Respiratory Investigations

Question 1

What respiratory investigations are commonly used?

Answer 1

• Oxygen saturation
• Vital signs
• Blood gases
• Oxygenation index
• Spirometry

Question 2

What is the purpose of measuring oxygen saturation’s?

Answer 2

For detection of hypoxaemia and monitoring of response to oxygen therapy

Question 3

What are the advantages of saturation monitors?

Answer 3

Non-invasive and allows continuous monitoring

Question 4

What do blood gases measure?

Answer 4

Direct measurement of arterial pH, PaO2, and PaCO2

Question 5

When is measurement of blood gases particularly important?

Answer 5

In intensive care for patients on respiratory support q

Question 6

Where is the ideal place to get blood gases from?

Answer 6

Arterial line

Question 7

What is the limitation of blood gases from a peripheral artery?

Answer 7

They need to be interpreted in conjugation with clinical features, as will be affected by the infant crying

Question 8

Where is spirometry widely used?

Answer 8

Outpatient settings

Question 9

What does a peak expiratory flow meter and spirometer allow the measurement of?

Answer 9

• Peak expiratory flow rate (PEFR)
• Forced viral capacity (FVC)
• Forced expiratory volume in 1 second (FEV1)
• Forced exploratory flow (FEF25-75)

Question 10

What is the forced expiratory flow?

Answer 10

The mean maximal flow in the middle of the FVC (forced expiration)

Question 11

How does FEF25-75 compare to FEV1 or PEFR?

Answer 11

FEF25-75 is more sensitive but more variable than FEV1 or PEFR in assessing obstruction of the small to moderate sized airways

Question 12

How is PEFR measured?

Answer 12

A child must give a short sharp expiration into the device

Question 13

What does the measured value reflect in PEFR?

Answer 13

The maximal flow able to be generated (in L/min)

Question 14

What is the limitation of PEFR?

Answer 14

It is a much less sensitive a marker of airway obstruction than FEV1 or the shape of a flow-volume curve, and is used less than in the past

Question 15

How is a flow-volume curve generated?

Answer 15

A child must take a maximal inspiration and then exhale into a mouthpiece as hard as possible and for as long as possible. The volume and flow of exhaled breath are measured

Question 16

How is reproducibility in the generation of a flow-volume curve ensured?

Answer 16

There should be 3 attempts producing results within less than 5% error

Question 17

At what age are most children able to perform good quality spirometry/flow-volume loops?

Answer 17

5 years

Question 18

What % of expiration is effort dependant?

Answer 18

The first 25-35%

Question 19

What is spirometry good for?

Answer 19

Sensitive way to assess airway narrowing

Question 20

What are the two main patterns of spirometry recognised?

Answer 20

• Obstructive

- Restrictive

Question 21

What is the most common pattern of spirometry?

Answer 21

Obsturctive

Question 22

What effect does asthma have on spirometry?

Answer 22

It causes reversible obstruction

Question 23

What is the clinical relevance of asthma causing reversible obstruction on spirometry?

Answer 23

Diagnosis is made based on spirometry before and after salbutamol usage to show improvement in the post-salbutamol measurement

Question 24

What bronchodilator reversibility is considered significant and can confirm a diagnosis of asthma?

Answer 24

More than 8-12%

Question 25

At what age is airway smooth muscle seen from?

Answer 25

Birth

Question 26

At what age is functional ß-adrenoceptor activity documented?

Answer 26

From infancy

Question 27

What happens to FEV1 and FEF25-75 in obstructive airway disease?

Answer 27

They are both reduced, FEF25-75 more so

Question 28

Why is the ratio of FEV1 to FVC a useful measure?

Answer 28

It gives an indication of severity, and ‘tracks’ throughout life