease due to a loss of elastic tissue. It’s easy to fill the lungs but difficult to get air out. VC is higher ~ 6L
What is an example of a restrictive lung disease? What does this do to our pulmonary compliance and how does it affect VC?
Fibrosis. This is a low compliance disease due to an increase in elastic tissue or tissue in general. It is much more difficult to fill the lungs with air. VC is ~ 3L
On inspiration is the lung more or less compliant than expiration?
less compliant
Is a lung filled with air or a lung filled with saline more compliant?
A saline filled lung would be much more compliant.
Why is an air filled lung less compliant? About how much pressure do you need to get air into the lungs?
Surface tension. Need about 8 cmH2O to get air into a low volume lung (good to know for vented surgical patients).
There are 4 surfactant proteins. What are the two proteins that are hydrophilic?
SP-A
SP-D
There are 4 surfactant proteins. What are the two proteins that are more hydrophobic?
SP-B
SP-C
How much of the surfactant is made up of proteins? of lipids?
proteins: 10%
lipids: 90%
What are the two main lipids that make up surfactant?
- Dipalmitoylphosphatidylcholine
- Unsaturated phosphatidylcholine
Surfactant is amphipathic, what does this mean?
It is soluble in both fat and water.
Which cells produce surfactant?
Goblet cells
Clara/ Club cells
Type II cells
What is special about Type I cells?
they are long and thin and good for gas exchange
What percentage of alveolar surface cells are Type I? Type II?
Type I: 90-95%
Type II: 5-10%
But there are 2x as many Type II cells (they are smaller)
What produces mucus and some surfactant in the upper airways?
Goblet cells
What produces surfactant deeper in the airways? Which cells produce surfactant inside the alveoli?
Clara/Club cells.
In the alveoli–> Type II cells
Where are the phosphatidyls and surfactant proteins made? Where do they go after they are made?
in the ER of the Type II cells. They are undergo exocytosis into the alveolus and attach to tubular myelin (like netting) and they chill there until we breathe.
Under normal conditions, when we breathe in, what happens to the tubular myelin and the surfactant?
The alveoli stretches and the “netting” gets pulled outwards and these surfactants get “knocked off the net” which activates them and they float to the surface where they can decrease surface tension.
When the surfactant falls apart it gets recycled… how does this happen? Who is the MVP of this process?
MVP: alveolar macrophages–> they break down surfactant into its component parts which can get recycled by Type II cells to produce more surfactant
How could putting someone on PPV effect surfactant?
The positive pressure is not as effective at pulling surfactant off of its storage netting. The expanded lungs likely contributes to some releasing of surfactant, but its not the same mechanics or as efficient.
If you have a lobe of the lung that has collapsed, how does this impact surfactant production?
Surfactant in that area of the lung will eventually run out and it wont be as useful at cutting surface tension.
If you have an area of the lung that collapses… can you re-recruit it?
right away maybe with an inspiratory pressure of 10 cmH2O, but in time it’ll be much harder to recruit. This is because of the lack of surfactant.
What’s another secretory cell we’ve talked about in the airways related to the inflammatory process? What do they secrete?
Mast cells
Histamine
How many alveoli do we have? Do we lose these as we get older? Can we make more?
500 million. Yes we lose alveoli with age, but we can make more also!
How many capillaries do we have associated with each alveoli?
about 1000 capillaries per alveoli
How much surface area do we have for gas exchange in a 20 year old healthy adult?
70 m^2 (about the size of a tennis court)
What are the two components of elastic recoil pressure / transpulmonary pressure?
Tissue factors “springs” (1/3)
Surface tension (2/3)
Simply put… what is the force that generates surface tension (this force pushes air out of the lungs)?
water wants to be close to other waters
With obstructive lung disease is there more or less elastic tissue surrounding the alveoli?
less springy tissue–> easier to get air in
With restrictive lung disease is there more or less elastic tissue surrounding the alveoli?
more springy tissue–> harder to get air in
How exactly does surfactant cut surface tension in water?
The polar heads of the surfactant insert themselves in between water molecules and the lipid tails stick out in the air. This separates the water molecules and decreases the surface tension.
At RV airway resistance is increased… give two reasons for this…
- the airway is narrower (increased resistance)
- alveoli are smaller
At TLC airway resistance is reduced… give two reasons for this…
- the airway is wider (less resistant)
- alveoli are really stretched out
What holds open the larger airways? How is this different from the smaller airways?
The larger airways are held open by traction created by the negative pleural pressures. The smaller airways are volume dependent.
