Investigating Respiratory Disease

Question 1

Describe Acute Respiratory Distress Syndrome (ARDS).

Answer 1

• Acute diffuse imflammatory lung injury, causing:
  
  • Hypoxaemia
  • Bilateral lung opacities
  • Increased physiological dead space
  • Decreased lung compliance
• Complication of severe sepsis (respiratory or extra-respiratory.
• Severity is graded according to O₂ requirements.

Question 2

What are the first-line investigations in respiratory disease?

Answer 2

• History and examination - PREJUDGE
• Bloods
  
  • Eosinophils
• Oxygen saturations
  
  • Conider exercise (clinic / ward) testing
• CXR
• ECG
• ABG
• Spirometry, PEFR
• Sputum culture

Question 3

What are the second-line investigations in respiratory disease?

Answer 3

• Extended blood tests:
  
  • According to disease.
  • ‘Sets’ - interstitial lung disease, connective tissue disease, bronchiectasis, severe asthma.
  • Immunology - BBV, IGRA, functional antibody testing (pneumococcal antibodies, tetanus antibodies).
• Allergen testing (total IgE, specific IgE (Aspergillus, HDM, avian)).
• Skin prick tests.
• CT chest
  
  • Volume CT, CTPA, high resolution CT.
  • Aortic phase angiogram.
• Perfusion scan
  
  • Ventilation / perfusion (V/Q), perfusion scan.
• PET
  
  • FDG uptake - cancer, PUO, sarcoid.
• Lung function tests
• Bronchoscopy
  
  • Routine flexible bronchoscopy.
  • Rigid bronchoscopy (GA, surgeons).
  • EBUS-TBNA - Endobronchial Ultrasound - Transbronchial Nodal Adpirate.

Question 4

What are the third-line investigations in respiratory disease?

Answer 4

• CardioPulmonary Exercise Testing (CPET)
  
  • Combination concurrent stress-testing of CV and respiratory systems.
• Right heart catheter studies
  
  • Right heart vs lung
• Sleep studies
  
  • Overnight pulse oximetry
  • Thoracic belts
  • Polysomnography
• Cryobiopsy
• Radial EBUS
• Navigational bronchoscopy
• TPNA - Transpulmonary nodal biopsy

Question 5

Describe the flow volume loops of normal, obstructive and restrictive lung diseases.

Answer 5

Question 6

What are the key diagnostic themes when investigating respiratory disease?

Answer 6

• What do you want from the test? Think beyond it.
  
  • Realistic medicine - How important is the test?
• Interpretation of the signs; the tests should work for you.
  
  • Pre-judge the result, be open to inconsistency, but not a slave to it.
• What is the impact of getting the diagnosis wrong?
• Involve the patient - you consider risks, they take them.
  
  • 2-20% risk of serious comorbidity or death in open lung biopsy.