Respiratory Failure Definition etc

• Respiratory Failure - Definition:

  • The inability to maintain the partial pressures in arterial blood of carbon dioxide (PaCO2) and oxygen (PaO2) within normal physiological limits
  • PaO2 < 8 kPa
  • PaCO2 > 6.7 kPa
• Type 1 Respiratory Failure

  • Decreased PaO2
  • Normal or low PaCO2 (due to increased respiratory drive stimulated by low PaO2)
  • Caused by V/Q mismatch within the lung e.g. with pneumonia or atelectasis
  • Treatment – supplemental O2
• Type 2 Respiratory Failure

  • Decreased PaO2
  • Increased PaCO2
  • Caused by alveolar hypoventilation
  • Failure of the respiratory muscles to generate pressure (failure of the ‘respiratory pump’) e.g. due to respiratory muscles being paralysed or fatigued
• Acute Type 2 Respiratory Failure

  • Decreased PaO2
  • Increased PaCO2
  • Normal levels of HCO3 (kidneys take 2 - 3 days to compensate for raised CO2 levels)
  • Decreased pH – respiratory acidosis
• Chronic Type 2 Respiratory Failure

  • Decreased PaO2
  • Increased PaCO2
  • Increased levels of HCO3 (kidneys compensate for hypercapnia - high CO2 levels)
  • Normal pH
  • Example - patient with COPD
• ‘Acute on Chronic’ Type 2 Respiratory Failure

  • Increased PaCO2
  • Decreased PaO2
  • Increased levels of HCO3
  • Decreased pH (acidotic)
  • PaCO2 normally high but due to sudden deterioration has risen further. Kidneys no longer able to compensate
  • Example: COPD in an acute exacerbation
• Non-Invasive ventilation:

  • ventilating pts via face masks
  • provides adequate amount of o2 to keep pao2 above 8 kpa
  • also increases ventilation/tidal volume to make sure co2 is cleared adequately
• Physiotherapy Problems:

  • Breathlessness / increased work of breath
  • Sputum retention
  • Decreased exercise tolerance
  • Reduced lung volumes
  • Chest pain (if musculoskeletal in origin)
  • Lack of understanding – educational need