Exam 2 - Pulmonary Lecture 4 Flashcards
What is basic spirometry incapable of measuring?
Anything that contains RV (FRC, TLC)
Hoe does advanced spirometry work?
What is it able to measure?
- An inert gas (usually helium) is inhaled by the patient and the amount that the helium is diluted by can tell us FRC
- If we know the beginning concentration and volume of hellium, and the end concentration - the amount of dilution should tell us FRC - from FRC we can subtract ERV to obtain RV
- Once we know FRC and RV, we can then calculate TLC
How can you calculate FRC using the helium-dilution technique?
Amount of solute (mg) = concentration of solute (mg/mL) ✖️ volume of solvent (mL)
Rework to solve for volume of solvent (FRC)
What equation can be used to solve for FRC when given helium fractional concentrations?
VLf is FRC
What is the second highest cause of lung cancer behind smoking?
Radon gas exposure - found in soil, usually found in basements
Explain pulmonary compliance in emphysema, shown in the image below:
- With a small increase in PTP, there is a large increase in lung volume → very compliant
- This occurs due to loss of elastic tissue making it easy to fill the lungs, but it is difficult for the air to escape (loss of passive expiratory force)
- A more steep line = increased compliance
Describe pulmonary compliance in fibrosis, as shown below:
- At very high PTP the lung volumes are not very high → less compliant
- This is due to scarring or stiffening of the alveoli making them difficult to fill
What volumes is this graph describing?
- Vital capacity
- TLC - RV = VC
Typically, what are lung volumes like in restrictive and obstructive lung diseases?
Restrictive - volumes are low (fibrosis)
Obstructive - volumes are high (emphysema)
What does this graph tell us about inspiratory compliance?
Anesthetic implications?
- At low lung volumes, the lungs are not very compliant - as shown it takes about 10 cmH2O before air actually begins to fill the lungs
- For patients who are at low lungs volumes (all anesthetized patients), we may need to use higher pressures to get air into the lungs
Why is the saline filled lung more compliant than the air filled lung?
How does the lung mitigate this?
- Because the air filled lung has much higher surface tension
- The interaction between water and air in the alveoli creates an increased difficulty to filling the lungs, especially at low lung volumes
- By use of surfactant to break up the water molecules from sticking together
How much of the surfactant production is proteins?
Describe the proteins produced?
- 10 %
- SP-A and SP-D are hydrophilic (majority)
- SP-B and SP-C are hydrophobic (minority)
How much of the surfactant production are lipids?
Describe the important lipids discussed?
- 90%
- Dipalmitoylphosphatidylcholine
- Phosphatidylcholine
- These are amphipathic - have a polar head and fatty acid tail
Where are goblet cells and what is their function?
- Upper airway
- Secrete mucous and some surfactant
Describe clara or club cells?
Found in the deeper airways and secrete surfactant
Describe Type I alveolar cells?
- Very thin, excellent for gas exchange
- Make up 90-95% of alveolar surface area
Describe Type II alveolar cells?
- Sit in between Type I cells and produce surfactant
- Large and cuboid
- There are twice as many as Type I cells but only make up 5-10% of the surface area of the alveoli
The process by which surfactant is released from Type II cells?
Exocytosis
This is where surfactant proteins and lipids are stored before they are needed?
Tubular myelin
How does surfactant move from storage to the air-liquid interface?
How is this effected by PPV?
- During inspiration, the alveolar pressure becomes negative pulling the surfactant molecules from tubular myelin up to the air-liquid interface where they arrange themselves in between the water molecules
- The use of positive pressure is less effective at moving surfactant to the air-liquid interfacing, resulting in increased difficulty to fill the lung
What is the role of alveolar macrophages?
They digest the old surfactant molecules and break them down into their component parts that can be uptaken back into the Type II cells for reuse
Why is hard to rerecruit collapsed alveoli?
- Alveoli that are not being used are not making surfactant at normal levels resulting in deficiency
- This causes there to be a higher surface tension making it even harder to fill those alveoli with air
- Air will choose to go to where it is easier to fill, meaning we may need to use high pressures to get those portions of the lung back open
- Also, the longer they’re collapsed, the harder they are to open back up
Mast cells function?
- Release inflammatory mediators
- Primarily histamine which causes vasoconstriction
How many alveoli do we have?
Can we make more?
- 500 million
- Yes, alveoli can be replaced overtime but very slowly
How many capillaries could 1 alveoli have?
1000
How much surface area does a healthy 20 year old have for gas exchange?
70 m2
What 2 things contribute to eleastic recoil pressure and what is their contribution?
- Elastic recoil of the tissues (1/3)
- Surface tension created by water molecules wanting to be by each other (2/3)
Explain why lung volumes are different in obstructive and restricitve lung diseases at a normal PIP?
- In obstructive disease, loss of ER means there is less resistance to filling and therefore increased volume
- In restrictive disease, there is increase in ER = more resistance to filling and decreased volumes
All lung disorders have ____ deficency
surfactant
Surfactant helps gas exchange by ?
Keeping the lungs “dry” by creating a thin layer of water as opposed to a collection of water if there was not surfactant
How is lung volume related to airway resistance, specifically in the alveoli?
- Higher lung volumes have lower airway resistance and lower lung volumes have higher airway resistance
- This is because at low volumes, the airway diameter is reduced and has higher resistance. At high volumes, the airway diameter is larger and has less resistance.
How are the small airways resistance affected by lung volumes?
- As lung volumes increase the airways are pulled open more, decreasing resistance.
- As the alveoli expand, the elastic recoil in their walls increases (along with PIP becoming more negative), which is transmitted to the attachments, pulling the airway open
How much anatomic dead space is there per body weight?
1 mL/lb of ideal body weight
