No wireless environment is immune to interference. As more and more data, voice, and now medical devices incorporate WLAN (802.11a/b/g), and eventually "n", it is important to have an enterprise 24/7/365 strategy for monitoring the health and integrity of the "air".  Here is a very good article from FLUKE that provides a real time example of rougue devices causing issues with a patient monitoring system.  Also attached is the Enterprise Tool from www.airmagnet.com

Real_Time_Charting 

Download 3495857_6511_ENG_A_W

Download AirMagnet_Enterprise_Datasheet