A client is experiencing chest pain and has a pulse oximetry reading of 84%. What should the nurse do first?

The priority action in this scenario is to increase the oxygen to 3 L/min. A pulse oximetry reading of 84% indicates that the client is experiencing significant hypoxemia, meaning there is not enough oxygen in the blood. This can lead to serious complications, especially given the symptom of chest pain, which may suggest a cardiovascular issue. Administering supplemental oxygen is a crucial first step in addressing hypoxemia and ensuring adequate tissue oxygenation.

While the other options may be necessary steps in managing the patient's condition, addressing the low oxygen saturation takes precedence. Administering nitroglycerin, for example, could lower blood pressure and potentially exacerbate hypoxemia if the patient is not adequately oxygenated. Taking vital signs or obtaining an ABG specimen could provide valuable information but would delay necessary immediate intervention for an urgent problem like low oxygen saturation. Thus, increasing the oxygen supply is the most immediate and appropriate action to take in this situation.