Lecture 11 & 12: Pulmonary (Exam II) Flashcards
What is normal alveolar ventilation (V̇A) ?
How is it calculated?
- 4.2 L/min
- VA x resp rate = V̇A
What is the highest that PAO₂ can be at room air O₂ concentrations at normal atmospheric pressure? Why?
- 150mmHg
- Cannot be higher than 150mmHg due to this being the oxygen concentration of the air.
What is the lowest that PAO₂ can be (and still have life)?
40mmHg
What could cause a left shift on the PAO₂ curve below?
- ↓ V̇A
- ↑ metabolism
What could cause a right shift on the PAO₂ curve below?
- ↑ V̇A
- ↓ metabolism
A decrease in V̇A would cause a __________ in PACO₂.
Increase
An increase in V̇A would cause a __________ in PACO₂.
decrease
What is the percentage of O₂ in a humidified inspiration?
19.69%
↓
149.7 ÷ 760 = 19.69%
How much of of an VA inspiration is O₂?
- 68.9 mL O₂
350mL x [0.1969] = 68.915 mL O₂
How much of VA O₂ (in mLs) leaves per exhaled breath?
Assume PAO₂ = 104mmHg
PAO₂ after equilibrium = 104mmHg
↓
104mmHg ÷ 760mmHg = 0.1368 O₂ content.
↓
350mLO₂ x 0.1368 = 47.88 mLO₂
=
47.88 mL O₂ is unabsorbed with each breath.
How much of VA O₂ (in mLs) is absorbed per breath?
Assume PAO₂ = 104mmHg
Total inspired O₂ per breath = 68.915 mLO₂
↓
Total expired O₂ per breath = 47.88 mL O₂
↓
68.915 - 47.88 mLO₂ = 21.035 mLO₂ absorbed per breath.
How much total O₂ is exhaled per breath?
VA = 350mL
VD = 150mL
↓
350mL x 0.1368[O₂] = 47.88mLO₂
+
150mL x 0.1969[O₂] = 29.54mLO₂
↓
= 77.42 is the total O₂ (both VA and VD) expired per breath.
How much CO₂ is exhaled per minute?
Assume the patient has a respiratory rate of 12bpm and give your answer in liters.
PACO₂ = 40mmHg
↓
VD CO₂ content = 0
+
VA CO₂ = 40mmHg ÷ 760mmHg = .0526
↓
350mL x 0.0526[CO₂] = 18.42mLCO₂
↓
18.42mLCO₂ x 12bpm = 0.221 Liters of CO₂ per minute.
What is the compliance of the lungs based on graph below?
ΔV / ΔP = Compliance
0.5L / 2.5cmH₂O = 0.2L/cmH₂O
What is normal lung compliance?
0.2 L/cmH₂O
An increase of 1cmH₂O in pulmonary compliance creates an increase in pulmonary volume by _________.
Assume normal physiology
200mLs
A decrease in pulmonary compliance by 2 cmH₂O results in a ________ in pulmonary volume by _________mls.
Assume normal physiology.
decrease: 400mLs
What occurs with very small airways in the lungs when we have low lung volumes?
Small airways can collapse
What lung volumes can normal spirometry not measure?
Residual Volume (RV) and thus FRC and TLC as well.
How can FRC be measured utilizing spirometry?
Helium spirometry.
Suppose you had a spirometer of 10L with a Helium concentration of 10%.
After being attached to a patient and a respiratory cycle, the helium concentration becomes 8%.
What is the patient’s FRC?
1L He starting out
↓
0.08 * x = 1L He
↓
x = 12.5 (new total volume)
↓
12.5 - 10 = 2.5L = FRC
What is the 2nd leading cause of lung cancer?
Radon
What would occur with the elasticity of lung tissue with emphysematous lungs?
↓ PER
Therefore, more compliant.
What would occur with the elasticity of lung tissue with fibrotic lungs?
↑ PER
Therefore, less compliant.
What would occur with alveolar size in fibrotic lungs? Why?
Alveolar size would decrease due to excessive PER.
What would occur with alveolar size in emphysematous lungs? Why?
Alveolar size would increase due to loss of PER.
Would total lung capacity (TLC) be increased or decreased (compared to normal lungs) at 30 cmH₂O in fibrotic lungs?
TLC would be decreased
Would total lung capacity (TLC) be increased or decreased (compared to normal lungs) at 30 cmH₂O in emphysematous lungs?
TLC would be increased
What pulmonary pressure works against PER?
PIP
What are the two components affecting lung PER and compliance?
Which one has the greater effect?
- Surface Tension (⅔ of PER)
- Tissue Elasticity (⅓ of PER)
PER or compliance? or both?
Why is there such a difference in the pulmonary compliance of an air-filled vs a saline-filled lung?
There is a loss of surfactant and thus loss of surface tension in the saline filled lung.
At what pressures is the lung most compliant during inspiration?
~ 9-16 cmH₂O
At what pressures is the lung least compliant during inspiration?
Why is this?
~ 0-8 cmH₂O
Lack of surfactant could be the cause of this period of non-compliance.
What term describes the change in lung behavior seen between inspiration and expiration?
Hysteresis
What substance counteracts the air-water interface surface tension?
Surfactant
What type of cell produces surfactant?
Type II cuboidal alveolar cells
What type of cell participates in gas exchange?
Type I alveolar cells
Which of the lung capacity figures below is indicative of obstructive disease? Why?
Trapping of air noted by the massively increased RV.
Which of the lung capacity figures below is indicative of restrictive disease? Why?
All lung volumes are decreased with no noted air trapping as seen with obstructive disease.
Which surfactant protein molecules are hydrophilic?
Which are hydrophobic?
- Hydrophilic: A & D
- Hydrophobic: B & C
What molecule forms the basis for most pulmonary surfactants?
Phosphatidylcholine
All lung pathologies feature a deficiency in __________.
surfactant
What composes surfactant?
Lipids (90%)
Proteins (10%)
What do the surfactant lipids do?
- Lower surface tension
- Limit lymphocyte cytotoxicity.
What do the surfactant proteins do?
- Enhance chemotaxis & phagocytosis.
- Aggregate & opsonize micro-organisms.
- Inhibit bacterial growth.
A strong IC is indicative of what?
Good lungs
A poor IC is highly correlated with bad lungs.
What prevents autodigestion of the lungs via proteases?
- α1AT (α-1 Antitrypsin)
How can EtOH abuse lead to damaged lungs?
The liver produces α1-AT, without this molecule, the lungs will undergo proteolysis.
What sort of pathology is seen from a lack of α1-AT?
Emphysema
- Lack of small alveoli
- Any alveoli left are distended and dysfunctional
What cells package surfactant for release into the air-water interface?
Lamellar bodies
What are the two components that make up a V/Q ratio?
V̇A = 4.2L/min
Q = 5L/min
What is a normal V/Q ratio?
V/Q = 4.2/5 = 0.8
What would a V/Q of 0 indicate?
0/5 so there is no airflow. Perfusion is occurring with no ventilation. Likely an airway obstruction.
What would a V/Q of ∞ indicate?
4.2/0 so there is no blood flow. Ventilation is occurring with no perfusion. Likely something like a pulmonary artery embolus.
What would PACO₂ and PAO₂ be in the event of a pulmonary embolus? Why?
PAO₂ = 150mmHg
PACO₂ = 0 mmHg
No change in either number from room air due to no gas exchange occurring.
What would PACO₂ and PAO₂ be in the event of an acute airway obstruction? Why?
PAO₂ = 40mmHg
PACO₂ = 45 mmHg
No change in either number from returning mixed venous blood due to no fresh air reaching the alveolus.
In normal physiology, an increased V/Q ratio would be seen at the _____ of the lungs.
Apex
In normal physiology, a decreased V/Q ratio would be seen at the _____ of the lungs.
Base
V/Q matching tends to _______ as we get older.
decrease
Anesthesia will induce _____ lung volumes
low
What change occurred between these two graphics?
Artificial PEEP was introduced to improve V/Q matching by increasing V̇A.
