The need for new and constantly improving technology to help ensure patient and healthcare personnel safety, while at the same time reducing overall healthcare costs, is a constant in today’s health care settings. Medical air and gas filtration devices, capable of removing bacteria, viruses and other contaminants are used in a variety of healthcare applications including insufflation, blood oxygenation, oxygen concentration, nebulized medication delivery, smoke evacuation, and general suction/vacuum protection.
Microporous hydrophobic membrane devices block liquids while allowing air to flow through the membrane. These devices are highly effective at keeping potentially infectious aerosols, particles and liquids from reaching medical equipment. Applying the unique properties of Pall’s hydrophobic membrane devices, design engineers have the flexibility to improve the performance of existing systems and enhance the designs of new medical prod- ucts. Pall provides filters to assist you in meeting OSHA Bloodborne Pathogen Standard 29 CFR 1910.1030, and bacterial filter requirements for Powered Suction Pump as suggested by the Center for Devices and Radiological Health Guidance Development. Moreover, incorporating hydrophobic membrane devices can reduce maintenance costs while improving safety benefits to patients.
Portable suction pumps, or aspirators, are generally used to remove bodily fluids from a patient in non-surgical procedures, such as gastric evacuation or postoperative procedures like wound drainage. Devices with hydrophobic media are used to protect the suction equipment and ambient air from biological aerosol contamination. In these applications, it is important for the hydrophobic membrane to exhibit and maintain an adequate water breakthrough pressure. Leading manu- facturers of collection or suction/vacuum devices, aspirators or compressors incorporate Pall’s disposable in-line filtration devices into their tubing sets as microbial and liquid barriers to protect their equipment from cross-contamination.
To create a reliable microbial barrier on clinical equipment, hydrophobic membrane devices must be capable of maintaining their bacterial and viral retention characteristics, sometimes under such extreme conditions as high pressure and varying temperatures, without compromising airflow rates. Hydrophobic membrane devices used in these applications must also be compatible with different sterilization procedures without reducing performance. At Pall, we have the required sterilization compatibility data needed to support your device development program.
Pall OEM medical filtration devices are evaluated under stringent test methods to ensure they meet high quality standards. Over the last few years, numerous regulations have emerged to protect both healthcare workers and patients from the potentially dangerous particles and substances that can be generated during standard operating room procedures. Minimizing the exposure to hazardous chemicals, microorganisms and non-viable particles can be achieved by integrating hydrophobic microporous materials into medical devices as a barrier between equipment and the patient. These devices can also protect the healthcare worker by reducing the spread of aerosolized particles. As a leading manufacturer of hydrophobic vent materials and devices, Pall can assist you in selecting the optimal filtration devices for your application.
Selecting Membranes for Air and Gas Filtration Devices
Removal of particulate matter from gas streams involves mechanisms beyond the normal interactions between particles and pore surfaces. Hydrophobic filter media are capable of retaining particles 10 times smaller than their rated pore size. This means that a hydrophobic filter medium with a 1 µm pore size rating may be able to retain particles as small as 0.1 µm in size. When filtering air and gases, one would select the largest pore size that provides effective retention of the specified particle size, including bacteria and viruses as needed, while achieving the highest flow rate at lowest pressure resistance possible. Due to the large variety of filtration media available, understanding the factors that govern air and gas filter efficiencies will help you make the correct selection for your specific use. Criteria most frequently considered when selecting a material for air and gas filtration include water breakthrough pressure, differential pressure, air flow rate and particle/bacterial retention. Other important material characteristics include oleophobicity chemical and temperature resistance, and compatibility with sterilization methods.
Air Flow Rate
What are the requirements for flow rate that your application demands? Is it a passive venting application where the movement of air through the membrane is minimal or does it require large volumes of air to pass in a short amount of time? Air flow rates of hydrophobic membrane devices are driven by factors such as pore size, porosity and differential pressure as well as the device effective filtration area (EFA) and housing design.
Particle and Bacterial Retention
One of the most common misconceptions about air filtration is that 0.2 µm particles can only be retained by a filter with a pore size no larger than 0.2 µm. This belief is not always correct. Due to the physics of how gases move through microporous materials, particles smaller than the pore size can be retained, usually at a particle to pore size ratio of 10:1. This can be seen with a 1.2 µm pore size membrane that has 99.98% efficiency when challenged with a 0.3 µm aerosolized particle. When considering bacterial retention capabilities of hydrophobic membranes, it is important to note that pore sizes larger than 0.2 µm can be used to reduce the bacterial load in air and gas filtration applications.
Water Breakthrough (WBT) Pressure
Water breakthrough pressure is the pressure at which water penetrates and passes through a hydrophobic porous material. This test is typically performed by placing water on one side of the membrane filter and gradually increasing the pressure until the water is forced through the filter. When selecting a hydrophobic membrane device for an application where the device needs to act as a water or liquid barrier, you must ensure the WBT pressure rating of the device is higher than the maximum system pressure the device will be exposed to. This will ensure the filter device is capable of preventing liquid from passing beyond the point where the filter is installed. It is important to recognize that hydrophobic membranes do allow water vapor to go through and that this vapor may condensate downstream of the filter.
Differential pressure (∆P) is the difference between the pressure measured at the filter inlet (upstream pressure), and the pressure measured at the filter outlet (down- stream pressure). When selecting a filter device for air and gas filtration, it is imperative to consider the impact of device pressure drop characteristics in downstream flow rate requirements.
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