I believe I am having a similar problem to this post [1], but it didn't answer my question.

I have completed a few drawings in Inkscape that I intend to use in PowerPoint (2013) presentations. To do so, I export them as PNGs. I planned on setting the DPI so the final images will be about 600 px x 600 px, which for my drawings, would be around 300 DPI. Through the course of my troubleshooting, I have tried many DPI values, going as high as 3000 DPI. While I don't recall exactly the resolution of the resulting image, it was more than 1920 x 1080. The extremely high DPI setting did not solve the problem.

My problem:
The images export just fine, and are the resolution the export dialog claimed they would be. They show up fine in windows picture viewer, MS paint, and GIMP. But when I insert them into PowerPoint, they show up at a considerably lower resolution than they did everywhere else. At first I thought PowerPoint was just inserting them at a strange default size, but when I scale them up, the images start to get blurry. A workaround I have found is to open the PNG in either MS paint, or GIMP, copy it, and paste into PowerPoint. When comparing the pasted image to the directly loaded image, there is a considerable improvement.

I would rather not have to go through these steps every time I load an image into PowerPoint. Other images seem to load fine, I have only ever experienced this problem with drawings I made in Inkscape.

[1]: viewtopic.php?f=5&t=13970&p=54950&hilit=powerpoint#p54950