Spirometry and Pethysmography

Question 1

Name the parameters we look for

Answer 1

Forced vital capacity (FVC) – total volume of air (liters), that is forcefully exhaled after a maximal inspiration.

Forced expiratory volume in 1 second (FEV1) – the maximal amount of air that can be forcefully exhaled in the 1st second started after a maximal inspiration.

FEV1/FVC ratio (FEV1/FVC%) – Tiffeneau index.

Question 2

What is the normal tiffno index

Answer 2

70%

Question 3

How do you interpret the tiffno index

Answer 3

If it is below 70% = Obstruction

If above 70% = Restriction

Question 4

How should the parameters values be to be normal?

Answer 4

The measured parameters are considered to be “normal” if they are between 80% and 120% from the reference or, if they are between 5th and 95th percentile.

Question 5

How should the parameters values be to show obstruction?

Answer 5

FEV1 : Have to be below 80%

FVC: Can either be normal or below 80%

Tiffno index: Belov 70%

Question 6

If we have obustruction and only FEV1 is decreased. What does this mean?

Answer 6

This means that we have isolated obstruction, only obstruction (Not mixed)

Question 7

If we have obstruction and both FEV1 and FVC is decreased. What does this mean?

Answer 7

If both are decreased we have to start to think about a mixed pattern. Which means obstruction and also restriction.

Question 8

How should the parameters values be to show restriction?

Answer 8

FVC: Have to be below 80%

FEV1: Can be normal or decreased

Tiffno index: Above 70%

Question 9

How do we also classify obstruction?

Answer 9

Reversible or nonreversible.

Question 10

How do we known if the obstruction is reversible or nonreversible?

Answer 10

We have to do bronchodilater test. If we see improvment of FEV1 >12% and/or 200 ml improvment of FEV1. Then this is Reversible. If no improvment of the values, then this is nonreversible.

Question 11

How do we classify the severity of the obstruction?

Answer 11

We look at the FEV1 in %:

Mild: >70%
Moderate 60-69%
Moderate severe: 50-59%
Severe: 35-49%
Very severe: <35%

Question 12

How do we do Bronchodilator test:

Answer 12

First choice – 4 puffs of 100µg salbutamol (short acting β2 sympathomimetic). Spirometry is performed before and 10-15 minutes after the use of medication

Second choice – 4 puffs of ipratropium bromide (short acting muscarinic receptor antagonist). Effect can be assessed after 30 minutes.

Question 13

When do we do plethysmography?

Answer 13

It can help us understand if it is mixed respiratory disease, both restriction and obstruction

It can also help us differentiate which type of obstruction. COPD or only emphyschema.

Can also see resitrctive changes

Question 14

What does the plethysmography show in obstruction?

Answer 14

We first look at the same values as we do on spiromotery. We also see that TLC and RV have to be increased

Question 15

What does the plethysmography show in restriction?

Answer 15

FEV1 and FVC have to show restrictive values. We also see that TLC and RV have to be decreased.