For the heart - connectors in medical technology
The following discussion gives a brief explanation of some of the highlights and features of connectors in medical technology, and also a few examples.
Connectors for medical technology account for only roughly 2 to 3% of the total global connector volume. But particularly in medical technology, connectors play a key role, because often they represent the interface between the person and the machine.
Connectors are used in diagnostic systems, such as magnetic resonance imaging systems, patient monitoring systems or endoscopes. But they are also used in therapy, such as in equipment for eye surgery (cataracts), cardiac support systems, catheters and defibrillators. Machine-oriented and patient-oriented connectors are used in both cases. Typical machine-oriented connectors in diagnostics are, for example, the ZIF (zero insertion force) connectors for ultrasound devices, frequently supplied by ITT. Or the connectors supplied by ODU all around the world for patient coils in magnetic resonance imaging. Patient-related connectors typically come into contact with the patient and can, for example, become bloody during the application, so that they have to autoclaved (sterilised). Examples of patient-related connectors are connectors for cardiac support systems, endoscopes or catheters.
In particular, the requirement for treatment by autoclave (steam sterilisation at +132°C or 270°F) often means that connectors for medical technology cannot be cabled with coupling nuts, but must instead be moulded. Injection moulding facilitates better cleaning and prevents dirt deposits. One consequence of injection moulding is that often solder joints are used instead of crimp contacts (because solder joints can be sealed better during the moulding process). If the connectors are autoclaved, the cable and connector plastic must withstand the temperature mentioned.
The use of disposable connectors represents an alternative to autoclaving the connectors.
Connectors for medical technology (particularly patient-oriented connectors) often have to be designed to DIN EN60601-1. The consequences are increased clearance and creepage distances.
Connectors for medical technology are frequently custom developments. Why is this?
Custom products are developed for reasons of function, design, cost and exclusivity. In medical technology, function and design are the primary factors.
The cables must also be considered in conjunction with the connectors. Polyurethane cables (PUR) are very frequently used for patient monitoring, such as for ECG, SpO2, and blood pressure and temperature measurements. This material is very suitable for injection moulding, but it tends to stick. One alternative is Santoprene, which is particularly suitable for autoclaving. This material gets dirty easily, however.
In the area of patient monitoring, so-called Lahn cables are often used. In this case, metal foils wrapped around a support casing are used, instead of round wires and strands. These cables are extremely flexible. Coax cables with diameters of only 50 µm (one-twentieth mm) or 3-strand cable, shielded, with a diameter of only 150 µm are used for catheters. Packaging these cables presents a special challenge.
Example 1: Cardiac support system
Several thousand heart transplants are performed each year in the West. There are far more patients than donor hearts, so that in many cases, the waiting time or the survival time can only be bridged with a cardiac support system. In an extreme case, this cardiac support system becomes an artificial heart, in that it takes over the pumping function of the left chamber of the heart.
This picture shows a customised push-pull connector, which, along with the cable connected to the pump, protrudes from the patient's chest. This connector joins the axial pump to the controller unit. Further exemplars of this connector join the battery packs to the controller unit. It goes without saying that this connector must operate absolutely reliably, because it will also need to be inserted by older and more nervous people.
ODU meanwhile has five customers in this field, with a wide range of connector concepts being selected.
Example 2: Special connector for patient monitoring
Patient monitoring includes recording and displaying the heart rate and the blood pressure, for example. Metal or plastic push-pull connectors are often used in this function. In the case at hand, the customer decided on a custom development because plans called for a very large number of pieces. The basis of the 24-contact-position connector system is a punched contact and a connector concept in which the insulator and housing form a single unit. Such a development naturally involves investments in moulds. In the case at hand, in fact, this meant a few hundred thousand euros. On the other hand, however, the connector costs only about a fifth as much as conventional push-pull connectors with turned contacts. Given the very high number of pieces, which are delivered around the world, the investment amortised very rapidly. In this special case, the design also specified that the colour had to match that of the main equipment. Exclusivity was an important concern here.
Example 3: Disposable connectors
In general, it can be said that more autoclaving is done in Europe and more disposable connectors are used in America. This could be connected to the law-suit happy lawyers in the USA. In any case, the use of disposable connectors means that there is a need for delivery of economical connectors in very large quantities (certainly several hundred thousand a year). Disposable connectors are distinguished by the fact that, as a rule, the housing, locking and insulator are made from a single moulded part into which the contacts are then mounted. Strain relief and sealing are provided by the injection moulding of the connector piece. The same can be said for the receptacle.
Summary: The multitude of applications in medical technology creates a very strongly fragmented market, with over 10,000 manufacturers globally. Because of the very wide range of requirements, there is a need for a large number of custom-developed connectors. The trend here is also: small, larger number of poles, lower prices. But the pricing pressure is kept within limits and the projects usually run for many years.
For more information, visit www.clarke.com.au/odu.html.
Reprinted on behalf of CSE with the kind permission of ODU.
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