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The Use of PVC Valves in Medical Applications
Among other applications, PVC valves have also found use in medical applications due to their low cost and absence of sterilization requirement before every use. Their inherent quality to resist formation of scales, avoid collection of organic contaminants and indifference to most organic chemicals made them popular with the medical valve manufacturers. In addition, PVC valves are chemically stable, inert, and easy to fabricate. To avoid contamination, virtually all the PVC valves used in medical applications are of non-return type.
Unlike other PVC products such as cable grade PVC, medical valves made of PVC have a different manufacturing process. The PVC tubes used in the health industry and PVC valves are made out of varying quality of PVC since tubes require flexibility and valves require rigidity. The PVC used in medical valves use lesser plasticizer and stabilizer. Moreover, the PVC needs adequate gel reduction to ensure high clarity. By nature, PVC has a wide range of melting points, from 100°C to 210°C, depending on the composition. During manufacturing under 210°C, non-melted particulates are present in form of gels. These non-melted particulates are removed by shear breakdown, heating to a temperature higher than 210°C, or filtering using screens. However, heating above 210°C runs the risk of thermal degradation and discoloration. Plasticizers such as DEHP diethylhexylphthalate that were widely used in medical PVC valves are now avoided due to toxicity concerns. Plasticizers with lesser toxicity, such as dioctyl adipate (DOA) and tri-2 ethylhexyl trimellitate (TOTM), are replacing DEHP in some places. Since TOTM and DOA do not offer some of plasticizing properties of DEHP, DEHP is still irreplaceable in some intricate valve designs. Medical valves made out of PVC also face a problem of producing vinyl chloride monomer. These monomers can cause a very unusual but fatal form of liver cancer called liver angiosarcoma. Since the 1970s, medical grade PVC undergoes rigorous cleaning procedures, automated production, and a sterilized production environment. Alongside rigorous manufacturing procedures, care is taken to keep the exposure of vinyl chloride monomer under one PPM over a period of eight hours.
Types of PVC Valves Used in Medical Industry:
At any given instance, there are a number of PVC valves being used in the medical industry. Following are some the valves currently in use:
- Anti-reflux flutter valve
- One-way check valve
- IV access valves
- Spill valves
- Expiratory valves
- Fine adjustment valve
- Foley Catheter Valve
- Swallowing and speaking valves
Anti-reflux flutter valve:
These are valves used in the urinary baggage for incontinent patients. These valves can be pedal operated, and are anti-reflux enabled to avoid patient infection.
One-way check valve:
These are the most widely used valves in the medical industry and a common feature in all valves. One-way check valves are used to regulate flow of organic, medicinal, and bodily fluids in one direction.
IV access valves:
In intravenous administration of medicine or blood, IV access valves are often the enabling valves with or without needles. These valves share close proximity with the patients and are therefore vital during drug administration.
These types of valves are also called bleed valves that, along with block valves, reduce the risk of leakage and can also be used to remove air bubbles and/or unwanted commodities inside the fluid.
To regulate the flow of oxygen and anesthesia, expiratory valves are used in anesthesia mask and tracheal connectors. These valves play an important role in breathing and expiration in patients under the effect of anesthesia.
Fine adjustment valve:
Oxygen cylinders or nitrous oxide need to be regulated very precisely to avoid unwanted eventualities. Fine adjustment valves equipped with pressure gauge and flow meter help in better regulation of gases.
Foley Catheter valve:
In catheters, valves are needed to avoid nephrological infection. These are non-return valves with connection to catheters.
Swallowing and speaking valves:
Valves are required to administer food, and allow the patient to talk after surgeries, and assist patients under artificial oxygen. Swallowing and speaking valves allow for contamination free exposure.
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