Disorders of Ventilation and Lung Mechanics

Question 1

In terms of cartilage and glands, what is the difference between small bronchus and bronchioles?

Answer 1

Small Bronchus: small islands of cartilage and glands in submucosa

Bronchioles: no cartilage or glands

Question 2

How are bronchioles kept open if they have no cartilage?

Answer 2

Bronchioles are attached to intact surrounding alveolar walls

positive outward pressure on exhilation keeps bronchioles open

Known as radial traction

Question 3

What is the interstitium?

Answer 3

A potential space between alveolar cells and the capillary basement membrane

Question 4

What is interstitial lung disease?

Answer 4

A group of diseases characterised by thickening of pulmonary interstitium causing ‘stiffer’ lungs

Question 5

What is contained within the interstitial space?

Answer 5

• Elastin Fibres
• Collagen Fibres
• Fibroblasts
• Matrix Substance

Question 6

Describe the pathophysiology of interstitial lung diease?

Answer 6

Deposition of fibrous tissue in the interstitium

• Lungs are stiffer and harder to expand
• Lung compliance is reduced
• Eleastic recoil of lungs is increased
• Due to elastic recoil lungs are smaller than normal

Question 7

Give some of the causes of interstitial lung disease

Answer 7

Question 8

What are some of the symptoms of interstitial lung disease?

Answer 8

• dry cough
• shortness of breath
• dyspnea on exertion
• fatigue
• gradual progression

Question 9

What are some of the signs of interstital lung disease?

Answer 9

• decreased lung excursion on palpation (thumbs not pushed apart)
• lung crackles
• increased resp rate (tachypnoea)
• finger clubbing
• pleural effusions

Question 10

Why is gas exchange impared in interstitial lung disease?

Answer 10

• alveolar walls thickened = increased diffusion distance
• effect great for O₂ than CO₂

Question 11

Describe the pathophysiology of Respiratory Distress Syndrome

Answer 11

• Premature babies <25 weeks are deficient in surfactant
• Without surfactant surface tension is high; lungs have reduced compliance and some alveoli are collapsed (no gas exhange here)
• Increased effort is needed to breathe
• Ventilation is impaired

Question 12

What are some of the symptoms of neonatal respiratory distress syndrome?

Answer 12

• Grunting
• Nasal Flaring
• Intercostal and subcostal retractions
• Rapid resp rate
• Cyanosis

Question 13

How can a baby with respiratory distress syndrome be treated?

Answer 13

• replace surfactant via endotracheal tube
• supportive O₂ treatment and assisted ventilation
• Give steroids to mum in prem labour → causes baby to make surfactant

Question 14

What is COPD?

Answer 14

Chronic Obstructive Pumlmonary Disease encompasses 2 medical conditions

1. Chronic Bronchitis
2. Emphysema

Question 15

What is Pre-COPD?

Answer 15

A patient with impared airflow but no clinical symptoms and normal spirometry

But at high risk of developing COPD in next 5 years

Question 16

What is chronic bronchitis?

Answer 16

A disease of the airways from bronchi to bronchioles characterised by mucus hypersecretion

Clinical diagnosis: cough productive of sputum for >3 months of the year for >1 year

Question 17

Why is mucus hypersecretion in chronic bronchitis problematic?

Answer 17

• Reduced cilia, mucus not cleared effectively
• airways occluded
• epithelial remodelling
• alterns airways surface tension predisposing to collapse

Question 18

What are some of the causes of increased mucus production?

Answer 18

Question 19

Why is airway obstruction worse on expiration than inspiration?

Answer 19

Inspiration: negative pressure in pleural space helps keep airway open

Expiration: Postive intra pulmonary pressure exacerbates the narrowing of thoracic airways

Question 20

Define Emphysema

Answer 20

The abnormal, permanent enlargement of the air spaces distal to the terminal bronchioles, with destruction of alveolar walls

Question 21

What are 90% of cases of COPD caused by? What is the hosts response?

Answer 21

Smoking

host responds by breakdown of elastin and alveolar walls

Question 22

What effects does loss of elastin fibres have on the lung?

Answer 22

• The lung is easier to expand (loss of elastic recoil)
• lungs become hyperinflated → barrel chest appearance
• loss of radial traction on small bronchioles narrows the small airways
  *

Question 23

What are some of the symptoms on emphysema?

Answer 23

• Shortness of breath
• Reduced exercise tolerance

Question 24

What is a much rarer form of emphysema?

Answer 24

Alpha-1-antitrypsin deficiency

(alpha 1 antitrypsin is an anti-protease, deficiency causes destruction of elastin)

Question 25

What is a pneumothorax?

Answer 25

A disorder where air enters the pleural space, with loss of pleural seal and lung collapse

Question 26

Describe the pathophysiology of a pneumothorax

Answer 26

• If chest wall/ lung is breached
• Air flows from high atmospheric pressure → lower negative pressure in pleural cavity
• Loss of pleural seal causes lung to collapse due to elastic recoil not being counteracted

Question 27

How do you treat a pneumothorax?

Answer 27

Draining air from the pleural space

Question 28

What is atelectasis?

Answer 28

Either:

• Incomplete expansion of the lungs (neonatal)
• Collapse of a previously inflated lung

Question 29

What are the main types of atelectasis in adults?

Answer 29

• Compression (pneumothorax or pleural effusion)
• Reabsorption atelectasis (from complete obstruction of airway) main cause = bronchial carcinoma

Question 30

What is hypoventilation?

Answer 30

Poor expansion of the thoracic cavity or lungs

Question 31

What is anatomical dead space?

Answer 31

The volume of air in the conducting airways

Question 32

What is alveolar dead space?

Answer 32

Air in alveoli that do not take part in gas exchange

Question 33

What is physiological dead space?

Answer 33

Anatomical dead space + Alveolar dead space