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Electrostatic Filters
Electrostatic filters use a a medium constructed of permanently bipolar charged rectangular split fibres which are able to capture airborne particles. The nature of this fibre material provides good strength and guarantees a long service life without significant degradation.
This type of filter is recommended for applications where high efficiency and low pressure drop is required. It offers excellent efficiency for anaesthetic breathing filters and pulmonary function filters.
Mechanical Filters
Pleated paper filters use tightly packed layers of mixed strands of glass fibre filter paper. This non-uniform method of packing produces a thick layer of material. Particles are trapped in the tortuous path created by the crisscross mat. In principle, the medium used acts as a sieve, holding back unwanted particles while allowing anaesthetic gases and humidified air to travel through with minimum obstruction.
Electrostatic filters use a a medium constructed of permanently bipolar charged rectangular split fibres which are able to capture airborne particles. The nature of this fibre material provides good strength and guarantees a long service life without significant degradation.
This type of filter is recommended for applications where high efficiency and low pressure drop is required. It offers excellent efficiency for anaesthetic breathing filters and pulmonary function filters.
Mechanical Filters
Pleated paper filters use tightly packed layers of mixed strands of glass fibre filter paper. This non-uniform method of packing produces a thick layer of material. Particles are trapped in the tortuous path created by the crisscross mat. In principle, the medium used acts as a sieve, holding back unwanted particles while allowing anaesthetic gases and humidified air to travel through with minimum obstruction.
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Filtration Principles
Efficiency Testing
The effectiveness of a filter is stated as a percentage (%) efficiency and is defined as:
The effectiveness of a filter is stated as a percentage (%) efficiency and is defined as:
cfu or pfu collected without BSF in place - cfu or pfu with BSF in place x100
cfu or pfu without BSF in place
cfu = colony forming units, pfu = plaque forming units, BSF = breathing system filter
cfu or pfu without BSF in place
cfu = colony forming units, pfu = plaque forming units, BSF = breathing system filter
Efficiency is measured by microbial penetration value which is defined as the number of colony forming units or plaque forming units passing through the filter per 10,000,000 challenge micro-organisms.
To test a filter for bacterial efficiency the filter is subjected to a pre-conditioning of 24 hours under relative humidity of 96% or more and temperature of 34° ± 1 at a tidal volume of 500ml at 20 breaths per minute with I/E ratio of 1:2. Following this pre-conditioning the filters are challenged with microbial aerosols using the Henderson Apparatus to deliver a challenge of over 10,000,000 Bacillus Subtillis Var.Niger Spores (NCTC10073). For viral efficiency a RNA-Phage (MS-2 Coliphage) which is similar to the smallest human viruses is to be used to test the efficiency of the filter. The test results certify the proven high efficiency of Venticaire filters.
To test a filter for bacterial efficiency the filter is subjected to a pre-conditioning of 24 hours under relative humidity of 96% or more and temperature of 34° ± 1 at a tidal volume of 500ml at 20 breaths per minute with I/E ratio of 1:2. Following this pre-conditioning the filters are challenged with microbial aerosols using the Henderson Apparatus to deliver a challenge of over 10,000,000 Bacillus Subtillis Var.Niger Spores (NCTC10073). For viral efficiency a RNA-Phage (MS-2 Coliphage) which is similar to the smallest human viruses is to be used to test the efficiency of the filter. The test results certify the proven high efficiency of Venticaire filters.
The efficiency of the Venticaire filter is tested by the Centre for Applied Microbiology and Research at Porton Down, Salisbury, UK. Testing was done for bacterial and viral efficiency using Bacillus Subtillis and MS-2 Coliphage.
The diagrams below highlight the size of test particles used in evaluating the efficiency of the Venticaire Filter.
Independent tests confirm that the Venticaire® range of breathing filters prevent bacteria and viruses from passing between patients and ventilator equipment.
Dead Space
This is the internal air filled volume of the filter or HMEF. Dead Space contributes to the compliance of the breathing system as filters are placed between breathing systems and the patient.
Moisture Output
This may be an important requirement for some patients who are being intubated over a long period of time. The unfortunate consequence of intubation is that the upper airway is bypassed and results in a loss of humidification of inspired air. Dry gases can have adverse effects and thus to prevent causing the patient trauma HMEF's play the role of acting as the humidifier in lieu of the upper airway.
However, humidification can cause rain-out in either direction. Venticaire® Filter medium has a double sided hydrophobic membrane which repels water and helps to maintain effective performance of the filter during its use.
Dead Space
This is the internal air filled volume of the filter or HMEF. Dead Space contributes to the compliance of the breathing system as filters are placed between breathing systems and the patient.
Moisture Output
This may be an important requirement for some patients who are being intubated over a long period of time. The unfortunate consequence of intubation is that the upper airway is bypassed and results in a loss of humidification of inspired air. Dry gases can have adverse effects and thus to prevent causing the patient trauma HMEF's play the role of acting as the humidifier in lieu of the upper airway.
However, humidification can cause rain-out in either direction. Venticaire® Filter medium has a double sided hydrophobic membrane which repels water and helps to maintain effective performance of the filter during its use.