Lung Function Tests

Question 0

FEV1

Answer 0

Forced expiration volume in the first 1 second

Below 80% of the predicted based on height and weight efforts both obstructive and restrictive illnesses

Question 1

FVC

Answer 1

Forced vital capacity
The total volume of air expired during forced expiration
Normal in obstructive illnesses but reduced in restrictive illnesses

Question 2

TLC

Answer 2

Total lung capacity (or tender loving care)
FVC + residual volume (the amount left in the lung following forced expiration
This is normal in restrictive problems but increased in obstructive problems

Question 3

FEV1/FVC

Answer 3

The proportion of the the total expiratory volume which can be expired in the first second
0.8-1 in restrictive illnesses
<0.7 in obstructive illnesses

Question 4

Obstructive diseases

Answer 4

Asthma, COPD and bronchiectasis
Reduced FEV1 which is less than 0.7 FVC
FVC is normal and TLC can be increased
TCO is usually normal, just getting air out of the lungs is hard

Question 5

Restrictive diseases

Answer 5

Pulmonary fibrosis, scoliosis or obesity
A reduced FEV1 and reduced FVC but FEV1/FVC is normal
TLC is reduced and TCO may be reduced as well
In this case the problem the lung capacity is too small

Question 6

TCO

Answer 6

Gas Transfer coefficient –> measure of gas exchange in 1lung acini. A reduced TCO indicates that the lung tissue there has a reduced ability to transfer gases
Eg pulmonary fibrosis causes thickening of the alveolar interstitium which reduces the TCO

Question 7

Asthma

Answer 7

Obstructive spirometry
Normal gas transfer
FEV1 shows reversibility after salbutamol use

Question 8

COPD/emphysema

Answer 8

Obstructive spirometry
Reduced gas transfer (TCO)
Doesn’t show the same salbutamol reversibility

Question 9

Gas transfer is dependant on…

Answer 9

Alveolar surface area–> reduced in emphysema
Thickness of the alveoli–> increased in pulmonary fibrosis
Blood supply –> reduced after a PE

Question 10

Pulmonary fibrosis

Answer 10

Restrictive spirometry

Reduced gas transfer

Question 11

Pulmonary hypertension

Answer 11

Normal spirometry

Reduced gas transfer

Question 12

Pulmonary haemorrhage

Answer 12

Normal spirometry
Increased gas transfer
Can be autoimmune (Goodpasture’s or wegener’s) with infiltrations around pulmonary capillaries causing their destruction and haemorrhage