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Test Findings

Reduced Oxyhaemoglobin

February 7th, 2020


The level of haemoglobin saturated by oxygen may be reduced in the context of reduced oxygen, right shift of the oxygen saturation curve, displacement of oxygen by carbon dioxide, or in the setting of haemoglobinopathies.
  • Causes of Reduced Oxyhaemoglobin

  • Reduced Environmental Oxygen

  • High altitude
  • Hypoventilation

  • CNS - drugs, trauma, encephalopathy, motor neurone disease, Guillain-Barré
  • Muscular / neuromuscular - myaesthenia, paralytics, myopathy, fatigue, malnutrition
  • Airway obstruction - foreign body, asthma, COPD, bronchiectasis
  • Decreased compliance - interstitial lung disease
  • Chest wall abnormalities
  • Ventilation / Perfusion Mismatch

  • Physiological shunt - atelectasis, pulmonary oedema, pneumonia, ARDS
  • Anatomical shunt - cardiac shunt e.g. tetralogy of Fallot
  • Dead space - asthma, COPD, pulmonary embolus, heart failure
  • Other

  • Right shift of the oxygen dissociation curve - acidaemia, hyperthermia, high 2,3-DPG
  • Carbon monoxide poisoning
  • Haemoglobinopathy - methaemoglobinaemia, foetal haemoglobin
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