Artifact Recognition & Correction - Polysomnography

If a 60Hz artifact is observed in one of the channels during the bio-cals process, the appropriate action would be to find the problem source and correct it before beginning the study. This is because the artifact could potentially interfere with the accuracy of the study results. By identifying and fixing the problem source, the artifact can be eliminated, ensuring reliable data collection during the study. Re-evaluating the problem after the patient goes to sleep, re-referencing to a back-up electrode, or using a 60Hz notch filter may not address the underlying issue causing the artifact and may not provide a long-term solution.

When deciding to enter the patient's room to correct artifacts, several factors come into play. The importance of the electrode channel in scoring is a crucial factor as it directly affects the accuracy of the data collected. Additionally, the ease at which the patient falls asleep is important as it determines the disruption caused by entering the room. Lastly, the skill at fixing the problem without waking the patient is significant to ensure minimal disturbance to their sleep. Therefore, all of the above factors need to be considered when deciding to enter the patient's room to correct artifacts.

The first step in differentiating high frequency artifact caused from muscle vs. a poor electrode connection is to perform an impedance check. This involves measuring the electrical impedance at the electrode site to determine if there is a good connection between the electrode and the skin. A high impedance reading could indicate a poor electrode connection, while a low impedance reading could suggest muscle artifact. By conducting an impedance check, one can identify the source of the artifact and take appropriate measures to address it.

If the size of the prepared electrode site is too large, it can lead to signal contamination or bridging. This means that the electrical signals being measured can get mixed or distorted, resulting in inaccurate readings. This can happen due to the electrode picking up signals from neighboring muscles or tissues, causing interference and compromising the quality of the recorded data.

Popping is not a physiological artifact because it is not a natural occurrence within the body. Physiological artifacts are typically involuntary bodily responses or movements that can interfere with accurate measurements or observations. Muscle movements, respiratory fluctuations, and cardio-ballistic artifacts are examples of physiological artifacts because they are inherent to the functioning of the human body. Popping, on the other hand, refers to a sudden, audible sound that occurs when a joint or bone is moved forcefully, which is not a normal physiological process.

Muscle artifacts are known to present as high frequency artifacts. This is because muscle activity can introduce electrical interference into the recording, resulting in high frequency noise. This can be observed as rapid fluctuations or spikes in the recorded signal. Therefore, muscle artifacts are considered to be a common source of high frequency noise in various physiological recordings, such as electroencephalograms (EEGs) or electromyograms (EMGs).

Both pressure against the electrode and poor ground connection are likely to cause electrode-popping artifact. Pressure against the electrode can cause the electrode to become dislodged or detached from the scalp surface, leading to artifact in the recorded signal. Poor ground connection can result in electrical noise and interference, which can also manifest as artifact in the recorded signal. Therefore, both A and C are the most likely conditions to cause electrode-popping artifact.

Passing input signals through differential amplifiers is the chief way of excluding undesirable interfacing signals in polysomnography. Differential amplifiers are designed to amplify the difference between two input signals while rejecting any common-mode signals, which helps in eliminating unwanted interference. This technique ensures that only the desired signals are amplified and recorded, improving the accuracy and reliability of the polysomnography measurements.

Muscle artifact in an EEG channel can occur due to electrical activity generated by muscle movements. Re-referencing the channel to a back-up exploring electrode can help eliminate the artifact by changing the reference point for that channel. This can reduce the influence of muscle activity on the EEG signal and improve the quality of the recording.

The preferred method of correcting undesirable artifacts during the recording process is to change the input signal derivations. This means altering the way the signals are obtained or derived from their source. By doing so, it is possible to minimize or eliminate the artifacts that may have been introduced during the recording process. This method is often more effective than manipulating filters or temporarily adjusting amplifier sensitivity or gain, as it directly addresses the root cause of the artifacts.

One of the contributing causes of EKG artifact in arm or leg leads is voltage differences resulting from increased electrode distances. When the distance between the electrodes is increased, it can lead to variations in the voltage measured, resulting in artifact on the EKG. This can occur due to improper placement of the electrodes or when the electrodes are not securely attached to the skin. These voltage differences can interfere with the accurate interpretation of the EKG.

Double-referencing (A1+A2) is useful for reducing EKG artifact in EEG and EOG channels. EKG artifact refers to interference caused by electrical activity of the heart, which can contaminate the EEG and EOG signals. Double-referencing involves using two reference electrodes (A1 and A2) instead of a single reference electrode, which helps to cancel out common-mode noise, including EKG artifact. By reducing the EKG artifact, the quality and accuracy of the EEG and EOG signals can be improved.