“Can you work in nuclear medicine if you have pre-existing respiratory conditions?”

There is no contraindication for people with respiratory ailments. However, if someone is coughing all of the time, it may look bad to the patient. The radiation exposure is minimal and should not affect lung disease.

I would like to ask for more detailed medical history of your respiratory problems, but you can always make your own decision by simply asking for the Employee’s safety handbook and guidelines. Here is an example:
https://open.alberta.ca/dataset/21700f6d-8e42-4e71-a764-69ac10a0ffdb/resource/22bf6448-8e69-4a7e-830c-89fafe5c8863/download/ohs-wsa-handbook-diagnostic-imaging.pdf