A patient with a history of chronic obstructive pulmonary disease presents with respiratory failure. What is the initial priority action?

In a patient with chronic obstructive pulmonary disease (COPD) presenting with respiratory failure, the initial priority action is to provide assisted ventilation with a bag-valve-mask (BVM) resuscitator. This approach is vital because it helps to ensure adequate ventilation, especially when the patient's respiratory drive may be compromised due to the disease process. In cases of respiratory failure, maintaining oxygenation and ventilation is crucial, and the use of BVM allows for the delivery of positive pressure to assist the patient in breathing.

High-flow oxygen, while important, may not be sufficient alone, particularly if the patient is unable to effectively ventilate. Intubation is a more invasive procedure that can be considered later if the patient's condition does not improve with non-invasive measures. Performing a nebulizer treatment may provide symptomatic relief but does not address the immediate need for ventilatory support in a patient who is unable to maintain adequate breathing. Thus, assisted ventilation is the most critical initial step in managing respiratory failure in this context.