We should assess the airways first and stabilize his head.
This patient's injury had a substantial injury mechanism. You cannot accurately evaluate his airway when he is prone. Therefore, you should manually steady his head as your initial step. The next step is to log roll him into a supine posture while maintaining his head alignment. Log roll him straight onto a long backboard if at all possible.
Once the patient is supine, evaluate the condition of his airway, his breathing capacity, and, if necessary, start assisted ventilations or high-flow oxygen therapy before moving on to your primary assessment. As soon as you can, put a cervical collar on him, but first look at his posterior neck.
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