October 23, 2016
A jet injector, also commonly referred to as an air gun, air jet injector, pneumatic injector, or jet gun injector, is a needle-free instrument that uses a high-pressure stream of liquid medicament to penetrate the skin and achieve a percutaneous administration of medicine or vaccine. The concept most resembles a powerful squirt gun penetrating through skin.
Initially jet injectors were developed as an easier method for delivering insulin to diabetic children who had a fear of needles. Soon thereafter developers designed a type of jet injector which reused the same nozzle tip to vaccinate multiple people. These jet injectors, known as high workload jet injectors, were designed for use in mass immunizations, in which a large population needed to be vaccinated at a rapid rate. The concept reduced the overuse and disposal of single-use syringes and needles, and prevented the accidental needle stick injuries to the immunizing staff.
Jet injectors are defined in law under Title 21 of the Code of Federal Regulation. These devices are listed under sections for General Hospital and Personal Use Devices and Dental Instruments.
Nonelectrically powered jet injectors are defined in section 880.5430 as a “nonelectrically powered device used by a health care provider to give a hypodermic injection by means of a narrow, high velocity jet of fluid which can penetrate the surface of the skin and deliver the fluid to the body.”
Other types of jet injectors have been defined by their design features. Gas-powered jet injectors are defined in section 872.4465 as a “syringe device intended to administer a local anesthetic. The syringe is powered by a cartridge containing pressurized carbon dioxide which provides the pressure to force the anesthetic out of the syringe.”
Spring-powered jet injectors are defined in section 872.4475 as a “syringe device intended to administer a local anesthetic. The syringe is powered by a spring mechanism which provides the pressure to force the anesthetic out of the syringe.”
These devices can be divided into various classes or categories based upon different factors. Factors such as:
- Intended Market—Is the intended population human or animal? Medical professionals have used jet injectors for administering vaccines, therapeutic drugs, anesthetics, antibiotics, anticoagulants, antivirals, corticosteroids, cytotoxics, immunomodulators, insulin, hormones, and vitamins (Weniger & Papania, 2008). Veterinarians have used jet injectors to deliver vaccinations to various animals, but mainly livestock.
- Intended Usage—Devices can be used by health professionals for vaccinating multiple patients or can be used solely for self-administration whereupon one patient uses one device (Weniger & Papania, 2008). The largest market for self-administering jet injectors is for administering insulin.
- Frequency of vaccinations—High Workload versus Low Workload Jet injectors. High workload jet injectors are devices which can inject more than 150 people per hour. These devices are designed for use in mass immunization campaigns, in which a large number of people need to be vaccinated at a rapid rate. Low workload jet injectors are devices which can inject on average 30 people per hour. These devices are intended for use in physicians’ offices (Bykowski, 1999).
- Design of the Drug Compartment—The drug compartment has been redesigned over the years to overcome the inherent risk of cross-contamination via the nozzle and internal fluid pathways. These design changes can be best classified by using the term “generation.” Below are descriptions of first generation, second generation and third generation jet injectors whereupon each succeeding generation has been an improvement to the faults of the previous generation.
First Generation Jet Injectors consisted of reusable nozzles and internal fluid pathways. None of these devices had any disposable parts. Parts that became contaminated with blood had to be substituted until contaminated parts could be sterilized through autoclaving, a procedure that sterilized devices through steam and high-temperature within an enclosed container. These first generation devices were termed multi-use nozzle jet injectors or MUNJI. In more recent years, researchers termed MUNJIs as reusable-nozzle jet injector, which describe the same device. Reusable-nozzle jet injectors are defined as a “Needle-free jet injector for high-speed vaccination which feeds vaccine from multidose vials through reusable fluid chambers, pathways, and nozzles that are in contact with consecutive patients without intervening sterilization” (Ekwueme, Weniger, & Chen, 2002). These devices were found to act as vehicles allowing blood and disease to pass from one patient to the consecutive patient. The photographs below show various MUNJI devices.
Second Generation Jet Injectors attempted to overcome this risk by implementing a single-use protector cap that covered the injector nozzle thus acting as a shield between the reusable nozzle and the patient’s skin. Following an injection the protector cap would be discarded and a new one put in its place. These second generation devices were termed protector cap needle-free injectors or PCNFI. The photographs below show PCNFI devices.
(Kelly et al., 2008)
Kelly and colleagues (2008) found in their study that PCNFIs still allowed cross-contamination of the hepatitis B virus through contaminating the internal fluid pathway. Researchers learned to overcome the risk of cross-contamination that the internal fluid pathway and patient-contacting parts cannot be reused. Third Generation Jet Injectors completely overhauled the design of preexisting devices, by making the drug compartment, internal fluid pathway, and nozzle as a single-use disposable cartridge. Once this cartridge dispenses an injection it can no longer be reused and must be discarded. Depending upon the manufacturer the cartridge may also be referred to as an “ampoule,” “syringe,” “capsule,” or “disc” (International Standards Organization, 2006). These third generation devices were termed disposable-cartridge jet injectors or DCJI. So far, this design has overcome the risk of cross-contamination although further tests are needed. The photographs below show various DCJI devices.
- (Bykowski, 1999) Bykowski M. Needle-Free Injection Devices Face Obstacles. Skin & Allergy News 30(8):13, 1999. Available at: http://www.us-medicalinc.com/needle-free.htm.
- (Ekwueme, Weniger, & Chen, 2002) Ekwueme DU, Weniger BG, Chen RT. Model-based estimates of risks of disease transmission and economic costs of seven injection devices in sub-Saharan Africa. Bull World Health Organ 2002;80:859–70.
- (International Standards Organization, 2006) International Standards Organization. Needle-free injectors for medical use — Requirements and test methods. 19 May 2006. ISO 21649:2006. Available at: https://web.archive.org/web/20070125081939/http://www.iso.org/iso/en/CatalogueDetailPage.CatalogueDetail?CSNUMBER=35954&ICS1=11&ICS2=40&ICS3=20.
- (Kelly et al., 2008) Kelly K, Loskutov A, Zehrung D, Puaa K, LaBarre P, Muller N, Guiqiang W, Ding H, Hu D, Blackwelder WC. Preventing contamination between injections with multi-use nozzle needle-free injectors: a safety trial. Vaccine (2008) 26, 1344-1352.
- (Weniger, 2004) Weniger BG. New High-speed Jet Injectors for Mass Vaccination: Pros and Cons of Disposable-cartridge Jet Injectors (DCJIs) versus Multi-use-nozzle Jet Injectors (MUNJIs). WHO Initiative for Vaccine Research: Global Vaccine Research Forum. 8-10 June 2004, Montreux, Switzerland.
- (Weniger & Papania, 2008) Weniger BG, Papania MJ. Alternative Vaccine Delivery Methods [Chapter 61]. In: Plotkin SA, Orenstein WA, Offit PA, eds. Vaccines, 5th ed. Philadelphia, PA: Saunders (Elsevier); 2008;1357-1392.