The practical nurse (PN) is caring for a client with a fractured left hip. The client develops tachypnea and deterioration in mental status. Which nursing intervention has the highest priority?

A. Performing an arterial stick to obtain a PaO2 level is important for diagnostic purposes but does not address the immediate need to improve oxygenation. B. Obtaining vital signs, including oxygen saturation, is important but should follow the initiation of oxygen therapy to address the immediate threat to the client’s respiratory status. C. Starting oxygen at 2 liters nasal cannula is the highest priority intervention to immediately improve the client’s oxygenation status and address the acute symptoms of tachypnea and altered mental status. D. Assessing pain level and last pain medication given is important but secondary to addressing the client's acute respiratory symptoms.