• Measure the distance from the top of the patient's shoulder to the angle of the jaw with your hand (image 1)
• On the collar, measure from the bottom of the rigid plastic to the "measuring post". This should correspond to the above measurement (image 2)
• Check that the collar fits correctly
  • The neck should not be overextended
  • The mouth should not be able to be fully opened (image 3)
    
    

Image 1: Measuring collar size on neck

Image 2: Checking collar size

Image 3: Appropriately fitting collar