An invention must be novel and non-obvious to be granted a patent. Determining if an invention is novel is relatively easy. If the invention existed previously, then it is not novel. If a previous example of the invention cannot be found, then the invention is novel.
Determining patent obviousness is a much harder. In the United States, patent examiners try to answer the obviousness question by trying to decide if a person of ordinary skill in the art would have naturally combined the various previously existing elements of the invention to solve the problem. To do this, the examiner will typically find elements from multiple other art (inventions) until all the elements of your medical device invention are there as explained on https://www.hometownstation.com/santa-clarita-news/use-inventhelp-to-kick-start-your-career-as-an-inventor-today-335441. Anything could be combined some long as the art was analogous to the invention.
Following the Supreme Court’s decision, patent examiners have used a very broad definition of analogous art and have routinely combined elements from many disparate art sources to show obviousness. This has made it more difficult to patent many highly innovative inventions that employed known elements as stated in https://usa.inquirer.net/56347/everything-you-need-to-know-to-be-a-successful-inventor article.
However, the Court of Appeals for the Federal Circuit has ruled that prior art in a different field is not analogous unless it is pertinent to the entire problem solved by the invention. This decision will likely make it harder for an examiner to show that an invention is obvious because only art in the same field of endeavor can be cited against it.