How This Catheter Is Built 68

Forming the Distal Tip Assembly 71

Other Ways to Tip a Catheter 71

Joining the Distal Tip Assembly and the Proximal Shaft 73

Punching the Air Hole for Balloon Inflation 73

Attaching the Proximal Luer Fitting 74

Attaching the Balloon to the Catheter Shaft Assembly 76

Assembling the Proximal Steering Hub 77

Glossary of Catheter Terms 79

Resources 86

Participating Vendors in the Relay Catheter 86

Other Resources 86

Acknowledgments 87

Catheters are one of the more common medical devices. A catheter is a flexible tubular device inserted into a vessel, duct, body cavity, or hollow organ. This device is used in the introduction or withdrawal of fluids, delivery of energy, placement of a balloon, or placement of a device or biologic to the body. The device may be steerable to navigate through curved or branching structures. The catheter may also contain electronic sensors.

At a recent industry conference, an executive R&D manager of a major medical device company outlined the company's vision for delivery therapies via the "vascular highway." He stated that nearly every structure in the body is accessible by this route. This means that there are significant future opportunities available for innovative catheter design in less invasive therapy.

Catheters have been at the foundation of the revolution in minimally invasive and less invasive therapy. Advances in plastics, metals, electronics, sensors, and innovative construction techniques have produced catheters of unprecedented capability. Some of the largest medical device companies (e.g., Boston Scientific and Guidant) were founded on catheter products.

This chapter will present an example study of building a generic deflectable balloon catheter. In this example, you will see some of the basic parts of a balloon catheter, manufacturing methods of the components, and basic assembly techniques and equipment. One of the most basic pieces of equipment is the hot-air station, which is described in Chapter 3. Common adhesive bonding materials will be described. The end of the chapter will have a glossary of common catheter types.

The example for this will be a basic steerable catheter, the relay catheter, which was a demonstration piece for the annual Beahm Designs medical device technology open house, held in Santa Clara, CA. The reason for the name is that the device was built at the show, in relay fashion from one vendor's booth to the other, while onlookers watched. The Medical Device R&D Handbook gratefully acknowledges the support of Venture Manufacturing, Santa Clara, CA, and all of the vendors who participated in the relay catheter for their assistance with this chapter.

This demonstration catheter serves as a valuable introduction to a number of catheter-building concepts. In this demo, there are examples of heat bonding of different durometer catheter shafts, tipping, and anchoring of a pull wire at the distal tip, and some basic principles of building a steerable catheter. Tools such as the hot-air box and tipping dies are demonstrated. Another important method in catheter building is also demonstrated: the use of shrink tubing to form heat-bonded joints.

Another feature of this demonstration piece is that many of the items to build this device are readily available, and some are even off-the-shelf components. Knowing what can be acquired quickly and inexpensively is a key skill of the R&D technician, as this will allow the rapid iteration of prototypes while consuming the least amount of scarce and expensive capital money, and while quickly converging on a usable solution.

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