卡特尼 = transliteration for the trade mark
隔水 = waterproof
防污 = anti-contamination
塑料 = plastic
纸 = paper
床垫 = bedsheet

So-called in-house service could be the recovering care given to patients in their home. The bedsheet made of high density polyethylene is most likely a kind of one time use bedsheet for the purpose of preventing contamination. Made of high density polyethylene, the most important feature of this sheet should be waterproof. In order to be distinct from the regular bedsheet, I would suggest “隔水塑料床垫”.

And in some case, this kind of bedsheet is composed of two layers, one is for waterproofing, the other is for water absorbing. The water absorbing layer is made of paper-like textual. If that is the case, It’s better to add a word “纸” to make it “隔水塑料纸床垫” or “防污塑料纸床垫”.