Mr. David Sletten: So, we’re going to demonstrate a full battery of the four tests. We’re going to Q-Sweat and then we’re going to move onto the deep breathing Valsalva. Unfortunately, we don’t have a tilt table test here, but we are going to demonstrate a stand for you today. So, we have Jade here, he is going to be our test subject. One of the things that we had him do to help with this was with the Q-Sweat, we want to make sure we are shaving any hair, so because Jade works with us, we know him, and we had him pre-shaved. So, you’re not going to see that step, but we are going to walk through everything that we would do as technicians. So, we’re going to start by cleaning the skin with some acetone to defat the skin, some alcohol to remove the acetone and finally some water to remove any of the residual alcohol. Then we’re going to dry these areas off very well before we go ahead and hook up the Q-Sweat device. So, I’m going to bring Toni up who is one of our technicians as well and been with Dr. Lowe forever. So, she is going to go ahead and start prepping Jade. I’m going to get his name in the computer here and they’re going to hopefully get this computer screen up there for us, so that you guys can see everything that’s going on real time.
Dr. Wolfgang Singer: Particularly, those in the back rows, this is very non-formal, so feel free to come up here and observe from closer up if you like.
Mr. Sletten: Yeah, come on up, it doesn’t matter and please feel free to ask questions during any part of this part of the presentation.
Mr. Sletten: So, the first thing I am going to do is go in and create a new patient.
Dr. Singer: So, normally we utilize acetone, alcohol, water and then dry gauze. That’s sort of a really nice and clean preparation that gets rid of not only skin debris, but also fat and allows for sort of cleanest response. We are abbreviating there is a little bit here with just using alcohol and dry gauze.
Mr. Sletten: So, one of the things that we have our technicians do right away is to actually start the suterometer device before we actually go and put the capsules on the subject and that’s just to be sure that everything is properly working. So, I’m going to go ahead and get that started after I select the different site. So, we’re going to use the left side, that’s the standard side, and then we’re going to go with the forearm, proximal leg, distal leg and foot, which is all predefine for us. And as a technician if anything happens, we do have this onscreen help for you as well as you are walking through this.
Anonymous: You have four probes, in theory you could use two and then do the upper limbs separate with two probes, right?
Mr. Sletten: Yeah, you can place these anywhere you want to, but.
Anonymous: I know, but it’s not necessary to have four probes.
Dr. Singer: Correct.
Mr. Sletten: Now the standard sites that we are using is 75% the distance between the epicondyle and the pisiform border on the ulnar distribution. We’re going to go at 5 cm distal to the fibular head, 5 cm proximal to the medial malleolus and then, we are going to try our best to go over the EDB muscle as much as we can. Now that is going to be a source of, that’s the technical aspect of it is getting it on the foot without the leaks and so, we’re going to do our best to not get a leak at that, but if we do, we’ll demonstrate what we would do to fix that as well.
Dr. Singer: Those locations are general guidelines you obviously have to keep individual anatomy in mind and if there’s a big bulky muscle that you can’t get a seal around, you just move it a little bit to the side and find a place we can get a good seal for the capsule.
Dr Singer: After cleaning the site, they’re just putting those capsules on with moderate amount of pressure with those elastic wraps here. You don’t want excessive pressure to cause cutting off the circulation, but you want it snug because if it gets too loose then there’s leaks and leaks are very annoying because it takes a while for the system to dry out and you have to wait. We have patients waiting that delays things unnecessarily.
Toni: You want to make sure that the bottom of your capsule has enough tension so that it doesn’t leak underneath. That’s the major thing because if you get a leak then it’ll flood your equipment and kind of let the machines dry out.
Dr. Singer: So, now the capsules are placed. Now, we put on the ground electrodes for the stimulation, the syringes that I filled with acetylcholine solution already in place as well.
Mr. Sletten: Now normally, we would have a cart or something with all of our equipment on that we could actually set all these up pre-ahead of time, but we’re going to attach both – black to black and red to red.
Dr. Singer: One other thing to keep in mind is that tests like for nerve conduction studies, skin temperature does play a role, particularly at the foot site. So, just like ideally for nerve conduction studies, you want to keep the skin temperature at about 32 degrees Celsius and you can utilize some heat lamp or any other option to warm up the skin a little bit before the test.
Anonymous: Would you comment on acetylcholine solution?
Dr. Singer: What’s the specific question, acetylcholine solution?
Anonymous: Where you add it, if it is a microfilter or sort of?
Dr. Singer: Yeah. Do you want to answer?
Mr. Sletten: Well, that’s a tricky question. So, there’s a lot of different manufactures that do make acetylcholine. You’ll just have to go with whatever’s in your list of preferred vendors for your institution. It’s a simple 10% weight to volume mixture. We use distilled water or deionized water. The actual product we get is 99.9% pure. We have done studies looking at HPLC grade versus non-HPLC grade and have found no difference in that.
Dr. Singer: We are aware that there are some pharmacies and some places that are very strict and would not allow anything other than the purest form. Our argument is that we are using acetylcholine not as a drug but as a reagent and we have not had problems as a result of that.
Mr. Sletten: And we have also done stability studies on that. So, we did find that it’s good for 30 days at room temperature and up to 90 days at refrigeration temperature. You could actually freeze it as well, but we didn’t find that that actually extended the life of it all. So, what we usually say is within 3 months if you’re not going to use it, get rid of it and we recommend always storing it in the fridge and not leaving it out on the counter unless you are pulling it out for the day’s patients.
Mr. Sletten: Now, what we’re waiting for now is for the screen to come down and these lines to kind of come to a baseline, which is giving us what the amount of moisture is just coming off the skin without being stimulated. Now, this is one difference that we do at Mayo Clinic that’s separate from a lot of the other sites that I’ve visited and may break the software when you go to do the analysis. And that is as we would like to put a mark in when we actually go to inject the acetylcholine solution into these capsules because what that’ll tell us is if there’s a leak during that time period, we know that it is due to the acetylcholine being injected and not due to the stimulus that’s about to start. So, while we’re waiting for this to come down, I’m going to go ahead and turn the stimulators on. So, you’re going to hear bunch of beeps and we’re just going to go through some settings and basically what we are going to do is set these, so that it is going to run for 5 minutes at 2 milli-amps. And as we are going through these, some of the settings are single phase, which is what we want. We don’t use the dual phase option of these. Our polarity is going to be a plus. If you are familiar with these, your dose will be set to 10 and then finally it’ll start getting ready for you to ramp up the current to 2 milli-amps. Now, during this time is normally once we got these set up, we’ll go over to the computer screen and will make our first mark and then inject these, each of the capsules, with acetylcholine. And when we’re filling, we like to go slow; if you go too fast with it you can actually put too much acetylcholine in too fast, which can cause it to kind of blow out and actually start to leak into that center chamber. The other couple of things that are important that I’ll go through when we actually start the stimulus is the way that we’re filling and the way that the capsules are. So, then the first thing we would do is we would look to make sure that we do not have a leak on our screen after we have injected. Everything looks pretty good to us here. So, then we are going to go ahead and make another mark and this is where our setup is usually conducive to the testing where we’re not running from one side of the bed to the other, but just so, you can kind of get the idea. Then we always warn our subject, “You are going to feel hot and prickly. If you have never had this done, the first minute seems to be about the worst. Once you actually start sweating, it’ll start to die down just a little bit.”
Mr. Sletten: So, couple of the other things that are really important is when we are filling these capsules, we always want to make sure we are filling from the very bottom of the capsule to the top. If you fill it from the top down, you’re not going to get enough acetylcholine into that chamber, which is going to cause a number of problems. One, it could be a hot pocket underneath there and could actually burn the patient or it would feel very uncomfortable for them. Another thing is, is that these stimulators if they don’t have enough solution underneath there, they will flash open and so, that’s a troubleshooting component is why is these things not working properly and there’s a lot of pieces that you can troubleshoot along the way. The other thing with the filling and why we would like to do the bottom, we actually like to twist our capsules up just a little bit when we are doing that filling. It’s so that we can actually completely fill that chamber. I can’t stress that enough. It’s one of the probably sources of error for a lot of people and trouble for a lot of people just because of the nature of the testing and the way it is. It’s something that we really have to know as technicians. Toni had mentioned it just a few minutes ago, but when we’re putting the capsules on, we like to use what’s called the “down and around” technique. In other words, we’re going to go around the bottom of wherever the skin is first, the limb and then attach it to the top side, so that the bottom side makes a really nice tight seal against the skin while we’re doing that. We found that that actually was able to help us prevent most of those leaks at the foot and it also allows us so that if we did have a leak or we needed to tighten one particular area at all, we’re pulling it off the top and being able to tighten it one rather than trying to pull from the bottom. So, just some of little tips and tricks that we found to help reduce errors or reduce some of these pitfalls of the testing.
Mr. Sletten: We’re starting to see the responses on the screen over there. The stimulus like I said, it’s like hot and prickly is what it reminds me of, itch weed, burning nettles, are kind of the two big terms that I’ve heard through the years. Some people like to describe it as a tattoo. I think the tattoo is a lot more intense than when you get here, a TENS unit, if you have ever felt one of those, is probably another good example if you are trying to help your patient understand what they’re going to feel. So, we are just going to let this go for another 2 minutes. Once, we hit the 5-minute mark, the stimulators are going to beep at us and turn off. Then we are just going to let Jade rest here for an additional 5 minutes and then we’ll be done with this test.
Dr. Singer: So, the actual integration for the analysis is the positive response during the 5 minutes of stimulation and then another 5 minutes afterwards. So, we integrate 10 minutes. The foot response is a little sluggish to take off and I had mentioned before the temperature being an important factor. Apparently, his feet are ice cold. So, that can be part of it, but the foot response taking off a little later is actually not all that unusual.
Mr. Sletten: Jade is happy. He said you could take a picture of his foot if you wanted to see the hook up here. So, you had it for later as well.
Mr. Sletten: So, some of the things that I was mentioning the “down and around” technique, so what we were meaning is, is we’re putting that rubber strap on the bottom first, going around the limb and then tightening it. The other thing that we’re looking at here is I’ve got this tube that is the out tube pointed as high as we can. We actually did two of these. This one, we should have actually twisted up just a little bit higher. So, I’m just going to go ahead and get all of this taken off of Jade and then we’ll start getting set up for the heart rate, deep breathing, Valsalva and tilt.
Wolfgang Singer, MD
Associate Professor of Neurology
Mayo Clinic Rochester, MN