EDAIC part-1: Questions with simplified explanations. FREE UPLOADS BY WWW.TARGETEDAIC.COM (41)

The section, EDAIC part-1: Questions with simplified explanations, covers a different topic each day with the intent that candidates can prepare one small topic each day, making steady progress in their exam preparation.

Question: True statements regarding carbon monoxide

1. Less than 10% COHb levels are considered normal
2. It leads to anaemic hypoxia
3. Hyperbaric oxygen significantly decreases mortality from CO poisoning
4. Physical exertion at the time of exposure increases uptake
5. ABG typically shows a normal PaO2 value

Answers:

1. false
2. true
3. true
4. true
5. true

Explanation:

• Normal COHb levels 1-3% (up to 10% in smokers)
• Carbon monoxide has ~210 times the affinity for haemoglobin than oxygen. Binding, therefore, renders haemoglobin oxygen-carrying capacity and delivery to the tissues. This can result in tissue hypoxia and ischaemic injury (anaemic hypoxia)
• Excretion: CO is eliminated unchanged from the lungs in an exponential manner
  • The biological half-life of CO in a sedentary healthy adult is 4–5 hours
  • This half-life decreases with oxygen administration
    • ~ 40–80 minutes with the administration of 100% oxygen
    • ~ 23 minutes with  hyperbaric oxygen (2 atmospheres)
    • Mortality and delayed neurologic sequelae are substantially less in patients treated within 6 hours of discovery.
• ABG
  • HbCO (elevated levels are significant, but low levels do not rule out exposure)
  • lactate (tissue hypoxia)
  • PaO2 should be normal, SpO2 only accurate if measured (not calculated from PaO2)
• Uptake (and elimination) of CO is increased by:
  • Decreased barometric pressure
  • increased activity
  • increased rate of ventilation
  • high metabolic rate
  • anaemia

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The ‘EDAIC part-1: Questions with simplified explanations’ section covers a different topic each day with the intent that candidates can prepare one small topic each day, making steady progress in their exam preparation.