Last Updated: Monday, 11 May 2020, 10:13AM (NZDT)
These filters can be placed in an inspiratory position, expiratory position, or both within a breathing circuit. They are designed to prevent pathogens (viruses and bacteria) from being transported in the breathing circuit and to minimize the amount of condensation entering the expiratory block of the ventilator..
Note: Not all filters and circuit kits are available in all countries. Filters are available for purchase in boxes of 20. Consult your local Fisher & Paykel Healthcare representative for information on availability.
Regarding Viral & Bacterial Filtration Efficiency of Fisher & Paykel Healthcare Filters and F&P Evaqua™ 2 Circuits
The filter media within the filter housing is responsible for stopping pathogens moving through the filter. There are several mechanisms by which filter media work. The RT016, RT019, and RT020 filters use an electrostatic media which attracts pathogens and particles to stick to the filter media (and not pass through the filter) via electrostatic attraction. Our filters are also hydrophobic, so they repel water to protect filter performance. An electrostatic filter has the advantage of requiring less material to trap pathogens which reduces resistance to flow.
Filtration efficiency reported as a percentage can be determined using both viruses and bacteria, and it reflects how effectively the filter blocks pathogens from passing through. This percentage is usually very high (>98%). However, it is crucial to understand the filter testing conditions when comparing filtration efficiency in filters.
Independent external laboratories tested F&P filters using methods from the following standards:
These filters can be placed in an inspiratory position, expiratory position, or both within a breathing circuit. They are designed to prevent pathogens (viruses and bacteria) from being transported in the breathing circuit and to minimize the amount of condensation entering the expiratory block of the ventilator.
Draft BS EN 13328‑1 determines filtration efficiency using viruses and bacteria to simulate real‑world results. The chosen bacteria and virus pathogens used for the F&P tests are relatively small and mimic pathogens of clinical significance. They are also stable both in liquid suspension and when aerosolized.
The BS EN ISO 23328‑1 test uses tiny salt particles to test filtration efficiency and provide a standardized test for comparing different filters. However, this test does not specify the testing conditions; instead, the manufacturer determines these. F&P conditioned our filters for 25 hours using heated and humidified gas to simulate 24 hours constant use in a ventilator circuit.
If selecting a filter from another manufacturer, compare filtration efficiency using BS EN ISO 23328‑1 and ensure it is tested under heated and humidified conditions.
The standard viral and bacterial tests use dry medical gas to measure filtration efficiency at a point in time. The BS EN ISO 23328‑1 test simulates exposure of the filter to heated and humidified gas (37 °C, 100% RH) for 25 hours and then measuring filtration efficiency.
This data also shows that F&P filters have very high filtration efficiencies when they are used ‘dry’ with only a small reduction in efficiency over 25 hours. This minimal reduction in filtration efficiency is due to the filter trapping humidity from the expiratory limb.
The BS EN ISO 23328‑1 test uses salt particles approximately 0.3 µm in size as this is the most penetrating particle size and therefore, an excellent size to test filtration efficiency.
Heat and moisture exchangers can come with (HMEF) or without a filter (HME). If you are using an HMEF, ensure you understand the filtration efficiency when it is both dry and wet (37 °C, 100% RH). Replace the HMEF following the manufacturer’s instructions.
In a study of six different HMEFs performed by Scott et al. (2010), all six filters allowed free passage of two different bacteria when wet.
Yes. As per the User Instructions for our filters, F&P recommends changing the filter every 24 hours to ensure filtration efficiency remains very high.
The RT016, RT019 and RT020 F&P filters are designed for use with the F&P adult invasive ventilation circuits. They are not intended for use with F&P neonatal invasive ventilation circuits. F&P recommends extreme caution when using filters in unapproved or improvised ways. If you use choose to use these filters with our neonatal invasive ventilation circuits, consider that resistance to flow and filter volume may affect ventilator performance.
F&P Evaqua 2 circuits (RT380, RT280, RT285, RT385, RT481) are designed so that exhaled humidity diffuses through the wall of the expiratory limb. This diffusion results in considerably less humidity reaching the expiratory filter, keeping it drier and ensuring high filtration efficiency. The RT019 and RT020 filters have also been designed with a double wall to provide additional insulation aimed at reducing condensation formation within them.
The filter media itself is also made from hydrophobic material to reduce the absorption of water.
No. F&P Evaqua 2 incorporates technology that allows water vapor to diffuse through the material of the expiratory limb. To verify that viruses and bacteria cannot permeate or diffuse through the material, F&P commissioned an independent external laboratory to test the circuits. They found that even incredibly small viruses particles (0.027 µm) cannot permeate through the material of the circuit wall. This test method utilized an organism that represents the smallest known viruses; tinier than any known pathogen.
The placement of a filter on the expiratory limb of the bubble CPAP system is not advised. F&P Healthcare recommends extreme caution when using filters in unapproved or improvised ways. Resistance to flow, filtration efficiency in different conditions, instrumental dead-space, flow dynamics through the system, and the potential for gas-trapping are just some of the important safety factors healthcare professionals should consider.
The placement of a filter between the T-piece and resuscitation mask is not advised. F&P Healthcare recommends extreme caution when using filters in unapproved or improvised ways. Resistance to flow, filter efficacy in different conditions, instrumental dead-space, flow dynamics through the system, and the potential for gas-trapping are just some of the important safety factors healthcare professionals should consider.
F&P has tested filtration efficiency and resistance to flow in accordance with BS EN ISO 23328‑1 under the conditions it will be used. We make recommendations for replacing the filter based on these results. F&P have not tested filtration efficiency and resistance to flow of other manufacturers filters. As such, we can make no recommendations regarding other manufacturers filters on F&P adult, pediatric or neonatal circuits.
If using a filter from another manufacturer, please consider the following:
No. If a HEPA filter is required, consider the impact on resistance to flow in addition to filtration efficiency.
No. When we conducted our viral filtration efficiency testing we used a ΦX174 bacteriophage virus particle. This is commonly used in testing as it is very small and mimics pathogens of clinical significance. ΦX174 bacteriophage is 0.027 µm and the SARS‑CoV‑2 is over twice the size at 0.06‑0.14 µm.
The above Frequently Asked Questions (FAQs) are based on our currently available knowledge as of the date of publication.
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