Arterial Blood Gas Collection (OSCE)


  1. Greet patient and introduce yourself πŸ‘‹
  2. Confirm patient details βœ 
  3. Make a note of the delivery device if patient is receiving oxygen therapy (increases PaO2✍ 
  4. Briefly explain the procedure in a patient friendly manner 
  5. Identify any absolute contraindications (peripheral vascular disease in limb/arteriovenous fistula/ cellulitis) 
  6. Identify any relative contraindications (impaired coagulation) 
  7. Check if the patient is allergic to local anaesthetic 
  8. Get patient consent βœ… 
  9. Ensure patient is sitting with wrist exposed 
  10. Check the patient is not in any pain 
  11. Wash hands βœ‹ 



πŸ’‰ Disposable gloves βœ‹ 

πŸ’‰ Apron 

πŸ’‰ Sharps bin πŸ—‘

πŸ’‰ Gauze/cotton wool 

πŸ’‰ Tape 

πŸ’‰ 70% isopropyl alcohol wipe 

πŸ’‰ Arterial blood gas syringe (pre-heparinised) πŸ’‰

πŸ’‰ Bung/cap 

πŸ’‰ 23 G blood gas needle πŸ’‰

πŸ’‰ 25 to 27 G Subcutaneous needle πŸ’‰

πŸ’‰ 1 to 2 ml syringe for lidocaine 

πŸ’‰ 1mL 1% Lidocaine  


Modified Allen’s Test 

  1. Occlude the radial and ulnar arteries by applying pressure over them whilst the patient clenches their fist βœŠ 
  2. Ask the patient to unclench their fist and check it looks β€˜blanched’ for confirmation that you successfully occluded the arteries βœ‹ 
  3. Maintain pressure over the radial artery, but remove it from the ulnar artery 
  4. Assess whether normal colour returns to the hand within 5 to 15 seconds (indicates the ulnar artery has sufficient blood supply β± 
  5. If it takes longer than 5 to 15 seconds for the colour to return to the hand, it indicates that the patient has poor collateral circulation and arterial blood gas sampling should NOT be performed βŒ 



  1. Collect unpackaged equipment on a tray 
  2. Prepare the ABG syringe by attaching the needle πŸ’‰
  3. Place the patient’s hand on a pillow, extended 20 to 30Β° πŸ“


ABG Sampling 


Palpate the radial artery: 

  1. Palpate the radial artery on the patient’s non-dominant hand, identifying the most pulsatile part, this is the ideal puncture site 
  2. Clean the identified site with the alcohol wipe, allow it to dry 
  3. Wash hands βœ‹ 
  4. Put gloves and apron on βœ‹ 


Administer local anaesthetic: 

  1. Prepare lidocaine 
  2. Administer it over the puncture site, subcutaneously 
  3. Wait for at least 1 minute to allow the anaesthetic to work β± 


Arterial Puncture: 

  1. Uncover the ABG syringe  
  2. Flush the heparin from the syringe πŸ’‰
  3. Hold patient’s extended wrist 
  4. Use your non-dominant hand to palpate the radial artery, 1cm above the puncture site πŸ“
  5. Inform the patient you are ready to insert needle πŸ’‰
  6. Insert needle at a 30 to 45Β° angle πŸ“
  7. Insert the needle further into the artery until you observe flashback πŸ’‰
  8. The ABG syringe should begin filling 
  9. Remove the needle from the artery when you have the required amount of blood πŸ’‰
  10. Apply pressure to the puncture site with some cotton wool or gauze 
  11. Tape the cotton wool or gauze in place on the skin 
  12. Apply the safety measure to the needle (cover it with a clip or bung) β— 
  13. Discard the ABG needle appropriately into the sharps bin πŸ—‘
  14. Put the cap on the ABG syringe, and expel any air 
  15. Label the patient’s details on the ABG sample βœ 
  16. Tell patient to continue applying pressure for 3 to 5 minutes β± 


ABG ranges: 


πŸ’‰ pH: 7.35 βž‘ 7.45 

πŸ’‰ PaCO2: 4.7 βž‘ 6.0 kPa/35.2 βž‘ 45 mmHg 

πŸ’‰ PaO2: 11 βž‘ 13 kPa/82.5 βž‘ 97.5 mmHg 

πŸ’‰ HCO3–: 22 βž‘ 26 mEq/L 

πŸ’‰ Base excess (BE): -2 βž‘ +2 mmol/L 



  1. Tell the patient the examination is complete βœ… 
  2. Thank patient 
  3. Dispose of all equipment appropriately 
  4. Wash hands βœ‹ 
  5. Take ABG sample for analysis immediately❗ 
  6. Document ABG results in patient’s medical records βœ 


  1. Greet the patient and explain the procedure
  2. Perform the Modified Allen's Test
  3. Palpate the radial artery
  4. Administer local anaesthetic
  5. Perform arterial puncture
  6. Complete the procedure by thanking the patient and dispose of equipment appropriately

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