A 66-year-old woman has sudden difficulty breathing and a history of DVT. What should the EMT suspect?

In this scenario, the sudden onset of difficulty breathing in a 66-year-old woman, combined with her history of deep vein thrombosis (DVT), is highly indicative of a pulmonary embolism. A pulmonary embolism occurs when a blood clot that has formed in the deep veins of the legs dislodges and travels to the lungs, obstructing blood flow and leading to respiratory distress. The presence of DVT significantly increases the likelihood of developing a pulmonary embolism, making it a critical consideration in this patient's assessment.

The other conditions listed do not align as closely with the presented symptoms and background. For instance, diabetic ketoacidosis typically presents with symptoms such as abdominal pain, altered mental status, or diabetic symptoms, rather than acute respiratory distress. Congestive heart failure could cause difficulty breathing due to fluid buildup, but it is usually associated with additional signs like edema or orthopnea and does not have a direct connection to her DVT history. Severe hypoglycemia would present with confusion, shakiness, or lethargy, and although it could cause distress, it is less likely to be the primary concern given her background and sudden respiratory issue. Therefore, the suspicion of pulmonary embolism is the most appropriate response in this case.