Pulmonary Function Tests

Question 1

What are the two types of respiratory disorders?

Answer 1

Restrictive disorders - extra-airway diseases, disorders that RESTRICT the ability for the lungs to fill

Obstructive disorders: airway diseases, disorders associated with OBSTRUCTED airflow, airway swollen and inflamed, goblet cells secreting hyperviscous mucus -> lumen space smaller -> increase airways resistance

Question 2

Peak flow meter:

What is it used for?
How to interpret results?

Answer 2

Peak flow meter is used to measure airways resistance

Once you get the reading you can use a graph to compare it to expected range for that age group/gender/height

Question 3

Volume - time curves

What is FVC?

What is FEV1?

What do volume time curves look like for people w obstructive and restrictive lung disorders?

FEV1/FVC ratios?

Answer 3

Forced vital capacity is the highest value measured

FEV1 - forced expired volume in one second

Obstructive volume-time curve:
shallower - because of the increased airways resistance, reduction in the rate that air can be moved.
Plateauing point is generally lower - FVC reduced —> bc of increase in residual volume due to emphysemic breakdown of tissue or muscular issue (respiratory musculature no longer strong enough to inflate lungs)

Restrictive volume-time curve:
FEV1 roughly the same
FVC reduced

FEV1/FVC ratio:
Normal - 83%
Restrictive - 100%
Obstructive- 53%

Restrictive pattern of FEV1/FVC ratio common in small sporty people bc they have relatively large airways and small lungs

Question 4

Flow volume loops:

How to read them?

Effect of obstructive and restrictive disorders on flow volume loops?

Answer 4

Anything going up - expiratory manoeuvre

Anything going down - inspiratory manoeuvre

Mild obstructive disease:
Narrower curve
Reduced FVC (3.5 L instead Of 5 L)
Coving - rate of expiration lower once you get beyond first 1/3rd
Max flow rate lower
-> the narrower the curve, the more coving (indented) and lower the peak expiratory flow, the worse the obstructive disease is

Restrictive disorder:
Normal peak at the start (maybe a bit lower bc you’ve got less stretch in the system to create the velocity)
FVC narrower/reduced

Question 5

Abnormal flow volume loops:

Variable extrathoracic obstruction

Fixed airway obstruction

Answer 5

Variable extra thoracic obstruction:
Blunted inspiratory curve otherwise normal
Blunted expiratory curve otherwise normal

Fixed airway obstruction:
Blunted inspiratory curve
Blunted expiratory curve
Otherwise normal