Physiology of Breathlessness

Question 1

What defines breathlessness?

Answer 1

arises when there is a recognition of an inappropriate relationship between respiratory work and total body work

Question 2

How is dyspnoea diagnosed?

Answer 2

checklist of clinical causes:

• respiratory
• cardiac
• muscle weaknes
• metabolic
• anaemia
• psychogenic

Question 3

What are the respiratory causes of dyspnoea?

Answer 3

• airways disease
  
  • upper - tumour, foreign body, angioneurotic oedema, croup
  • lower - asthma, COPD, bronchiolitis
• alveolar disease
  
  • pneumonia, lung collapse, pulmonary odema, pulmonary fibrosis
• pulmonary vascular disease
  
  • pulmonary embolism, vasculitis, primary pulmonary hypertension
• pleural and chest wall disease
  
  • pleural effusion, pneumothirax, chest wall deformity
• respiratory muscle disease
  
  • respiratory muscle weakness, phrenic nerve palsy

Question 4

Noisy breathing (wheeze, stridor) is idicative of

Answer 4

airway pathology causing dyspnoea

Question 5

What clinical test is ordered for suspected airway obstruction?

Answer 5

Spirometry

*unless haemoptysis of unknown origin, or TB

Question 6

What is stridor indicative of?

Answer 6

upper airway obstruction

Question 7

What does wheeze indicate?

Answer 7

lower airway obstruction

Question 8

How can lung parenchyma be assessed?

Answer 8

• e.g. exposure to tobacco smoke/some indication of parenchymal damage
• CXR (less sensitive)
• CT (more sensitive)

Question 9

How is A-C membrane functionality assessed?

Answer 9

diffusion capacity of CO

Question 10

A CT scan of airways with emphysema shows

Answer 10

dark, black spots = holes in lung

Question 11

Pathology of presentation of SOB, cough, and crepitations is likely in

Answer 11

terminal lung units: alveoli, parenchyma, intersitium

(AC membrane)

Question 12

What are likely causes of upper airways disease causing dyspnoea?

Answer 12

• tumour
• foreign bodies
• angioneurotic oedema
• croup

Question 13

What are likely causes of lower airways disease causing dyspnoea?

Answer 13

• asthma
• COPD
• bronchiolitis

Question 14

What are likely causes of pulmonary vascular disease causing dyspnoea?

Answer 14

• pulmonary embolism
• vasculitis
• primary pulmonary hypertension

Question 15

What are likely causes of pleural and chest wall disease causing dyspnoea?

Answer 15

• pleural effusion
• pneumothorax
• chest wall deformity

Question 16

What are likely causes of respiratory muscle disease causing dyspnoea?

Answer 16

• weakness
• phrenic nerve palsy

Question 17

What is orthopnea?

Answer 17

SOB when lying down

Question 18

What are likely causes of alveolar disease causing dyspnoea?

Answer 18

• pneumonia
• lung collapse
• pulmonary oedema
• pulmonary fibrosis (diffuse interstitial lung disease)

Question 19

Haemoptysis in dyspnoea indicates

Answer 19

Pathology of the pulmonary vasculature

e.g. PE, hypertension, vasculitis

Question 20

How does pulmonary embolism lead to presentation of haemoptysis and pleuritic chest pain?

Answer 20

can cause infarct that irritates pleura (pain) and bleeding into alveolar spaces (haemoptysis)

*can be difficult to clinically diagnose, CXR may appear clear; use Wells score*

Question 21

What is the Wells score?

Answer 21

• determines likelihood of PE
• if probability is greater than 4, CT pulmonary angiogram or pulmonary perfusion scan to assess V/Q units is odered and tx started immediately
• if probability is less than 4, D-dimer test is ordered to rule out PE

Question 22

breathlessness occurs as a result of

Answer 22

increased respiratory drive or increased load on the respiratory system