Lung Function Tests

Question 1

What are lung function tests helpful for?

Answer 1

• Lung disease diagnosis

- Especially helpful for obstructive and restrictive lung disease

Question 2

Discuss the use of spirometry.

Answer 2

• Used to establish objective measures of lung function.
• It involves different breathing exercises into a machine that measures volumes of air and flow rate and produces a report.

Question 3

What is reversibility testing in spirometry testing?

Answer 3

Give a bronchodilator (eg salbutamol) prior to repeating the spirometry to see if this has an impact on the results.

Question 4

Discuss spirometry results in an obstructive pattern.

Answer 4

An obstructive pattern is typical if you have a lung condition that narrows your airways, such as COPD or asthma.

FEV1< 75% of FVC (FEV1:FVC<75%) can diagnose obstructive respiratory disease.

Question 5

MILD Obstructive Lung Disease

Answer 5

MILD
FEV1 is 80% or more of the predicted value. If you have mild COPD, your spirometry test results can be normal after you take medication.

Question 6

MODERATE Obstructive Lung Disease

Answer 6

MODERATE

FEV1 is 50-79% of the predicted value after medication

Question 7

SEVERE Obstructive Lung Disease

Answer 7

SEVERE

FEV1 is 30-49% of the predicted value after medication

Question 8

VERY SEVERE Obstructive Lung Disease

Answer 8

VERY SEVERE

FEV1 is below 30% of the predicted value after medication

Question 9

Discuss spirometry results in restrictive patterns.

Answer 9

With a restrictive pattern, the total amount of air you can breathe in is reduced but the speed you can breathe out is preserved.

In this situation, both the FEV1 and FVC will be lower than predicted (equally reduced), but the ratio between the two will not be reduced.

Question 10

COPD Spirometry Results.

Answer 10

People with COPD have an FEV1/FVC ratio lower than 70%.

Question 11

Discuss breathing in obstructive disease

Answer 11

A person may have good air volume but is only able to move air out of the lungs slowly due to obstruction.

Question 12

Discuss breathing in restrictive diseases

Answer 12

Restriction of the ability of the lungs to expand and fill with air.
Lungs are restricted from effectively expanding,

Question 13

Causes of restrictive lung diseases

Answer 13

• Interstitial lung disease - pulmonary fibrosis
• Sarcoidosis
• Obesity
• Motorneuron disease
• Scoliosis

Question 14

What is peak flow a measure of?

Answer 14

The peak or fastest point of a person’s expiratory flow of air.
It can be referred to as a peak flow expiratory flow rate (PERF).
A simple way of demonstrating how much obstruction to airflow is present in the lungs.

Question 15

What is PERF useful in?

Answer 15

Obstructive lung disease, in particular, asthma.

Can measure how well asthma is controlled and how severe an acute exacerbation is.

Question 16

How is peak flow recorded?

Answer 16

As a percentage of predicted.
Prediction varies dramatically based on sex, height, and age. Use of reference chart needed.

For example:
An asthmatic patient has predicted peak flow of 400 that only manages a score of 200 on their best attempt, therefore, has a peak flow of 50% of predicted.

Question 17

Define Tidal Volume (TV)

Answer 17

The volume of air breathed in and out of the lungs at each breath.

Question 18

Define Expiratory Reserve Volume

Answer 18

The maximum volume of air which can be expelled from the lungs at the end of a normal expiration.

Question 19

Define Inspiratory Reserve Volume

Answer 19

The maximum volume of air which can be drawn into the lungs at the end of a normal inspiration.

Question 20

Define Residual Volume

Answer 20

The volume of gas in the lungs at the end of a maximal expiration.

Question 21

Define Vital Capacity

Answer 21

The greatest volume of air that can be expelled from the lungs after taking the deepest possible breath.

Vital Capacity (VC) = tidal volume + inspiratory reserve volume + expiratory reserve volume

Question 22

Define Total Lung Capacity (TLC)

Answer 22

Lung capacity or total lung capacity (TLC) is the volume of air in the lungs upon the maximum effort of inspiration.

Total Lung Capacity (TLC) = vital capacity + residual volume

Question 23

Define Inspiratory Capacity (IC)

Answer 23

The maximum volume of air that can be inspired after reaching the end of a normal, quiet expiration.

Inspiratory Capacity (IC) = tidal volume + inspiratory reserve volume

Question 24

Define Functional Residual Capacity

Answer 24

Functional residual capacity (FRC), is the volume remaining in the lungs after a normal, passive exhalation.

Functional Residual Capacity = expiratory reserve volume + residual volume

Question 25

Define FEV1:FVC

Answer 25

FEV1:FVC = Fraction of forced vital capacity expired in 1 second.

Question 26

How can you assess reversibility?

Answer 26

To assess reversibility, administer 400 micrograms of salbutamol and repeat spirometry after 15 minutes

Question 26

Results of reversibility testing?

Answer 26

The presence of reversibility is suggestive of a diagnosis of asthma.
The absence of reversibility suggests fixed obstructive respiratory pathology such as chronic obstructive pulmonary disease (COPD).
Partial reversibility may suggest a coexisting diagnosis of asthma and another obstructive airway disease (e.g. COPD).

Question 27

Typical results in restrictive lung disease spirometry

Answer 27

Typical spirometry findings in restrictive lung disease include:

Reduced FEV1 (<80% of the predicted normal)
Reduced FVC (<80% of the predicted normal)
FEV1/FVC ratio normal (>0.7)

Question 28

Typical results in obstructive lung disease spirometry

Answer 28

Reduced FEV1 (<80% of the predicted normal)
Reduced FVC (but to a lesser extent than FEV1)
FEV1/FVC ratio reduced (<0.7)