Introduction:



A new disease has emerged as the most dangerous, tenacious, incurable and contagious disease in recent memory. The disease is transmitted by common human practices thus causing it to reach epidemic proportions in the last decade. Indeed, the disease has just become the leading cause of death in Americans aged

25-44. years. The disease has struck fear into the lives of both young and old, rich and poor, for it does not discriminate when targeting its victims. All of medicine's powerful technology has yet to yield a cure or vaccine for this disease, because the disease's survival skills are far better than our own. The disease is Acquired Immuno-deficiency Syndrome, commonly known as AIDS.

The only known effective way to prevent the spread of AIDS is to eliminate the unsafe practices which facilitate its transmission. Human Immunodeficiency Virus (HIV), the virus that causes AIDS, is transmitted through the exchange of body fluids such as semen and blood. The sharing of hypodermic syringes contaminated with infected blood accounted for approximately 54% of AIDS cases reported in 1993. Drug users who inject illegal substances often share their syringes. The invention and universal implementation of a non-reusable syringe would, by eliminating the reuse and thus sharing of hypodermic syringes, reduce the rate of infection among injecting drug users and rob AIDS of an important vehicle for exacting its cruel punishment. We have developed a non reusable syringe which does not alter the existing method of injection. The syringe utilizes the force inherently exerted during an injection.



History of the Problem:



Over the past few decades, injection of illegal drugs has become more widespread because it is more economical and more powerful than other modes of ingestion such as inhalation. As more drug users turned to injection, HIV found an efficient vessel for transmission. During an injection, the recipient's blood affixes itself to the needle. If the recipient has HIV or any other disease transmitted through blood, then the needle will be contaminated. Drug users who share their contaminated syringes thus cause other users to inject infected blood into their bodies.

Injecting drug users have difficulty obtaining fresh syringes for a number of reasons. The purchase of hypodermic syringes without a prescription is a crime in New York State. In those states without such a law, many pharmacists are unwilling to sell syringes to people suspected of illegal drug use. Another factor in the difficulty of obtaining clean syringes is money: drug users who inject several times a day cannot afford to buy clean needles for each injection. They must therefore find other means of obtaining syringes to maintain their addiction.

Demographics:



The sharing of syringes among injecting drug users has advanced the spread of AIDS. While concrete data are difficult to procure because of the illegal nature of drug use, the private nature of the AIDS virus, and the sheer numbers of people involved, trends have been visible. In New York City, which has the highest number of AIDS cases among metropolitan areas, injecting drug use as a single mode of exposure accounts for the largest percentage of reported AIDS cases. According to Dr. Susan Crown, head of the AIDS Clinical Trials Unit at Memorial Sloan-Kettering Cancer Center in New York City, injecting drug use has overtaken male homosexual contact as the primary method of transmission in the most recently reported cases. In New York City, from 1980 to 1993 the cumulative percentage of AIDS cases contracted through injecting drug use was 45%; in 1992 the level rose to 51%; in 1993 the level was 54%. Approximately half of the city's injecting drug users are thought to be infected with HIV. The problem is global in scope; there are roughly five million injecting drug users throughout the world.



Current Measures:



The spread of AIDS among injecting drug users is a well-recognized problem with several solutions already implemented. The most widely accepted solution is drug and AIDS education. As knowledge of AIDS spreads, there are indications that some injecting drug users are indeed taking precautions against unsafe practices without outside encouragement.

Needle exchange programs have addressed the issue of supplying injecting drug users with clean syringes. This solution is, however, controversial. In such a program, injecting drug users can exchange used syringes for new, sterile syringes. Illegal needle exchanges began outside the United States in the mid-1980s; today in New York City there are several programs. Data on the effectiveness of needle-exchange are limited, but a recent two-year study of 2,500 needle-exchange participants conducted by the Beth Israel Medical Center Chemical Dependency Institute in New York City showed a 50% reduction in HIV infection rates for participants in the program. National and global indications are that needle-exchange is effective in reducing the risk of HIV infection for those who participate.

Current measures cannot reach everyone. Education can affect only those who listen and care enough to take action. Public campaigns reach those who see the signs, and can read them. Needle exchange programs are limited by many factors. First, needle-exchange is controversial. Some say that giving out clean syringes only encourages illegal drug injection and would constitute tacit acceptance of drug abuse. Needle exchange programs are only quasi-legal in New York State, because they require exemptions from the needle prescription law. The controversy surrounding needle exchange leaves it under-supported and thus limited in outreach. Furthermore, these programs can only help those who come forward and wish to be helped.

How Our Non-Reusable Syringe Will Address the Problem:



Current disposable syringes, although intended for single use, nevertheless can be used repeatedly. If the non-reusable syringe is implemented universally, injecting drug users will no longer be able to use contaminated needles; they will be forced to use a fresh syringe each time they wish to inject.



Our Non-Reusable Syringe:



A standard hypodermic syringe consists of a needle, a barrel, a piston and a piston driver. The needle is attached to the front of the barrel. The piston sits in the barrel attached to the piston driver which exits at the back of the barrel. When the piston driver is pushed or pulled the piston moves in or out. When the piston is at rest, the pressures inside and outside the barrel are equal. When the piston is pulled out, the volume of air in the barrel increases. Boyle's Law states that pressure and volume are inversely related. The volume of air in the barrel has increased; therefore the pressure must have decreased. A pressure imbalance results between the inside of the barrel and the outside, and the higher pressure outside forces the liquid into the barrel, reducing the volume of air and equalizing pressure. The system's tendency to compensate for the "stress" or pressure differential is known as Le Chatelier's Principle.

Our non-reusable syringe draws in liquid in the same way as a standard hypodermic syringe, but is slightly modified in design. There is a small circular opening at the bottom of the piston, which leads to a larger cylindrical cavity within the piston. A ledge is thus formed at the bottom of the cavity. The piston is elongated to allow space for the cavity. Friction between the piston and the barrel will not increase because the piston is shaped to form "piston rings" (see fig. 1). A narrow bar crosses the top of the neck of the barrel. Attached perpendicularly to this bar is a pole that extends into the bottom of the barrel, parallel with the sides of the barrel. Two additional parts are a washer and a spring member. The spring member is a piece of resilient plastic bent in half to form two flaps. It is affixed to the top of the pole, with the ends of the flaps pointing towards the needle. The syringe would be packaged with the piston flush with the bottom of the barrel; the spring member enclosed in the cavity; and the flaps held closed by the washer

(see fig. 1).

In operation, when the piston driver is pulled up, the spring member slides through the opening in the piston because the flaps are held closed by the washer. The washer, however, is too big to fit through the opening, and so is pulled off the spring member and remains in the piston (see fig 2). The piston can move freely back and forth above the spring member. When the syringe is "fired," thus returning the piston to the original position, the washer is pushed up and out of the way by the spring member and the flaps of the spring member open in the piston (see fig. 3). If, in an attempt to reuse the syringe, the piston driver is pulled up, the flaps catch on the ledge in the piston and the piston cannot move. If the piston driver is pulled with enough force, it will detach from the piston, rendering the syringe useless.

Hypodermic syringes are intended to be used in medical injections. Our syringe would not in any way change the current injection procedure because it utilizes the force already needed for an injection. Also, the piston can be moved freely above the mechanism. This freedom is necessary for medical injections. There should be no air bubbles in a loaded syringe, largely for accuracy of volume but also for safety. A health care professional draws liquid, then removes air bubbles by gently striking the side of the barrel and pushing the piston in slightly, then draws more liquid to obtain the proper volume.



Possible Negative Consequence of the Solution



We interviewed two medical technicians to get their opinion on a non-reusable syringe and on our design in particular. If a non-reusable syringe were universally implemented, members of the medical community would have to adapt to the feel of our design. One characteristic of our design is that the injector will sense the mechanism engaging. Sandy Morvat, a nurse in a private pediatric practice in New York City, said that she liked the idea of a non-reusable syringe, and that the idea of the mechanism "kicking in" at the end of an injection (as would occur with our design) did not bother her. Craig A. Bannister, a Medical Assistant who gives hundreds of injections per day at a private allergy practice in New York City, was also enthusiastic about the idea of a non-reusable syringe. He indeed pointed out that it would be helpful to feel some sort of "click" to alert the injector that all of the liquid had been injected.

In an age when society recognizes the importance of preserving the environment and places emphasis on reducing waste, a non-reusable syringe would slightly increase waste. The increase would not be very large, because most current syringes are intended to be used only once. Occasionally, an injector must return the piston to the original position in order to remove all of the air bubbles. With our syringe, it would be impossible to pull out the piston once returned to the starting position; a fresh syringe would have to be used. This occurs only rarely, however. Nurse Morvat said that she very rarely had to return the piston to the starting position. In order to quantify the increase in waste, we performed an experiment. n Using an empty medical vial, we filled one hundred new syringes to .5cc with saline solution. Of those hundred syringes, only two had to be returned to the starting position to remove the air bubbles. Thus the implementation of our non reusable syringe would increase waste by approximately 2%.

The benefits of a non-reusable syringe are indeed considerable. First and foremost, a non-reusable syringe would save thousands of lives annually. Additionally, eliminating such a major source of HIV transmission would have a significant effect on ballooning health care costs. Furthermore, a non-reusable syringe would prevent much transmission of other blood-borne diseases such as hepatitis. Finally, injecting drug users are not the only victims of AIDS contracted through contaminated syringes. Their children and sexual partners are also at risk. A non-reusable syringe will thus indirectly benefit other members of the community.

A non-reusable syringe, like a needle exchange program, is only a harm-reduction measure. The syringe does not address the fundamental problem of drug abuse. But this measure is a safeguard which is sociologically necessary. Government and industry must work together to make the implementation of the syringe both feasible and worthwhile. u