Final answer:
The nurse should first take the patient's oxygen saturation with a pulse oximeter.Hence, option 2 is the correct answer.
Step-by-step explanation:
The nurse should first take the patient's oxygen saturation with a pulse oximeter. This will provide immediate information about the patient's blood oxygen levels and help the nurse determine the severity of the shortness of breath. Based on the results, the nurse can then take appropriate actions such as raising the head of the bed to improve ventilation, taking vital signs, or notifying the healthcare provider.