Physiological consequences of lung disease

Question 1

Obstructive vs restrictive lung disease

Answer 1

Obstructive = flow of air is obstructed, affecting ventilation

Restrictive = chest volume is restricted, increasing the work of breathing

Question 2

Obstructive vs restrictive lung disease differences in spirometry?

Answer 2

1. Obstruction
   - Ratio of FEV1/FVC is reduces
   - <70% ratio
2. Restriction
   - FEV1 is reduced in proportion to FVC as the lungs aren’t as big, so ratio of FEV1/FVC is almost normal
   - >70% ratio

Question 3

Examples of obstructive vs restrictive airway diseases

Answer 3

Obstructive:

• Asthma
• COPD
• Bronchiectasis

Restrictive:

• Pulmonary fibrosis
• Obesity
• Chest wall deformities
• Neuromuscular disorders

Question 4

Different ways to measure airflow in the diagnosis and management of airflow obstruction

Answer 4

1. Spirometry
2. Helium dilution method
3. Flow rate (volume/time) and its measurement
4. Peak flow
5. Spirometer
6. Flow/volume loop

Question 5

What does the flow/volume loop show?

Answer 5

Shows you the rate of flow dependent on volume

• As you start, you breathe out hard and fast
• Maximum rate then starts to fall as you run out of air in the lungs
• When you breathe in, it follows a similar pattern
• Can help show if someone has narrowed airways

Question 6

How can you measure perfusion?

Answer 6

• CT pulmonary angiogram

- Echocardiogram

Question 7

What are the different types of restrictive lung disease?

Answer 7

1. Interstitial
   - Disease of the structure of the lung with scarring
   - Makes lungs stiff
   - Increases the distance that gas has to diffuse across to get between air and blood vessels
2. Chest wall deformities/neuromuscular disorders

Question 8

Effects of restrictive lung disease on lung function?

Answer 8

1. Thickened, fibrotic alveolar membrane
2. Small lungs with reduced compliance
3. Relatively normal airways with preserved airflow

Question 9

Effects of restrictive lung disease on FEV1, FVC, FEV1/FVC, diffusion and perfusion?

Answer 9

• FEV1 = reduced
• FVC = reduced
• FEV1/FVC = normal (or raised)
• Impaired diffusion - due to increased thickness of interstitium
• Normal perfusion

Question 10

Interstitial lung disease typically has a type 1 respiratory failure pattern, true or false?

Answer 10

TRUE

Question 11

Causes of normal perfusion but reduced ventilation

Answer 11

1. Pneumonia
2. Pneumothorax
3. Obstructive lung diseases such as asthma