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Arterial blood gas (ABG) sampling procedure

Please note this information is for educational purposes only and procedures should not conducted based on this information. OSCEstop and authors take no responsibility for errors or for the use of any content.


  • Wash hands
  • Introduce self
  • Patient’s name, DOB and wrist band
  • Explain procedure and obtain consent
  • Check for allergies (including chlorhexidine)
  • Ask preferred (or non-dominant) arm 
Arterial blood gas equipment


  • Wash hands 
  • Clean tray
  • Gather equipment around tray (think through what you need in order)

Equipment list

  • Gloves
  • Alcohol 70%/chlorhexidine 2% skin-cleansing wipe
  • Arterial blood gas kit
    • Heparinised 1-3ml syringe with 23G needle
    • Rubber cube or needle cover
    • Cap for syringe
  • Sterile gauze
  • Tape

  • Wash hands
  • Open packets and place neatly in tray, keeping items in plastic parts of packets (without touching the instruments themselves)
  • Put needle on syringe if not already attached
  • Return to patient


Modified Allen’s test

  • Wash hands 
  • Expose wrist and place a pillow beneath it
  • Perform modified Allen’s test
    • With patient’s palm facing upwards, occlude both radial and ulnar arteries
    • Ask patient to open and close hand until the palm becomes pale, then ask them to hold it open
    • Release the ulnar artery and time how long the hand takes to reperfuse (i.e. become pink again)
    • If ≤10 seconds, continue with ABG


  • Firmly hyper-extend the patient’s wrist (ask them, or hold it down yourself)
  • Palpate radial artery with index and middle fingers
  • Wash hands
  • Put on gloves
  • Sterilise area using skin-cleansing wipe (clean for 30 seconds, then allow to air-dry for 30 seconds)
  • Expel air from the heparinised syringe (only necessary for some ABG kits)


  • With the index and middle fingers of your non-dominant hand, re-palpate the artery just proximal to the point of insertion
  • Holding the bevel of the needle as close to your non-dominant hand’s fingers as possible (without touching them), insert the needle (bevel up) into the site of pulsation, at 45˚ to the skin
  • When blood enters the syringe, hold it still while it self-fills (no need to aspirate)
  • Place gauze loosely over the puncture site while you remove the needle. Then apply pressure to the gauze once the needle is fully removed.
  • Secure needle with rubber block or needle cover
  • Maintain pressure over the gauze for 5 minutes. Check it has stopped bleeding before taping down the gauze.

To complete

  • Thank patient and restore clothing
  • Remove the needle from the syringe and dispose of it in the sharps bin
  • Put the cap on the end of the syringe and expel the air
  • Discard waste and clean tray; then discard gloves; wash hands
  • Label the sample and take it to the blood gas machine or call the porters to collect it on ice
  • Document procedure and results in patient’s notes with the patient’s FiO2 and temperature

Learn how to interpret the results too…

ABG interpretation is covered here!

Try it out now!

  1. Arterial blood gas
  2. More procedure OSCE stations here

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