Final answer:
If you are unable to effectively ventilate a critically injured patient using a BVM (bag-valve-mask), the best option would be to begin ventilations using the mouth-to-mask technique.
Step-by-step explanation:
If you are unable to effectively ventilate a critically injured patient using a BVM (bag-valve-mask), the best option would be to begin ventilations using the mouth-to-mask technique. This involves creating an airtight seal with a pocket mask over the patient's mouth and nose, and delivering breaths using your mouth. This technique provides a more secure seal and helps ensure effective ventilation.