Good morning, my name is Kirsten Frenchew. I'm currently a third year and chief fellow at Temple University Hospital. I wanted to take the next 15 minutes or so to discuss an important topic, which I've entitled Oolala French Sizing and Why Size Matters. I'd also like to thank my collaborators, director of our cath lab, Dr. Brian Omerku, and our CIS Joanna Cannon, who both helped contribute to this presentation. We have no relevant disclosures. As a brief outline, we'll be going over catheters and sheaths. I'll explain French sizing and how that works. And then we'll go over some special cases, closure considerations and spend a little time on sheath removal. Catheters and sheaths are of course a critical part of what we do in the cath lab. They serve as the pathway for how we deliver equipment and contrast, but also of course, as a path to introduce thrombus and air. They possess an inner diameter and an external diameter and they're sized in French based on this diameter, as well as the length, which is measured in centimeters. Now the name French actually comes from a French instrument maker who was alive in the 1800s, whose name was Joseph Frédéric Benoit Charrière. And he founded the sizing system for catheters that we use today. And the sizing system used to really be called a Charrière, which was equivalent to 0.33 millimeters. But it was felt that his name was too difficult to pronounce. Thus French was adopted in its place. Catheters and sheaths. So here's an example of an animation I drew of a sheath and also of a catheter and how they sit in a vessel with this red being the arterial wall followed by a sheath and then a catheter within it. It's important to always prep and flush catheters and sheaths before they enter into the body. So you don't accidentally deliver a column of air. And radial and femoral sheaths are what we typically use and they vary slightly. Typically radial sheaths are longer and they have more lubricity as to help reduce arterial spasm. Sheath exterior and length. Most sheaths are covered in hydrophobic, sorry, hydrophilic exterior to make it nice and slippery like the lubricity I said before, which will allow smooth entry into the vessel. Radial sheaths are typically 10 or 21 centimeters with many operators opting for a longer sheath to reduce radial spasm and also to have more secure access. In special cases in the groin, a longer sheath may also be used typically with severe iliac tortuosity. Longer sheaths are chosen. Now sheaths, important to know, are measured by the inner diameter. So if you focus again on this cross-sectional cartoon that I've drawn with gray being the sheath, you can appreciate that the inner diameter here is where we measure sheath size. And comparing that to a catheter, whether it's a guiding catheter, a guide, or a diagnostic catheter, we measure those by the outer diameter. So these dotted lines correspond effectively to the same size. Thus, a 5 French sheath and a 5 French catheter fit snugly inside each other because of how the diameters are measured with, again, the sheath being an internal diameter measure and a catheter or guide being the external. So that's really important. As a brief note, there are some differences between diagnostic catheters and guides. We use these every day in the lab as well. Typically, guide catheters are thinner walled to allow for a larger lumen. So you can imagine delivering more equipment. And even though they're thinner, they're actually reinforced shafts. So they're stronger and help prevent kinking. Catheter lengths are typically 100 to 110 centimeters. Sheath colors are also important. So this is a way you can recognize sheath sizes by their color. They also are labeled in very small print if you want to try to find it on the sheath itself. These are the most common sheaths we use in the lab, 5, 6, 7, and 8 French. We also occasionally will use 9 French for larger access procedures. But it's important to know and understand the colors and what they mean. There are some variable internal diameters, and this is based on manufacturer. So just keep that in mind. There can be slight variations as pictured here by different companies manufacturing the same 6 French guiding catheter. The average case we do in the cath lab, as you can imagine, it may be what we all say is 5 and 5. That's for when we do coronary angiography and also right heart cath. The 5 French sheaths typically what we use for all diagnostic procedures, radial or femoral access, and a 5 French sheath also for right heart, whether that's brachial, IJ, or femoral access. For most interventions, a 6 French sheath and guide is what we use for access. And as you can imagine, very large sheaths or guides cannot be delivered into small radial arteries, and therefore the access should be femoral. Thin-walled sheaths are a newer technological development, and effectively are two French sizes in one. And the way that these companies have developed these what we call slender sheaths, which are tapered hydrophilic coated sheaths, are to develop a thinner wall. So allowing for a larger lumen without making the external wall bigger. Thus, a 5-6 thin-walled sheath can accommodate a 6 French guide in their lumen while remaining a 5 French external diameter. There is also something called sheathless guides, which some of your labs may use. Typically, you still need a sheath to get into the vessel, but then this can be removed for a sheathless guide. And as you can imagine, this is a guide that sits in the vessel without a sheath being needed in place. So you can have larger catheters and equipment delivered and less radial trauma. And these are safe and effective and developed by several companies, and typically used in very small radial arteries. There are also some special cases that require increasing your French size, and one of those most common is the use of a rotoblader for your really calcified lesions. So if you look at this chart, dependent on the burr size you require, you may need to increase your French size here. So if you're going from 1.7 to a 2, you'll have to exchange your sheath size to accommodate that. There's also some other special cases to note. CTO procedures, the use of bioptomes require a larger sheath. And then simultaneous stenting or bifurcation stenting often requires a larger lumen to deliver simultaneous balloons or stents. And also in the case of Joe stents, larger French sizes are required. And to finish up here with closure and removal. So the method of closure varies depending on the size of the sheath used for access. Typically, small sheaths can be done with a manual hold for hemostasis without issue. For six to eight French sheaths, closure varies by operator choice, and that depends largely on the anatomy of the patient. So if they have a favorable anatomy as a non-calcified vessel, you can consider a closure device. Or if they're severely calcified, typically you do a manual hold. And then for large burr access, pre-closure techniques may also be used. And to conclude here on femoral sheath removal, which is a lecture in itself, I just wanted to make sure we briefly talk about sheath removal. And femoral sheath removal is less common these days, but is also the one that I think is most challenging. So to just briefly touch on how we remove a sheath from the artery and the groin, we typically do it when the ACT is less than 180 or 170 for some labs. You remove the dressing, you have your PPE on, your absorbable pads, et cetera, and you check the patient's pulse, examine the groin, make sure their vitals are okay and they have other access in place before you remove. Typically, as number three states here, you waste at least five cc's of blood and examine for a clot. If there is thrombus within your syringe, you should waste again until the syringe is free of clot and then flush that through with five cc's of saline. Sheath removal is really important. So again, you've already palpated and examined the groin, you're appropriately positioned over the femoral head. I typically do a three-finger technique. So I put two fingers proximal, my ring finger and middle finger above where the skin entry site is, recognizing of course that the arteriotomy is superior to the skin access and one finger below. And then I remove holding with my left hand, remove the sheath with my right hand. And for arteriotomies, allow for a small spurt of blood back in the event that thrombus is at the tip of the sheath. After that, I enforce very strong hemostasis, so fully occlusive pressure over the femoral head with all three fingers and maybe another hand to provide this really strong force for the first five minutes of the hold. And that fully occlusive force should obliterate the distal pulses, that's how strong it should be. And then you can ease up slightly to allow for your full length hold. The hold of your pressure varies depending on your venous sheath access or whether you're doing arterial sheath access. Typically, it's three minutes per French size and five minutes for venous and five minutes for arterial. So, as you can see in this blue chart on the right side, venous access is typically 15 minutes on average and arterial about 30 and large bore being a special case usually 45 or more. So, it may be nice to have a second person come help you with that. Once you've completed your hold, you've examined for hemostasis, you can inspect the site, check the pulses, apply the dressing sterilely as you do and inform the patient of signs of bleeding to look for. If you have an arterial and a venous sheath in place, it's important that you always remove the arterial first, maintain venous access in the event of an emergency. And basically, in the last 75% of your hold or the last 25% of your hold when you're 75% of the way through of the arterial hold, you can remove your venous access and hold. But you want to maintain your venous sheath as long as possible. So, we've spent a lot of time this morning discussing these important topics. Hopefully, it has helped build a foundation for you on catheters and sheaths, how they work, their coating, the French sizing and why it's important and some cases to consider as well as sheath removal and closure. Thank you very much.

catheters

sheaths

French sizing system

catheter types

sheath removal