Digital images do not have a resolution. They are simply images with pixel dimensions. For example, with my 24 megapixel camera the images are 6000 x 4000 pixels. The only value a resolution setting has is to indicate or enable you to calculate how large the image will be at any given resolution setting. For example, if I wanted a 300 PPI setting the calculations would look like this:
6000 pixels / 300 PPI = 20 inches
4000 pixels /300 PPI = 13.333 inches
So I could have an image that is 13 x 20" at 300 PPI. I could change the PPI setting to 200 and the image would be 20 x 30". But the number of pixels in the image won't change. The image itself remains exactly the same.