1. Interpreting Lung Function

Question 1

When interpreting Lung Function, what values are important to consider before doing so?

Answer 1

Patient’s

1. Age
2. Sex
3. Height
4. BMI
5. Ethnicity

Question 2

What different types of Lung Function tests exist?

Answer 2

1. Spirometry (Lung Volume)
2. Total Lung Capacity (Helium)
3. Peak Flow Measurement (Airflow using Vitalograph)
4. V/Q Test Matching (Isotopes)
5. Measuring Gas Transfer (Comparing PO2 at different sites)
6. Exercise Testing (Challenge)

CR1 (L26)

Question 3

What does a spirometer measure? And what values are often obtained?

Answer 3

Volume and Flow of Air that can be Inhaled and Exhaled.

FEV1 (Forced Expiratory Volume in a second)
FVC (Forced Vital Capacity, total amount you can blow in a breath)

Question 4

Of the two, which lung function method is more reproduceable?

Answer 4

PEF is less reproduceable than Spirometry

Question 5

What is PEF?
What do we use it to test?
How do we test it?

Answer 5

Maximum rate/HOW FAST a person can exhale during a Short Maximal Expiratory Effort after Full Inspiratory

Assesses for Airway resistance
COPD/Asthma control at home/GP

Full inspiration + Sharp blow
- Average of Three attempts

Question 6

With regards to Spirometry, how would the values change in an individual with Obstructive Lung Disease?

Answer 6

Decrease in All Three
---------------------------------
FEV1
FVC
FEV1/FVC

Question 7

With regards to Spirometry, how would the values change in an individual with Restrictive Lung Disease?

Answer 7

FEV1
FVC

Increase in FEV1/FVC Ratio

Question 8

What conditions could lead to Obstructive Lung Diseases?

Answer 8

Foreign Bodies
Asthma
COPD
Endobronchial Tumour

Question 9

What conditions could lead to Restrictive Lung Diseases?

Answer 9

Pleural
Alveolar
Interstitial
Neuromuscular 
Thoracic Cage

Though usually, it is more due to

1. Intrinsic (Parenchyma Inflammation/Scarring ILD)
2. Extrapulmonary Causes (Chest Wall/NMA Pleura, Myasthenia Gravis)

Question 10

How do we measure TLC/Lung Function?

Answer 10

TLC cannot be measured directly with Spirometry

1. Measured by inspiring a FIXED VOLUME of gas (with Helium)
2. You then rebreathe it until the Helium is evenly distributed in lung gases
3. Helium does not get absorbed into the blood, thus the sample has a lower [Helium] since it is now part of the RESIDUAL VOLUME
4. Volume is determined by amount of Tracer Gas is diluted

TLC = V2 = (C1xV1)/C2

• C1 = Helium Inspired
• V1 = Inspired Gas
• C2 = [Rebreathed Gas]
• V2 = Volume

Question 11

How do we test for Restrictive Lung Disorders?

Answer 11

DLCO (Diffusing capacity of the lungs for CO)

1. Quantity of CO transferred per minute from Alveolar Gas to RBCs
2. Lung SA available for GE (Va) x Rate of Capillary Blood CO Uptake
3. 80-140% is generally a good score
4. Below 40% is not

Question 12

For a Flow Volume Loop, what would we see in Obstructive Lung Diseases?

Answer 12

There would be a reduction in area and a steeper slope