Go to
http://www.nice.org.uk
This is the website for The National Institute for Clinical Excellence. They provide guidelines for best practice in a variety of subjects, all up to date and research based.
They have published guidelines for pressure relieving devices, and pressure ulcer management which are free to download.
Chronic diseases that can make people more susceptable to pressure sores are:
CVA (stroke)
MS
Diabetes
Neurological disturbance.
There are many risk factors broken down into two sections:
Extrinsic (factors from outside body) eg
Pressure
Friction
Shear
Moisture
Intrinsic (factors from inside body) eg
Poor nutrition
Smoking
Circulatory problems