Final answer:
The most appropriate next step in management for a 66-year-old female with hypertension and diabetes experiencing chest pressure, based on her vital signs, is to administer oxygen, give aspirin, and conduct further assessments. Hence, option (3) is correct.
Step-by-step explanation:
A 66-year-old female with a history of hypertension and diabetes presents with substernal chest pressure of 2 hours' duration. Given her vital signs, including a blood pressure of 140/90 mm Hg, pulse of 100 beats/min and irregular, respirations of 22 breaths/min, and an oxygen saturation of 92, the most appropriate next step in management would be option 3) Administer oxygen, give her 324 mg of aspirin, and assess her further.
This approach is in line with standard treatment protocols for suspected acute coronary syndrome (ACS), which considers the administration of oxygen if saturation is below 94%, giving aspirin unless contraindicated, and performing further assessments to confirm the diagnosis and decide on additional interventions.