Expert Insight

Leah recently presented a poster at the ASET 2016 Annual Conference. To view please click here: EEG Electrode Shape Affects Skin Safety and Breakdown for Longer Studies


For more expert answers, or to submit your own question, please visit Sleep Review Magazine online.

What is the proper way to store EEG electrodes in between patients?

The official answer can only come from the manufacturer of your reusable EEG electrodes. In general, after the electrode has been disinfected in compliance with high-level disinfecting processing (which is required because when you prep the skin you create non-intact skin and thus our electrodes become semi-critical items) ensure the electrodes dry completely and are stored in an area where no risk of recontamination can take place. Remember to high-level disinfect the entire electrode. That’s really the general guidelines, but again contact your manufacturer on the specific recommendation or consider single-patient disposable EEG electrodes to eliminate any risk of cross-contamination.

My question is about the technique of “Floating an electrode” by building up the conductive paste in a ball and applying the electrode on top. I am told that using this method and not pressing down the electrode will avoid skin breakdown. However I am wondering about using this in the case of AmbEEG’s in patient’s home. As the patient’s head sweats and the paste melts down-is there a chance of forming a salt bridge and isoelectric tracing? I was taught that you never allow paste/gel to touch. Is that a possibility with FLOATING ELECTRODES?

You are 100% correct with your concern of a salt bridge. I understand why this would be an assumption to help since “pressure” from the electrode rim on the skin is one of the main assumptions causing skin breakdown. But, it is nearly guaranteed to produce a salt bridge depending on the amount of paste used. And add to the situation patient movement and perspiration and you have a recipe called salt bridge. The salt bridge occurs when the conductive material of two locations touch each other and create one big conductive area. And this is a problem because you use a differential amplifier. Differential amplifiers only amplify what is “different” and if you create one big conductive area versus two areas then you have no “difference”. And, thus your data will look flatter/lower amplifier than it should.

If the challenge is skin breakdown, that is a completely different topic. A lot of factors can affect skin breakdown such as the amount of skin prep performed, type of prep used, shape of the electrode (example, is it a big deep cup style, a slimmer version or a flat electrode), length of time the electrode is applied, if a wrap is used to secure electrodes, skin of the patient, heat, humidity, and more.

ASET has organized a task force that has been investigating skin breakdown/skin safety and I’d recommend checking out their information. Also, I am passionate about the skin breakdown topic and presented a poster at the 2016 ASET meeting comparing “shapes” of electrodes and the impact electrode shape and rim has on skin breakdown. Check out these sources and hopefully they will help with the skin breakdown issue. But, avoid adding extra paste as you won’t solve the skin issue and you’ll be introducing a much bigger problem of potentially inaccurate data representation. https://www.aset.org/files/public/Skin_Safety_Duri... and http://rhythmlink.com/assets/uploads/ASET_2016_Pos...

Is there any advantage to using separate ground and reference leads for EEG or is a single ground/ref lead sufficient? Could you also supply your best description of the function of ground and reference leads?

Such a terrific question due to the technology of today’s systems. Love this topic! In general, for today’s systems the Ground is typically used as a baseline point versus a patient safety ground. ( I know there is a better engineering way to describe that so if you know an engineer they can give you a more technological answer !) Machines sold today have isolated grounding unlike the systems of the past which means you most likely don’t have to be concerned with grounding loops and safety. It also means if your ground falls off you probably won’t see any difference in data except the data may shift/sway more. But, the ground can also be used as part of the impedance calculation so your overall impedance can go wacky if Ground is off. Check with your manufacturer and they can explain the effect of Ground with their specific unit. The reference lead has a bigger function. This lead is critical to your amplifier function. Our amplifiers are differential amplifiers ( except a few cases in research where they can be different types) which means they compare two inputs to each other and the difference between the two is what produces the signal that gets saved to the hard drive. Once this data is saved to the hard drive I can mathematically eliminate the “reference” and this is magic of montage /display reformatting! That’s how we can look at different data configurations after the patient leaves the department ( most data that is) compared to different electrodes. Example, the machines saves to the hard drive the following: Cz – Ref, C3 – Ref, but once the data is saved I can mathematically cancel out the REF and end up with only CZ – C3. The huge benefit of digital technology! For folks like myself who grew up with analog system, this is a big deal! So, to answer your question, you can use the same electrode for ground and reference but verify with your manufacturer how they use Ground with their gear so you don’t experience any odd impedance issues etc. Personally, I’d use separate leads just to assist if I have to troubleshoot where a problem may be. But regardless, pay close attention to the reference lead(s) as it can be a very critical electrode(s) to the land of “clean data”.

I am new to sleep studies. We tried golden electrodes, but did not get clear signal. Instead, collecting quite a lot noise. I am wondering if there is any kind of “cleaning” step on the first time use of golden electrodes. I know there might be some influence since gold might have some chemical changes exposed in the air.

Good question and welcome to the PSG field! Typically artifact or noise is not caused by the metal of the electrode but other factors. Most leads sold today do not need any “prep” before usage especially gold plated electrodes as you don’t want to damage the plating so I’d start with investigation of a few other things first. I am assuming these are new electrodes so I am not going to suggest you replace them. If you are getting noisy data verify you have obtained low and balanced impedances as an electrodes acts as an antenna for noise if impedances are high or unbalanced. Next ensure your lead wire is not crossing any power source such as laying across a power cable or hanging loosely in a way that could pick up artifacts from the environment. Also try unplugging other devices in your environment such as motorized beds, etc. which can cause artifact issues. If all of those are acceptable, the next test you can perform is a quick and easy way to verify the electrode artifact level without a patient connected. You can perform this test by taking your set of electrodes and placing them into a cup of water and recording data. Check the impedances ( they all should be low and balanced) and the data should look pretty good! Now, if the data is still noisy I suggest moving one of the noisy electrodes to a different amplifier jack and see if the noise stays with the amplifier jack (this could indicate an amplifier problem) or if the noise follows the electrode this indicates an electrode problem and I’d swap the electrode for a new/different one. Artifacts can be a tough problem but methodically eliminating the different sources (environment, amplifiers, electrode, etc) .. and you’ll find the cause. Good luck!

Is there a recommended maximum length of electrodes used for sleep recordings (excluding legs, of course)?

The recommendation is to use a lead that is as short as possible to get the job done. The electrodes act like antennas for noise and artifact and the longer the electrode the better the antenna. It’s just like an antenna on a TV, to get a better signal you raised the antenna so you can get more signal. Our leads really function in the same way so whether you are using short or longer electrode always be sure to “bundle” the electrodes together so each electrode (aka your antenna) receives the noise and unwanted signals in a similar manner. If you have 10 electrodes that you have connected to your patient and nine electrodes are bundled together and one lead is hanging by itself, the bundle will receive the noise in a similar way and this allows the Common Mode feature of your amplifier to eliminate the noise better because the noise is “common.” But, that dangling electrode will receive noise completely different than the rest thus making the Common Mode feature ineffective and will allow the noise into your recording. So, use whatever length you need but do your best to keep the length as short as possible to assist your data collection efforts and ensure clean data signals and bundle any extra length and leads together.

Is there a separate billing code for disposable EEG electrode headgear, or is it included in the total professional component testing fee?

This is a great question and a popular question. No, there is not a specific code at this time designated specifically for EEG disposable electrodes. Electrodes are typically bundled under the bigger umbrella of the DRG or other reimbursement strategies. Each region has their own specific regulations and permissible reimbursement options, and contacting your state contacts regarding reimbursements would be a good start.

We want to move into disposable EEG electrodes. Can you discuss pros/cons? Are there any you would recommend?

You have a lot of good choices. My recommendation is to first make a list of what you need in a disposable electrode, and I don’t simply mean a low price but also features. For instance, 1) what cable length do you need; 2) what “shape” of electrode is best suited for your service as not everything is a cup shape and not all cups are the same shape; 3) any other features such as CT imaging capability or clearance for MRI? Once you have created your features list, contact the companies who manufacture and sell disposable EEG electrodes and ask for samples. Next, record data with each product “side by side” on the same patient/subject head so you can see the data quality side to side. Next, call the company and discuss price as they have dropped in price in the past couple years and are very cost effective and can be justified using a thorough cost justification template.

What are the options and electrode types, single leads or head caps, best suited for continuous EEG monitoring up to 24 hours? Our department is starting this service with a Nicolet ICU monitoring system.

That is a big question because you have a variety of options depending on your patient’s imaging needs and your staffing structure. First, I’d strongly recommend whatever you use is single-patient disposable, if possible, as body fluid concerns are significantly higher in the ICU and emergent care areas than anywhere else. If you can’t use single-patient disposables, make sure you can have an option to sterilize your reusable electrodes when needed. Next, talk with your team about what kind of imaging the patients may need, CT and/or MRI? (CT imaging is probably the most popular in most patient situations.) This will help determine the right leads. Denser electrodes (like metal-based reusables) will cause starburst style artifacts on the image and in many cases can’t remain on the patient. If this is the case, you’d need staff to be available to reconnect electrodes EVERY time the patient has a CT, which can be very costly and tough to manage from a staff perspective. Plastic-based disposables are the electrode of choice for frequent CT imaging. They do not distort the image and can be left on the patient. Shop around and ask for samples from the various manufacturers. Next question, will the patient population need MRIs frequently? If so, this can help your electrode path as well because only FDA-cleared EEG Electrodes can enter an MRI unit, unless other modes of internal approval are completed. So if you use leads that aren’t MRI-cleared, you need to make a technologist available to reconnect the electrodes after each MRI image. There are two companies with FDA-cleared MR Conditional Electrodes on the market. Also, make sure the electrode you choose has been cleared for your MRI strength (of either 1.5T or 3T). Shop around and you can talk to these manufacturers. You can use non-FDA-cleared products, but you’d need internal approval to ensure patient safety. Only in the past 4 months have any FDA-cleared EEG electrodes been available to the market, so you are entering at a good time. So, if these answers are “yes” to frequent CTs or MRIs, your options are only a few (due to the FDA clearance issue), but you still have a lot to choose from in the market. You can use these MR conditional leads with templates, such as the Jordan NeuroScience template for ICU, to help with placement and security; you can use a new patented electrode designed for cEEG called the PressOn EEG Electrode made for quick, fast application by a technologist or nurse (which can save some dollars for application); you can use electrodes designed to reduce skin breakdown such as the Disposable Webbed Electrode; you can use standard non-MR EEG Electrodes (as long as you have staff for reconnection); you can use non-FDA-cleared electrodes with internal authorization; there are other products designed for cEEG such as the StatNet product, etc. I highly recommend doing some research and asking for many samples to evaluate and to give to your radiology team for evaluation and approval for use. If possible, you want to avoid having to remove electrodes each time the patient goes in and out of imaging to decrease labor costs and data recording wait time for the patient, and to protect the patient’s skin as multiple reapplications can take their toll on the patient’s skin integrity. So that's a long answer to your question, but, in short, you have lots of choices if you do your research to see what’s the best fit for your patient population and budget restraints.

What types of disposable electrodes do you recommend? And what are the pluses and minuses of using disposable leads?

Really any type of disposable can be considered as the quality has gotten very good. Disposable single patient EEG cups are available through a variety of sources (research Disposable EEG Cup Electrodes online to get a wide variety of options) and they function very well. Benefits to disposables are felt in a couple of areas but the most obvious is: lowered risk of cross contamination with patients. Despite all of our efforts to clean and disinfect thoroughly, we cannot dispute that a risk of cross contamination is always present when using reusable electrodes (with the exception of sterilization). The next benefit is: cost. That’s right--cost. I know many of you won’t believe it, but I encourage you to do a FULL cost analysis of use of reusable to use of disposables. There are sources available who offer this service at no charge and you will be shocked how equal or less expensive it is to use disposables versus reusables in your service. Contact your favorite source and get a quote for disposable EEG cups for your service and spend time running through an analysis exercise. But, analyze the costs completely including every minute of labor (including salary and benefits), cost for chemicals, cost of unused inventory in your storage room, etc. The direct purchase price of disposable electrode will be much higher per year than reusable, but that is only a portion of the actual cost of maintenance of our electrodes. Disadvantages to disposables is the absence of a gold disposable electrode. The truth is gold plating (that is what is on the outside of the electrode) is expensive and the cost of using a “gold” disposable would be difficult to justify in the budget. Notice I did not list “quality” anywhere in either the pro or con section. This is because you need to determine quality using your staff, your application techniques, your patient demographics, etc. I strongly encourage you to contact Disposable EEG Cup Electrodes sources and ask for a sample of disposable EEG cup electrodes and test them on one of your patients and see how they perform compared to your reusable. I predict you will find the quality is equal to a reusable but I recommend that you test this for yourself.

Can you mix electrodes (length and thickness of leads; cup leads with flat leads)?

The answer to the above question is “yes, in most cases." Any variable between electrodes has the potential to introduce artifacts but with the capabilities of today’s data collection amplifiers the concerns of years past can be overcome with a good amplifier. But, that does not mean that as clinicians we are not responsible to understand what potential artifact are being introduced with each variable. First is the length difference. Your lead wires are basically antennas. So, the longer the lead wire the “better” the antenna to bring in artifact. If I have one short lead wire electrode and one long lead wire electrode, the artifacts between those two electrodes will be different because of the length difference. But, if my impedances are equal and low my amplifier should be able to handle the difference in noise. Second is thickness of the lead wire. Thick would probably indicate a different type of lead wire. Differing lead wire can manage artifacts and noise differently so again just as with the length issue a difference in “type” of lead wire should be avoided but if it cannot be avoided the amplifier should be able to handle the difference. Lastly, the difference in design of the electrode such as cup versus flat. This probably has the least amount of issue since the design does not introduce artifacts as long as the application technique can achieve solid impedances and the surface area of the overall electrode is similar.

How do I safely remove a PressOn electrode from a patient?

To remove the PressOn cEEG/EEG Electrode, hold skin taut with one hand and pull straight “up” with the lead wire. A tip is to grab close to the electrode by the black heat shrink and pull straight up. Little or no blood is expected in most cases. Care for the application area appropriately. For an example https://www.youtube.com/watch?v=K88PBKkZqRw

Are there any machines or technology being developed to make cleaning wires easier than by hand?

Beyond disinfecting solutions and wipes, not to my knowledge.

One reason is because most facilities are getting pressure to go fully disposable to reduce/eliminate any risk of cross contamination and subsequent Hospital Acquired Infection (HAI). And, it has nothing to do specifically with our PSG/EEG field. We are getting caught in the larger trend of eliminating/reducing any risk of HAIs. According to 1 Klevens R, Edwards J. Estimating health care-associated infections and deaths in U.S. hospitals, 2002. CDC Public Health Reports. 2007 Mar–Apr;(122):160–166, each year patients acquire an estimated 1.7 million infections while being treated at U.S. Hospitals accounting for 98,987 deaths. And it adds an average $15,275 in excess healthcare costs according to 2 Roberts RR, Scott RD 2nd, Cordell R, Solomon SL, Steele L, Kampe LM, et al. The use of economic modeling to determine the hospital costs associated with nosocomial infections. Clin Infect Dis. 2003 Jun 1;36(11):1424-32.
And, it’s not just our medical area, for instance other fields like ECG are experiencing the same pressure, as one study found 77% of reusable ECG leads harbor more than one antibiotic resistant pathogens- even after being cleaned and disinfected and prepared for the next patient. And imagine the complexity to transition a huge field like ECG to disposable lead wires and the “costs” associated? I encourage you to take a moment and watch this video on the subject presented by 3M named “Patient Monitoring 3M ECG Electrodes Reduce Infection Risks with Disposable Lead wires”, https://www.youtube.com/watch?v=nJNXEdex3lw .
And why does this matter? Because in short, facilities may not get paid if a patient acquires a HAI during their stay. So facilities are reevaluating any area where even a minor risk could exist which includes any area using reusable electrodes from one patient to another. So, that means PSG and EEG.
So, I will be surprised if you find any significant advancements in machines or other technology that assist with the cleaning and disinfecting process. And, with Disposable EEG lead prices dropping as low as $.50 -$.75 each in some cases it would be a hard business case for companies to invest the resources to develop the product you are searching to find. But, good luck with your search and I hope you are able to find a product that assists with the efficiency of the disinfecting process.

What type of wires give the best impedance- gold or silver ?

The type of wire isn't the main factor of impedance. It's really more your technique to achieve a good impedance that matters. The material on the outside of the electrode, whether gold or silver, silver chloride or tin, or whatever, is simply a conductive covering. You should be able to get a balanced impedance with any metal type. The critical points for a balanced and low impedance is good skin prep and appropriate use of the conductive material such as NuPrep, 10/20, Elefix, etc. You can survey everyone you know and you will find gold, silver, and silver chloride being the most popular metal types more because of affordability and historical preference than anything else. So choose your preference and practice good prep technique and you should be fine. But, also be aware that from vendor to vendor other factors can affect your experience with an electrode such as the lead wire type (not the metal type but what the wire is made out of). So if you decide you want to use silver electrodes be open to trying a few different versions from various vendors as the lead wire can have as much to do with your preferred electrode as the metal type.

What is the best electrode to be used with a PSG ? Is it gold or silver/silver-chloride electrodes, and why ?

Given the technology available today with high-end sleep systems, this question has become more subjective than ever. Historically, the gold cup electrode has been preferred because the gold did a better job of accentuating the slower frequencies than silver or silver chloride electrodes. This characteristic was a benefit for PSG as those frequencies were, in general, of greater interest than the faster frequencies. But, fast forward many years and the equipment manufacturers have made such advancements with the amplifier technology and the ability to re-montage and re-display digital data that our electrode metal choice has become less of a concern.

To really answer this question for your lab or service, you must do a comparison test. Use a volunteer and connect a small set of gold electrodes and run a short study. Then, remove those electrodes and repeat on the same volunteer. This head-to-head comparison will show you and your staff if any differences are present between the electrodes types and your particular equipment. In most cases I would bet no noticeable differences are evident but depending on the age of your equipment and the manufacturer, filters, etc., some slight differences may exist and you may find you have a preference. And this test can be done any time you are testing out options and want to verify if data quality will be affected negatively (or positively).

But, I want to warn you of one more difference that should be documented: the type of lead wire being used on the electrodes. Whether you prefer gold or silver chloride electrodes the type of lead wire can affect artifacts and data quality, so don't ignore that piece of your electrode. To accurately test as mentioned above, ensure both electrode types have the same lead wire type attached.

Meet our Expert


Leah Hanson, R.EEG/EP T.

For the past 24 years, Leah Hanson had been involved within the EEG, Epilepsy, IOM and Sleep Diagnostics, both as a technologist and as a provider of equipment and accessories. For the past five years, Hanson’s focus has been on electrodes for these applications and pursuing alternative methods to facilitate more effective and comfortable electrodes.