Lung Function Tests (Spirometry) - Obstructive vs Restrictive

Question 1

FEV1

Answer 1

Forced Expiratory Volume in 1st one sec

Question 2

FVC

Answer 2

Forced vital capacity, total volume of air expired

Question 3

FEV1/FVC

Answer 3

Ratio helps in diagnosing Obstructive vs restrictive lung disease.
Decreased in Obstructive (COPD, Asthma, Bronchiectesis) - coz of decrease in FEV

Increased in restrictive (Chest wall D’s, Obesity, Fibrosis, Scoliosis) - Coz of decrease in FVC

Can be normal in Restrictive - coz decrease in FEV1 and FVC

Question 4

Which test differentiates between Asthma and COPD?

Answer 4

Bronchodilator test (Salbutamol or ..)

FEV1 change >12% in Asthma, condition reversed
FEV1 change <12% or no change in COPD

Question 5

Which drug test can help diagnose asthma when FEV1 is normal?

Answer 5

Methacholine test or histamine, Causes pptn of asthma

FEV1 decreased by >20%
Only done when spirometry (FEV1 and FVC) values are normal.

Question 6

Which test helps differentiate the cause of restrictive lung disease i.e., Chest wall disease or …lung disease?

Answer 6

DLCO
Carbon monoxide diffusion test, one inhalation of CO, Helium and room air, gas exchange measured

Diffusion normal - chest disease
Diffusion decreased - Lung disease (alveoli, fibrosis, interstitial lung disease)

In emphysema, pulm capillaries destroyed, decreased DLCO seen

Asthma shows increased DLCO

Question 7

DLCO in COPD increased or decreased?

Answer 7

Decreased

Question 8

DLCO in Asthma increased or decreased?

Answer 8

Increased (shunt like exchange as air is trapped in alveoli)

Question 9

DLCO in Good Pasteur syndrome increased or decreased?

Answer 9

GPS - Pulmonary haemorrhage
DLCO - increased

Question 10

PFT showing obstructive pattern, DLCO decreased, probable diagnosis?

Answer 10

COPD, emphysema

Question 11

PFT showing obstructive pattern, DLCO increased, probable diagnosis?

Answer 11

Asthma