Respiratory System >
Respiratory Failure

“The inability of the lungs to perform sufficient gas exchange (Type 1 and Type 2) to oxygenate the arterial blood adequately and/or fails to prevent CO2 retention

Risk Factors
  • Modifiable:
    • Smoking
    • Alcohol
  • Non-Modifiable:
    • Chronic respiratory condition
    • Muscle/nerve injury
Aetiology
  • Type 1 respiratory failure:
    • Associated with all chronic respiratory conditions (e.g COPD, asthma), cardiopulmonary shunts, pneumonia, and pulmonary oedema
  • Type 2 respiratory failure:
    • Associated with worsening type 1 RF (as pt gets exhausted can transition from type 1),  reduced respiratory drive (e.g. drug overdose, sedatives) neuromuscular disease, and chest wall abnormalities
Pathophysiology
  • Type 1 – Gas exchange problem:
    • Any cause of a low PaO2 caused by V/Q mismatch i.e. damage to lung tissue & impairment of gas exchange  (¯ O2 & normal CO2)
    • Blood is insufficiently oxygenated through the pulmonary circulation
    • CO2 has greater solubility than O2, so V/Q mismatch has greater effect on PaO2 because CO2 is more able to diffuse through areas of impaired exchange
  • Type 2 – Ventilatory problem:
    • Failure to excrete CO2 caused by alveolar hypoventilation or a shunt (insufficient to remove CO2) with or without V/Q mismatch (¯ O2 & ­ CO2)
    • Alveolar hypoventilation can be caused by reduced ventilatory effort, inability to overcome increased resistance to ventilation, failure to compensate for increased dead space or carbon dioxide production, or a combination of these factors
    • Can also be caused by cardiopulmonary shunt:  deoxygenated blood bypasses the alveoli without being oxygenated and mixes with oxygenated blood that has flowed through the ventilated alveoli
Clinical Presentation

Will vary by the underlying cause of respiratory failure

  • General symptoms may include:
    • Shortness of breath
    • Respiration rate
    • Heart rate
    • Sweating
    • Central cyanosis
    • Agitation & confusion
  • If Type 2:
    • May also appear less breathless (due to general exhaustion)
    • May show signs of CO2 retention
      • Headache
      • Peripheral vasodilatation,
      • Bounding pulse
      • CO2 tremor
  • Signs of the underlying disease:
    • Fever
    • Cough
    • Sputum production
    • Chest pain in cases of pneumonia
Investigations

Investigations dependent on underlying cause based on clinical judgement

  • Bloods:
    • Blood cultures
    • FBC & U+Es
    • Arterial Blood Gasses – ↓O2 & normal/­↑ CO2
Expected Arterial Blood Gasses (ABG) results for Type 1 and Type 2 Respiratory Failure. Red indicates abnormal results. Green indicates normal values
  • Imaging:
    • Chest X-Ray
    • CT brain/spine/chest
    • ECHO
    • Bronchoscopy
  • Special:
    • ↓O2 sat of 88-92%
    • Sputum samples
Management
  • Type 1:
    • Treat underlying cause
    • Oxygen therapy- normally NIV (maintain sats ~90%)
    • Assist ventilation if required- BIPAP or ITU
  • Type 2:
    • Treat underlying cause
    • Controlled oxygen therapy starting at 24%
    • Re-check ABG after 20 minutes to ensure oxygen is not damaging
    • Invasive ventilation if required
Complications
  • Pulmonary embolism
  • Pneumothorax
  • Heart failure
  • Arrhythmias
  • Irreversible brain damage
  • Acute renal failure

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