Intravenous Tubing Organizer

Intravenous Tubing Organizer

BME 200/300

University of Wisconsin - Madison

December 10, 2003

Team:

Blake Hondl

Amit Mehta

Ryan Pope

Kristen Sipsma

April Zehm

Katie Zenker

Client:

Timothy E. Corden, M.D.

Medical Director, Pediatric Critical Care Unit

UW Children’s Hospital

University of Wisconsin

Advisor:

Willis Tompkins

University of Wisconsin

Department of Biomedical Engineering

Abstract

The pediatric critical care unit of the UW Children’s hospital currently has no organizational system for IV tubing. IV lines extend from multiple syringe pumps to one patient, becoming entangled. They are especially hard to differentiate when placed on the patient’s bed during transport. A prototype was assembled to minimize line confusion, in which each length of IV tubing is individually wound around a central core. Automatic recoil is controlled by a constant force spring-loaded system that allows for patient movement by retracting or extending extra lengths of IV tubing. This design will ultimately separate the IV lines and improve hospital efficiency.

Problem Statement

The goal of this project is to design an intravenous (IV) tubing organizer to prevent the entanglement of several IV lines, while maintaining the functionality of each IV tube. This device should ultimately eliminate the potential hazard caused by multiple IV lines for pediatric patients, increasing patient safety. In addition, use of this device should decrease the amount of time spent untangling IV tubing, thereby improving hospital efficiency.

Background Information

An intravenous (IV) tube is a soft, flexible catheter of which one end is attached to an electronic syringe pump (Figure 1)and the other is inserted into a vein, usually in the lower arm or wrist. IV tubes have numerous purposes, such as administering medication, hydrating a person who is unable to obtain nutrition orally, replacing fluids lost through vomiting, surgery, or injury, giving blood transfusions or blood products, and drawing blood samples (Discovery Health, 2003). The syringe pump is a small machine that can be unplugged for up to two hours as the patient is being moved. Its function is to eject a precise quantity of medication through the IV tube and into the patient. Though unlikely, it is possible for IV tubing to kink where it is attached to either the machine or the patient. If the flow of solution in the tube is obstructed for any reason, an alarm sounds, alerting hospital staff of a problem. An IV line is usually left in for just a few days, but may be kept in for a longer time (Discovery Health, 2003). Hospitals including the UW Children’s Hospital use IV tubes to administer medication to pediatric patients.

Figure 1: An electronic syringe pump.

Our client represents the children’s critical care unit of the UW Hospital; pediatric patients in this unit often have numerous IV tubes attached to their limbs (up to eight to ten linesat a time). With one syringe pump per each IV line, multiple lines can potentially cause confusion and make it difficult to differentiate between separate tubes. Furthermore, since each IV tube is approximately 1mm in diameter and 2.5 m long, they become easily tangled and intertwined. Hospital personnel refer to this entanglement as “spaghetti.” Spaghetti is especially problematic during the transport of a patient within the hospital. During this critical time, the IV tubing must be easily accessible and organized, so staff can immediately locate and correct a problem, should one arise. Currently, massive amounts of disorganized tubing on the patient's bed during transport makes this event dangerous. Even while the patient is stationary, loose IV tubing can be hazardous. Accidentally stepping on the tubing can cause kinking, which consequently stops the flow of vital nutrients and/or drugs. Tripping on the excess tubing can also rip the IV out of a patient, which aside from preventing flow to the patient, can be extremely painful. Pediatric patients, in particular, are at a high risk posed by spaghetti, simply because of their small size. There have been reports of infant strangulation, suffocation, and even death due to the entanglement of IV tubing (CMAJ, 2002).

The design of a device that could separate multiple IV lines as well as minimize disorder would allow doctors and nurses to place more emphasis on the patients rather than spending time untangling the IV tubes. Our client is interested in a double-ended, spring-loaded device, with tape measure-like capabilities. However, this is not a mandatory requirement. In addition to reeling in tubing, the device should have some organizational features. It should distinctly separate or identify multiple tubes, possibly via color coding.

Literature Search

Further research followed in the form of patent searches to identify any products already in existence that were similar or identical to the one the team was trying to design. This was accomplished via the United States Patent Office (USPTO, 2003). The most closely related device found was an IV line separation system, which separates various IV lines from different sources by channeling them in parallel and fixing them prior to reaching the patient(Appendix B, Patent 1). While these simple devices may separate multiple IV lines, they fail to address the problems that arise from the excess lengths of the tubing, entanglement in particular. Based on the team’s research, a device that dispenses IV tubing via a spring-loaded system does not exist at the present time.

Numeroustape measure patents were analyzed, sincethese tools utilize a particular spring recoil mechanismthat was discussed as a possible springboard design idea (Appendix B, Patent 2). Another patent was found of a tape measure having a rewinding mechanism that incorporates gears rather than a spring system, which may provide one way to avoid the quick, uncontrolled recoil of a spring (Appendix B, Patent 3).

The team also spent a good deal of time determining how much force a spring (if used) would need to exert so that the IV tubing would always remain in tension but not be restrictive to patient movement at the site of the IV attachment. We estimated that a spring force between 0.25 lbs and 0.75 lbs would be ideal. However, one major problem with extension springs is load build-up. Force is proportional to the uncoiled distance of the spring. This means that as IV tubing is extended from the device (and the internal spring is consequently uncoiled), the force by which the spring recoils increases. An increased tendency to “snap back” is a potential safety hazard to users of the device. A seemingly simple solution to this problem is the use of a constant force spring. Constant force springs are extremely similar to common extension springs, in that they consist of a metal strip that coils tightly so that each “layer” is wrapped around a previous inner coil(Globalspec, 2003). The difference lies in the following: the innate stress in a constant force spring resists external forces (such as the pulling of an IV tube) at a constant rate, rather than linearly, as in a common extension spring (Figure 2). Therefore, constant force springs have obvious beneficial applications in longer extensions, and is being recommended for use in the team’s final design.

Figure 2: Force-length relationships of linear and constant force springs.

Design Constraints

There were a number of issues the team had to keep in mind when designing the IV tubing organizer, due to the unique nature of the environment in which the organizer will reside.

First and foremost, the safety of the patient cannot be overly stressed. It is important to be sure that this device does not cause any discomfort to the patient, such as pulling on the IV tubing. Furthermore, the device must be small and mobile. Since the IV tubing itself accompanies a patient in transport, so must the organizing device. Most equipment is placed directly on the patient's bed prior to translocation, so the device must be relatively lightweight. The device should be as compact as possible, as requested by the client.

Also considered were the performance requirements and target cost of the device. While the device need not be sterilized, it must be disposable in accordance with hospital sanitation regulations. The device will be discarded after the patient is discharged from the hospital. However, IV tubing sometimes must be changed every few days, which often precedes a patient’s length of stay. For this reason, the device will need to accommodate tubing replacements for at least a week, if not longer, and should exhibit some sort of reloading feature. Because the device will be used at least twice as long as the IV tubing, which costs about $5.00 for an 8’ length (National Health, 2003), it is acceptable for its cost to equal the tubing’s cost. If the device were to be fully implemented in the client’s operating environment, a minimum of 3,000 devices would be needed annually. This figure could be even greater if the device were to be used for adult patients.

The functionality of the IV tube cannot be compromised, since the IV tubing will be in use within the device. For this reason, it must not allow kinking or tearing of the tubing. The device should smoothly let out a line when needed and retract and store excess line when not in use. Ideally, the tubing should be adjustable from either direction, so that both the end leading to the pump and the end directed toward the patient can be altered independently of one another.

Since our target audience consists of critically ill patients in a hospital, the device's interaction with an MRI machine must also be taken into consideration. The device will accompany a patient to the MRI room. Therefore, iron or any other magnetic material must not be used in manufacturing this product. Doing so would place the patient and hospital staff in danger when in close proximity of an MRI machine.

See AppendixA for a complete and detailed Product Design Specifications outline.

Design Options

After extensive brainstorming, the team generated multiple design alternatives to minimize the clutter caused by IV tubes. The designs varied in some aspects but were very similar in others. Three distinct design alternatives were developed, and the team has analyzed and compared the advantages and disadvantages of each.

Manually-Retractable Line Holder

The principle of this design is to have a cable coiled around a spool rather than coiling the IV tubing itself. The design would consist of a manually-retractable reel, which would have a handle with a geared advantage over the spool, on which the cable would be wound.

Along the length of the retractable cable would be five tubingholders. These holders will run perpendicular to the cable with the top holder fixed to the retractable reel(Figure 3). The other four holders could be moved along the length of the cable as desired. At the bottom of the cable, a stopper will prevent the holders from falling off the cable. The attachment of the holders to the cable can be made of rubber with a diameter that allows for movement along the cables if the holders were moved manually. When no manual forces are exerted on the holders, they will be stable.

Figure 3: Frontal view of manually-retractable device.

The holders will all be of the same length and will each hold four tubes. There would beidentical indentations on each holder so that when the holders are lined on top of each other along the cable, the indentations from subsequent holders will form a vertical line. The indentations in the holders will be of a circular shape with a circumference that is equal to the circumference of the IV tube. The circle will be open to the edge of the holder for a distance that is slightly smaller than the outer diameter of the IV tube (Figure 4). This is where IV tubing will be inserted.

Figure 4: Topview of manually-retractable device.

To operate the manually-retractable line holder, the device would first have to be completely extended. To do this, the cable can wind out to its maximum extension using the handle. The holders can then be moved an equidistance apart. Next, a tube can be placed into each vertical row of indentations on the holders. The holders would then be moved along the cable until the desired length of tubing from the last holder to the patient is attained. When the holders are moved with the tubes inside of them, the tubes will form a loop and protrude from the side of the device(Figure 5). In this position, they will be free from entanglement. Tubes can be removed when the holders are fully extended or compressed, although it is recommended to extend the cable and holders before removing tubing.

Figure 5: Operation of manually-retractable device.

This device would be advantageous over a design in which the tube itself wraps around a spool because multiple IV tubes can be contained in one device. The length of the tubes can be varied by a manual handle and therefore can be set to any desired length. Since the tubing itself would not be wrapped cyclically, there would be no threat of flow restriction from that regard. Because the tubes would be placed into the indentations in the holders, the IV tubes can be fixed to both the pump and the patient before they are placed into the device. Doctors and nurses using this device could also benefit from a color coding system in which each indentation in the holder could be labeled to easily identify different tubes.

One major disadvantage of this design is that all four tubes placed in the device would have the same length of tubing going from the end of the device to the patient. Since IV lines are inserted in different places on the patient’s body, there will inevitably be extra line that may become tangled. In addition, when the holders are at their maximum length, the length of IV tubing between the end of the device and the patient will be at a minimum. When the holders are completely compressed, this length is maximized (Figure 5). To achieve a length that is beyond this restricted patient-to-device range, the tubing must be completely removed and replaced into the holders.

When the tubing is in place in the holders, they will be compressed together to reduce the length of excess tubing. Since the tubing will loop out (Figure 5), it may become pinched at the point of the initial bend and fluid flow would be restricted. Unpredictable interaction between the looped IV tubing when the device is compressed is also a concern.

The team decided not to choose this device as the final design because of the difficulty in determining what length of excess tubing will exist. If the wrong extension length is selected, the tubing must be removed and replaced in the holders. This factor as well as the potential for fluid flow restriction caused the team to eliminate this particular design idea.

Spindle with Hand Crank

The second design alternative would be comparable to a garden hose reel. It would involve a thin, flat circular disk, approximately 2 cm thick. The outside circumference of the disk would contain a groove a few millimeters thick (slightly larger than the diameter of the IV tubing). This is what the IV tubing would reel around. The disk would be symmetrical, in that it could be snapped open, resulting in two identical halves (Figure 6).

Figure 6: Side view of spindle design.

This is how the tubing would be loaded and unloaded into the device. One half of the reel would contain a small exterior crank, which would act as the manual winding mechanism. The device would also have a semi-large hole through the center of each half, so that tubing could be fed through it (Figure 6). Tubing would be stationary, or fixed at one end (most likely at the patient), and would then feed through the central hole on the side without the crank attached to it. From here, the tubing would feed up through the middle of the closed device and around the reel as the crank is wound (Figure 7).

Figure 7: Back view of design.

The tubing would then extend away from the patient and to the syringe pump. It is this length of tubing (from the device to the syringe pump) that would be adjustable. The direction the crank is turned would determine whether or not the tubing is being reeled in or being let out. Gentle pulling on the IV tubing would also release tubing from the device. The device would need to be clamped to some stationary object, such as the hospital bed. This would make it easily accessible and would ensure that the weight of the device itself would not pull on the IV tubing.

Although this device is not a spring loaded system per request by the client, it would be much safer and easier to use. By using a retractable IV tubing organizer, the user would have total control over exactly how much IV line is necessary to extend from the patient to the syringe pump. Because the fixed end would be directed toward the patient and the device would be located close by, the risk of the IV tubing being pulled from the patient would be minimized. In addition, having the adjustable end of the tubing directed toward the syringe pump could be useful, since it is the syringe pump that moves with the patient in transport. Thus, the part of the tubing that is most frequently adjusted can be altered with ease. The device would be comprised of mostly plastics, which would ensure a low manufacturing cost and would help to keep the device lightweight

One problem would be the material of the clamp. Since this device could be used near an MRI machine, non-magnetic materials must be used in order to avoid potential problems while using the MRI scanner. In addition, the fixed end of the IV tubing that is directed toward the patient must be long enough to anticipate movement of the patient. This is especially a concern with pediatric patients, and is somewhat arbitrary. One final downside to this solution is the fact that it would only address the excess tubing of a single IV line. To eliminate the problem of multiple IV lines, multiple devices would be necessary, and could cause clutter on the bed or near the patient.