instruction: provide me the number of patients taking medication via inhalation who have diagnoses icd9 code 1418.
response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN diagnoses ON demographic.hadm_id = diagnoses.hadm_id INNER JOIN prescriptions ON demographic.hadm_id = prescriptions.hadm_id WHERE diagnoses.icd9_code = "1418" AND prescriptions.route = "INHALATION"