Final answer:
Upon noticing paradoxical movement of the chest wall after blunt trauma, the next step is to continue to monitor the patient while ensuring oxygen administration and preparing for immediate transport to a medical facility for further treatment.
Step-by-step explanation:
When you observe paradoxical movement of the left chest wall in a patient with blunt chest trauma, it could indicate a life-threatening condition such as a flail chest. This condition occurs when segments of the ribcage break and detach from the chest wall. The most immediate concern is to stabilize the chest wall and ensure adequate ventilation and oxygenation.
While administering oxygen is already being done by your partner, applying a chest tube or performing a needle decompression should only be done by a qualified healthcare provider in an appropriate setting and usually after radiographic confirmation of a hemothorax or pneumothorax. Administering pain medication at this point, without further assessment and stabilization, may not be the priority. Therefore, the best course of action is to continue to monitor the patient, ensure oxygen delivery, and prepare for immediate transport to a medical facility for further treatment and evaluation.