Investigations

• Arterial blood gas ^d  

N.B. Do not use pulse oximetry alone - it can be deceptively wrong. ^c  

Why?

• Pulse oximetry is unable to distinguish HbCO from HbO₂, and may give false high ("normal" ) readings ^c  
• The higher the carboxyhaemoglobin level, the greater the inaccuracy in pulse oximetry. ^c