Chronic Ventilatory Failure (pathology)

Question 1

What vitals would indicate chronic Ventilatory failure?

Answer 1

• Elevated pCO2 > 6.0 kPa
• pO2< 8 kPa
• normal blood pH
• elevated HCO3-
  
  • compensate for ↑ pCO2
  • pH 𝝰((HCO3-)/pCO2)

Question 2

Respiratory conditions causing chronic Ventilatory failure

Answer 2

COPD

Bronchiectasis

Question 3

Chest wall abnormalities causing chronic Ventilatory failure

Answer 3

Kyphoscoliosis

TB surgery

Question 4

Respiratory muscle weakness causing chronic Ventilatory failure

Answer 4

Motor neuron disease (ALS)
Muscular dystrophy
Glycogen storage disease (Pompe’s disease)

Question 5

Central Hypoventilation causing chronic Ventilatory failure

Answer 5

Obesity Hypoventilation syndrome (OSA)

Congenital central Hypoventilation syndrome

Question 6

Symptoms and signs of chronic Ventilatory failure

Answer 6

• SOB
• Orthopnoea- breathless lying flat because no help from gravity
  
  • Paradoxical diaphragm movement – diaphragm drawn into chest on inspiration
• Ankle swelling- chronic low pO2- pulmonary vasoconstriction- ↑ RH pressure - ↑ venous pressure- oedema – hypoxic cor pulmonale
• Morning headache - ↑ pCO2 at night- dilatation of cerebral vessels
• Disturbed sleep
  
  • Worse during REM when muscles paralysed (all but diaphragm- but if diaphragm not working= evidence of resp failure in REM sleep)

Question 7

Investigations for chronic Ventilatory failure

Answer 7

• Spirometry
  
  • Restrictive in neuro muscular weakness
  • Supine FVC < standing FVC
• Mouth pressure
• SNIP sniff nasal inspiration pressure
• Early morning ABG
• Overnight oximetry
• Transcutaneous CO2 monitoring
• Fluoroscopic screening of diaphragm – imaging while performing movements that require diaphragm (sniffing)

Question 8

Management and treatment of chronic Ventilatory failure

Answer 8

Not curable unless underlying cause is curable

• domiciliary non-invasive ventilation (NIV)
• oxygen therapy
• t-IPPV tracheostomy ventilation