Diffusion

Question 1

What are four causes of respiratory insufficiency with adequate ventilation?

Answer 1

1. Reduced blood volume
2. Abnormal hemoglobin
3. Diffusion impaired
4. Va/Qc mismatch

Question 2

What three variables affect diffusion rate?

Answer 2

1. Pressure gradient
2. Surface area
3. Distance/thickness

Question 3

What are the pros of using the Steady State method for measuring diffusing capacity?

Answer 3

Natural
Easier for pts w/ lung disease
Exercise

Question 4

What are the pros of using the Single Breath method for measuring diffusing capacity?

Answer 4

Rapid, less invasive

Question 5

What variables can affect your DLco?

Answer 5

1. Age
2. Sex
3. Height
4. Anemia - always correct for it

Question 6

Why is CO a good gas to use when calculating DL?

Answer 6

Diffusion limited
Hb has a high affinity for CO
Partial pressure stays low
Gradient is always maintained irrespective of perfusion

Question 7

What is the average DLco of a resting adult patient via single breath method?

Answer 7

~25ml of CO/min/mmHg

Question 8

What is the most common disease mechanism to contribute to decreasing DLco?

Answer 8

Loss of surface area