A Device for Enabling Placement of Intra-Osseous Infusion Tools1 (2016)

The World Health Organization declared the Ebola outbreak in West Africa to be the “most severe, acute health emergency seen in modern times” [1]. Individuals infected with Ebola virus suffer symptoms similar to septic shock, including severe watery diarrhea, and massive dehydration; this fluid loss eventually results in electrolyte imbalances, which can ultimately lead to death.A key treatment strategy is rehydration of the patient. Placement of an intravenous (IV) line requires healthcare workers with both the training and skill necessary to perform such a procedure, neither of which may be available in many outbreak areas. Moreover, even with appropriate training, providers may not reliably be able to place an IV line in a patient with severe dehydration since blood vessels may be more difficult to locate. Healthcare workers are also at risk for being stuck with a needle containing Ebola-infected blood products, and can subsequently contract the disease. Given these risks and limitations, an alternative fluid delivery modality is needed.Intra-osseous (IO) infusion, already adopted by many emergency medical services in the U.S., as well as the U.S. military, enables delivery of fluids at equal or greater rates than two large-bore IV lines [2]. Placement of an IO needle in the proximal tibia requires knowledge of lower extremity anatomy and palpation of the tibial tubercle. Thus, current placement techniques require training, which may not be available to community responders, as well as direct patient contact, which places healthcare workers at risk of infection.There is a need of an IO fluid delivery system that mitigates the risk of disease transmission and that can be easily and reliably placed by a minimally trained individual. Thus, the aim of this work was to develop an alignment tool to aid in the placement of an IO needle in the proximal tibia.Based on the need and in consultation with healthcare workers with experience in emergency medicine and in global healthcare, a set of specifications were developed:Development of the tool began as a design exercise, Stage 1 of which was performed over a 1 week period in October of 2014. Team members interviewed physicians, practiced with an existing IO placement system, and familiarized themselves with the design space. After the first stage, a 3-month design period (Stage 2) incorporated input from clinicians, untrained users, anthropologists, human factors experts, manufacturers, and anthropometric data collected at the William M. Bass donated skeletal collection at the University of Tennessee. An iterative approach, incorporating a 48-hr “design, prototype, test, criticize, and iterate” cycle, was employed guided by the design criteria.From the phase II design, three concepts emerged which met all of the design criteria. These concepts were: (1) the “ice skate,” consisting of a primary plane containing a hole for alignment of the needle, and a secondary plane forming a “T” on the primary plane which is used for aligning the device onto the shin (Fig. 1(a)); (2) the “airplane,” consisting of a primary plane with a hole for alignment of the needle and a “wings” coming off the primary plane which serve to align the device onto the shin and to align the IO drill perpendicular to the skin (Fig. 1(b)); and (3) a “shin guard” design consisting a single curved face that fits onto the shin and wraps up against the patella, and containing a hole for alignment of the needle (Fig. 1(c)).Each concept went through several iterations, performing basic testing with an IO drill to evaluate different variations on their basic geometry and different types of handles. After some informal alignment testing on individuals of varied height and body type, it became clear that a rigid guide relying on a 90 deg pocket to engage with the tibia would not achieve consistent alignment. In individuals with thinner builds, and less tissue on either side of the tibia, the guide sits well on an angular shin. However, in individuals with thicker builds and more muscle or tissue in the calf, the shin is much less angular. This results in the guide sitting higher off the tibia, which significantly hinders proper alignment. Adding a large fillet radius at the base of the guide lets it sit close to the tibia on a wider range of individuals, but allows the guide to more freely rotate around the leg to either side of the target region. These challenges are illustrated in Fig. 2.With this design and usability insight, the shin guard became the most promising design candidate as it did not suffer from these complications as severely. By adjusting the shape and flexibility of the guide, it could be made to easily conform to the patient's leg when the guide is pressed down against the leg by the user.Three options for the alignment scheme of the shin guard were discussed. A single patellar slot with two holes would result in one guide with only one possible orientation, but left or right sides would need to be delineated in the instruction manual. The possibility of inserting an IO needle into the incorrect side of the leg is much more likely with two holes. The same shape could be made with one hole, but that would require one guide for each side of the body. Mirroring the patellar slot in the shin guard so that one was located on both the superior and inferior aspects of the body, combined with a single hole, meant that the device had a mechanical safety built in. When oriented in the proper direction, it is impossible to drill a hole on the incorrect side of the leg (Fig. 3(a)).Determining the correct length and geometry of the patellar wings was informed by the design team's experience with user testing of the device. The first design that was tested had very long wings and was a snug fit around the patella. This required users to push down firmly on the guide and in order to flex the wings and achieve correct alignment. However, users were initially apprehensive of applying so much force to the device and so it was modified to reduce this apprehension by widening the patellar slots, shortening the wings, and flattening the guide slightly so as to require less flex to properly engage the tibia, and subsequently less force on the part of the user to induce said engagement (Fig. 3(b)). Users were observed in testing to be able to correctly place the IO needle, but the guide was easy to rotate away from the correct alignment. As a countermeasure to this newly discovered failure mode, the final iteration utilized widened patellar slots, but tightened up the bottom curve of the guide so it would still require some flex to sit flat on the patient's leg (Fig. 3(c)). This combination of geometries proved successful in user testing.The location of the hole for needle placement was based on anthropometric data from the Bass donated skeletal collection at the University of Tennessee. One hundred skeletal specimens were evaluated with a total of 195 tibiae measured. The location of the target zone was defined as the region in which an existing IO needle would achieve access to cancellous bone, and the location of this region relative to the patella was compared for all measured tibia to yield a target zone which would achieve access in 99% of patients.A pictorial instruction manual was developed separately based upon consultation with anthropologists, healthcare workers, and lay-persons.An ongoing usability study was conducted with the final shin guard design and the pictorial guide. Participants ranging from trained doctors (n = 5), nurses (n = 15), and emergency medical professionals (n = 20) to lay-persons with no medical knowledge (n = 15) and with no medical or technical knowledge (n = 15) were asked to place an IO needle into the proximal tibia of a mannequin using only the provided IO drill, alignment guide, and pictorial manual. Success was defined as a needle located within the target zone defined by anthropometric data and with intracancellous access. Every individual successfully placed the IO needle into the cancellous bone of the proximal tibia.In 90 days, an alignment guide for placement of an IO infusion device has been developed, prototyped, and tested with positive results. The design is human centered, and has been built around sound, diverse anthropometric data. To our knowledge, this is a first-of-its-kind alignment tool, with the potential to allow for IO needle placement by anyone capable of handling a drill and following a simple pictorial guide. This device has the potential to provide lifesaving capability to anyone in the world in need of rapid rehydration, under even the most challenging of environmental conditions.