Final answer:
A nurse should first perform a quick physical examination to assess breathing, circulation, and oxygenation in a patient showing acute respiratory distress.
Step-by-step explanation:
The first action a nurse should take when admitting an older adult woman with a diagnosis of pulmonary hypertension and right-sided heart failure who is complaining of shortness of breath is to perform a quick physical examination of breathing, circulation, and oxygenation. This is critical to assess the patient's immediate needs and to determine the severity of their shortness of breath, which could necessitate emergency interventions such as the administration of oxygen. In this scenario, the patient's symptoms and their potential danger take precedence over collecting a medical history or reviewing orders, which although important, can be addressed immediately after ensuring the patient's stability.