What is a likely cause of elevated respiratory distress in a patient with a history of breast cancer?

In a patient with a history of breast cancer, metastasis causing pleural effusion is a likely cause of elevated respiratory distress due to the implications of metastatic spread and its effects on the lungs. Breast cancer can metastasize to the pleura, leading to the accumulation of fluid in the pleural space, which can restrict lung expansion and result in difficulty breathing. This condition can manifest as significant respiratory distress because the fluid buildup impairs the lungs' ability to function effectively, decreasing oxygen exchange and leading to symptoms such as shortness of breath.

While pneumonia, asthma attacks, and cardiac events can also cause respiratory distress, they are not directly linked to the patient's history of breast cancer in the same way that pleural effusion is. Pneumonia could cause respiratory issues in anyone, while an asthma attack would be more related to a prior history of asthma rather than cancer. A cardiac event, while serious, does not typically arise as a direct consequence of breast cancer. Therefore, considering the patient's specific medical history, metastatic pleural effusion is the most plausible cause of elevated respiratory distress in this scenario.