Lung Diseases and Lung Function Tests Flashcards
What X2 TYPES of lung disease should you know the lung function tests results for?
What is the physiological change associated with each of these diseases?
Give some examples of each.
Obstructive lung disease
= narrowing of the airways
= hinders the ability to EXPEL air
= asthma/chronic bronchitis/emphysema (COPD)
Restrictive lung disease
= poor lung compliance
= can not fully EXPAND the lungs to inhale
= lung fibrosis/muscle weakness/phrenic nerve damage
Which obstructive lung disease is reversible?
Asthma
What happens to the:
1) airways
2) alveoli
…in asthma?
1) airways = bronchoconstrict with mucosal oedema
2) alveoli = normal
What happens to the:
1) airways
2) alveoli
…in chronic bronchitis?
1) airways = inflamed, glands hypertrophied and excess mucous produced
2) alveoli = normal
What happens to the:
1) airways
2) alveoli
…in emphysema?
1) airways = poorly supported due to loss of elastic tissue therefore likely to lead to dynamic compression on exhalation.
2) alveoli = destroyed therefore decreased gas exchange surface area.
What happens to the:
1) airways
2) respiratory muscles
3) alveoli
…in lung fibrosis?
1) airways = normal
2) respiratory muscles = normal
3) alveoli = stiff/scarred/fibrosed
What happens to the:
1) airways
2) respiratory muscles
3) alveoli
…in respiratory muscle weakness?
1) airways = normal
2) respiratory muscles = weak
3) alveoli = normal
What type of test/graph may help you determine the difference between an obstructive or restrictive lung disease?
What subcategories of tests exist within this blanket term?
How long does this test continue for?
Forced expiration volume vs time graphs.
FEV1 =forced expiration volume in 1 second
FVC = forced vital capacity
NB: both involve inhaling to TLC then exhaling as fast as possible
NB: both can be plotted as one curve on one graph
The rest usually ends after 5 seconds
When plotting volume the units are L, BTPS.
What does the ‘BTPS’ stand for?
Body temperature and pressure saturated.
What is the name of the ratio calculated from FEV1/FVC graphs and what is a normal value for this measurement?
Interpret this result.
It is the FEV1:FVC measurement (forced expiratory ratio).
A normal value is >75%.
This means that in health greater than 75% of vital capacity should be exhaled within the first second.
What happens to the forced expiratory ratio in obstructive lung disease?
The FEV1 is GREATLY reduced due to airway obstruction, and is described as like ‘breathing through a straw’.
The FVC is also reduced.
This means the ratio of the two decreases.
What happens to the forced expiratory ratio in restrictive lung disease?
The FEV1 and the FVC tend to go down concordantly. This is due to the main issue with restrictive lung diseases being the inability to inhale large amounts of air which decreases TLC. The patient is still able to breathe out >75% of their intake within the first second, the intake itself is just reduced.
Restrictive lung disease patients will therefore have a normal FEV1:FVC (forced expiratory ratio).
What two opposing forces determine FRC?
This is the opposing forced between the elastic recoil of the lungs and the recoil of the chest wall.
What happens to the forces involved in FRC in:
1) lung fibrosis
2) emphysema
…describe how this affects chest shape and FRC.
1) lung fibrosis sees an increase in elastic lung recoil and therefore reduces FRC. It does nothing to the shape of the chest however.
2) emphysema sees the elastic tissues destroyed therefore elastic lung recoil is greatly reduced, increasing FRC. This causes the characteristic ‘barrel’ shaped chest seen in these patients.
