Of course! I was being facetious...thus my response. Actually the blood is not isolated from ambient, it's "housed" inside a very flexible container, so is always exposed to the vagaries of the atmospheric pressure. Blood pressure is always stated relative to the ambient pressure of the environment.
But, that doesn't help nightwish3r.
As bobledoux said there commercial units available over the counter.
nightwish3r, can you detail the requirements of your assigned(?) project?
Ken