A slow-rolling (sway) artifact has been identified in all of your patient’s EEG and EOG derivations. EKG artifact has been identified in the right-sided EEG and EOG derivations as well. Explain in det

Troubleshooting Polysomnography Artifacts
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First, there is a need to determine the type of prevailing artifact: whether physiological or mechanical. Both the slow rolling and EKG artifacts are physiological artifacts, and each is resolved differently. The slow rolling is a type of sweat artifact in reference to Spriggs (2015), and it can be best correct by correcting the environment. Therefore, there is need to cool the patient prior to trying out other troubleshooting techniques. This cooling effect can be achieved by wiping the area between the electrodes with alcohol or some form of antiperspirant. Also, the low frequency can be increased, for example, from 0.3Hz to 1Hz, in the EEG and/or EOG channels or fan the patient while ensuring that the electrodes are not swayed to avoid another type of artifact (Mattice, Brook, & Lee-Chiong, 2012).
In reference to the EKG artifact, the therapist should try repositioning or reapplying the reference electrodes. These electrodes should be positioned in the right manner by ensuring that the mastoid electrodes overlie the bone because it does not transmit the EKG readily compared to fatty tissue. Often, this helps to resolve the issue, but if it persists, then a linked reference should be used. Whereas the linked reference is beneficial, there is a need to ascertain the nature of the artifact: linked EOG and EEG reference electrodes are only used an EKG artifact occurs. Otherwise, it may cause a reduction in the amplitude of the EEG and EOG signals; hence, poor recording.

The use of a linked reference, for instance, linking M1 and M2 leads allows common mode rejection, which helps to block extraneous ECG signals (Mattice et al., 2012). Double referencing results in the creation of three divergent ECG signals that cancel one another; thus, reducing the artifact. Linking references should be sparingly applied because it can exacerbate the artifact.

References
Mattice, C., Brooks, R., & Lee-Chiong, T. (2012). Fundamentals of sleep technology (2nd ed.). Philadelphia, PA: Wolters Kluwer. Retrieved on 11 December 2016.
Spriggs, W. H. (2015). Essentials of polysomnography: A training guide and reference for sleep technicians (2nd ed.). Burlington, MA: Jones & Bartlett Learning. Retrieved on 12 December 2016.