When a client presents with severe chest pain and dyspnea, what is the nurse's first line of action?

Delivering oxygen at 4 L/min is the most appropriate first line of action when a client presents with severe chest pain and dyspnea. This step is critical because it addresses potential hypoxia and ensures that the patient receives adequate oxygenation, which is essential in cases of cardiac distress. Oxygen therapy can help to relieve the symptoms of dyspnea and support the body's needs while further assessments and interventions are planned.

In situations involving chest pain, particularly when dyspnea accompanies it, the immediate concern is to stabilize the patient and prevent further complications, such as myocardial ischemia. Providing supplemental oxygen can help mitigate these risks, especially if the patient is experiencing difficulty breathing or has low oxygen saturation levels.

Once oxygen is administered, further evaluations, such as obtaining an electrocardiogram or administering medications like morphine, can be considered based on the patient’s condition and the healthcare provider's assessment. However, ensuring adequate oxygenation is foundational to the treatment approach in emergency settings.