Diffusion of Gases

Question 1

What is the primary determinate of the rate of diffusion?

Answer 1

Difference between partial pressures

Other factors:

Thickness and properties of membranes

Surface area of the alveolus

Question 2

What is perfusion limitation and what is the physiological implication of this property?

Answer 2

Refers to a gas diffusing through the membrane and quickly equilibrating

This means that in order to deliver more oxygen to the body, more blood needs to be pumped through the pulmonary circulation

O2, N2O, and CO2 are all perfusion-limited

Question 3

What is Diffusion limitation and what gas is a common example?

Answer 3

The gas does not equilibrate by the time blood reaches the end of the pulmonary capillary, the partial pressure difference is maintained

CO

Question 4

What is the diffusing capacity (DLco) of the lung?

Answer 4

Pulmonary function test that is used to measure how well the patient’s lungs exchange gases - measure of conductance

CO is the only gas for which you can determine deltaP across pulmonary capillaries

Question 5

Why do obstructive and restrictive lung disease reduce DLCO?

Answer 5

Obstructive - alveolar simplification and loss of pulmonary capillary structures

Restrictive - thickening of the alveolar capillary membrane, impairing diffusion