Obstructive Lung Disease

Question 1

What are obstructive lung diseases? List examples.

Answer 1

Airway diseases leading to outflow obstruction.

E.g. emphysema, chronic bronchitis, asthma, bronchiectasis

Question 2

What makes up COPD?

Answer 2

Emphysema
Chronic bronchitis
- permanent and coexist = grouped together to make COPD

Question 3

Is asthma reversible?

Answer 3

Initially yes, but chronic irreversible obstruction can eventually occur

Question 4

What is bronchiectasis?

Answer 4

Permanent dilation of the bronchi due to destruction of their walls

Question 5

What happens in emphysema?

Answer 5

Destruction of the air spaces distal to the terminal bronchioles
Irreversible enlargement

Question 6

What is the most common form of emphysema?

Answer 6

Centriacinar emphysema - respiratory bronchioles are affected but distal alveoli remain normal

Question 7

What is the appearance of centriacinar emphysema?

Answer 7

Holes in lung parenchyma = emphysematous airspaces (dilated respiratory bronchioles)

Question 8

What is anthracosis?

Answer 8

Due to centriacinar emphysema.

Holes appear black due to the carbon pigment deposition seen in the lungs of smokers (tar in cigarette smoke)

Question 9

What makes the centriacinar pattern?

Answer 9

Normal alveoli exist between the areas of emphysema

Question 10

What is the pathogenesis behind emphysema?

Answer 10

Cigarette smoking and inhaled pollutants produce oxidants, causing an ongoing accumulation of inflammatory cells in the lungs.
Oxidants and proteolytic enzymes - proteases (mainly elastases) released from inflammatory cells destroy elastic tissue in airspaces’ walls.

Question 11

What does smoking impair?

Answer 11

Activity of the alpha-1 antitrypsin (anti-protease)

Genetic predisposition to emphysema occurs in patients with alpha-1 antitrypsin deficiency

Question 12

What type of emphysema do patients with an alpha-1 antitrypsin deficiency have?

Answer 12

Panacinar type of emphysema

Question 13

What is bullous emphysema?

Answer 13

Several dilated airspaces become confluent (amalgamated) creating large bullae (bubbles)

Question 14

What does emphysema show in a chest X-ray?

Answer 14

Hyperinflated chest

• flattened diaphragm
• inflation of apex above clavicle
• horizontal orientation of ribs
• decreased bronchovascular lung markings
• overtaking of the heart shadow by opacity of hyperinflated lungs

Question 15

What is the clinical picture of emphysema?

Answer 15

Obstruction to expiration due to loss of elastic recoil of airspaces (due to destruction of elastic fibres in the walls by elastases)
Airways collapse during expiration & patients purse their lips to prevent this from happening = pink puffers
Patient’s chests become hyperinflated due to air trapping “barrel chest”, develop dyspnoea
Advanced cases = right side heart failure “cor pulmonale”
Most have some degree of chronic bronchitis

Question 16

What is chronic bronchitis?

Answer 16

Persistent cough with sputum production for at least 3 months in at 2 consecutive years

Question 17

What is the initiating factor for chronic bronchitis?

Answer 17

Noxious inhaled substances e.g. cigarette smoke (90% of patients are smokers)

Question 18

What happens to the bronchi in chronic bronchitis?

Answer 18

Mucus hypersecretion, inflammation, recurrent infections, fibrosis

Question 19

What can happen to patients with chronic bronchitis?

Answer 19

May become hypoxaemic and cyanosed (blue) & edema from right side heart failure = Blue bloaters

Question 20

What is the pathogenesis behind chronic bronchitis?

Answer 20

Chronic inflammation in bronchi and bronchioles
Metaplasia of surface lining epithelium (change into goblet cells or squamous epithelium)
Mucus hypersecretion = contributes to airway obstruction
Obstruction predisposes infection.
Smoking also interferes with movement of cilia & resp epithelium = preventing clearance of mucus and infective organisms

Question 21

Final thing to note for COPD:

Answer 21

Element of small airway disease exists - bronchioles show marked narrowing of their walls by inflammation and fibrosis
= chronic bronchiolitis
= contributes to obstruction in COPD

Question 22

What is asthma?

Answer 22

Reversible bronchoconstriction caused by a variety of stimuli

Question 23

Name the several types of asthma.

Answer 23

Atopic asthma (allergy induced)
Non-topic asthma (triggered by resp viral infections, air pollutants, cold, exercise)
Drug-induced asthma (NSAIDs)
Occupational asthma (inhalation of toxic industrial gases and fumes)

Question 24

Type I hypersensitivity

Answer 24

Introduction of allergen
Stimulates TH2 responses and IgE production
IgE binds to mast cells = secrete mediators responsible for inflammation

Question 25

What type of hypersensitivity is atopic asthma?

Answer 25

Type I hypersensitivity

Question 26

Describe the pathogenesis of Type I hypersensitivity in atopic asthma.

Answer 26

TH2 cells - release cytokines --> production of IgE, eosinophils, mucus production

Question 27

What does cross linking of IgE onto mast cells lead to?

Answer 27

Leads to mast cell degranulation and release of performed mediators causing immediate phase reaction.

Question 28

What occurs in the immediate phase reaction of atopic asthma?

Answer 28

Bronchoconstriction Increased vascular permeability --> bronchial wall oedema Mucus production and plugging of airways Leukocyte recruitment

Question 29

What is the late phase of atopic asthma pathogenesis?

Answer 29

Marked by leukocyte recruitment - eosinophils, neutrophils and more lymphocytes Major basic protein produced by eosinophils damages the lining epithelium of the airways

Question 30

Describe what happens in the airway remodeling in asthma.

Answer 30

Structural changes in bronchial walls Irreversible element of chronic obstruction - Basement membrane thickening - Hypertrophy/hyperplasia of bronchial smooth muscle - Hypertrophy of submucosal glands and hyperplasia of goblet cells lining the epithelium - Damage to the lining epithelium

Question 31

What is seen in the Chest X-ray of someone with acute severe asthma.

Answer 31

Hyperinflated chest showing: - flattened diaphragm - inflation of apex above clavicle - horizontal orientation of ribs - normal heart shadow - preservation of lung markings (different from the lung in emphysema)

Question 32

What is bronchiectasis?

Answer 32

Permanent dilation of the bronchi and bronchioles due to the destruction of their walls.

Question 33

What causes bronchiectasis?

Answer 33

Repeated cycles of infection with subsequent destruction of the bronchial smooth muscles and elastic tissues and healing by fibrosis.

Question 34

What is cystic fibrosis?

Answer 34

A genetic disorder of ion transport (Cl) that affects fluid secretion in the exocrine glands of the resp, gastrointestinal and reproductive tracts.

Question 35

What is the mode of inheritance for CF?

Answer 35

Autosomal recessive

Question 36

What is the primary defect in CF?

Answer 36

Abnormal function of an epithelial chloride channel encoded by CFTR gene on chromosome 7 - main manifestations stem from the defective chloride channel and its interactions with a neighbouring sodium channel

Question 37

What happens to the mucus produced in the airways in those with CF?

Answer 37

Sodium is drawn out of mucus = thick, dehydrated, viscid and difficult to clear Thick mucus results in recurrent infections

Question 38

Which individuals are likely to suffer from bronchiectasis?

Answer 38

Those with CF.