Exam 2 Lecture 11 (3-6-23) The Lost Pulmonary Lecture (Alveolar Compliance, Airway Disorder, Surface Tension, Surfactant)

Question 1

In terms of alveolar compliance, what does a steep slope tell us?

What does a horizontal slope tell us?

Answer 1

Steep slope = compliant

Horizontal slope = no compliance

Question 2

At FRC, alveoli at the ______ of the lungs are way more compliant than the alveoli at the _____ of the lung.

Answer 2

At FRC, alveoli at the base of the lungs are way more compliant than the alveoli at the apex of the lung.

Question 3

What is the lung volume of this graph?

Answer 3

1.5 Liters (Residual Volume)

Question 4

What would be the average intrathoracic pressure of this graph?

Answer 4

Intrathoracic Pressure = 1.3 cmH2O

1.3 mmHg will be the halfway point (average ) of -2.2 cmH2O and +4.8 cmH20

Question 5

At a pleural pressure of -2.2 cm H2O on the alveolar compliance graph at RV, what is the percent fullness of the alveoli?

Answer 5

30% full

Question 6

At a pleural pressure of +4.8 cm H2O on the alveolar compliance graph at RV, why is the slope 0?

Answer 6

The small airways at the base of the lungs have collapsed as a result of positive intrathoracic pressure trying to force all the air out of the alveoli.

Question 7

What is the reason why alveolar volume doesn’t dip below 20% fullness?

Answer 7

The pressure used to force the air out also forces the small airways to close. The likelihood of collapsing an airway before the alveoli are completely empty is the reason why alveoli volume does drop below 20% fullness.

Question 8

This term is used to describe areas of the lung more affected by gravity in terms of blood flow and airflow.

Answer 8

Dependent

For an upright position, the dependent portion of the lung would be the inferior lungs.

Question 9

What does PAO2 stand for?

Answer 9

Alveolar PO2 or Partial Pressure of Oxygen in the Alveolus

Question 10

Calculate the normal Minute Alveolar Ventilation rate.

What will Alveolar PO2 be at the calculated Minute Alveolar Ventilation rate?

Answer 10

4.2 L/min

Respiratory Rate x Alveolar Volume
12 breaths/min x 350 mL = 4200 mL/min

At 4.2 L/min, PAO2 will be about 100 mmHg

Question 11

Calculate the normal Minute Dead Space Ventilation rate.

Answer 11

1.8 L/min

Respiratory Rate x Dead Space Volume
12/breaths/min x 150 = 1800 mL/min

1.8 L/min

Question 12

According to this graph as alveolar ventilation increases, what happens to PAO2 assuming that the metabolic rate is unchanged?

Answer 12

Alveolar PO2 will increase.

Question 13

If we are breathing room air, PAO2 will never be above _________.

Answer 13

150 mmHg

Our alveolar PO2 could never be above 150mmHg. Because we can’t take in oxygen with a higher PO2 than from our normal environment.

Question 14

What is the PCO2 of inspired air?

What is the PACO2 under normal alveolar ventilation after equilibrium according to this graph?

Answer 14

0 mmHg

Normal alveolar ventilation is 4.2 L/min. PAO2 will be about 40 mmHg.

Question 15

Normally after gas exchange, our alveolar PCO2 is about _______ if we bring in twice as much fresh air, PCO2 should drop down to ________.

Answer 15

40 mmHg

20 mmHg

Question 16

If there is a normal amount of alveolar ventilation and an abnormally high metabolic rate. What would be expected from the alveolar PCO2?

Under the same conditions, what would be expected from alveolar PO2?

Answer 16

PACO2 will increase.
PAO2 will decrease.

Metabolism will result in more CO2 being produced in the body, and if alveolar ventilation is constant at 4.2 L/min, PACO2 will increase and PAO2 will decrease.

Question 17

If there is a normal amount of alveolar ventilation and an abnormally low metabolic rate. What would be expected from the alveolar PCO2?

Under the same conditions, what would be expected from alveolar PO2?

Answer 17

PACO2 will decrease.
PAO2 will increase.

With low metabolic rates, the body is producing less CO2. If alveolar ventilation is constant at 4.2 L/min, PACO2 will decrease and PAO2 will increase.

Question 18

Calculate the oxygen concentration after it has been inspired and displaced by water vapor.

Answer 18

Partial Pressure of O2 = [O2] x Total Pressure
[O2] = Partial Pressure of O2 / Total Pressure
[O2] = 149 mmHg / 760 mmHg
[O2] = 0.1961
[O2]= 19.61%

Question 19

How much O2 is brought into the gas exchange region during each breath?

Answer 19

VA (volume of air for gas exchange) = 350 mL
[Inspired O2] = 19.61%

350 x 0.1961=
68.62 mL of O2 enter the gas exchange region.

Question 20

How much O2 is expired from the gas exchange regions during each breath?

Answer 20

VA (volume of air for gas exchange) = 350 mL
PAO2 (alveolar PO2 after gas exchange) = 100 mmHg
Total Pressure = 760 mmHg

Need to calculate [O2] after equilibrium (gas exchange)
[O2 after equilibrium] = PAO2 / Total Pressure
[O2 after equilibrium ] = 104 / 760
[O2 after equilibrium] = 0.1368

mL of O2 expired = [O2 after equilibrium] x VA
mL of O2 expired = [0.1368] x 350 = 47.89

47.89 mL expired from the gas exchange region during each breath

Question 21

How much O2 is normally absorbed over the course of one breath?

How much O2 is normally absorbed in one minute?

Answer 21

O2 is brought into the gas exchange region during each breath: 68.62 mL

O2 is expired from the gas exchange regions during each breath: 47.89 mL

68.62 - 47.89 =
20.73 mL of O2 absorbed during each breath

20.73 x 12 breaths/min = 248.76 mL absorbed/min

Question 22

From this graph calculate the normal pulmonary compliance.

Answer 22

Compliance = ΔVolume / ΔPressure
ΔV = 500 mL (Vt)
ΔP = 2.5 cmH2O (Difference in Transpulmonary Pressure)

500 mL / (7.5 cmH2O - 5 cmH2O)
500 mL/ (2.5 cmH2O)
200 mL/cmH2O
0.2 L/cmH2O

Question 23

If we’re entirely healthy, we should be able to get up to total lung capacity using about ________ centimeters of water transpulmonary pressure.

How much intrapleural pressure would be used?

Answer 23

30 to 35 cmH2O of transpulmonary pressure

-30 to -35 cmH2O fo intrapleural pressure

Question 24

What kind of airway disorder is emphysema?

Answer 24

Obstructive Airway Disorder

The alveoli lose their natural recoil ability which makes it difficult to expire old air resulting in less fresh air inspiration.

Question 25

Describe the pulmonary compliance of a normal lung to a lung with emphysema.

Answer 25

Normally, it would take a transpulmonary pressure of 30 or 35 cmH2O for a lung to reach TLC. A lung with emphysema only takes a transpulmonary pressure of 10 cmH2O to reach TLC (more compliant).

“So the problem here isn’t with filling the lung. It’s filling the lung with fresh air after you’ve expired some of the old air.” - Dr. Schmidt

Question 26

Describe how air trapping occurs with emphysema.

Answer 26

With emphysema (COPD), if we push to make our thoracic pressure positive to get air out, pushing on the alveolar walls also ends up applying pressure to the small airways causing them to collapse leading to air trapping.

Question 27

What was another example of an obstructive airway disorder described in lecture besides emphysema?

Answer 27

Asthma is described as an obstructive disorder d/t the narrower airways.

Question 28

What can happen to the lungs as a result of sucking in asbestos or working at a steel mill?

Answer 28

Lungs can become scarred or fibrotic leading to restrictive lung diseases.

With fibrosis, there is an increase in the stiffness of our alveoli and small airways. This makes it more difficult to get air into the lungs.

Question 29

What is the TLC of a fibrotic lung depicted in this graph?

Answer 29

TLC is about 3 Liters above residual volume (4.5 L).

Given that the fibrotic lung has a normal RV, this lung is about 1.5 L short of normal TLC

Question 30

What is the intrinsic protease inhibitor in our lungs called?

Where is this protease inhibitor produced?

Answer 30

Alpha1 Antitrypsin (α1A/T)

Produced in the Liver.
If we have liver problems, the lungs will end up digesting itself. (terrible alcoholics can end up having lung problems)

Question 31

________ activity tends to cause loss of these elastic stretchy fibers that we rely on to get the air out of our lungs.

___________ is a circulating protein that shuts down the intrinsic proteolytic activity.

Answer 31

Protease

Alpha1 Antitrypsin (α1A/T)

Question 32

If someone lacks the normal gene for α1A/T, life expectancy is somewhere between ____ and _____ years old.

Answer 32

25 to 40 years

Question 33

Which letter represents a normal lung?

Answer 33

A

Question 34

Which letter represents restrictive lung disease?

Answer 34

B

Restricted lung diseases shrink all lung volumes proportionally

Question 35

Which letter represents obstructive lung disease?

Answer 35

C

There will be a much larger total lung capacity. A large chunk of lung volume will be stale air that we can’t get it out (increased RV). As a consequence of this, there will also be a decrease in vital capacity by decreasing IRV.

Question 36

Describe what happens to the following lung volumes with obstructive lung disease:
RV:
ERV:
FRC:
IRV:
TLC:
VC:
IC:
VT:

Answer 36

RV: Increase
ERV: Decrease
FRC: Increase
IRV: Decrease
TLC: Increase
VC: Decrease
IC: Decrease
VT: Increase (The breathing frequency may be decreased to reduce the work expended overcoming the airway resistance. There will be an increase VT to compensate for this.) - Lange

Question 37

What two components discussed in the lecture make up pulmonary compliance?

How much does each factor contribute to pulmonary compliance?

Answer 37

1. Behavior of the lung tissue itself (one-third of pulmonary compliance)
2. The effect of surface tension (two-third of pulmonary compliance)

Question 38

Describe the compliance between inspiration and expiration of the dashed black line.

Answer 38

The lungs are more compliant during expiration than inspiration.

When the lungs are deflated, it requires about 8-10 cmH2O of transpulmonary pressure to inflate the lungs.

Question 39

A term used to describe the behavior of the lung between inspiration and the behavior of the lung during expiration.

Answer 39

Hysteresis

Question 40

In reference to the blue line, what was done to the lung? What has been removed?

Answer 40

All the air was massaged out of the lung and replaced with normal saline. Removing all of the air out of the lungs and replacing it with fluid, results in the removal of surface tension from the lungs.

No air-water interface will result in no surface tension.

Question 41

What does surface tension do to our alveoli?

Answer 41

Surface tension would shrink the size of the alveoli to minimize the air-water interface. This is what makes up two-thirds of the recoil pressure of the lungs.

Question 42

What substance manages surface tension force?

Answer 42

Surfactant

Question 43

What is surfactant composed of?

Answer 43

Surfactant is a combination of four proteins and a bunch of phospholipids.

Question 44

Which surfactant proteins are hydrophilic?
Which surfactant proteins are hydrophobic?

What percentage of the surfactant is composed of surfactant proteins?
What percentage of the surfactant is composed of phospholipid compounds?

Answer 44

Hydrophilic: Surfactant Protein-A, Surfactant Protein-D
Hydrophobic: Surfactant Protein-B, Surfactant Protein-C

10% of the surfactant is composed of these four proteins
90% of the surfactant is composed of phospholipid compounds.

Question 45

What phospholipid compound makes up the majority of surfactants?

Answer 45

Phosphatidylcholine (31%)

Question 46

Where is surfactant produced?

Answer 46

Surfactant is produced in the alveolar wall, by type II alveolar pneumocytes.

Question 47

What happens to our alveoli if we have a surfactant deficiency?

Who can develop this deficiency?

Answer 47

If we have a surfactant deficiency, it becomes very difficult to put air into the alveoli due to increased surface tension (decreased compliance).

Premature kids that are born ~2 months early, sometimes they’re born before their lungs can produce their own surfactants. You might have to ventilate them and put some exogenous surfactant into a ventilator to help get air into their lungs. Other examples: Emphysema, Restrictive Lung Disease, and Lung Cancer.