FI110236B - Heat and moisture exchange filters - Google Patents

Description

This invention relates to heat and moisture retaining filters.

5 In humans, the nasal cavities and the upper respiratory tract protect the inhaled air. In addition, in most climates, the inhaled air contains some of the water vapor, and as it passes into the lungs, the inhaled air is completely saturated with moisture from the mucus secreted by the mucosa cells in the respiratory tract. In certain medical procedures, and also in the air supplied to confined spaces such as aircraft interiors, the humidity content of the inhaled air may be sub-optimal for satisfactory breathing.

For example, in procedures such as intuition or tracheostomy, these upper airways are bypassed, and thus the gases from the respirator used in these procedures are not subject to filtration and impregnation activities. Clinical inhalation of • unfiltered and unsaturated gases. · The consequences are well documented. See for example

Lloyd and Roe's article "Filtration and Humidification" (Problems in Respiratory Care 4, No. 4 (October-December, 1991). Reference should also be made to Ballard, Cheeseman, Ripiner and Wells, "Humidification for Vitalized Patients" (Intensive and Critical Care Nursing 8: 2-9 (1992)).

To overcome this problem, the breathing apparatus 30 is normally provided with a device which both filters out the exhaled air and warms and humidifies the inhaled gases. Such instruments are discussed in the two publications mentioned above and in Hodley and Allt-Graham's article "A Comparison of the Filtration 35 Properties of Heat and Moisture Exhangers" [Anaesthesia 47 I * * 2 110236 (1992) 414-420] and Berryn and Nolten in the article "An

An Alternative Strategy for Infection Control of Anesthesia Breathing Circuits: A Laboratory Assessment of the Pall HME Filter "(Anesth. Analg. 72: 651-655 (1991)).

5 According to Lloyd and Roe, three groups of heat and moisture exchange filters are known. The first group is called "hygroscopic (first generation)" heat and moisture exchange filters. They contain wool, foam or paper-like materials, which are usually impregnated with hygroscopic chemicals, such as lithium chloride or calcium chloride, to chemically absorb water vapor molecules in the exhaled air. The second group is called "hygroscopic (second generation)" heat and moisture exchange filters. They are similar to first generation filters, but with the addition of electrodeposited filter material. Electrodes are materials that are permanently electrically polarized and form an electric field around them without an external electric field. Such materials eliminate microorganisms ·;> *: through electrostatic interaction. One example . They are disclosed in EP-A1 0 011 847.

EP-A2 0 265 163 discloses a hydrophobic filter material layer and a hydrophilic foam layer. 25 using it in a case. These layers are formed by bonding \; flat tower, contacting ** panels. The hydrophobic layer consists of polypropylene fibers electrostatically charged to carry out the filtration of viruses and bacteria and acts as an electret of the second set of filters described above. The foam layer is treated to absorb moisture. It serves as a material similar to the arrangement of EP-A1 0 011 847 with the resulting disadvantages.

4 ·

The third group employs a hydrophobic membrane, '··' 35, which removes microorganisms through a pure filtration effect 3 110236 and retains moisture on the membrane surface due to hydrophobicity.

All three groups of filters work broadly in the same way. During exhalation, the inhaled water vapor condenses on the filter, and inhaled inhaled gases collect water vapor (and heat) from the device by evaporation. Microorganisms such as bacteria and viruses are removed from the exhaled and inhaled air by filters in the corresponding passageways 10.

The first group of filters are currently of limited use. They have a poor ability to remove bacteria in the air, even when impregnated with bactericidal agents. In addition, due to their mode of operation, they do not immediately achieve maximum-15 heat and moisture exchange power and have a relatively long adaptation time before reaching the static level. In addition, their pores are relatively large and relatively thick, allowing liquids to penetrate the pores and pass through the material, leading to a water-occluded state and consequently an increase in resistance.

. The second group of filters provide an improved level of filtration of microorganisms compared to the first generation hygroscopic filters. However, there is still. There is also the problem of contaminated fluids; the passage of roads through the layers due to the relatively large pore size. As described in Lloyd and Roe's article, the filtering power may not reach the 99.9977% suggested minimum for a clinical filter filter removal power of 30.

In a third group of filters using hydrophobic membranes, the pores are extremely small and typically have a bubble point when moistened with alcohol of more than 710 mm H 2 O (28 in H 2 O). Bubble score is measured by the ··· 35 American Society of Testing Materials. They 4,110,236 prevent the passage of contaminated fluids under conventional ventilation pressures. These filters also act as a barrier to microorganisms in the water and allow power levels above 99.9977% to be achieved.

In many cases, hydrophobic membrane filters have been shown to provide heat and moisture exchange comparable to normal nasal breathing. The optimal wetting effect is evident almost immediately.

The exhaled air contains not only water in the form of water droplets and spherical particles but also water in the form of water vapor. It is possible that such water vapor will pass through the filter and disappear into the system. This means that not all exhaled water is available for humidification when inhaled. 15 This is usually not a problem. As described in the technical report entitled "Use of the Pall Heat and Moisture Exhange Filter (HMEF) with Cold Humidification" (Belkowski and Brandheim, Pall Technical Publication PCC19210M, Pall Corporation 1992), a small number of long-term patients stronger wetting than the heat of the third group. , · Can provide a moisture change filter. This technical report suggests that this problem can be overcome by incorporating a humidifier into the respiratory circuit. One, 25 alternative attempts to overcome this problem is to combine the hydrophobic material with the hygroscopic material used in the first and second group of devices to absorb water.

GB-A-2,167,307 discloses a heat-30 and a moisture exchange filter comprising alternating hydrophobic and hydrophilic scrubbers mounted in a housing, wherein the hydrophilic scrubbers are impregnated with hygroscopic material. They are likely to be obstructed by water.

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"F" * "" 5 110236 According to this first aspect of the invention there is provided a heat and remove moisture exchange filter micro-organisms, which comprises a housing having a first part of the coupling to make a respirable not-5 of the gas supply and exhalation line and the other part to make the coupling of gas in and exhaled, and the housing comprising hydrophilic sheet material and hydrophobic filter material of the sheet arranged in series on a flow path between the first and second portions, wherein the hydrophilic material is closer to the first portion of said flow path and hydrophobic material has an alcohol bubble point

In all three sets of filters, it is necessary that the filtering materials do not cause such a significant pressure drop that it would make it difficult to breathe in and out of the air. This is generally not a problem for first and second group filters because the pore size of the filter materials is so large that they do not produce sufficient pressure drop to cause problems. However, the third group: 'filters may suffer from this problem.

The filter material sheets are preferably pleated. This increases the surface area of the materials and thus reduces pressure loss.

I '·'; According to a second side 25 of the present invention there is provided a method of heat and the preparation of the moisture exchange of the filter, which takes sheet of hydrophobic material having an alcohol bubble point of greater than 710 mm H20 (28 inH20) and having two opposite faces, into disk-tetrahydro-30 hydrophilic material having two opposite surface, "· * · and attaching one surface of the hydrophobic material to another surface of the hydrophobic material.

The following describes this in more detail: ···. some embodiments of the invention, by way of examples, with reference to the accompanying drawings in which 6,110,236

Figure 1 is a schematic side view of a heat and moisture exchange filter formed of pleated filter materials, Figure 2 is a schematic view of a first structure of hydrophilic material of the filter 5 of Figure 1 and Figure 3 is a schematic view of a second structure of hydrophilic material of the filter 1.

Figure 4 is a schematic diagram of an artificial patient for use in testing the heat and moisture exchange power of the filter 10, Figure 5 shows an artificial patient of Figure 4 connected to a ventilator in a first pre-test configuration and Figure 6 illustrates an artificial patient of

Fig. 7 is a diagram of a device used to determine filter power by aerosol exposure.

According to Figure 1, the filter comprises a sheet of hydro-20 phobic material 10 folded together with a sheet of hydrophilic material 11. The two layers may be separate or bonded to each other by laminating or bonding them in any suitable manner. The materials are enclosed in a housing 12 having two ports 13 and 14, which lead to the opposite sides of the materials, respectively. As can be seen in Figures 1 and 6, the pleated materials fill the housing 12 so that the pleats are on one side of the materials very close to one of the gates 13 and the matte, 30 on the other side of the plies very close to the other gate | 14.

! The hydrophobic material 10 preferably consists of: resin-bonded ceramic fibers and removes microorganisms directly by mechanical capture, and so on. 35 has a bubble point moistened with alcohol greater than 710 ramH2O 7 110236 (28 inH2O). It is measured using the method of the American Society of Testing Materials to perform such a test. The hydrophilic material is preferably a cellulosic material. No particles should be removed from the material.

Preferably, the filter has a pressure drop of no more than 3.0 cmH 2 O at a flow rate of 60 rpm and has an aerosol removal rate of bacteria, as measured by the aerosol challenge test described below, of> 99.999%.

As shown in Figure 2, the hydrophilic material 10 may be a continuous sheet of material. However, as shown in Figure 3, it could be discontinuous, with a series of parallel rows of spaced apart slits formed through the material. When used, the slots ensure that the hydrophobic material controls 15 maximum pressure drops between opposite sides of the device. The slits allow flow through the hydrophilic material if it were to "get wet" (i.e.

. get tired of water).

The device is used in intensive care units in the "patient head", which is primarily used for open breathing systems such as 20. Such systems are used for a long time by patients and patients in respiratory care who, due to the nature of their clinical condition, require additional wetting during ventilation.

Such systems include a respirator, a hose that connects the respirator to a port on the device 11 on the hydrophilic material, and a hose that connects the other port on the side of the hydrophobic material to a patient inhaling and exiting gas from the respirator. The system is equipped with a vent brick system that allows the exhaled air to escape through the exhalation line after passing through the device.

· '· The hydrophobic material 10, when in use, does not dampen • • 35 the patient's fluids and provides low resistance to 8 110236 airflow and also high micro-organism removal through mechanical capture.

The hydrophilic material 11 functions as follows. Due to its hydrophilic nature, the hydrophilic material binds water which passes almost completely through the hydrophobic material in the form of water vapor. This moisture is then spread over the entire surface area of the hydrophilic material 11. The inhaled gases thus first pass through the hydrophilic material 11, where they receive this moisture before the additional moisture is removed from the hydrophobic material in the normal manner. This has the advantage of raising the humidification level and avoiding the need for an additional humidifier.

In addition, one additional problem with the hydrophobic material 15 is avoided. This problem is that since water does not spread evenly on the hydrophobic material, there may be areas in the material that are not covered by water. They can form the primary pathway for inhaled gases through the hydrophobic material, with very little or no wetting. Because moisture is evenly distributed throughout the hydrophilic material, this problem is compensated.

The ability of the filter to become clogged because hydrophilic material is thoroughly wetted, i.e. i * 25 saturated with water, is avoided by selecting a cellulosic material of appropriate pore size and thickness so as to have a sufficiently low bubble point pressure to allow excess water to escape during gas flow. For example, Pali Corpration is available in cellulose. . 30 materials having an alcohol bubble point of 64 to 114 mm H 2 O (2.5 to 4.5 in H 2 O). It is measured by the American Society of * ·; , Testing Materials.

Joining the layers together, if done, facilitates the folding of the layers so that the layers are not separated. 35 lines form water collecting gaps. In addition, bonding 9 110236 is advantageous to reduce or prevent wetting of the hydrophilic layer 11.

The fact that the materials 10 and 11 fill the housing 12 minimizes dead space in the housing 12. This is advantageous because it minimizes the volume of gas to be breathed again.

The following describes the tests performed on the apparatus described above with reference to the drawings, in comparison with the two commercially available filter data (2A and 2B, respectively) belonging to the second group described in the preamble of this specification, two filters belonging to the third group. (3A and 3B, respectively) and two third-order filters with added hygro-15 scopic material to retain moisture (M3A and M3B).

An exemplary filter of the invention was formed as described above and had an area of about 640 to 650 cm 2.

The exemplary filter of the invention had a hydrophobic (1) material consisting of pre-mixed ceramic fibers bonded to a suitable destabilized resin, and had a · · · · · · · · · · · · · · · · The 25% was 10% by weight of the fiber The bound fibers were then hydrophobic made by any of the methods known in the art.

The hydrophilic material of the exemplary filter of the invention consisted of binder-bound cellulose fibers and had the following composition and the following »· | features:

| I

. Fibers: 100% Hemp <»· y Binder: Viscose" Loss of pressure: 74 mmH 2 O (2.0 in H 2 O). 35 Tensile strength: 92 to 115 kg / mm (8 to 10 lb / in) t 1 · 2 * 10 110236

Thickness: 0.081 mm (3.2 x 10.3 in)

Tensile strength wetted with oil: 103 kg / mm (8.9 lb / in) Tensile strength wetted with water: 44 kg / mm (3.8 lb / in) Breaking strength (Muller test): 3,520 - 4,400 kg / mm 2 (12 - 5 15 lb / in2).

All filtration was tested for water loss, bacterial removal, and viral removal using the tests described below.

Water Loss Test 10 This test is described with reference to Figures 4-6.

The artificial patient shown in Fig. 4 comprises a humidifier 20 capable of supplying exhaled air having a predetermined moisture content and temperature. The first outlet 21 of the humidifier is connected to a rubber lung 15 22 having a capacity of 21 liters and to the connecting tube 23 via a non-return valve which prevents flow from the outlet 21. connecting tube 23 and allowing flow in the opposite direction.

The second outlet 25 of the humidifier 20 is connected to the T-yh-20 nozzle 26 via a non-return valve 27 which allows flow from the second outlet 25 to the T-connector; and block the flow in the opposite direction.

. ·. The T-connector 26 is connected to one end of the connecting tube 23 by a third non-return valve 28, which may1. 25 lists the flow from the T-connector 26 to the connecting hose 23 and blocks flow in the opposite direction.

The humidifier 20 includes a temperature regulator 29 that controls the temperature of the air leaving the humidifier 20.

In use, the humidifier 20 is filled with distilled water. Thus, the outlet 30 leading to the T-piece 26 is connected * ·: ·) to the socket 31 of the Y-piece 32 as shown in Figure 5, the second leg 33 of the Y-piece is connected to the inlet of the tubing 34 and the Y-piece the second leg 36 of the piece 32 is connected by a hose 37 to the body; 35 output device 35.

11 110236

The ventilator supplies breathable gases in pulses, the volume and frequency of which can be controlled. The volume injected during the pulse is called the "respiratory volume" and the unit of frequency is "respiratory rate 5 rpm".

When testing the heat and humidity exchange power, the respiratory volume of the ventilator 35 is adjusted to a known value, for example 660 ml, and the frequency is adjusted to a known value, for example 15 breaths / min. Each volume of air supplied by the breathing apparatus 35 passes through a hose 37 to a T-connector 26. Thanks to the non-return valves 24, 27 and 28, this gas circulates through the connecting hose 23 to the rubber lung 22 which expands when it receives air. When the air pulse stops, the rubber lung 22 expels air which, through the non-return valve 15, passes through the humidifier 20 and exits the second outlet 25 and the T-piece 26 to return to the inlet of the ventilator 35 via the hose 34.

The T-connector 26 is insulated to prevent condensation 20.

: The system is operated for 30 minutes to allow it to: warm the artificial patient to a temperature that is. . ·. set to 30 or 34 ° C. Breathing Apparatus 35 and Artificial ·. ; its patient temperature regulator 39 is turned off. 25 After 30 minutes.

! Next, the hose 34 is removed from the first leg 33 of the Y-connector 32 and replaced with a hose having a housing 38 containing 100 g of desiccant. The housing 38 is thus connected to the first jaw 33 of the Y-connector 32 and to the inlet of the respirator 35.

In addition, a heat and humidity exchange filter 39 to be tested is placed in a hose between outlet 30 and socket 31 of Y-connector 32.

Next, the artificial patient and the 12,102,236 components between the 35 T-piece 26 and the ventilator are weighed. This includes a housing 38 with its contents and a filter 39. The masses are recorded to one decimal place.

The respirator 35 and the artificial 5 patient are then turned on for an hour. Unless the ambient air temperature is controlled during this period, the exhalation line temperature (i.e., the temperature in hose 37) will be recorded at regular intervals. It should be about 20 ° C and should not exceed 23 ° C. If the temperature rises above 10 to 23 ° C, ice or chilled water should be added around the hose to lower the temperature.

After one hour, the ventilator 35 and the temperature controller 29 are turned off. The components weighed above shall be reweighed and their weights recorded to one decimal place.

The water loss is then calculated from the following equation: TV · f · t G = - 20 1000 where G = gas flow (1 / min); TV = Respiratory Volume (ml), 25 f = Respiratory Rate (breath per minute); t = test duration (min).

In addition, calculate the percentage area of the circuit from the equation: 30,100 · (Wi - wf) · / ·, · 'E = -

Wi where '···' 35 E = power 13 110236. w ± = mass of test circuit before test (g) wf = mass of test circuit after test (g) wx = mass loss of artificial patient (g).

This result should not exceed 10%; if it is more than 5 10%, the test is invalid and should be retried.

Finally, the patient's water loss is calculated from the following equation: W1 10 PL = -

G

where PL = water loss of patient (mg water / 1 air) and 15 W! and G are as defined above.

Aerosolialtistustesti

The apparatus comprises a nebulizer 50 similar to the device sold by DeVilbiss as a Model 40. The nebulizer inlet is connected to the ambient air via a filter 51 and a control valve 20. The outlet of the nebulizer 50 is connected to the inlet of the filter 53 being tested by means of a hose 54. The hose should also be vented from a second inlet; : '· Via the air flow meter 55, the control valve 56 and the protective filter 57.

; ·, · 25 The output of the filter 53 to be tested is switched to under! to a pressure source (not shown) through a protective filter 58 and a pressure gauge 59. The outlet is also connected to a liquid collision probe 60 having a valve-controlled outlet 61.

The first step in use is the preparation of a bacterial suspension; This is done by incubating 100 ml of tryptone soybean broth with a single swab taken from the surface of the tryptone soybean agar. This culture is incubated overnight in a shaking water bath at 30 ± 2 ° C to ensure optimal growth.

14 110236

Next, centrifuge two 5 ml aliquots of the overnight culture (10 minutes at approximately 2300 G). The supernatant is discarded and the cell pellets are resuspended in 3 ml of sterile water. Washed cells are then resuspended by centrifugation for 10 minutes at approximately 2300 G. The washed cell pellets are then resuspended in sterile water to give a cell suspension of about 1 x 10 8 bacteria / ml.

10 Gram staining is then performed. The preparation is examined with a composite microscope equipped with a calibrated eyepiece micrometer and an oil immersion objective lens (x100). From a few fields of the microscope, the size of the organism and the organization of cells are examined. The pseudomonas dimi-15 nut should be a gram-negative small rod-shaped organism with dimensions of about 0.3-0.4 pm times 0.6-1.0 pm and which is predominantly single cells.

Next, the equipment is checked for flow rate 20. This check removes the filter 53 being tested and replaces it with a flow meter (not shown). Su-:; the mutant 50 is filled with 5 ml of sterile water and the collision probe 60 is filled with 20 ml of sterile water. The control valve 52 leading to the nozzle 50 is closed and the control valve 56 leading to the flow meter 55 is opened, a negative pressure is drawn and air is drawn into the system for 30 seconds. At a vacuum of at least 0.5 bar, the air flow rate, which is controlled by the critical orifice of the collision probe, should be 28 rpm.

The nebulizer 50 is then activated by fully opening | The associated control valve 52. At the same time, the control valve 56 leading to the air flow meter 55 is closed. ·; · To partially maintain the airflow through the apparatus at 28 rpm. The flow nozzle through the control valve 56 leading to the air flow meter 55 is registered »* i · * • · * 15 110236 of the present invention. meter. The equipment is operated for 20 minutes to ensure that the air flow rate of 28 rpm is maintained.

The operation of the equipment is then checked for Pseudomo-5 nas dimlnuta recovery. To do this, the filter 53 of Figure 7 is removed and replaced with a six-stage Anderson sampler. A glass petri dish accompanying the probe is filled with tryptone agar at each step. Air sample 10 enters the inlet of the probe and passes through successive orifices as the velocity at the orifice increases from one aperture to the next, from step 1 to step 6. At each stage, smaller particles than the preceding step are struck on the agar collecting surfaces.

Next, 1 ml of Pseudomonas dlminuta suspension with a cell density of about 1 * 108 / ml is diluted to 1 * 104 / ml with sterile water. The nebulizer 50 is filled with 5 ml of this suspension.

Vacuum is drawn into the device when control valve 56 20 is open and control valve 52 is closed and air is drawn into the apparatus for 30 seconds. With a vacuum of not less than 0.5 bar the critical orifice of the impact probe; regulated airflow is 28 rpm.

Next, the atomiser 50 is actuated by fully opening the associated control valve 52. At the same time, ·, · the control valve 56 is partially closed by a flow rate check test in a predetermined manner. Thus, additional air is introduced into the apparatus and air flow through the apparatus is maintained at 28 rpm. After 30 minutes of the test, valve 52 is closed and valve 56 is fully opened. After allowing the air to flow for another 30 seconds to purge the system from the aerosol, the vacuum source will be turned off.

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The agar harvest plates are then removed from the Anderson sample tray and incubated at 30 ± 2 ° C.

• * ft »I * 16 110236

Colonization units (cfu) are counted after 24 and 48 hours.

The apparatus will function properly if Pseudomonas dlminuta is recovered in steps 6 or 5 of the Anderson probe 5, confirming that the apparatus produces monodispersed organisms.

Following these verification tests, the equipment is used to test the power of the filters as follows.

The filter 53 to be tested is inserted into the apparatus as shown in FIG. 7. Liquid sampler 60 is charged with 20 ml of sterile water and filled with 5 ml of Pseudomonas dlminuta suspension having a cell density of about 1 x 10 8 / ml.

Next, the control valve 56 is opened and 15 closed. control valve 52. The system is vacuumed and sucked for 30 seconds. At a vacuum of at least 0.5 bar, the air flow rate controlled by the critical orifice of the impact probe 60 is 28 rpm. The nebulizer 50 is then actuated by fully opening the associated control valve 20 and partially closing the control valve 56 as defined in the control test '·' so that the air flow is maintained at 28 rpm.

: After 15 minutes of test, valve 52 will close: * ·, and valve 56 will be fully opened. After allowing air to flow for Γ. · 25 seconds to purge the system, from V aerosol, the vacuum source is turned off.

* #

The fluid remaining in the nebulizer 50 is then aspirated using a 5 ml syringe and needle. The remaining volume is measured with a 10 ml volumetric flask and the dilution series is prepared by diluting the solution 7 times with water to 10 times the volume. Dilutions containing about 102 bacteria / ml are then filtered through a 0.2 µm assay membrane (Sterifils). The assay membranes are then placed on tryptone agar plates incubated at 30 ± 2 ° C. After 24 and 48 hours, the colony forming units are counted and the number of colonies 17,102,236 recorded on membranes having 20 to 200 colonies. The nebulizer challenge titer is then calculated.

The liquid in the collision probe is then also aspirated. The volume is measured on a 20 ml volumetric flask and a dilution series of 5 liquids is prepared by sequential dilution 7 times with water to 10 times the volume. The remaining undiluted solution and the dilutions prepared are filtered through a 0.2 µm assay membrane (Steri-fils). The assay membranes are then placed on tryptone agar plates and checked for collision probe opening obstruction. The agar plates are then incubated at 30 ± 2 ° C. Colony forming units are counted after 24 and 48 hours and the number of colonies recorded on membranes with 20 to 200 colonies, 15 and the number of bacteria recovered after the filter is counted. The hardware power is calculated from the following equation:

Bt · 100 20 Re = -

Tf - Vn. k; where

Re = assembly power (%) 25 Bt = total number of bacteria recovered,>, Tf = final titer of spray solution (cfu / ml)

Vn = volume sprayed.

The bacterial exposure to the filter is then calculated from the following equation: 30: Λ C = Vn · Re · nt + i, *: * where C = total exposure 35 Vn and Re are as defined above and t i

Nt = nebulizer challenge titer (cfu / ml).

t t «18 110236

Next, calculate the decrease in titer in the filter from the following equation:

C

5 TR = -

Bt where TR = filter titer reduction and 10 C and Bt are as defined above.

From this, the filter power percentage can be calculated using the following equation:

Filter Power = (1 - 1 / TR) ♦ 100 15

The water loss is calculated as described above. Breath volume was 660 ml, frequency 15 breaths / min, and artificial patient exhaled air temperature 32 ° C.

The bacterial killing efficiency was tested by the above aerosol challenge test using Pseudomonas dimin. The viral killing efficiency was tested by the aerosol challenge test described above using M52 bacteriophage.

'·: The test results are shown in Table 1.

25

table 1

Filter Water Loss Removal Power Type (mg / 1) Bacteria (%) Viruses (%) 30 2A 10.1 99.9976 99.999 ·. "I 2B 5.3 99.91 no data 3A 8.9 99.9992 (alleged) 99.999 . ·! ' 3B 10.4 99.999 99.999: .. M3A 4.2 99.95 99.1 35 M3B 7.0 99.981 no data available

Invention 8.4 ± 0.4 (n = 18) 99.999 99.999 19 110236

It should be noted that the filters in the second group had either a high water loss and a relatively high drainage power (2A) or a much lower water loss but a correspondingly weaker drainage power (2B) The third group of filters had a much higher drainage capacity, but the water losses were relatively high. The modified third group filters had much less water loss due to the presence of hygroscopic material 10, but the removal efficiencies were relatively lower. Instead, the filter described above with reference to the figures has high power and relatively low water loss (less than 8.5 mg / L).

The filter described above with reference to Figure 1, which gave the test results shown in Table 1, was also included in the respirator in a clinical trial and compared with the commercially available filter shown in Table 2. The filters were tested under two conditions (A and B); The baseline water loss for 24 hours is shown in Table 2. At condition A, the respiratory volume was 480 ml, the respiratory rate was 15 breaths / min, and the exhaled air temperature was 32.4 ± 1.0 ° C. At Condition B, the respiratory volume was 780 ml, the respiratory rate: 15 breaths / min, and the exhaled air temperature was 25.3.2 + 1.0 ° C.

Table 2

Filter type Water loss (mg H2O / 1 air)

Conditions A Conditions B

30___ 0 ·: 3A 7.2 ± 1.1 (n = 12) 12.1 ± 1.2 (n = 12): - Invention 5.3 ± 1.0 (n = 12) 8.8 ± 1, 2 (n = 12)

It should be noted that under both operating conditions, the filter described above with reference to the drawings had a ·, · 'much lower water loss.

110236 20 This reduced water loss is maintained over a wide range of operating conditions. Table 3 gives the water loss measured under different operating conditions of the ventilator. It will be observed that the water loss does not vary significantly (7 -5 to 10 mg / L) over a wide range of minute volume (respiratory volume1 inhalation rate) at constant temperature (32 ° C).

In the examples above, certain materials have been used. However, it will be appreciated that other suitable hydrophobic and hydrophilic materials may be used in filters such as those described above.

While the above examples relate to medical use, the combination of hydrophilic and hydrophobic materials can be used in other systems that filter inhalation and exhalation air and have problems requiring the use of a heat and humidity filter. For example, air in the cabin and cockpit of an aircraft is fed through a filter and may not be suitable for temperature and humidity. By using a filter such as the one described above, air of a suitable temperature and humidity can be provided to the cabin of the aircraft and; directions.

Table 3; · 25 Breathing Volume (ml) 480 660 800 1000 660 660 • Frequency (min11) 15 15 15 10 15 15 I:; Temperature (-C) 32 32 32 32 30 34

Minute volume (rpm) 7.2 9.9 12.0 10.0 9.9

Water loss 30 (mg H2O / l air) 8.1 ± 0.2 8.4 ± 0.4 8.6 ± 0.8 9.4 ± 0.5 7.3 ± 0.5 10.05 (n = 5) (n = 18 ) (n = 3) (n = 4) (n = 3) (n12) t! i

Claims (20)

A heat and moisture exchange filter comprising a housing with a first portion for connection to a supply of breathable gas and an exhalation line, and a second portion for connection to a person inhaling and exhaling the gas, the housing containing a disk of hydrophilic medium. (11) and a disk of hydrophobic filter medium (10) arranged in series in a flow path between the first and second portions and the hydrophilic medium (11) is closer to the first portion of said flow path, characterized in that the hydrophobic medium (10) ) has an alcohol bubble point above 710 mm (28 turns) of H20 for the removal of microorganisms. Filter according to claim 1, characterized in that the plate of hydrophilic medium stays in contact with the plate of hydrophobic medium. 3. Filter according to claim 2, characterized in that the discs are joined together. 4. Filter according to claim 2, characterized in that the sheets are laminated together. Filter according to any one of claims 1 to 4, characterized in that the hydrophobic medium * (10) consists of resin joined ceramic fibers. Filter according to any of claims 1 to 5, characterized in that the hydrophilic medium (11) is a cellulose material. Filter according to any of claims 1 to 6,. Characterized in that the sheets of filter medium are wrinkled. 8. Filter according to claim 7, characterized in that the housing comprises a chamber bounded by a F * perimeter wall and two enclosures at opposite ends of the housing, one of the enclosures forming a part for connection to said stock. of breathable gas and said exhalation conduit and the other enclosure comprises a portion for connection to said person inhaling and exhaling the gas, respectively, and the pleated discs fill said chamber in such a way that the folds on one side of the discs are adjacent to the one part while the folds towards the other side of the disks are adjacent to the other part. Filter according to any one of claims 1 to 8, 10, characterized in that the sheet of hydrophilic medium (11) is continuous. Filter according to any one of claims 1 to 8, characterized in that the plate of hydrophilic medium (11) is provided with a plurality of parallel slots extending therethrough extending therethrough. Filter according to any of claims 1 to 10, characterized in that the filter has a pressure drop not exceeding 3.0 cm H 2 O at an air flow of 20 60 l / min. Filter according to any of claims 1 to 11, characterized in that the filter has an efficiency for removing aerosol bacteria from. > 99.999% when measured according to the aerosol load test. Filter according to any of claims 1 to 12, characterized in that the filter has a <· * water loss (as defined herein) of between 7 mg / 1 and 10 mg / 1 within a range of minute volume from 7 1 / min to 1 12 l / min at 32 ° C. 14. A respiratory circuit, characterized in that it comprises a fan, a tube such as "I I ft". the fan connects to the first portion of a filter according to any of claims 1 to 13, an exhalation line v. 1, which leads from said first portion and a tube leading to said II, use of 1 »ft in» 26 110236 a person inhaling or exhaling gas from the fan. A method of manufacturing a heat and moisture exchange filter, comprising taking a slice of hydrophobic medium (10) with two facing surfaces and taking a slice of hydrophilic medium (11) with two facing each other surfaces, characterized in that the sheet of hydrophobic medium (10) has an alcohol bubble point above 710 mm (28 turns) H2 O and of connecting a surface of the hydrophobic medium (10) j with a surface of the hydrophilic the medium (11). 16. A method according to claim 15, characterized in that the connection comprises joining. 17. A method according to claim 15, characterized in that the connection comprises lamination. 18. A method according to any one of claims 15 to 17, characterized in that the hydrophobic medium is made up of resin joined ceramic fibers and that the hydrophilic medium is a cellulose material. 20 19. A method according to any of claims 15 to 18, characterized in that the filter has a pressure drop not exceeding 3.0 cm H2 O at an air flow of:: 60 l / min. 20. A method according to any of claims 15 to 19, characterized in that the connected »'I | , V discs are folded. i »« »I t» * I i <* * • t I I I »» * »» »*