Pulmonary Function Tests

Question 1

Define FEV1

Define FVC

What component of the PFT are these a part of?

Answer 1

FEV1 = forced expiratory volume in 1 second

FVC = Forced vital capacity = full volume exhaled after maximal effort

Part of Spirometry

Question 2

What are the components of a PFT?

Answer 2

Spirometry
Lung volumes (rarely done)
Diffusion

Question 3

Define Functional Residual Capacity

Define Residual volume

What component of the PFT are these a part of?

Answer 3

Functional residual capacity is the volume remaining in the lungs after normal expiration

Residual volume is the volume remaining in the lungs after maximal expiration

Part of Lung volumes

Question 4

The diffusion component is characterized by a formula. What is it?

Answer 4

KCO = DLCO/VA

Question 5

Define the following:

DLCO:
VA:
KCO:

What component of the PFT are these a part of?

Answer 5

DLCO: Diffusion capacity for CO (carbon monoxide)
VA: Alveolar volume = measure of the volume of the lungs
KCO = DLCO/VA = How well the lungs transfer gas per alveolar unit

Part of Diffusion

Question 6

What are the 3 components of spirometry?

Answer 6

Functional mechanics of the lungs (FEV1/FVC)
Reversibility testing
Flow volume loop

Question 7

Using the components of spirometry, what would an obstructive picture look like?

What about the diffusion component?

Answer 7

Obstructive:
FEV1/FVC <0.7 due to reduction in FEV1
ASTHMA ONLY: Increase in FEV1 by 12% and 200ml with reversibility testing (absent in other obstructive diseases)
+ Flow volume loop showing !!Scooped out/concave exhalation curve

DLCO reduced in all !!except asthma where it is normal!!

Question 8

With regards to restrictive lung disease in PFT testing, they can be separated into 2 categories. What are they? Give examples

How will you differentiate them?

Answer 8

Intrinsic Restriction (Pulmonary fibrosis/sarcoid). Reduced DLCO

Extrinsic Restriction (Motor neuron disease, scoliosis, hyperkyphosis). Normal DLCO

Should make sense not memorised

Question 9

Using the components of spirometry, what would a restrictive picture look like?

What about the diffusion component?

Answer 9

Both FEV1 and FVC are <80% predicted
Reversibility testing not relevant
+ Flow volume loop with normal shape but reduced overall size

Reduced DLCO in intrinsic restriction and normal in extrinsic

Question 10

In terms of lung volume, how will you differentiate between an obstructive and restrictive pattern?

Answer 10

Obstructive: Hyperinflation => increased TLC and RV

Restrictive: Reduced TLC, RV, VC