There are some issues, you will just have to figure out what you are comfortable with from a risk perspective.
Details Here If you are using it to communicate for medical reasons, you may need access to your network, otherwise, you could take other approaches to minimize the risks to your network.
The easiest solution is to Skype from a mobile device like a Nexus 7 or 10 - most of the attacks are designed to run against Windows, much less mobile devices [currently].
Other options are to connect the machine to a DMZ so that it is isolated from your network and run as a NON-Administrator account.
Better is to recycle an old machine, install Ubuntu or Fedora on the old beast and run Skype or other software on that machine where your risks are much lower. Most everyone has a old machine that they can give new life to, while also protecting their patient data and network.
So, fastest is to spend $200-$400 for a Nexus.