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