Lecture 4 - ventilation, lung mechanisms and disorders

Question 1

Functional residual capacity in patient with emphysema

Answer 1

Increases - air filled alveolar spaces

Chest wall expansion has a greater force than lung elastic recoil

Question 2

Functional residual capacity in patient with pulmonary fibrosis

Answer 2

Decreases

Elastic recoil greater than compliance

Therefore can’t stretch as much

Question 3

Bronchus structure

Answer 3

Small islands of cartilage

Glands in submucosa

Question 4

Bronchiole structure

Answer 4

No cartilage or glands in submucosa

Thin walls

Question 5

Radial traction

Answer 5

Outward tugging force exerted by surrounding alveoli on the bronchioles to prevent collapse during expiration when the pressure increases.

Question 6

What type of cells are type II pneumocytes?

Answer 6

Cuboidal

Type I is simple squamous

Question 7

What can arise if there is an inability to expand the chest?

Answer 7

Hypoventilation
CO2 increases
O2 decreases - Type 2 respiratory failure

e.g. in Duchene’s muscular dystrophy

Question 8

Pneumothorax

Answer 8

Air in pleural space with loss of pleural seal therefore lung collapse as loss of negative pressure

Question 9

Conditions where there is decreased compliance

Restrictive

Answer 9

Interstitial lung disease - increased collagen in alveolar walls therefore stiffer

Respiratory distress syndrome - decrease in surfactant increases surface tension

Question 10

Conditions where there is decreased elasticity

obstructive

Answer 10

Asthma - narrowed airways therefore increased resistance and loss of elastin

COPD - emphysema - loss of elastic recoil and alveoli are distended

Question 11

Why are problems with air flow worse in expiration?

Answer 11

During expiration, pressure increases as airways decrease in volume as compressed.

Therefore more likely to collapse e.g. due to loss of radial traction

Passive so not controlled by muscles

Question 12

Interstitial lung disease

Answer 12

Diffuse lung fibrosis - thicker pulmonary interstitium, increasing the diffusion pathway

• Stiffer lungs
• Reversible and irreversible fibrosis

Question 13

Pathophysiology of interstital lung disease

Answer 13

1. Deposition of fibrous tissue in the interstitium
2. Lungs are less complaint
3. Elastic tissue is replaced by collagen therefore decreased compliance as stretch less
4. Elastic recoil increases therefore SA decreases
   (airways are not narrowed as the alveolar still exert radial traction)
5. Restrictive ventilatory defect as chest expansion is reduced as greater elastic recoil force
6. Thickening of the alveolar walls increases the diffusion pathway

Question 14

What type of ventilation defect is interstitial lung disease

Answer 14

Restrictive

FVC decreased

FEV1/FVC - normal or greater than 70%

Question 15

Symptoms of intersitial lung disease

Answer 15

Shortness of breath (dyspnea)
Dry cough
Reduced exercise tolerance
Fatigue

Question 16

Signs of interstitial lung disease

Answer 16

Tachypnoea
Tachycardia
Coarse crackles
Finger clubbing
Reduced bilateral chest movement 

Pleural effusions

Question 17

What does the interstitium contain?

Answer 17

Fibroblasts
Elastin fibres
Collagen fibres

Question 18

What can cause interstitial lung disease?

Answer 18

Exposure to:

• Asbestos
• Drugs - methotrexate
• Radiation
• Mouldy hay

Autoimmune- mediated inflammation - sarcoidosis

Connective tissue disorder:
SLE
Rheumatoid arthritis

Idiopathic pulmonary fibrosis

Question 19

Neonatal respiratory distress syndrome

Answer 19

Do not produce surfactant in babies less than 30 weeks

Increased surface tension
Decreased lung expansion
Some alveoli collapse therefore no gas exchange
Impaired ventilation

Question 20

Presentation of neonatal respiratory distress syndrom

Answer 20

Grunting
Nasal flaring
Intercostal and subcostal retractions
Tachypnoea
Central cyanosis

Question 21

How to treat respiratory distress syndrome

Answer 21

Give steroid in utero

Give surfactant in ventilator when 34 weeks old

Question 22

COPD

Answer 22

Chronic
Impaired airflow
Irreversible

Emphysema and chronic bronchitis

Mucus hypersecretion - mucous plugging
Reduced cilia - mucous not cleared
Obstructive ventilation

Question 23

Clinical diagnosis of COPD

Answer 23

Productive cough for more than 3 months for more than once a year

Question 24

Cause of COPD

Answer 24

Smoking

Inhaled pollutants

Question 25

Pre COPD

Answer 25

Impaired airflow but no clinical symptoms yet with normal spirometry.

High risk of COPD in 5 years

Question 26

Causes of mucous hypersecretion on COPD

Answer 26

Loss of cilia
Decreased PEF
Airway occlusion

Increased production:
Oxidative stress
Viral infection 
Inflammatory celss
Bacterial infection

Question 27

Chronic bronchitis

Answer 27

Increased mucus production in bronchi

Question 28

Emphysema

Answer 28

Loss of elastin (destruction) in alveolar walls therefore loss of elastic recoil and radial traction. Increased compliance

Permanent enlargement of air spaces distal to the terminal bronchioles (air trapping)

Dried mucus plug block - Inflammatory cells accumulate which releases elastases and oxidants, destroying alveolar walls and elastin + protease-mediated destruction (alpha 1 antitrypsin deficiency)

Increased lung volume and takes longer to completely expel air

Barrel chest

Question 29

Asthma

Answer 29

Reversible airway obstruction triggered by a stimulus
Smooth muscle hypertrophy - thicker airway walls
Bronchoconstriction
Mucosal oedema

In bronchi and bronchioles

Question 30

Emphysema on CXR

Answer 30

Flattened diaphragm

Hyperinflated lungs - air trapping

Question 31

Difference between emphysema and pulmonary fibrosis

Answer 31

Emphysema:

• Loss of elastin
• Decreased elastic recoil and increased compliance
• Hyperinflated lungs (Barrel chest)
• Small airways collapse during expiration due to loss of radial traction
• Air trapping
• Obstructive

Pulmonary fibrosis:

• Increased collagen deposition
• Increased elastic recoil and decreased compliance
• Lungs are stiffer and harder to expand
• Smaller lungs
• Decreased functional residual capacity
• Restrictive

Question 32

Causes of atelectasis

Answer 32

Respiratory distress syndrome

Compression collapse:

• Pneumothorax
• Pleural effusion

Compression from abdominal distension - after major abdominal surgery don’t want to take deep breaths

Resorption collapse:

Tumour in bronchioles - obstructed airway

Question 33

How to treat pneumothorax

Answer 33

Chest drain using an underwater seal - prevents fluid or air from entering the pleural seal

Question 34

Resorption collapse

Answer 34

The airway is obstructed
Air downstream is slowly absorbed into the bloodstream but new air cannot enter distal to the site of blockage
- Alveoli collapse

Question 35

Causes of hypoventilation

Answer 35

Duchene's muscular dystrophy 
RDS
Opiates 
Head injury 
Guillain Barre syndrome
Myasthenia gravis 
Pneumothorax
Severe asthma
End-stage COPD
Foreign body
Pulmonary fibrosis 
Kyphoscoliosis
Severe obesity

Question 36

Cough reflex

Answer 36

Coordinated by the cough centre in the medulla oblongata

• Deep inspiration
• Glottis is closed due to adduction of the vocal cords
• Strong contraction of expiratory muscles
• Increase in intra-pulmonary pressure
• Sudden opening of the glottis by abduction of the vocal cords causes an explosive discharge of air