Except by the express stipulation and consent of all parties to a proceeding before the Board or any of its investigatory bodies, in a civil action, the proceedings, records, and files of the Board or any of its investigatory bodies are not discoverable and are not admissible in evidence. This section does not apply to a civil action brought by a party to a proceeding before the Board who claims to be aggrieved by the decision of the Board. If any medical or hospital record or any other exhibit is subpoenaed and otherwise is admissible in evidence, the use of the record or exhibit in a proceeding before the Board or any of its investigatory bodies does not prevent its production in any other proceeding.