Electric devices, even in normal and intended use may also damage other devices. Particularly true with the electrosurgical units that apply very high voltages (300 9000 V, @500kHz 2MHz, w/100 750W)
If the ground connection to these units, are faulty, and/or if higher then normal output resistance is present, they may elevate patients'potential significantly over the ground. Even at very short intervals, this may be adequate to fry an ECG machine, or at a minimum cause transient effects.
How to make sure that high voltages are not applied to other devices, such as ECGs, when they are present?