Final answer:
The first action should be to administer high-concentration oxygen to the woman with headache and vision difficulties, who also shows signs of respiratory distress. This approach ensures that she receives adequate oxygen while further assessments and interventions are prepared.
Step-by-step explanation:
A woman in her late 40s complaining of headache and vision difficulties, who is responsive to pain with a droopy eyelid, unequal pupils, and slow shallow respirations, represents a possible case of anaphylaxis or a neurologic event such as a stroke. The individual's symptoms of difficulty breathing and potential airway compromise take precedence. Therefore, the first action should be to administer high-concentration oxygen. Oxygen support is critical to ensure that the brain and other vital organs continue to receive adequate oxygen. While preparing to administer oxygen, it's important to assess for further signs of anaphylaxis or other causes and prepare for additional emergency interventions as needed. Assisting the patient with an EpiPen may be appropriate if anaphylaxis is confirmed.