Principles of Gas Diffusion + PFTs

Question 1

Which law can dictate the partial pressure of a gas in a gas mixture

What is the equation

Answer 1

Dalton’s law

Px  = Fx × Ptot

Question 2

Which law can dictate the concentration of a gas dissolved in a liquid

What is the equation

Answer 2

Henry’s Law

Cx = K × Px

Question 3

Which law can dictate the rate of diffusion of a gas

What is the equation

Answer 3

Vx = (D x A x Px)/ T

Question 4

Which characteristic of CO2 causes patients to develop problems in O2 diffusion through the alveolar-capillary barrier before CO2

Answer 4

CO2 has a higher solubility than O2 so it dissolves about 20x faster.

This means patients will have a more difficult time obtain O2 rather than CO2

Question 5

If the gas does not reach diffusion equilibrium then the transport is ______ limited

Answer 5

diffusion limited

Question 6

If the gas can reach diffusion equilibrium then the transport is ______ limited

Answer 6

perfusion limited

Question 7

An example of a gas that is solely diffusion limited

Answer 7

CO

Question 8

An example of a gas that is solely perfusion limited

Answer 8

N2O

Question 9

Which gas that is usually perfusion limited can become diffusion limited when there is an abnormal alveolar-capillary barrier

Answer 9

CO2

Question 10

Which gas that is usually perfusion limited can become diffusion limited under strenuous exercise

What mechanisms during exercise causes this

Answer 10

O2

the thickness of the blood gas barrier and alveolar hypoxia

Question 11

Which gas is used to measure diffusion capacity of the lung and why

Answer 11

CO is used because it is a purely diffusion limited gas

Question 12

What is the normal diffusion capacity of the lung and how do you calculate it

Answer 12

~25 ml/min/mm Hg

DLco = Vco/PAco

Question 13

Under what circumstance does diffusion capacity of the lung increase

Answer 13

during exercise

Question 14

Three determinants of diffusion capacity of the lung

Answer 14

area, thickness of the blood-gas barrier, and volume of blood in the pulmonary capillaries

Question 15

Three factors that can affect the interaction of CO2 with red blood cells

Answer 15

interaction with Hb, carbonic anhydrase and Cl-HCO3 exchange

Question 16

interstitial or alveolar edema/fibrosis can affect which factor that determines diffusion capacity of the lung

Answer 16

Blood-gas barrier (thickens the barrier)

Question 17

emphysema, tumors, low cardiac output and low pulmonary capillary blood volume can affect which factor of diffusion capacity of the lung

Answer 17

Area (decreases surface area)

Question 18

anemia and low pulmonary capillary blood volume decreases diffusion capacity of the lung because

Answer 18

there is decreased uptake by RBCs (less RBCs)

Question 19

Which condition that decreases diffusion capacity of the lung can lead to hypoxemia

Answer 19

Ventilation-perfusion mismatch

Question 20

Two categories of lung diseases

Answer 20

Restrictive and Obstructive

Question 21

Which type of lung disease is characteristic of

• low lung volume
• compliance curve shifted to right
• normal or elevated FEV1/FVC

and what would the DLco be

Answer 21

Restrictive

The DLco would be normal or low

Question 22

Which type of lung disease is characteristic of

• being episodic
• FEV1/FVC is usually low but improves with a bronchodilator

Answer 22

Asthma (obstructive)

Question 23

Which category of obstructive lung disease is characteristic of

• Low FEV1/FVC
• low PEF

give examples

Answer 23

variable expiratory obstructive diseases

eg. asthama, COPD (bronchitis, emphysema)

Question 24

Variable inspiratory effects is characteristic of which type of lung disease

Answer 24

Obstructive

Question 25

Inspiratory and expiratory effects are characteristic of which type of lung disease

Answer 25

Obstructive

Question 26

Which type of lung disease is characteristic of

• sputum production
• DLco is normal
• low Pao2, w/ cyanosis
• high Paco2
• RV, FRC high

Answer 26

Chronic bronchitis (obstructive)

Question 27

Which type of lung disease is characteristic of

• sputum production
• DLco is low
• slightly low Pao2
• normal or slightly increases Paco2
• , TLC, RV, FRC high
• compliance curve shifts to left

Answer 27

Emphysema (obstructive)

Question 28

Does a fixed upper airway obstruction affect inhalation, exhalation or both

Answer 28

both equally

Question 29

Does an intrapulmonary obstruction (emphysema) affect inhalation, exhalation or both

Answer 29

decreases the volume of air for both but especially affects exhalation towards the end

Question 30

Does an intrathoracic bronchial obstruction affect inhalation, exhalation or both

Answer 30

exhalation

Question 31

Does an extrathoracic bronchial obstruction affect inhalation, exhalation or both

Answer 31

inhalation