What are the key clinical features of CO poisoning?

• Symptoms:

  • Headache (dull, persistent, worse in enclosed spaces).

  • Nausea, dizziness, fatigue.

  • Confusion, difficulty breathing, syncope (severe cases).

• Key clue: Symptoms improve when leaving the affected environment (e.g., home).

• High-risk sources:

  • Faulty gas boilers, indoor barbecues, generators, car exhausts in garages.

Why this matters:

• CO poisoning is often missed (mimics flu/viral illness).

• Delayed diagnosis → neurological damage or death.

What investigations confirm CO poisoning?

• 1st-line: Carboxyhaemoglobin (COHb) blood test (venous heparinised sample).

  • Normal: <3% (non-smokers), <10% (smokers).

  • Toxic: >20% (symptoms), >40% (life-threatening).

• Exhaled CO breath test (bedside screening).

• ABG: May show metabolic acidosis (severe cases).

Why this matters:

• Pulse oximetry is unreliable (SpO₂ may appear normal despite hypoxia).

What is the emergency management of CO poisoning?

• Immediate actions:

  • Remove patient from exposure.

  • 100% oxygen via non-rebreather mask (until COHb <3%).

• Hospital referral if:

  • Loss of consciousness, confusion, pregnancy, or COHb >25%.

• Hyperbaric oxygen (HBO) for severe cases:

  • Reduces long-term neurological sequelae.

Why this matters:

• CO binds Hb 240x more than O₂ → tissue hypoxia.

• Half-life of CO:

  • Room air: 5-6 hours.

  • 100% O₂: 90 minutes.

  • HBO: 30 minutes.

What safety advice would you give to prevent CO poisoning?

• Install CO alarms near gas appliances/bedrooms.

• Annual servicing of boilers, heaters, chimneys.

• Never use:

  • BBQs/camping stoves indoors.

  • Generators in enclosed spaces.

  • Cars in garages with engine running.

• Seek urgent help if:

  • Headache + nausea indoors, especially with gas appliances.

Why this matters:

• CO is odourless/colourless – alarms are the only warning.

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How would you differentiate CO poisoning from viral illness?

Why this matters:

• Misdiagnosis leads to recurrence and risk of death.

   

What are the long-term complications of CO poisoning?

• Neurological: Memory loss, Parkinsonism, cognitive deficits.

• Cardiac: Myocardial infarction (due to hypoxia).

• Psychiatric: Depression, anxiety.

Why this matters:

• Early HBO reduces complications.

Key OSCE/PLAB 2 Tips: