There could be 100 different things causing this.
Below are the common troubleshooting methods of Biomeds will use to systematically isolate the suspect part, accessory or component.
Step 1. replace the electrodes with a freshly opened pack since the others may be dried out. Put them on yourself. Problem gone? electrodes.
Step 2. replace the patient lead wires/trunk cable. Problem gone? defective cables.
Step 3. since on the Dash you cannot replace the ECG module, then replace the AC power cord and verify it has an excellent electrical bonding to the DUT. Problem gone? defective power cord.
Step 4. Troubleshoot the DUT in a different environment. If it is simple to move the monitor to another room then do so. Test it with the AC power cord plugged in to a different electrical circuit than the previous room. If possible, plug it into a circuit that is even on a different electrical panel. Problem gone? The facility engineers need to correct the poor electrical receptacle, appliance or lighting installation in the room. Remember that electrical noise can potentially be generated from ANY device or appliance in a patient room. Even just changing the fluorescent lamps can create this issue.
One other question to bear in mind, has the ICU bed been exchanged out recently? If so, this may also be your culprit.
Hope this is of use, please tell us what you find. Thanks