How does a plastic syringe work


English: syringe

1 definition

A syringe is a medical instrument that is used for injections, rinsing or the removal of body fluids (e.g. blood) - usually in combination with a cannula. Syringes are class IIa medical devices.

Note: Colloquially, the term "syringe" is usually equated with an injection. The classification as a medical device only applies if it is not a single-dose, pre-filled syringe. In these cases it was about the outer packaging of a drug and is therefore not subject to the CE marking

2 structure

A syringe consists of a hollow, cylindrical jacket in which a movable plunger, the Syringe stamp can slide up and down. At the front end of the syringe jacket is closed by a cover plate, which is in a cone that is open at the front Syringe nozzle or runs out in a thread (e.g. LuerLock). Suitable cannulas, valves or hoses can be connected here. At the rear end of the syringe jacket there is usually a plunger stop to prevent the syringe plunger from sliding out. A scale is printed on the outside wall of the cylinder, on which the respective injection or withdrawal volume can be read off.

Most commercially available syringes are made up of two parts and only consist of a cylinder and a syringe plunger. 3-part syringes also have a small rubber stopper at the upper end of the syringe plunger to ensure an optimal seal. 4-part syringes also have a safety ring that makes it impossible to pull out the plunger.

Older models are made of glass, metal and rubber. The sizes (syringe volumes) depend on the area of ​​application and range from 0.5 to 100 ml.

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3 classification

3.1 ... according to frequency of use

  • Disposable syringe: sterile packed syringe for single use
    • AD syringe: special form of the disposable syringe that excludes reuse
  • Reusable syringe: Syringe for multiple use, can be cleaned after use and sterilized in the autoclave.

Disposable syringes in sterile packaging are the standard today in outpatient and clinical settings. Reusable syringes are only rarely used. However, due to the raw material and waste problems associated with disposable syringes, they could experience a renaissance in the future.

3.2 ... according to area of ​​application

3.3 ... according to the mode of operation

4 Principle of Operation

When the syringe plunger is withdrawn, suction is created on the nozzle, with the help of which the inside of the syringe can be filled ("aspiration"). Conversely, during the injection, the pushing in of the plunger leads to the outflow of the liquid in the syringe by generating a pressure. This pressure depends on the plunger area of ​​the syringe and its outlet opening. A smaller piston area and / or a smaller outlet opening cause a higher pressure than a larger one with the same expenditure of force. For certain injections (e.g. port injections) it is recommended to use at least a 10 ml syringe to prevent damage to the port catheter.

5 Disposal

Needle-attached syringes are a common cause of needlestick injuries. Sliding the protective cap back on after an injection or blood sample ("recapping") should therefore be avoided in any case. The cannulas are best disposed of in special, puncture-proof and break-proof cannula disposal boxes. The syringes themselves are also to be collected in closed waste boxes. These containers should be set up as close as possible to the place of use.

The closed syringe containers can generally be disposed of with the residual waste. If the garbage cans are accessible to other users, e.g. in a shared property, the garbage can should be lockable. Alternatively, the boxes can be picked up by a medical disposal service.

Syringes and needles that are contaminated with notifiable pathogens are infectious waste (C-waste). Special rules apply to them when it comes to disposal, including:

  • Collection in puncture-proof and break-proof disposable containers
  • Container marking "Biohazard"
  • Preventing unauthorized access during storage, transport and disposal
  • Disposal as hazardous waste in approved waste disposal facilities

6 story

In the medical field, syringes in a primitive form were first used in the Arab region in the 9th century. However, the syringes, which have evolved over time, were not used regularly until the middle of the 18th century when injections became more common. Today, syringes have become indispensable in medicine and are probably the most frequently used medical instruments. They are used in a wide variety of variants, sizes and purposes.