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EGR 212
Project Checkpoint 5 – Draft Report
Cameron King
Motivation, Relevance, and Background
A. Motivation
Needle-free (NF) injection devices are an innovative system that have the potential to greatly improve the world from a biomedical engineering perspective. There are many medical and environmental benefits to using NF injection devices over the most commonly used hypodermic needle. However, there are inherent drawbacks of using a new medical technology, most of which are socially and economically focused. The continued improvement of the NF injection technology will increase the viability of using it over the needle and syringe. I am interested in needle-free technology because of its ability to directly improve individuals’ quality of life. For individuals with conditions requiring daily injections, alleviating some of their stress associated with injections is important to me. Since individuals unfairly develop diseases due to their genetic makeup, I believe it is important to support them the best we can as a society.
B. Relevance
Needle-free injection devices are relevant in modern engineering because of the vast room for improvement of the system. Engineering is a system approach of problem-solving to improve the lives of the people living in the growing man-made world [6]. Engineers can isolate the various components of the entire system to enhance their function and efficiency. Then, the entire system can be improved by isolating and experimenting with the individual components.
The environmental benefits of using NF injection devices over hypodermic needles should interest environmental conservationists. NF devices can be reused whereas needles are used once, then sent to a landfill. Around 500 million needles are added to landfills every year [3]. This large number could be drastically reduced with the increased use of NF devices. In addition, the percentage of the public with a phobia of needles may be interested in NF technology. An individual may not get suggested vaccinations due to a fear of needles. NF injection devices provide a second option for those individuals, which would increase the overall health of the world population. Lastly, the medical field and the public sees value in NF injection devices because they prevent needlestick injuries and cross-infection. Each needlestick injury costs around $3,000 which can be eliminated with the implementation of NF devices [3].
C. Background
Needle-free injection devices are currently used as an alternative to the typical hypodermic needle. Each injection method has strengths and weaknesses, making their use a personal preference. The use of NF devices has social, environmental, and medical benefits over the use of hypodermic needles. The major obstacle of using NF devices is the cost. One hundred hypodermic needles can be bought online for under $5 [7]. In comparison, NF injectors cost between $50 and $200 on the market.
Historical Analysis and Evolution
A. History
The hypodermic needle became the first injection system, in 1853, while the concept of a jet injection was first introduced on accident many years later. In 1925 and 1937, the first injuries from jet injection were documented. The injuries were both accidents, caused by using high-powered grease guns. Ironically, the injuries sparked thought on the possibility of using injection technology in the medical field. The first known thought of a needle-free injection device was in 1936 when Marshall Lockhart filed a patent for his idea of a NF injection system. Lockhart’s idea did not come to fruition until 20 years later when Dr. Robert Hingson developed the “Hingson Peace Gun.” The device used a fine jet of liquid capable of piercing the skin under high pressures. The initial goal of the NF injection device was to eradicate many diseases by increasing global immunization. The “Hingson Peace Gun” was initially used for the military to provide vaccines to troops in the 1950s. In the 1960s, Aaron Ishmack refined Dr. Robert Hingson’s design with the development of the “ped-o-jet” mass inoculation gun. Compared to hypodermic needles, these new devices allowed the medical staff to quickly provide vaccines, because each individual dose for patients was already prepared. Also, use of NF devices eliminated the possibility of any needlestick injuries. However, mishaps with NF injections did occur, in the form of cross-contamination. Both innovative devices were used to increase global immunization, but their drawbacks outweighed their benefits, leading to the drastic withdrawal of NF injectors in medicine. Research and technology improved steadily over time, causing the recent reintroduction of NF injection devices. Now, there are many different competing devices on the market. As the technology and public opinion of needle-free injection technology continues to improve, use of the system will increase [1].
B. Evolution
The first significant NF system, the “Hingson Peace Gun,” was too bulky, contained many different parts, and required the use of electricity, increasing the likelihood of malfunctions. The “ped-o-jet” no longer required electricity, allowing the device to be used anywhere. The first NF injections were painful and left a circular scar on many patients. In addition, the design allowed for cross-infection of patients which caused many soldiers to develop Hepatitis C [1]. The disadvantages of using early needle-free injection devices outweighed the benefits, which lead to public disapproval of the new technology. The issues caused the use of NF devices to significantly decline. Recently, NF technology has reemerged, with many different competing companies. Current designs vary but almost all have become smaller and sleeker. There are different injection techniques
System Architecture and Functional Model
A. System Architecture
There are several different variations for current needle-free injection devices. There are gas powdered, liquid, and depot injection devices which all serve the same basic function. An example of a gas powdered NF injector is shown below.
Figure 1: Gas powdered NF injection device [2]
B. Evolution
Initial designs for needle-free injection systems were bulky with many different parts. The “Hingson Peace Gun” in Figure 1 required electricity, which severely limited the functionality of the system. To use the device, one had to be close to an electrical outlet, making it impractical to use in the field.
Figure 2: “Hingson Peace Gun” [5]
The “ped-o-jet” improved the design by eliminating the need for electricity. Also, the design was simplified since it contains less parts. The simpler design decreased the likelihood for malfunctioning because when one piece malfunctions, the entire system stops working.
Figure 3: “Ped-o-jet” mass inoculation gun [4]
Current needle-free devices are sleek and simple in their design. This decreases the possibility for malfunction and the need to replace parts even more. Also, the small design makes it comparable to hypodermic needles, which is important for some consumers. There are three separate injection types
A. Functions
The main function of a needle-free injection device is to inject a patient with a liquid or gas, depending on the device. There are several subfunctions of the system that relate to individual components. Each component has its own function in the system that contribute to the main function.
Table 1: Each individual component and their respective function(s) is shown below.
A. Functional Model
For gas powdered injectors, the gas cartridge provides the drug in the form of pressurized gas. Pressing the activation lever activates the injection by opening the gas cartridge. The gas is then propelled down the device by the plunger and compressed by the piston. The compressed gas exits the injector through the orifice, which decreases the injection area and increases the fluid’s velocity. Lastly, the luer cap is in contact with the skin at the point of injection.
Figure 4: The functional model above describes the main functions during operation of a gas powdered NF injection device and the individual component that provides each function.
System Performance
A. Performance
The performance of needle-free injection devices is based on different factors according to the perspective of a customer, an engineer, or a stakeholder. A customer would analyze the performance of NF devices with greater regard for functionality, ease of use, safety, speed, induced pain level, and reusability. Customers would want to self-operate and prepare the device in as little time as possible. Regarding safety, customers would favor injection devices with a lower risk of cross-contamination. Certain customers will prioritize the environmental impact of the device, making its reusability important. From an alternate perspective, an engineer would focus on the precision of drug delivery when analyzing the NF injection system. The pressure must be enough to inject the drug through the skin. In addition, the pressure must be low enough to ensure the molecules of the drug are not damaged [2]. An engineer would focus on the success of the injection as the most important aspect of NF devices. The overall function of a NF injection device is to inject a drug into the body. Therefore, the success of the system depends on the success rate of each injection compared to a typical needle. Stakeholders view the performance of needle-free injection devices differently, depending on the type of device which they are investing.
System Characterization
A. Qualitative Assessment
The needle-free injection device operates as an open system because mass crosses the boundary in the form of the injected substance. Important qualitative variables relating to the performance of the system include pain level, safety, reusability, training time, and time required to administer each injection. Pain tolerance is different for everyone, so there is no way to quantitatively measure pain. Pain could be measured by giving test patients a scale of 1-5 for example where a 1 or 2 represents a small amount of pain, a 3 is an average amount of pain, and a 4 or 5 is a large amount of pain. Analyze the safety of NF injection devices will take years to complete. The effect on each patient is not known immediately after injection. Sometimes it takes years for injuries and diseases to present themselves in the body. However, it is known that NF injection devices are safer than hypodermic needles in two ways. First, there is no risk of needlestick injury because there is no needle. Second, there is no chance of cross-contamination [3]. The training time required to be able to self-administer an injection from a NF device is only 20 minutes [8]. The devices are incredible easy to operate, requiring only a press of a button. The time required to administer each injection includes four steps. First, the injector needs to be prepared. Then, the syringe needs to be filled. Lastly, the injector needs to be loaded before the injection is given [8]. The pain, safety, reusability, training time, and time required to administer each injection should also be compared to a typical hypodermic needle, because that is the only competition to NF devices.
B. Quantitative Assessment
Important quantitative variables relating to the performance of the system include pressure of substance, velocity of substance, volume of substance, and injection speed. The pressure and velocity of the injection substance translates to the penetration depth into the skin. There are intramuscular, subcutaneous, and intradermal injections which require different injection depths and volumes. For intramuscular injections, the depth of the injection must be between below the skin. For subcutaneous injection, the depth of the injection must be between 2mm and 5mm below the skin [10]. From the mass flow rate equation below, the residual left in the injection chamber must be small enough to ensure the proper volume is injected. The injection speed is the amount of time the injection takes after pressing the activation lever. The injection speed depends on the speed of the moving parts in the system and the velocity of injection.
C. Mass and Energy Flow
The system boundary identified is just the NF injection device. The substance being injected is the only mass leaving the injection system. However, a small amount of the residual is left behind in the injection chamber [9]. Using the conservation of mass equation, the mass flow rate of the system is the following:
From a conservation of energy perspective, heat transfer occurs in the system when the system boundary is altered. The system boundary now includes the NF injection device and the person being injected. The representative conservation of energy equation is the following:
References
[1] History of Jet Injection. (2019, January 18). Retrieved from https://jtip.com/history-of-jet-injection/
[2] Kale, Tejaswi R.; Momin, Munira. (2014). Needle free injection technology - An overview. University of Minnesota, College of Pharmacy. Retrieved from the University of Minnesota Digital Conservancy, http://hdl.handle.net/11299/171730.
[3] Needle-Free Syringe. (n.d.). Retrieved from https://pharmajet.com/needle-free-technology/
[4] Science Museum. Brought to Life: Exploring the History of Medicine. (n.d.). Retrieved from http://broughttolife.sciencemuseum.org.uk/broughttolife/objects/display?id=11560
[5] The Wood Library-Museum. (n.d.). Retrieved from https://www.woodlibrarymuseum.org/museum/item/109/hingson-peace-gun
[6] What is Engineering? (n.d.). Retrieved from https://www.linkengineering.org/what-is-engineering.aspx
[7] Care Touch Hypodermic Needle 25g x 1.5", BX 100. (n.d.). Retrieved from https://www.medical-and-lab-supplies.com/caretouch-hypodermic-needle-25g-x-1-5-bx-100.html?gclid=EAIaIQobChMInOT7g_iz4QIVVgOGCh3R6gDVEAkYBCABEgLaVfD_BwE
[8] Needleless Injection Device and Jet Syringe Products. (n.d.). Retrieved from https://pharmajet.com/stratis-imsc/
[9] Portaro, R. (2013). Experiments and Modeling of Air-Powered Needle-Free Liquid Injectors. Journal of Medical and Biological Engineering. doi:10.1007/s40846-015-0075-y
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