Jet Injector Manufacturers Acknowledge Retrograde Flow

Linda D’ Antonio, spokeswoman for the now defunct Association of Needle-Free Injection Manufacturers, stated in a news article, “With the older style jet-injection devices, it was possible for blood to be drawn back into the nozzle…that blood then could be passed to the next person” (Snowbeck, 2001). Here an industry trade association made-up of 19 jet injector manufacturers, whose aim was to “promote understanding and advancement of needle-free injection technology, provide news and communication, and represent the industry to regulatory and technical standards organizations and the public” (CDC, 2006) admits to inherent design faults that permitted the transmission of blood to subsequent recipients.

Although this was not the only admission of a design flaw by the industry. Throughout the years, various manufacturers and engineers had acknowledged back flow, reflux, and back leak. All of these terms refer to retrograde flow.

Kenneth Dunlap acknowledged “flow back” within his 1991 patent for a disposable nozzle assembly jet injector. Dunlap stated,

In the case of the prior art needleless injectors heretofore described, during the administration of an injection, the fluid jet driven at high pressure through the patient’s skin may result in some minor amount of bleeding and because the nozzle assembly of the jet injector is pressed firmly against the skin at the moment of release and for a short time thereafter, there is a possibility that blood might flow back into the ejection orifice to contaminate the nozzle. As such, to avoid cross-contamination of blood between different patient’s being treated in a hospital or clinic situation, it would heretofore be necessary to disassemble the drug injector and sterilize those portions of the assembly that could conceivably retain contaminated blood (U.S. Patent 5062830).

Sergio Landua wrote about “blood reflux” within his 1998 patent for a disposable syringe jet injector.

It is considered that replacing the nozzle tip alone after each injection is not sufficient to guarantee complete elimination of cross contamination between patients, since by particles of blood reflux during the injection, viruses or pathogens may be carried on to the inside of the dose chamber, and therefore contaminate the following medication dose to be injected in the next patient (U.S. Patent 5782802).

Bruce Joseph Roser described “reflux flow” within his 2003 patent for a disposable injection device. Roser explained,

It appeared that high pressure occurring in the tissues, which were suddenly distended by the injection, coincided with falling pressure inside the jet injector. Ultimately, this caused a reflux flow or “sucking-back” of tissue fluid into the injector. Because of this serious drawback, single-use vials which insert into the mechanical injector were developed (U.S. Patent 6602222).


  • (CDC, 2006) Centers for Disease Control and Prevention. Needle-free injection technology. Department of Health and Human Services. 12 September 2006. Accessible at:
  • (Snowbeck, 2001) Snowbeck C. Reviving an old technology for large-scale vaccination. Post-Gazette. 20 November 2001. Accessible at:
  • (U.S. Patent 5062830) Dunlap KW. “Dry Disposable nozzle assembly for medical jet injector.” United States Patent 5,062,830. 5 November 1991.
  • (U.S. Patent 5782802) Landau S. “Multiple use needle-less hypodermic injection device for individual users.” United States Patent 5,782,802. 21 July 1998.
  • (U.S. Patent 6602222) Roser BJ. “Disposable injection device.” United States Patent 6,602,222 B1. 5 August 2003.

© Jet Infectors, 2016 – 2021
Fair Use Notice (17 U.S.C. § 107)

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