Chronic Obstructive Airway Disease

Question 1

The three most common characteristics of COPD

Answer 1

o Smooth muscle cell contraction, airway oedema (wheezing)
o Mucus hypersecretion (excessive sputum production)
o Dynamic compression

Question 2

Emphysema pathophysiology

Answer 2

• Elasticity is low thus increased compliance
  o Pressure volume curve shifted to left & upwards = for the same increase in the pressure
  there is a significantly larger increase in volume
• incr FRC incr residual vol
• decr vital capacity incr TLC due to air trapping
• Expiration is prolonged
• dynamic collapse on expiration
• reduced traction that keeps the bronchioles and alveoli open

Question 3

Chronic bronchitis

Answer 3

• Bronchospasm = stimulation of muscarinic receptors incr bronchomotor tone
• Secretions
  o Hypertrophy of mucus cells = excessive mucus production
  o Chronic infection leads to fibrotic changes in the airway = reduced airway diameter with incr resistance to air flow
  o Infections are common due to inability to produce effective expiratory air flow

*** Treat with antimuscarinics e.g. atropine, biperiden, clozapine

Question 4

What does COPD entail

Answer 4

Emphysema & chronic bronchitis

Question 5

What does COPD lead to

Answer 5

o deterioration of elasticity
o decr rigidity of bronchiolar wall
o Predisposition to collapse during exhalation
o Increased gas flow velocity in narrowed bronchioli
o Decreased pressure inside bronchioli favours airway collapse
o Active bronchospasm & obstruction due to increased pulmonary secretions
o Destruction of lung parenchyma, enlargement of air sacs, and development of emphysema

Question 6

Difference between COPD & asthma

Answer 6

COPD = Disease of progressive loss of alveolar tissue & airflow obstruction = irreversible!

Question 7

Gold standard for COPD diagnosis

Answer 7

patients with FVC <0.7
- GOLD I = mild FEV >80%
- GOLD II = moderate FEV less 80 more 50
- GOLD III = Severe more 30 less 50
- GOLD IV = v severe FEV <30%

Question 8

Signs of COPD

Answer 8

• Smoking history
• Chronic cough
• Prolonged expiration  > 6 seconds
• Wheeze  forced expiration
• Signs of hyperinflation
• Signs of right heart failure  cor pulmonale
• Signs of hypercarbia

Question 9

What is a NB red light sign on lung function test with COPD

Answer 9

shouldn’t be >15% increase = COPD

Question 10

What is the significance of NO2 in COPS

Answer 10

• Avoid N2O if there are bullae NB!
• increased accumulation in air pockets compared to nitrogen

Question 11

Consequences of airtrapping

Answer 11

• incr intra-thoracic pressure
• decr venous return
• incr pulmonary vascular resistance
• hyperinflated lungs
• distended right ventricle

Question 12

How do you detect airtrapping

Answer 12

o Capnography = carbon dioxide concentration does not plateau but is still upsloping at time of next breath suspect there is air trapping