When a patient has chest pain that could be ACS, the priority is to ensure oxygen delivery and quickly assess the patient's status. Administering high-flow oxygen per protocol helps optimize oxygen availability to the heart muscle, especially if the patient is hypoxic or in distress. At the same time, obtaining baseline vitals gives you an immediate snapshot of heart rate, blood pressure, respiratory rate, and oxygen saturation, which are essential for spotting deterioration and guiding further treatment. Consulting medical control ensures you’re aligned with local protocols for subsequent steps, such as medication administration and transport decisions. Giving nitroglycerin without precautions isn’t appropriate because it can cause dangerous drops in blood pressure or interact with other medications; you must verify blood pressure and contraindications first. Delaying treatment to obtain an ECG first, then oxygen, risks worsening the patient’s condition since oxygen is often needed promptly if hypoxia is present and vitals need to be monitored continuously. Administering an IV fluid bolus isn’t a standard initial action in ACS unless there are signs of shock or dehydration, and it can worsen heart failure or pulmonary edema in these patients.