Physiology of Breathlessness Flashcards
What defines breathlessness?
arises when there is a recognition of an inappropriate relationship between respiratory work and total body work
How is dyspnoea diagnosed?
checklist of clinical causes:
- respiratory
- cardiac
- muscle weaknes
- metabolic
- anaemia
- psychogenic
What are the respiratory causes of dyspnoea?
- 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
Noisy breathing (wheeze, stridor) is idicative of
airway pathology causing dyspnoea
What clinical test is ordered for suspected airway obstruction?
Spirometry
*unless haemoptysis of unknown origin, or TB
What is stridor indicative of?
upper airway obstruction
What does wheeze indicate?
lower airway obstruction
How can lung parenchyma be assessed?
- e.g. exposure to tobacco smoke/some indication of parenchymal damage
- CXR (less sensitive)
- CT (more sensitive)
How is A-C membrane functionality assessed?
diffusion capacity of CO
A CT scan of airways with emphysema shows
dark, black spots = holes in lung
Pathology of presentation of SOB, cough, and crepitations is likely in
terminal lung units: alveoli, parenchyma, intersitium
(AC membrane)
What are likely causes of upper airways disease causing dyspnoea?
- tumour
- foreign bodies
- angioneurotic oedema
- croup
What are likely causes of lower airways disease causing dyspnoea?
- asthma
- COPD
- bronchiolitis
What are likely causes of pulmonary vascular disease causing dyspnoea?
- pulmonary embolism
- vasculitis
- primary pulmonary hypertension
What are likely causes of pleural and chest wall disease causing dyspnoea?
- pleural effusion
- pneumothorax
- chest wall deformity
What are likely causes of respiratory muscle disease causing dyspnoea?
- weakness
- phrenic nerve palsy
What is orthopnea?
SOB when lying down
What are likely causes of alveolar disease causing dyspnoea?
- pneumonia
- lung collapse
- pulmonary oedema
- pulmonary fibrosis (diffuse interstitial lung disease)
Haemoptysis in dyspnoea indicates
Pathology of the pulmonary vasculature
e.g. PE, hypertension, vasculitis
How does pulmonary embolism lead to presentation of haemoptysis and pleuritic chest pain?
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*
What is the Wells score?
- 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
breathlessness occurs as a result of
increased respiratory drive or increased load on the respiratory system
