<prompt> A 55 year old man who has been on bed rest for the past 10 days, complain of breathlessness and chest pain. The chest x-ray is normal. The next step in investigation should be:Lung ventilation - perfusion scanPulmonary aeriographyPulmonary venous wedge angiographyEchocardiography  <response>: A i.e. Lung Ventilation Perfusion Scan The hO breathlessness chest pain after 10 days of bed rest points towards diagnosis of Pulmonary thromboembolism. So for diagnosing PTE the Vt screening investigation is Ventilation perfusion scanQ and the bestgold standard investigation is Pulmonary angiographyQ 