Medical device for drainage of the pleural cavity

The surgical drain tube with an embedded electrode is a new medical device for drainage of the pleural cavity designed to decrease pressure buildup inside wounds and speed up patients' recovery time after surgical procedures.

Industry:

Medical Devices

TRL:

1 → 7

Project duration:

1 year

Challenge

In any surgical procedure, good hemostasis, precise and meticulous surgical technique, along with minimal tissue trauma limits the need for operative drain placement. However, in some situations, the placement of a drain is invaluable and is actually needed to prevent catastrophes. When indicated, it is important that a drain be used with prudence because as useful as it may be, it may cause more problems than it prevents. 

Understanding this complex context, a startup offering products for the healthcare industry tried to address this problem with the help of EnCata. Therefore, we were tasked to develop a solution that would not require doctors to perform additional open surgery to remove the drain tube and thus provide patients with faster recovery.  

The major challenges our design team faced while working on this project were:

  • Complex position of elements in the medical device. We had to devise a way to precisely place a flexible electrode with a diameter of 0.6 mm inside the thin wall of a silicone drain tube with a diameter of 2 mm. An inset element shape and its tension and positioning were tricky blockers to get that job done.
  • Selection of the materials for manufacturing. The components had to be certified to conform to medical standards, the product material had to provide high thermal stability to ensure the opportunity to autoclave the product and meet appropriate technological characteristics to provide a minimal of melting pressure on an inset element.
  • Choosing the manufacturing technology that could prevent the melt flow to stretch the electrode and put it to the tooling wall. The product should provide solid electrode isolation for an atraumatic dissolution of surgical filament inside the wound;
  • The product should be comfortable for the patient while at the same time be solid to provide secure placement of electrodes and avoid any chance it cuts through the drain tube wall while bending.

Our Role

  • Requirements Analysis
  • Industrial Design
  • Mechanical Engineering
  • Simplified manual tooling production for thermoplastic machines
  • Manufacturing technology scouting and testing
  • Design for Manufacturing (DFM)
  • Rapid Prototyping
  • Alfa/Beta Testing
  • Mass production manufacturing support

Technologies Used

Engineering R&D

Engineering R&D

CAD Design

CAD Design

BOM Development

BOM Development

5x CNC Machining Milling

5x CNC Machining Milling

Plastic Pressure Melting

Plastic Pressure Melting

Welding

Welding

Moulds Manufacturing

Moulds Manufacturing

Injection Moulding

Injection Moulding

Silicon moulding prototyping

Silicon moulding prototyping

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Approach & Solution

Drains are important in the management of surgical patients. They are appliances that act as a deliberate channel through which established or potential collection of pus, blood, or body fluid egress to allow a gradual collapse and apposition of tissue.

Long recovery time after surgeries that drain the pleural cavity is a big problem in the hospital industry that has already faced a massive financial crisis during 2020 as systems have struggled with low patient volumes and big hits to liquidity. Extra days the patient spends in the medical institutions cost tens of thousands of dollars to the hospitals and extra operations cause the patient to have more complications and thus larger medical bills.
This is why we designed such a medical device for drainage of the pleural cavity that avoids the necessity of performing additional open surgery to remove the tube so it provides patients with faster recovery time.

During the initial surgery, a surgeon sews on the tube with the special knots which are possible to burn by means of a short-term high-voltage current pulse going through the electrodes that were already placed in the tube.


After that, the loop which holds the tube will be destroyed. Then, the surgeon could retrieve the tube with the rest of the filament without performing additional open surgery. Also, atraumatic removal eliminates further complications such as ruptures of parietal pleura, bleeding or spastic processes.

After the form of the design was chosen, the team still had to determine what type of material to use for the design. There are two primary options at this point in time: silicone or reticulated polyurethane foam. Silicone is a polymer containing silicon, carbon, hydrogen, and oxygen. Because this compound is highly inert, medical devices and implants commonly use silicone. Silicone also shows flex fatigue resistance. The ease of fabrication is another benefit to this material, as silicone can be formed into virtually any shape. In addition, silicone bonds very well to other silicones, creating a very durable product. Polyurethane is another type of polymer that is commonly used in medical equipment. Because polyurethane remains durable and relatively inexpensive, it is commonly found in polymer foams that release drugs in a biological environment. Polyurethane also comes in various textures, all exhibiting different properties. However, reticulated polyurethane foam would work the best for the drug delivery system. One concern is the bonding strength of silicone and polyurethane foam.

After researching those materials extensively, we came to the conclusion to proceed further with some customized material in order to isolate electrodes and ensure protection of the patient’s organs.

The material should be highly fluid and should have a minimal Shore hardness as the lowest material hardness could lead to electrode rupture at bends, while in contrast the highest material hardness could harm the patient. Nevertheless, it’s obligatory to have a medical certificate and maintain strict disinfection conditions in autoclaves. As the key parameter was thermal conductivity, plastic-polyurethane was appropriate. This material has many advantages:

A design matrix was used to determine both the shape of the final design and the type of material to be used.

To decrease the impact on the patients’ health while the drain tube is extracted and facilitate electrode tension inside the tube’s wall, we redesigned the initial ‘Y-shape’ form of the medical device and developed the new product concept based on parallel branches.

The categories that were used were determined from developed specifications. The categories that were chosen for the final design are as follows: feasibility, cost, safety, ergonomics, and flexibility. Each category was weighted.
Safety was weighted the highest as the design’s impact on the patients’ health is of central importance. Care must be taken to be sure that nothing, especially the electrode embedded inside the tube, will inflict any harm upon the patient.
The second highest weight was the design's flexibility. This is because it is vital that the 0.6 mm diameter electrode is able to fit through the 2 mm diameter tube. Without being capable of fitting through the incision, the design is essentially unusable.
The third highest weighted category was ergonomics. Ergonomics is extremely important in that it must not significantly detract from the surgeon’s normal procedure, as surgeons are often wary of deviating from a specific procedure.
Finally, the cost was weighted the lowest. This is because the materials for production are relatively cheap.

Then, we developed the auxiliary mechanism of the tension device and sorted out the technological process of manufacturing on thermoplastic machines.

To avoid the possibility that the drain tube is self-cut while bending, eliminate the likelihood of defects in assembly, and, optimize the design for volume production, EnCata’s engineers placed the electrode in the center of the tube wall.

In order to precisely place the core component containing the electrode in the tube wall, our technologists suggested changing the initial design of the tube shape. Initially, the product was proposed to go with a 'Y-configuration', however, the final design is no longer circular but has an elliptical section of the tube base. The base moves to the circular sections of the two branches and branches are parallel to the tube base. Such design allowed:

When the product was ready for manufacturing, we engineered a custom press mold with a unique electrode tension system integrated into it.

That solved the problem with the precise placement of electrodes in the tube wall. As the copper base makes it impossible to stretch the electrode with more than 5 kg effort, while the normal injection pressure produces a flow of more than 5 kg, we figured out such a working thermoplastics mode at which force is not more than 5 kg.

Results

EnCata satisfied the Client’s requirements through an improved design, the manufacture of a prototype, and the production of the first batch of devices. We provided the client with custom tooling for self-prototyping along with all the design documentation for further volume production.

200+

experiments were run to get the right electrode placement.

0.3 mm

allowable shift of electrode in the drain tube wall.

100 sets

were manufactured. Each set consists of a drain tube, surgical thread and needle.

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