I think the pertinent fact is the water would still need to boil. The only thing increasing pressure does is increase the temperature at which water boils. NOTE: I probably mixed this up in my original post. This means that the pressure cooker would raise the boiling point (thus allowing cooking at a higher pressure WITHOUT boiling water off).

"Maximum vaporization occurs at the boiling point, 100°C (212 °F) at 1 atmosphere. Conversely, the vapor pressure of water, that is, the pressure of the vapor in equilibrium with the liquid, is 760 mm Hg at 100 °C. If the atmospheric pressure is reduced to say, 525.8 mm Hg, as would be the case if the same kettle is boiled on the top of a mountain, the boiling point will be reduced by several degrees to 90 °C (194 °F). The reason: at this temperature the vapor pressure of water is 525.8 mm Hg."

http://www.unesco.org/webworld/ramp/html/r8707e/r8707e06.htm

Sorry about the earlier typo: I wasn't reading as thoroughly as I should have (studying at the time). Notice also how little the boiling point changes, even with rather significant changes in pressure.