Final answer:
If a client develops pulmonary edema, the first step is to administer oxygen to rapidly increase blood oxygenation, followed by other supportive measures and calling emergency services.
Step-by-step explanation:
If a client suddenly goes into pulmonary edema, the first action you should take is to administer oxygen. Administering oxygen can help to increase the oxygen saturation of the blood rapidly, which is critical in a situation where the lungs are impaired and not able to function properly due to the accumulation of fluid. While checking blood pressure, elevating legs, and auscultating breath sounds are important subsequent steps in managing the situation, they are not the initial emergency response. Once oxygen is administered, the client's breathing and heart rate should be monitored, and emergency medical services should be called immediately if this has not already been done.