Foster had an interesting post about finding some very high-resolution bitmaps in a CorelDRAW file that a client had sent him. It can easily be a concern, especially with modern digital cameras being able to generate very detailed photos.

Some years ago, we created a macro to help with these situations. The Macromonster.com Bitmap Manipulator has powerful options. Its the fastest tool to convert numerous bitmaps to another color
model, and/or change the resolution of bitmaps inside your CorelDraw
file.
It has the capability to find bitmaps inside Groups, Powerclips, and Tables.

• It also features a single Undo.
• 8-bit Alpha Channels are preserved when found in an image.
• A handy Adaptive Unsharp option helps restore detail in downsampled images.
• Images under the new desired resolution can be ignored. For
  example, this allows images over 300 DPI to be reduced, while leaving
  existing images under 300 DPI alone.