instruction: what is the number of patients whose primary disease is aortic insufficiency\re-do sternotomy; aortic valve replacement and drug route is pb?
response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN prescriptions ON demographic.hadm_id = prescriptions.hadm_id WHERE demographic.diagnosis = "AORTIC INSUFFICIENCY\RE-DO STERNOTOMY; AORTIC VALVE REPLACEMENT   " AND prescriptions.route = "PB"