Principles of Gas Diffusion + PFTs Flashcards
Which law can dictate the partial pressure of a gas in a gas mixture
What is the equation
Dalton’s law
Px = Fx × Ptot
Which law can dictate the concentration of a gas dissolved in a liquid
What is the equation
Henry’s Law
Cx = K × Px
Which law can dictate the rate of diffusion of a gas
What is the equation
Vx = (D x A x Px)/ T
Which characteristic of CO2 causes patients to develop problems in O2 diffusion through the alveolar-capillary barrier before CO2
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
If the gas does not reach diffusion equilibrium then the transport is ______ limited
diffusion limited
If the gas can reach diffusion equilibrium then the transport is ______ limited
perfusion limited
An example of a gas that is solely diffusion limited
CO
An example of a gas that is solely perfusion limited
N2O
Which gas that is usually perfusion limited can become diffusion limited when there is an abnormal alveolar-capillary barrier
CO2
Which gas that is usually perfusion limited can become diffusion limited under strenuous exercise
What mechanisms during exercise causes this
O2
the thickness of the blood gas barrier and alveolar hypoxia
Which gas is used to measure diffusion capacity of the lung and why
CO is used because it is a purely diffusion limited gas
What is the normal diffusion capacity of the lung and how do you calculate it
~25 ml/min/mm Hg
DLco = Vco/PAco
Under what circumstance does diffusion capacity of the lung increase
during exercise
Three determinants of diffusion capacity of the lung
area, thickness of the blood-gas barrier, and volume of blood in the pulmonary capillaries
Three factors that can affect the interaction of CO2 with red blood cells
interaction with Hb, carbonic anhydrase and Cl-HCO3 exchange
interstitial or alveolar edema/fibrosis can affect which factor that determines diffusion capacity of the lung
Blood-gas barrier (thickens the barrier)
emphysema, tumors, low cardiac output and low pulmonary capillary blood volume can affect which factor of diffusion capacity of the lung
Area (decreases surface area)
anemia and low pulmonary capillary blood volume decreases diffusion capacity of the lung because
there is decreased uptake by RBCs (less RBCs)
Which condition that decreases diffusion capacity of the lung can lead to hypoxemia
Ventilation-perfusion mismatch
Two categories of lung diseases
Restrictive and Obstructive
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
Restrictive
The DLco would be normal or low
Which type of lung disease is characteristic of
- being episodic
- FEV1/FVC is usually low but improves with a bronchodilator
Asthma (obstructive)
Which category of obstructive lung disease is characteristic of
- Low FEV1/FVC
- low PEF
give examples
variable expiratory obstructive diseases
eg. asthama, COPD (bronchitis, emphysema)
Variable inspiratory effects is characteristic of which type of lung disease
Obstructive
