Urogynecology - New Catheters


OBGYN.net Conference CoverageFrom FIGO Washington D.C., USA - September 2000

Audio/Video Link *requires RealPlayer - free download

Dr. Hans van der Slikke: “Next to me is Professor Timothy McKinney who is the Chief of Urogynecology at the University of New Jersey. Professor McKinney, I understand you’re here to present the paper about a special urethral catheter, what’s so special about this catheter?”

Dr. Timothy McKinney: “Basically, what we’re talking about is a technology for investigating and understanding the pathophysiology behind incontinence and pelvic floor dysfunction, and it’s called urodynamics. In the process of evaluating these patients for incontinence, we require certain catheters to be able to monitor the pressures. In the past there have really been three main technical groups and potentially a fourth in which the pressure transmission from the bladder and urethra are monitored. Those catheters that have been standardized out there were the microtip transducers, the water-filled catheter type of technology, which has an external transducer, as well as a fiberoptic technology. There was a fourth in there as far as water balloon technology with a transducer down at the end. Our problem with a lot of the present day standard catheters that are out there are that they were point sensors, they looked in one single direction. That was fine and normal and easy to use within large environments such as within the bladder. However, when you get in compliant spaces like the urethra, you are looking in one point direction and can show variation in those catheters.”

Dr. Hans van der Slikke: “So you were looking for a catheter used to measure the intrauterine pressure and fetal monitoring yet they were too big for using in the urethra.”

Dr. Timothy McKinney: “What you’re elucidating to is how do we come up with the technology for this. There’s a company called Clinical Innovations that made an intrauterine pressure monitor system called the Koala. This intrauterine pressure monitor used air charged balloon technology and between that technology and our resources from T-doc, we designed an intrauterine pressure catheter to use for urodynamics. We had to change all the technologies and change all the patent ability around how this worked, but we were able to bring it down to a 4-French technology as well as down to as low as a 4-French to be able to do urodynamic monitoring. We wanted to make sure that we covered a full realm of needs for urology as well as gynecology for the evaluation of the incontinent patients so we needed to have the whole family of catheters. Right at present, we have a dual sensor catheter for measuring both intrauterine pressure, as well as intraurethral pressure, and filling the bladder at the same time. We have a single sensor with filling, we have an abdominal pressure catheter, which is a single pressure transducer, we have a 4-French, and we have radiopaque catheters. The beauty of this is that it’s a plug-and-play type of a catheter. It’s very easy to use, it is a disposable product so it rapidly turns over, and you don’t have the problem of contamination that’s going on.”

Dr. Hans van der Slikke: “You’re advertising your catheter at this moment very well but what are the figures on which you base your enthusiasm?”

Dr. Timothy McKinney: “My enthusiasm is based on the fact that we needed to evaluate urethra pressures a little bit more carefully. My fellow Sam Hessami and myself just picked up the Urogynecology Award for Urogynecology from the American College of Obstetrics and Gynecology this year. We’re looking at an objective index for the severity for incontinence and the object data required a more specific intraurethral catheter for measuring pressures. The present day technology, as I can show you in a cadaveric data on reproducibility of urethra pressures, was far from acceptable for any kind of standardization. We basically ran through with the urodynamic different technologies on a set pressure system on a cadaveric model. Basically, we were looking at the reproducibility of the data. We found that for the water transmission catheters, we had a standard deviation of approximately 15, which is demonstrated here. For the fiberoptics, we were at a pressure transmission standard deviation that was about 13 ranging all the way from a number of intrauterine for pressure which would register as something normal which was up at 42, and normal being anything above 20 mm of water pressure all the way down to zero pressure depending upon where that single sensor was ending up directed. The microtips were off by about a factor of 9-10, whereas we ended up working with a circumferential catheter which was able to then measure data points from all around in an average point and an area point within the urethra, and we were able to get a reproducibility of 1 standard deviation from this catheter. What that has enabled me to do is be able to see some of the pathophysiology going on during the process of urodynamic evaluation without having to have fancy video urodynamics to actually see the urethra maybe giving out. We’re actually able to see some changes, and subtle changes in the urethra that may revolutionize how we’re able to evaluate the incontinent patient. So it’s pretty exciting and this is what I based my excitement over besides it being easy to use, its reproducibility and its standardized aspect, and its ability to be dead on one time after another for pressures.”

Dr. Hans van der Slikke: “It’s almost so convincing that you tend to not believe it because it’s so small this…”

Dr. Timothy McKinney: “That standard deviation, correct. It’s an exciting aspect, I think the technology or the idea for the technology has been out there. There were balloon water transmission type of balloon catheters that measured area and circumferential aspects, and they were known to be better at detecting some of the urethra pressures. But still a little bit more difficult to use, and there were changes and drifting of it because with the water transmission, the fact that the water heats up and as it enters into the body there is changes that way. There is also gravitational pull so there is change in the pressure from the anterior wall of the balloon to the posterior wall of the balloon giving it some deviations that way. Whereas with air, there was no change in the pressures that way so from that standpoint this was an easier setup, easier to use, and a simpler system with just air being utilized in the catheter. This is one study that I’m presenting at IUGA - the International Urogynecology Society meeting in Rome, we’re also…”

Dr. Hans van der Slikke: “In September?”

Dr. Timothy McKinney: “In October around the 25th is when I think this paper is being presented. I’m reproducing the data from Dr. Harry Johnson’s laboratory. We’re doing another totally separate running of this just to re-document and re-verify and get a little bit more technical with the comparison study as well as an IRB study on human patients. At this point, I’d like to at least show you the catheter.”

Dr. Hans van der Slikke: “Yes, of course, we can do that.”

Dr. Timothy McKinney: “Basically, this is one of the catheters. It comes in just a little sterile packet and essentially this opens up with the catheter coming out. This one’s been through the mill, however, it is color coordinated for ease of use. We have one, which will be the intraurethral pressure and the other, which will be the intra-vesicle pressure, and they line up to the cable that ends up coming into the computer for the urodynamics machine. The actual catheter ends up hooking in with a laurel lock exchange, which just locks into place, and matching the colors makes it pretty simple so that you can’t mess up. We have a little filling channel so that we can fill the bladder. We end up placing the catheter into the bladder. At that point, we zero out the machine for the pressures and then once we’re zeroed out, we just charge the balloon so we end up pushing the lever forward which puts a specific amount of air-gas that travels down to the little sensor and blows up the balloon just enough to separate it off the catheter, thereby creating a seal that transmits the exact pressure from up here back into the microtransducer and back into the computer. We have a dual sensor so we can have both bladder and urethra pressures going at once; so you can see instability within the urethra, and you can see which gives out first. I’ve had numerous patients that had what I thought was just a straight out bladder instability or an overactive bladder that it turned out it was a urethral instability. The urethra actually gave out before the bladder contraction began and it’s a totally different pathophysiology that’s going on and treated totally differently. So seeing data like that is exciting and makes some difference, I think.”

Dr. Hans van der Slikke: “You can see it while you have two balloons at the same time?”

Dr. Timothy McKinney: “Right, basically, you have your computer screen and you can actually see the pressures for the vesicle pressure lined up right on top of the urethra pressure, right on top of the abdominal pressure. Then you can see the subtraction of the abdominal from the vesicle and the true pressure so with that you’re able to see all kinds of variations. I’ve seen sinusoidal patterns within the urethra with this instability finally ending up with you seeing the pressure start dropping below the inter-vesicle pressure within a spike upwards of the bladder pressure then giving the true instability and incontinence but really it was an urethral problem that occurred and caused the whole problem. So from this standpoint, it’s simple; you take and you throw it away, throw it in the garbage, hook up another one, and you’re ready to go for another procedure if you need to. From a standpoint of my research, it was totally necessary that I had to have this to be able to proceed with any kind of objective reproducible index for the severity for incontinence. Hopefully you’ll start seeing that data coming out or at least the pilot study will be done this year, and that’s what we got the grant money from ACOG for.”

Dr. Hans van der Slikke: “We’re looking forward to the results of that study. Thank you very much.”

Dr. Timothy McKinney: “Thank you.”

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