Claim 1 of the disputed patent relates to a micro visual endoscopy. The claim language of claim 1 does not define whether the "endoscope" is a single lumen or a double lumen. In determining the protection scope of claim 1, Wuhan Intermediate People's Court ruled that the disputed patent is a further improvement on the existing double lumen tube based on the record of the background of the disputed patent. Therefore, the "endoscope" is a double lumen. In addition, when the patentee tried to maintain the validity of claim 1 in the invalidation phase, they made the interpretation of claim 1 "endoscope" as a double lumen. Although the plaintiff claimed that the statement has not been affirmed by the Decision of invalidation review, nor the examination agency maintain the validity of claim 1 based on this. However, according to Article 13 of the Interpretative [2016] No.1, the plaintiff failed to prove that the patentee made limitations or modifications on claims, description, and figures during the patent examination procedure was clearly denied. Therefore, the principle of prosecution history estoppel can be used to determine that the "endoscope" is a double lumen tube. In this case, the endoscope of claim 1 was determined to be a double-lumen tube, and further, the disputed infringing product was deemed to be a single lumen, so that the judgment did not constitute infringement. This case is a typical case applicable to Article 13 of the judicial interpretation after the promulgation of Law Interpretation [2016] No.1. The judicial interpretation of this law reflects the latest provisions applicable to the principle of prosecution history estoppel.