Richard,
I would recommend using one leg of an off-the-shelf pressure sensor, such as
the type sold by NovaSensor or IC Sensors. (I believe that NovaSensor has a
product approved for medical use.) The piezoresistors are temperature
sensitive as well as pressure sensitive. Perhaps you can adapt one of these
for development purposes. If you need a custom device I can help you with
that, however, the first approach would be more cost effective for now.
Regards,
Mike Mattes
MicroMechatronics