Basic Technical Requirements For Balloon Catheters

Basic Technical Requirements For Balloon Catheters – Medical Coating – Cheersonic

Balloon catheters are divided into balloon dilatation catheters, balloon occlusion catheters and balloon remodeling catheters.

Balloon dilatation catheter is a flexible catheter with an inflatable balloon at the head, which is used to dilate narrow hollow organs in the human body under image guidance, such as blood vessels, digestive tract, urinary tract, etc. In the case of no inflation, the balloon catheter enters the target lesion, and after successful treatment, the balloon can be retracted to withdraw the balloon catheter to the outside of the body. Several basic properties of vasodilator balloons are as follows:

Balloon compliance and expansion force

In the strictest sense, compliance refers to the change in volume for each unit change in pressure. For the vast majority of PTA balloon catheters, increasing the pressure does not change the length. Therefore, the change in volume is mainly reflected in the change in the diameter of the balloon.

hoop stress

The non-radial force exerted on the circumferential surface of the balloon during inflation is called hoop stress. Because the pressure is equal to the pressure per unit area, when the pressure is constant, a balloon with a larger surface will experience greater circumferential stress than a balloon with a smaller surface. The circumferential stress T is equal to the pressure P and the balloon diameter D: T=P×D For a given balloon material and inflation pressure, the larger the balloon diameter, the greater the circumferential stress on its surface. Therefore, of the same material, a large balloon will rupture under less pressure. In other words, different sized balloons made of the same material are chosen, each bursting when subjected to the same hoop stress. However, due to the relationship mentioned above, for a given hoop stress, the pressure is inversely proportional to the balloon diameter. Therefore, for large balloons, the pressure required to achieve hoop stress at rupture is relatively small. As a result, the largest balloon has the smallest burst pressure value.

Balloon cross-sectional area

The cross-sectional area can be thought of as the maximum cross-sectional area or diameter of the PTA catheter, using F units. A 5F PTA catheter with a slightly increased balloon cross-sectional area may actually be 5.7F. Angiographic sheaths with hemostatic valves and side ports are used in most PTA procedures. A 5.7F section requires the use of a 6F sheath. When using a balloon catheter with the balloon position significantly larger than its catheter portion, the insertion site is prone to oozing without the angiographic sheath.

tracking force

Tracking force refers to the ability of the PTA catheter to follow the guide wire through the tortuous path to the lesion site without dislodging the guide wire. In either case, the specific anatomy, operator skill and experience, and guidewire-catheter combination all affect the ability of the catheter to reach the intended site. Traceability is not an essential consideration when performing early superficial peroneal and retrograde iliac angioplasty. Therefore, relatively large and rigid PTA catheters are perfectly acceptable. It is because these rigid catheters are easily advanced that they can pass through and dilate most lesions. But for PTA across the iliac artery to the contralateral femoral artery, renal artery, and splanchnic artery PTA, such catheters are clearly substandard, placing new requirements on manufacturers.

Fracture resistance

The balloon catheter has to pass through severely tortuous blood vessels and severe stenosis, which often leads to the bending of the balloon catheter, so that the contrast agent filling the balloon cannot pass through the catheter to inflate the balloon. Ideally, to pass the catheter through a bend with a small radius, the catheter should not bend. Small cross-section balloon catheters produced from very thin materials are prone to buckling, especially when making small radius turns and when the guide wire is withdrawn. There is currently no fully flexural, small-section PTA catheter. The best way to prevent buckling is to use the techniques described above.

Pushability

Although there are pushability problems in the PTA of the femoropopliteal artery contralateral to the iliac artery, the PTA of the tibial artery, as well as the renal and visceral PTA, and even the intracranial artery PTA. But this question may have been first raised in the PTCA, not the PTA. A PTCA catheter with a very small cross-section may not have difficulty reaching a severe stenosis, but if the catheter is poorly pushable, perhaps reaching the lesion does not mean that the stenosis can be passed.

To address this problem, manufacturers have now produced catheters with a very soft balloon tip (guide tip) and a relatively stiff shaft, allowing the tip to be easily pushed along the guide wire. The longer and smoother the transition zone between the hard part and the soft part, the less likely the catheter is to bend. The pushability of the PTA balloon catheter modifies most situations encountered with transiliac arterial procedures as well as peripheral PTA. In this way, the surgeon can use the rigid portion of the guide wire to support the catheter and push the catheter through the lesion. Even in this situation, it is helpful to use a balloon catheter with a tapered tip and small cross-section angioplasty. In order to push the catheter through the lesion area, it is very important to support the guide wire, which is typical of the advancement technique in recanalization of chronic occlusive iliac arteries and stent placement PTA.

Balloon catheter tip

The balloon catheter tip should be tapered to accommodate the guidewire to facilitate passage through the stenotic lesion. Excessive diameter or poor head shape design makes it difficult for the catheter to pass through severe stenosis even with a stiff guide wire. A catheter assembled with a poorly morphed head and a poorly propelled shaft is particularly detrimental to traversing the lesion. The length of the balloon catheter tip is another aspect of the problem. In many procedures, such as inverse balloon PTA of the common iliac artery, the catheter tip may not be a problem. However, short balloon catheter tips are required when vessels with distal branches are easily damaged by the catheter tip (for renal and tibial arteries).

Balloon inflation and deflation times

Deflection refers to the time it takes to expand or deflate the balloon. Although the “flow” of dilute contrast agent through the balloon during inflation and deflation of a PTA catheter is not laminar, imagining it as laminar helps us understand the factors that influence the actual observed deflation and deflation times.

Modern PTA catheters have small cross-sections and corresponding small-diameter balloons or channels. Liquid “flow” is proportional to the 4th power of the channel radius and inversely proportional to the length of the conduit. So if we compare two PTA balloon catheters, both 12mm in diameter and one 40cm and one 80cm in length, we can see that the 80cm catheter takes about twice as long to deflate as the 40cm catheter times.

Other Features of Balloon PTA Catheter

At present, the new progress of balloon catheter mainly revolves around the development of new balloon technology to prevent the chronic complications of endovascular interventional therapy: vascular dissection, thrombosis, distal embolism and restenosis. These techniques include cryogenic balloons and cutting angioplasty balloons.

In addition to the mechanical angioplasty effect of other catheters, the cryoballoon can lower the temperature of nearby tissues to -10°C. Experimental evidence suggests that such hypothermia induces apoptosis or programmed cell death, thereby reducing stenosis. This technique has a preventive effect on the treatment of refractory and repeated stenosis of dialysis grafts.

Cutting balloon angioplasty, which can be used in both coronary arteries and peripheral arteries, is used for the treatment of patients with intractable stenosis of blood vessels after endovascular brachytherapy or repeated stenosis of arteriovenous fistulas for dialysis.

Source: Medtec China

Cheersonic is the leading developer and manufacturer of ultrasonic coating systems for applying precise, thin film coatings to protect, strengthen or smooth surfaces on parts and components for the microelectronics/electronics, alternative energy, medical and industrial markets, including specialized glass applications in construction and automotive.

UAM7000-M Ultrasonic Drug Balloon Coating Machine is designed for drug eluting balloons. It provides a uniform drug coating for the balloon catheter through ultrasonic spray technology. UAM7000-M can also be used to adjust and control the deposition process of drug coatings for different liquid formulations. With the help of a special fixing device design, the entire balloon catheter can be sprayed with a maximum spraying length of 280 mm., It also has the functions of solvent doping, pre-heating, humidity control, and drying. The equipment has the characteristics of precise application amount, uniform film layer, and high utilization rate of chemical liquid. Cheersonic has extensive experience in surface coating of implantable medical devices (such as drug stents and balloons), and can provide customers with complete solutions.