A client with a Deep Vein Thrombosis (DVT) suddenly develops shortness of breath and chest pain. What is the nurse's first action?

When a client with DVT suddenly develops shortness of breath and chest pain, pulmonary embolism must be suspected immediately. The nurse's first priority follows the ABCs — airway and breathing come first. Raising the head of the bed promotes lung expansion and reduces the work of breathing, while applying oxygen corrects hypoxemia and reduces hypoxic vasoconstriction in the pulmonary vasculature. These are immediate, life-sustaining interventions that can be implemented within seconds. Starting a 12-lead ECG is important for diagnostic purposes and should occur shortly after, but it does not address the client's acute respiratory distress and is therefore a secondary action. Administering sublingual nitroglycerin is inappropriate here because the client's symptoms are likely due to a PE, not angina; nitroglycerin can cause dangerous hypotension in this scenario. Assessing pedal pulses evaluates peripheral circulation and would not address the acute cardiopulmonary emergency at hand. The principle guiding this decision is that oxygenation and positioning to maximize respiratory function must precede diagnostic or pharmacological interventions when a client presents with acute respiratory compromise.