Critical Initial Intervention for COPD Patient

A 68-year-old male patient with a history of chronic obstructive pulmonary disease (COPD) presents to the emergency department with severe dyspnea, cyanosis, and use of accessory muscles for breathing. The patient reports a recent upper respiratory infection. The nurse notes that the patient has an oxygen saturation of 84% on room air. Given this scenario, what is the most critical initial intervention the nurse should perform?