An 86-year-old male has sudden right-sided chest pain and difficulty breathing after a cough. What should you administer first?

In the scenario presented, the most appropriate first action is to administer oxygen. The patient is experiencing sudden chest pain and difficulty breathing, which are critical symptoms that may indicate a respiratory or cardiac issue, such as a pulmonary embolism or a myocardial infarction. Oxygen should be prioritized to ensure that the patient receives adequate oxygenation, especially since the difficulty in breathing suggests a potential for decreased oxygen levels.

Providing oxygen can help alleviate hypoxemia (low oxygen in the blood) and improve overall respiratory function, which may stabilize the patient and buy sufficient time for further assessment and treatment. Once the immediate needs for oxygenation are addressed, other interventions such as medications for pain relief or treating the suspected underlying cause can be considered, depending on the patient's response and ongoing assessment.

Initiating oxygen therapy right away is critical in emergency situations like this, where time and adequate tissue oxygenation can significantly impact outcomes.