Disposable Medical Syringe

Introduction

A syringe consists of a syringe with a small hole at the front end and a matching piston core rod. The syringe is used to inject a small amount of liquid or gas into or extract from areas that are inaccessible by other methods. When the core rod is pulled out, the liquid or gas is sucked from the small hole at the front end of the syringe, and when the core rod is pushed in, the liquid or gas is squeezed out. The process of extracting or injecting gas or liquid with a syringe and a needle is called injection.

Working principle

1. Liquid aspiration stage: Insert the injection head of the syringe into the medicine bottle, and push the piston of the syringe toward the injection head to form a negative pressure environment. The negative pressure causes the drug to be drawn into the cavity of the syringe.

2. Filtration stage: When some syringes aspirate, they will filter out impurities or solid particles through a filter to ensure that the liquid injected into the body is pure.

3. Injection stage: Insert the syringe into the area to be injected, and slowly push the piston of the syringe downward to push the liquid drug gradually into the body.

4. Emptying stage: After the syringe is completely used, continue to push the piston of the syringe downward to empty the remaining liquid medicine as much as possible.

Common structural types of syringes

1. Three-piece type: It consists of a barrel and a plunger assembly (push rod and sealing piston). From a structural point of view, no matter how the syringe is deformed, the basic structure and components include the limitations of the above three components.

2. Two-piece type: Under strict adaptation conditions, the piston component can be omitted, and the front end of the plunger (with all the functions of the piston) can form a good sliding seal with the inner wall of the outer barrel, which is a typical two-piece syringe structure.

Structural design considerations of syringes

1. Three-piece basic structure: The convenience of the manufacturing process meets the requirements of large-scale assembly of industrial production; for example, in order to meet the quality consistency of industrial mass production and the mutual adaptability between components, the plunger structure is decomposed into a push rod and a piston when the relative tolerance of the components is allowed to be as large as possible.

2. Comprehensive requirements for clinical application: meet the requirements of clinical medical staff: mainly the safety and reliability of the operation process, the use process is simple and comfortable, and the operation process is stable, reliable and safe. Effectiveness is the most basic.

3. Basic requirements for the barrel: the barrel should be as transparent as possible to facilitate observation of the natural properties of the liquid medicine, and the curling edge should be elliptical or similar to prevent it from rolling and falling. There should be a volume scale on the surface of the barrel.

4. Special requirements for the structure of the syringe:

(1) Dental syringe: the firmness of the barrel material, the length requirements for hand holding, and safety protection requirements.

(2) High-pressure contrast syringe: the material's high-pressure explosion resistance, the safety and reliability of the interface, and suitable for use with equipment.

(3) Balloon dilatation syringe: the firmness of the interface and material, the stability and firmness of the operation, and the high sealing performance.

(4) Insulin syringe:

A: According to the treatment needs, the minimum and maximum doses are the maximum capacity of the syringe.

B: There should be a very clear dose scale to meet the precise injection and prevent inaccurate measurement from causing a decline in treatment quality.

C: There must be a protective device. The insulin syringe is used to extract the liquid medicine (dose) in advance and then divide it into meals for preventive injection. The medicine is stored (generally not more than 24 hours); there must be a reliable protective device to prevent the liquid medicine from being discharged due to the movement of the push rod.

D: The insulin syringe must have a self-destruct function to prevent infection and related problems caused by repeated use.

E: There must be a suitable structure. For subcutaneous injection, the needle tip is small, the cap is short, and the barrel is also short. It is not necessary to make 1.0ml. It is enough (maximum dose); but there must be enough space at the rear end cap to ensure that the push rod can be protected from being touched when the maximum dose of insulin is extracted.

(5) Subcutaneous allergy test syringe: requires a small dose, small specifications, as long a barrel as possible, accurate scale, and clear distinction. After returning the injection needle, it can be used repeatedly; it is necessary to set the connection part to be safe and reliable, and the best design has a fixed dose setting. There must also be a structure to prevent back-drawing immediately after each push (after injection).

(6) Syringes for vaccination: small size, precise dosage, self-destruction or safety protection, complete destruction, and cannot be reused. They cannot be taken away by children as toys. The barrel and the injection needle must be completely destroyed and incinerated. This needs to be designed with this in mind.

5. Meet the performance requirements of safety protection

(1) Safety syringes: During use, the needle (including the syringe) is structurally destroyed, the needle tip is shielded, and the syringe is locked so that it cannot be reused, avoiding needlestick injuries and infection and spread of blood-borne diseases.

(2) Self-destructive syringes: During use or at the end of use, the syringe is structurally destroyed so that it cannot be reused, avoiding infection and spread of blood-borne diseases caused by repeated use.

6. Meet ergonomic requirements

(1) The outer barrel of the syringe must have clear transparency: it is very easy to observe the color, clarity, foreign matter, particles, floccules or precipitation of the liquid or medicine in the barrel.

(2) There is a discernible minimum scale line, which can accurately determine the amount of liquid medicine injected by pushing the plunger;

(3) The shape, structure and size of the syringe should preferably be the best size for one-handed operation: The shape and size of the syringe should meet the requirements of stability, safety, convenience, and comfort for one-handed control, holding and operation.

① Safety: The Luer interface of the syringe should adopt the international standard locking type to prevent the risk of the injection needle falling off due to increased pressure during the injection process.

②Reliability: The distance between the curled edge of the syringe barrel and the hand at the end of the plunger should not be too small. If it is too small, it will be difficult to open with one hand, and both hands are required to pull the plunger open. Therefore, the minimum distance between the hand and the curled edge of the syringe plunger must meet the width of a single finger. It can be reliably opened and clamped with one hand.

③Comfort: When the length of the syringe barrel and the plunger contains 70% of the liquid volume, the total length is still within the range that can be comfortably clamped and pressed (pushed) by one hand, and cannot exceed 70% of the maximum distance between the thumb and the index finger of an ordinary person.

④Stability: During the interventional puncture, the size of the syringe (outer barrel) held by medical staff in one hand should not be too small. It should meet the interventional methods used by medical staff in different tissue interventions, and they should be able to accurately and stably control the direction and position of the puncture action in the palm of their hand. The syringe (volume) should not be too small or too short, resulting in an unstable grip, easy deviation of the (intervention angle), and difficulty in achieving precise intervention.

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