GB2598622A

GB2598622A - A respirator system

Info

Publication number: GB2598622A
Application number: GB2014003.4A
Authority: GB
Inventors: Thomas Stevenson Alec
Original assignee: Qinetiq Ltd
Current assignee: Qinetiq Ltd
Priority date: 2020-09-07
Filing date: 2020-09-07
Publication date: 2022-03-09
Also published as: GB202014003D0

Abstract

The respirator system for delivering filtered atmospheric air to a user for inhalation comprises a respirator 40, an air filter system 10 for filtering and drawing air from the atmosphere and a reservoir 30 for storing filtered air. The air filter system is arranged in fluid communication with the reservoir and the respirator such that when the user’s inspiratory flow rate is lower than the base flow rate of the filter system at least a portion of the filtered air entering the respirator system is stored in the reservoir. When the user’s inspiratory flow rate exceeds the base flow rate of the air filter system, filtered air stored in the reservoir is drawn into the respirator for inhalation to supplement the filtered air provided by the filter system.

Description

A respirator system

Field of the Invention

The present disclosure relates to a respirator system for delivering filtered atmospheric air to a user for respiration, and to a method of delivering filtered atmospheric air.

Introduction

Respiratory protection allows users to breathe atmospheric air without inhaling any potentially harmful particles such as airborne pathogens, pollution and dust that may be present in the ambient environment. A need for highly effective respiratory protection has been of the utmost importance during the COVID-19 pandemic, particularly for frontline responders working in close proximity to individuals infected, or potentially infected, with the coronavirus disease.

Respiratory protection must provide a high level of protection to the user, by preventing them from inhaling any potentially harmful particles in the air. The degree of protection can be quantified by the 'protection factor': the number of harmful particles inside the respirator when in use, as a proportion of the number of harmful particles in the atmosphere outside the respirator.

A conventional form of respiratory protection takes the form of a negative-pressure fabric respirator that seals around a user's mouth and nose. In this form, the fabric respirator acts as a filter medium, thereby removing particles of at least a certain size -the filter allows smaller air particles to pass through to the user for inhalation, but prevents larger harmful from passing through to the user for inhalation.

High levels of respiratory protection are associated with increased breathing resistance, since the user must inhale hard to draw atmospheric air through the filter making it harder for the individual to breath in and out. Additional discomfort can be caused by heat and moisture building in the respirator (as expired air is saturated with water vapour at a temperature of between 33-37°C).

To provide a high level of respiratory protection and to overcome some of the limitations associated with high breathing resistance, high air temperature and high humidity within a respirator, Powered Air-Purifying Respirators (PAPR) have been used. PAPRs typically include a respirator, or face mask, that is arrangeable to communicate with a user's nose and mouth, or whole face, and a fan, configured to draw air from the ambient environment through a filter and into the respirator. Such systems can offer a much higher level of protection than the conventional respirators described above. Moreover, as the fan draws air through the filter, less effort is required by the wearer to breathe and the air within the mask is maintained at a lower temperature and humidity.

However, these PAPRs have some drawbacks. It will be appreciated that a user's inhalation profile is not constant. In particular, referring to Figure 1, which shows how a user's inspiratory flow rate varies with time, a user inhales intermittently, such that a user's inspiratory flow rate varies between a peak inspiratory flow rate 2 (i.e. the maximum rate at which a user inhales) and a zero inspiratory flow rate 4 (e.g. while the user is exhaling, or neither inhaling nor exhaling). To provide enough air flow to the respirator to allow the user to breathe, the fan must constantly draw air into the system at a flow rate 6 which at least matches the user's anticipated peak inspiratory flow rate 2. This puts a very high demand on the fan, which therefore requires large fans and hence a large power supply, typically in the form of bulky and expensive batteries -indeed, the batteries are typically so heavy that they usually must be attached to, and supported by, the user's waist. Such respirators can therefore be impractical and cumbersome, causing significant discomfort to the user. What is more, the batteries only a have a short battery life of a few hours, after which the battery must be recharged or replaced.

As a result of this, although PAPRs have been referred to as the 'gold-standard' in respiratory protection, they have severe limitations. As such, they are typically only used in situations where the risk of particle inhalation is very significant, for example in aerosol-generating procedures. Even in these cases, the cumbersome nature and short battery life of the devices may make them very impractical for use in some applications.

The system and method according to the present invention aims to solve at least some of

the problems associated with the prior art.

Summary of the invention

Against this background, the invention resides in a respirator system for delivering filtered atmospheric air to a user for inhalation. The respirator system comprises: a respirator through which a user can inhale filtered air at an inspiratory flow rate; an air filter system for filtering and drawing air from the atmosphere into the respirator system at a base flow rate and delivering filtered drawn air to the respirator; and a reservoir for storing filtered air. The air filter system is arranged in fluid communication with the reservoir and the respirator such that: when the user's inspiratory flow rate is lower than the base flow rate of the filter system, at least a portion of the filtered air entering the respirator system is stored in the reservoir; and when the user's inspiratory flow rate exceeds the base flow rate of the air filter system, filtered air stored in the reservoir is drawn into the respirator for inhalation to supplement the filtered air provided by the filter system.

This system allows the air filter system to run at a flow rate that is lower than a user's peak inspiratory flow rate, while still supplying adequate air to the user for peak inhalation. When the user's inspiratory rate is less than the base flow rate, surplus air drawn by the air filter unit is stored in the reservoir. Mien the inspiratory rate exceeds the base flow rate, stored air from the reservoir supplements the air drawn by the air filter system to supply sufficient air for the user's needs. The ability to run the air filter system at a low flow rate means that a relatively small power is required to power the respirator. This in turn can allow the battery to be smaller, lighter, more compact and inexpensive compared to batteries of known PAPRs.

The respirator system may be configured such that when the user's inspiratory flow rate is less than or equal to the base flow rate of the filter system, filtered air flows from the air filter system to the respirator for inhalation by the user without supplementation from the reservoir.

The respirator and air filter system may be arranged along a first airflow path, and the reservoir and the air filter system are arranged along a second airflow path, such that the air filter system is common to both airflow paths.

The first airflow path may be uni-directional from the air filter system to the respirator, and the second airflow path may be bi-directional from the air filter system to the reservoir and vice versa. The first airflow path may be uni-directional by virtue of a valve arranged along the path.

The air filter system may comprise a junction chamber that is in fluid communication with the reservoir and the respirator, and that is configured to receive the filtered air drawn into the respirator system.

In this way, both the reservoir and respirator are fluidly connected with the junction chamber. Thus, the reservoir is directly connected to the filter system, and indirectly connected to the respirator via the junction chamber. The filter system is directly connected to the reservoir and the respirator. This allows filtered air drawn by the filter system to flow to either the respirator or the reservoir, depending on the inhalation rate of the user, and allows filtered air to flow from the reservoir to the respirator via the junction chamber.

The respirator system may comprise a first conduit arranged to fluidly connect the filter system to the respirator, and a second conduit arranged to fluidly connect the filter system to the reservoir.

The first conduit may connect the air filter system directly to the respirator.

The respirator system may be configured such that when the user's inspiratory flow rate is greater than zero but lower than the base flow rate of the filter system, air drawn into the respirator system by the filter system is directed to both the respirator for inhalation and the reservoir for storage.

The respirator system may be configured such that when a user exhales, air drawn into the respirator system by the filter system may be directed only to the reservoir for storage.

The respirator system may comprise a respirator inlet through which filtered air enters the respirator, and a respirator inlet valve configured to prevent a flow of air through the respirator inlet when the user exhales into the respirator.

The respirator inlet valve may be a non-return valve. The respirator inlet valve may be configured to prevent a flow of air through the valve in either direction when the user exhales into the respirator.

The respirator inlet may comprise an opening defined in a body of the respirator. The respirator system may comprise a conduit that fluidly connects the filter system to the respirator. The conduit may meet the respirator at the opening. The inlet valve may be arranged at a junction between the conduit and the opening.

When the respirator inlet comprises an opening in a body of the respirator, the inlet valve may be arranged within or adjacent to the opening.

In such a location, the inlet valve, particularly in the form a non-relief valve, is most responsive to the inhalation and exhalation of the user. Moreover, due to this location, less exhaled breath is able to be stored in the respirator system after exhalation by the user.

The reservoir may comprise an expandable air bag.

The respirator system is preferably portable.

The respirator system may comprise a support for securing the respirator to a user's face by extension around the user's head. The respirator may be secured to a forward portion of the support and the filter system may be secured to a rearward portion of the support.

In this arrangement, in use, when the respirator is arranged over a user's mouth, the filter system will be arranged at the back of the user's head. In this location, the filter system does not obstruct the user's view. Furthermore, arranging the filter system at the rear of the head provides balance (i.e. the weight of the filter system at the rear partially offsets the weight of the respirator at the front), increasing comfort.

The support may be a strap.

The first conduit may be incorporated into the support. The second conduit may be arranged to depend downwardly from the filter system when the respirator system is arranged for use, with the reservoir arranged at the bottom of the second conduit.

In this way, when the respirator system is worn for use, the second conduit depends downwardly from the filter system at the back of user's neck, such that the reservoir lies behind the user's back in use. In this position the reservoir can be particularly easily accommodated.

The respirator may be configured to seal around the user's nose and/ or mouth area such that an air cavity is defined between the respirator and the user's face for receiving filtered air from the fan-filter system and/ or reservoir.

With this sealing arrangement, air received in the air cavity by the filter system and/or reservoir, may create a positive (i.e. above ambient) pressure in the cavity.

The seal guards against air flow from the atmosphere into the air cavity, thereby maintaining a high protection factor. To provide the seal, a periphery of the respirator is shaped to the typical contours of a face, and the periphery is formed of a flexible material to accommodate the contours precisely. Where it is provided, the support may allow the respirator to be held in position and sealed against the person's face.

The respirator may comprise a respirator outlet through which exhaled air can exit the respirator, and an outlet valve arranged in or adjacent to the respirator outlet, wherein the outlet valve is configured to permit air flow out of the respirator when the user exhales and to prevent air flow into the respirator from the atmosphere.

The outlet may also be provided with a flow regulator, for example in the form of a filter, to regulate the rate of air flow out of the respirator. This can assist in maintaining a positive pressure in the respirator by ensuring that air does not flow too quickly out of the respirator through the valve. Alternatively or additionally the outlet valve can be spring loaded such that air is released therefrom only when the pressure inside the respirator is raised to a sufficient level to offset the inherent spring force of the spring. This prevents leakage from the respirator when the user is not exhaling, thereby maintaining the positive pressure in the respirator. The spring force can be tuned to ensure that the valve will only open on exhalation.

The respirator outlet may comprise an opening in the or a body of the respirator, and the outlet valve may be arranged within or adjacent to the opening. The outlet valve may be a non-return valve.

The respirator comprises a mouth-cover region that is shaped to cover a user's mouth, and the outlet valve is preferably located on the mouth-cover region, and the inlet valve is located remote from the mouth-cover region, such that when the respirator is arranged over a user's mouth, the outlet valve is located in front of the mouth, while the inlet valve is located away from mouth. This allows exhaled breath to be removed more effectively.

The respirator system may comprise a power source, such as a battery, for powering the air filter system. The air filter system may comprise a fan powered by the power source.

The respirator system may be for use by medical and/ or non-medical personnel. In particular, the respirator system can protect a user from inhaling any pathogens (e.g. viruses) and/ or particulates (e.g. pollution and dust) that may be present in the ambient environment. Furthermore, the respirator system may be used in any setting where filtering of the ambient environment is required.

The invention also extends to a method of delivering filtered atmospheric air to a user for respiration, the method comprising: drawing air from the atmosphere into the respirator system at a base flow rate, filtering the drawn air, and delivering drawn filtered air to the user for inhalation. The method further comprise i) when a user inspiration rate is less than the base flow rate, delivering drawn filtered air to a reservoir for storage, and ii) when the user inspiration rate exceeds the base flow rate, supplementing the drawn filtered air delivered to the user with stored filtered air from the reservoir.

The method may be for delivering filtered atmospheric air to medical and/ or non-medical personnel. In particular, the method can protect users from inhaling any pathogens (e.g. viruses) and/ or particulates (e.g. pollution and dust) that may be present in the ambient environment. Furthermore, the method may be used in any industry where filtering of ambient environment is required.

The invention extends further to a respirator system configured to operate the method described above.

Features of any one aspect or embodiment of the invention may be used, alone or in appropriate combination, with other aspects and embodiments as appropriate.

Brief Description of the Drawings

Figure 1, which is a graph of inspiratory flow rate over time, has already been described above in relation to the prior art. Embodiments of the invention will now be described, by way of example only, with reference to the remainder of the accompanying drawings, in which: Figure 2 is a schematic of a respirator system according to an embodiment of the invention; Figures 3a to 3c are schematics showing the airflow in the respirator of Figure 2 in different circumstances; Figure 4 is a graph showing inspiratory flow rate overtime, and volume of a reservoir bag forming part of the respirator system of Figure 2 over the same time period; Figure 5 is a side view of another respirator system incorporating a head support; and Figure 6 is a comparative graph of the pressure in the respirator of the respirator system of Figure 2, compared to the corresponding pressure in negative pressure respirators of

the prior art.

Detailed Description of Embodiments of the Invention The invention relates to a portable respirator system 1 which delivers filtered atmospheric air to a user 100 of the respirator system 1 for inhalation. That is to say, the respirator system 1 can be used in such a way that the user 100 is prevented from breathing any unfiltered atmospheric air. In this way, should the atmospheric air, i.e. the air outside the respirator system 1, contain any harmful particles such as airborne pathogens, pollution or dust, the respirator system will filter out such particles, and deliver only the filtered air to the user.

As shown in Figure 2, the respirator system 1 comprises an air filter system, exemplified here as a fan-filter system 10, for drawing atmospheric air into the respirator system 1 and for filtering all air passing therethrough, a respirator 40 for receiving filtered air and arrangeable to communicate with a user's nose and/ or mouth (not shown) so that user can inhale the filtered air received in the respirator 40, and a reservoir 30 for storing filtered air.

To draw and filter the air, the fan-filter system 10 comprises an air drawing means, exemplified here as a fan 22, for drawing the air from the atmosphere (or ambient environment) into the respirator system 1 and a filter medium 20 for filtering the air drawn through the fan 22.

The fan 22 draws air into the respirator system 1 at a base flow rate, while the user 100 inhales air from the respirator 40 at an inspiratory flow rate. As described in the introductory section and shown in Figure 1, when a user inhales, the inspiratory flow rate is greater than zero, and while the user is exhaling, or neither inhaling nor exhaling, the inspiratory flow rate is zero. The inspiratory flow rate may vary from one inhalation cycle to another, and highest inspiratory flow rate is known as the 'peak inspiratory flow rate'.

In the respirator system described, the base flow rate of the fan 22 is lower than the peak inspiratory flow rate of the user 100.

In the systems of the prior art, where the base flow rate of the fan is set to be at least equal to the peak inspiratory flow rate of the user 100, the fan 22 is always running at or above the capacity required by the user 100. By contrast, in this system 1, the base flow rate of the fan 22 is sometimes lower than the actual inspiratory flow rate of the user 100, and is sometimes higher than the actual inspiratory flow rate of the user 100.

That is, the fan 22, on its own, does always not deliver sufficient air to the respirator 40 to allow the user 100 to inhale at the desired inspiration rate.

The respirator system 1 can accommodate the low base flow rate of the fan because of the reservoir 30 that stores filtered air from the fan-filter system 10. The respirator system 1 is configured such that when the base flow rate of the fan 22 exceeds the actual inspiratory flow rate, excess filtered air not required by the user is stored up in the reservoir 30 for later use. When the user's inspiratory flow rate exceeds the base flow rate of the fan 22, the respirator system 1 is configured such that filtered air stored in the reservoir 30 supplements the air provided by the fan 22, and is drawn into the respirator 40 for inhalation. In this way, the reservoir 30 provides the supplementary filtered air required to allow the user 100 to breathe at an inspiration rate that is greater than the base flow rate of the fan 22. As such, it can be understood that the reservoir 30 allows the fan 22 to work at a lower base flow rate.

Since, by way of the reservoir 30, the fan 22 can operate at a lower base flow rate, the power required to drive the fan 22 is reduced compared to conventional PAPRs. As a result the battery that powers the fan 22 can be smaller, lighter and less expensive and/or can power the fan for a longer period of time.

As such, by including the reservoir component 30, there is the unforeseen technical effect that the respirator system 1 can be lighter, more easily carried and used for longer, and at the same time the cost of the respirator system 1 is substantially reduced.

Of course, the skilled person will appreciate that the inspiratory flow rate of the user 100, and hence its peak, varies in dependence on the user 100 (since humans breathe at different inspiratory flow rates). For the purposes of this application therefore, the peak inspiratory flow rate of the user 100 is therefore defined as the typical peak inspiratory flow rate of an adult man. Likewise, the skilled person will appreciate that the inspiratory flow rate of the user 100 also depends on the extent to which the user 100 is exerting themselves (i.e. whether they are resting or working). The peak inspiratory flow rate of the user 100 for these purposes is therefore defined as the typical peak inspiratory flow rate of a man while resting, i.e. approximately 60 L/min, and the typical peak inspiratory flow rate of a man during light work, i.e. approximately 100-125 L/min. Other relevant values are easily sourced by the skilled person.

Considering the structure of the respirator in more detail, and referring still to Figure 2, the respirator system 1 comprises the fan-filter system 10, the reservoir 30 and the respirator 40. The fan filter system 10 is in fluid communication with the respirator 40 via one or more first conduits 44. The fan filter system 10 is also in fluid communication with the reservoir via a second conduit 34.

In this way, the fan-filter system 10 is separately and directly connected to each of the reservoir 30 and to the respirator 40. The reservoir 30 is directly connected to the fan-filter system 10, and only indirectly connected to the respirator 40 via the fan-filter system 10 (and vice versa).

The reservoir 30, the fan filter system 10 and the respirator 40 are thereby arranged along two parallel air flow paths: a first airflow path from the filter system 10 to the respirator 40 and a second airflow path from the filter system 10 to the reservoir 30. The air flow path from the filter system 10 to the respirator 40 is uni-directional, such that air flows only from the filter system 10 to the respirator 40, while the air flow path to the reservoir 30 is bidirectional, such that air flows both from the filter system 10 to the reservoir 30 and from the reservoir 30 to the filter system 10.

This allows filtered air drawn by the fan-filter system 10 to flow to the respirator 40 and/ or the reservoir 30, in dependence on the inspiration rate of the user 100, and allows filtered air to flow from the reservoir 30 to the respirator 40 via the junction chamber 18, also in dependence on the inspiration rate of the user 100 (as will be explained in detail later on).

Considering the fan-filter system 10 in more detail, to house the fan 22 and filter 20, the fan-filter system comprises a body in the form of an enclosed housing 11, having an internal housing cavity that defines a junction chamber 18. The body of the housing may be made from any suitable material, such as for example metal, wood, a plastics material or an elastomeric material.

The fan-filter system also accommodates a power source such as a battery (not shown) for powering the fan. The battery may be any suitable battery that is capable of powering a fan. For example, the battery may supply a voltage of 5V. The battery may preferably be a thin flexible battery, for example a battery of the type described in EP2534713B or W02017-207735, or a standard pouch/ cylindrical cell.

The body is provided with various openings that open into the junction chamber. A first opening is an air inlet 24, through which atmospheric air is drawn into the fan-filter system 10 via the fan and filter. A second opening is a respirator opening 14 that communicates with the first conduit 44, and hence with the respirator 40. A third opening is a reservoir opening 16 that communicates with the second conduit 34 and hence with the reservoir 30. Each of the first, second and third openings may comprise multiple apertures or sub-openings, so as to improve air flow into the housing 11.

In this example, the air inlet 24 is preferably located on a first side of the housing 11, while the reservoir opening 14 and respirator opening 16 are located on different sides of the housing 11.

The filter 20 is arranged in the fan-filter housing 11 and is configured to prevent unwanted airborne particles from entering the internal housing cavity. To this end, the filter 20 is arranged to extend across the air opening 20. In this way, no air can enter the junction chamber 18 without first passing through the filter 20. In one preferred embodiment, the filter 20 comprises a P100 filter.

The filter 20 provides a suitably large resistance to flow such that when the user's inspiratory flow rate exceeds the base flow rate of the fan 22, air is drawn from the reservoir 30 into the respirator 40 for respiration and not from the from the atmosphere and through the fan-filter system 10 into the respirator 40. The skilled person appreciates that in the exceptional circumstance that i) the user's inspiratory flow rate exceeds the base flow rate of the fan 22 and ii) insufficient air is contained within the reservoir 30 for inhalation, additional air will be drawn in from the ambient environment through the fan-filter system 10 and into the respirator 40 for inhalation, as a result of the additional pressure created by the high inspiratory rate of the user.

The fan 22 is configured to draw air from the atmosphere into the internal housing cavity through the filter 20, and into the respirator 40 and/or reservoir 30. Aside from the pressure differential in the respirator 40 caused by the user's inhalation, only the fan 22 is used to move air through the respirator system 1. The fan 22 is arranged within the internal housing cavity, preferably in or adjacent to the air inlet 12.

The base flow rate of the fan 22 is preferably constant for any given operational mode, although fans with variable base flow rates can be used also. If the base flow rate of the fan 22 varies during a single operational mode, the base flow rate is taken to be an average value of the fan's variable base flow rate.

Furthermore, the fan 22 can be configurable to work at different base flow rates in different operational modes. For example, one mode may be a resting mode with a lower base flow rate and one mode may be a moderate intensity work mode with a higher base flow rate.

In this case, the fan-filter system 10 is provided with a user input (not shown) where the user 100 can change the operational mode.

Regardless of the base flow rate, the base flow rate of the fan 22 is selected to be less than half of the user's peak inspiratory flow rate and in some embodiments less than a third of the user's peak inspiratory flow rate. For example, the base flow rate of the fan may be between approximately 15 and 35 L/min, and preferably approximately 30 L/min for a resting mode, and between approximately 40 and 70 L/min, and preferably approximately 60 L/min for moderate intensity work.

In further embodiments, a fan 22 with an even lower base flow rate may be used. Such a fan 22 may be configurable to operate at both the base flow rate and an elevated base rate during any particular operational mode. In this way, if, during inhalation, the user's inspiratory flow rate exceeds the base flow rate of the fan 22 and insufficient air is contained within the reservoir 30, the fan may be selected to operate at the elevated base rate. Thereafter, the fan 22 then operates at the base flow rate again. The elevated base rate may be selected for use in dependence on a user selection at the user input or even in dependence on a reservoir sensor sensing automatically that the reservoir is empty.

In one preferred embodiment, the fan 22 comprises a single (Delta Electronics) 5V blower (50 x 10 mm). This embodiment is particularly suitable for use during resting and low work intensity tasks. In another embodiment, the respirator may be provided with two such fans.

This embodiment is more appropriate for moderate work intensity tasks. For other uses requiring a higher flow rate, a combination of larger fans, or an additional fan exclusively designated to fill the reservoir, can be used.

Turning to the reservoir 30, the reservoir 30 is configured to store filtered air. To this end, the reservoir 30 takes the form of an expandable air bag comprising an expandable body 31 defining a variable internal volume. The reservoir 30 is made out of a flexible material such as a polymer. The maximum volume of the reservoir 30 is preferably approximately 0.5 to 2 litres, but may be larger in some embodiments. The reservoir 30 may be any suitable shape, though a generally elongate shape is preferred, having a length greater than its width.

The reservoir 30 can be adapted in size and/ or shape not only for ergonomic reasons, but so that the respiratory system 1 may better accommodate a user's particular breathing pattern On relation to both flow rates and/ or depths). Such adaptation has not been possible for prior PAPS designs where reservoirs were not included.

The reservoir 30 further comprises a reservoir opening 32 defined in the body 31 of the reservoir 30 that serves as both an inlet to and outlet from the reservoir 30. The second conduit 34 meets the reservoir 30 at the reservoir opening 32.

The respirator 40, or mask, comprises a respirator body 41 that is arrangeable to cover the user's nose and/ or mouth (not shown). The respirator body 41 generally defines a dome shape.

A periphery 48 of the respirator body 41 is shaped such that it may be arranged to lie in contact with the user's face 101b around the user's nose and/ or mouth. In other words, the periphery 48 of the respirator body 41 is shaped to the typical contours of a face 101b. The periphery and may also be formed of a flexible material to accommodate the contours precisely. As a result, the respirator body 41 can seal against the user's face when worn.

This seal can restrict against air flow from the atmosphere into the air cavity, thereby maintaining a high protection factor. Preferably, the respirator 40 seals around the user's nose and/ or mouth.

The respirator 40 further comprises a respirator inlet 42 through which filtered air from the fan-filter system 10 and reservoir 30 enters the respirator 40 and a respirator outlet 46 through which user exhaled air exists the respirator 40, and hence the respirator system 1. The respirator inlet 42 and outlet 46 each include an opening defined in the respirator body 41.

The first conduit 44 meets the respirator 40 at the respirator inlet 42 to connect the fan-filter system 10 directly to the respirator 40. A respirator inlet valve 50 is arranged at or adjacent to the respirator inlet 42, i.e. at a junction between the first conduit 44 and the inlet 42. The respirator inlet valve 50 preferably takes the form of a non-return valve. The inlet valve 50 is configured to prevent a flow of air out of the respirator through the respirator inlet 42 whenever the user 100 exhales, and to permit a flow of filtered air through the respirator inlet 42 into the respirator 40 whenever the user 100 is not exhaling into the respirator 40, (i.e. when the user 100 is inhaling or when the user 100 is neither inhaling nor exhaling).

This inlet valve 50 therefore advantageously prevents any exhaled air from being drawn back out of the respirator 40 into the reservoir 30 or fan-filter system 10, and assists in ensuring all exhaled air is expelled through the respirator outlet 46.

The position of the respirator inlet valve 50 at a junction between the first conduit 44 and the inlet 42 means that the valve 50 is as close as possible to the respirator 40. In this location, the inlet valve 50 is most responsive to the user's breathing. Moreover, this location minimises the amount of exhaled breath that is storable in the respirator system 1 for re-inhalation by the user 100.

The respirator outlet opening is preferably arranged in a mouth-cover region of the respirator body, i.e. the region of the respirator body 41 which, when the respirator 40 is arranged over the user's face 101b, lies opposite the user's mouth (not shown). Meanwhile, the respirator inlet opening is preferably arranged away from the respirator outlet opening. This arrangement allows the exhaled breath to be removed more effectively.

The respirator outlet 46 comprises a respirator outlet valve 52 arranged in or adjacent to the respirator outlet 46. The outlet valve 52 is configured to permit air flow out of the respirator 40 when the user 100 exhales into the respirator 40 and to prevent any air flow from the atmosphere directly into the respirator 40. This therefore prevents any unfiltered atmospheric air from being drawn into the respirator 40 through the respirator outlet 46, which would otherwise compromise the protection factor of the respirator system, while at the same time allowing exhaled air to be expelled from the respirator 40 as the user 100 breathes out, thereby preventing a build-up of CO2 in the respirator 40. To this end, the respirator outlet valve 52 preferably takes the form of a non-return valve that may be spring loaded to prevent the valve 52 from opening purely as a result of the low level of positive pressure that is generated by the fan.

The respirator outlet 46 may further comprise a flow regulator (not shown), for example in the form of a filter, to regulate the rate of air flow out of the respirator 40. This can assist in maintaining a positive (i.e. above ambient) pressure in the respirator 40 by ensuring that air does not flow too quickly out of the respirator 40 through the respirator outlet valve 52.

When the respirator 40 is arranged to fit around the user's nose and/ or mouth area (not shown), an air cavity is formed between the respirator 40 and the user's face 101b. Due to the operation of the fan 22 and/ or reservoir 30, a positive (i.e. above ambient) pressure is maintained within this air cavity. Such an arrangement is advantageous if the respirator 40 does not form a perfect seal around the user/s mouth and/ or nose. Due to the positive pressure in the respirator 40, filtered air is pushed out of the respirator through any openings, and this outward flow of air guards against atmospheric air from outside the respirator 40 entering the respirator, thereby preventing the user 100 from inhaling potentially harmful particles in the atmosphere.

As a result of this arrangement, the respirator 40 need not be arranged so tightly on the user 100, since the consequence of a break in the seal should not result in any harmful particles entering air cavity. As such, the respirator 40 is more comfortable to wear and can be used with ease for longer periods of time.

The flow of air around the respirator system 1 when the respirator system 1 is in use will now be described with reference to Figures 3a to 3c.

In all circumstances (Figures 3a to 3c), atmospheric air is drawn into the fan-filter system 10 by the fan 22 from outside the respirator 40 at the base flow rate. In particular, air is drawn through the filter 20 and into the junction chamber 18.

Where this filtered air then travels next depends on whether the user 100 is exhaling, or inhaling, and the user's inspiratory flow rate.

Figure 3a shows the airflow when the user 100 is inhaling with an inspiratory flow rate that is equal to the base flow rate. In this case, filtered air in the junction chamber 18 is drawn through the second conduit 34 to the respirator 40 for inhalation by the user 100. Because the user's inspiratory flow rate matches the base flow rate, all filtered air in the junction chamber 18 is drawn to the respirator 40 for inhalation.

Figure 3b shows the airflow when the user 100 exhales. Exhalation causes the respirator inlet valve 50 to close, so that filtered air in the junction chamber 18 or first conduit 44 is prevented from entering the respirator 40. With this route closed, all the filtered air drawn into the junction chamber 18 is drawn into the reservoir 30 for storage. Meanwhile, in the respirator 40, exhaled air exits the respirator through the outlet 52.

While the inlet valve 50 is closed, some air pressure may also build up behind the inlet valve 50 as the user exhales. When exhalation stops, the inlet valve 50 can open, relieving the air pressure and pushing air into the respirator 40.

Figure 3c shows the airflow when the user's inspiratory flow rate exceeds the base flow rate. This is expected to be the situation for most inhalations by the user, since the base flow rate of the fan is selected to be significantly below the peak inspiratory rate. In this case, since the airflow from the fan is insufficient to match the inspiratory of the user, the user's inhalation creates a pressure differential that draws filtered air stored in the reservoir 30 into the respirator via the junction chamber 18. In this way, the air from the reservoir supplements the air that is drawn directly from the fan filter system 10, to meet the user's inspiratory requirement.

Figure 4 is a graph showing the user's inspiratory flow rate over time, with a peak inspiratory flow rate indicated at 2, and the base flow rate of the fan indicated at 8. Also shown is the volume of the reservoir bag over the same time period.

As can be clearly seen in Figure 4, when a user inhales at a rate above the inspiratory flow rate, part of the air for inhalation is provide by the fan (block A), and part is provided by the reservoir (block B). During this time, the volume in the reservoir decreases. When the user's inspiratory flow rate drops below the base flow rate 8 of the fan, air is supplied to the reservoir 30 (block C), and the volume of the reservoir increases. If the user's inspiratory flow rate matches the base flow rate of the fan, the volume of air in the reservoir remains substantially constant.

As shown in Figure 5, the respirator system 1 is portable, and is securable to a user in such a way that it can be used handsfree, thereby allowing the user to use their hands for other purposes.

To maintain the respirator 40 in place on the user's face 101b, the respirator system 1 is provided with a support 60, preferably in the form of a strap arrangement, for securing the respirator 40 to a user's face 101b by extension around the user's head 101a below the user's ears 102. In another preferred embodiment, the strap arrangement extends around the top of the user's head 101a above the user's ears 10, thereby improving the comfort and fit of the respirator 40 on the user's face 101b.

An example arrangement is shown in Figure 5, which shows the system of Figure 2 when incorporated into a wearable respirator arrangement. In this arrangement, the support additionally comprises ear supports 62.

The respirator 40 is secured to a forward, or front, portion of the support 60, such that when the support 60 is arranged around a user's head 101a the respirator 40 is arrangeable to communicate with the user's mouth and/ or nose (not shown).

The fan-filter system 10 and its power supply (not shown) are secured to a rearward portion of the support 60. Securing the fan-filter system 10 and power supply to a support 60 that is worn on the head, rather than a support worn elsewhere on the body, is feasible in this system due to the reduction in size and weight of the power supply.

In this arrangement, when the support 60 is arranged around a user's head 101a, the fan-filter system 10 and its power supply can be supported at the back of the user's head 101a. In this arrangement, neither the fan-filter system 10 nor the power supply is able to obstruct the user's field of view or the user's actions, when the respirator system 1 is worn.

Arranging the respirator 40 at the front of the head and the fan-filter system 10 at the rear of the head provides a balanced weight, which is more comfortable for the user. At least some parts of the fan-filter system housing 11 may be made of an elastomeric material such that is conformable to and hence arrangeable on the back of the user's neck.

The first conduit 34 is incorporated into the support 60 such that, in use, when the support 60 is arranged around the user's head 101a, the first conduit 34 extends around the user's head 101a between the respirator 40 towards the front of the user's head 101a and the fan-filter system 10 towards the rear of the user's head 101a. The conduit may be incorporated into the support by attachment to the interior of the support 60, or it may be integrally formed in the support 60.

Meanwhile, the second conduit 44 is arranged to depend downwardly from the fan-filter system 10 when the respirator system 1 is arranged for use, with the reservoir 30 arranged at the bottom of the second conduit 44. Again, in this arrangement, the first conduit 34, the second conduit 44 and the reservoir 30 are all arranged away from the front of the users face, so that they do not obscure the user's field-of-view or actions when the respirator system 1 is in use. In some embodiments, particularly where the reservoir 30 is large, the reservoir is preferably contained within a small container securable either to the user's back (e.g. as a back-pack) or to the user's chest (e.g. as a chest vest). Smaller volume reservoirs 30 are instead suitable for mounting to the back of the user's head and/ or neck.

In one embodiment, the reservoir extends over the top of the user's head 101, and can optionally be secured to the support 60. In this embodiment, the second conduit 44 is arranged to extend upwardly from the fan-filter system 10.

Figure 6 is a comparative graph of the pressure drop in the respirator 30 as a function of the peak flow rate (data set A), compared to the corresponding pressure drop in a negative pressure respirator of the prior art (data sets B and C). As can be clearly seen, at all peak flow rates, the pressure drop in the respirator of the system described above is significantly lower (approximately 190% lower) than the corresponding pressure in the respirators of the prior art. A large pressure drop indicates a high resistance to breathing, and the larger the drop in pressure, the higher the resistance. Breathing resistance affects user comfort, so the lower the pressure drop the more comfortable the respirator. Moreover, larger pressure drops to more negative pressures increase the likelihood of leakage of unfiltered air into the respirator 30.

It should be note that the negative pressure respirators of the prior art will not achieve a zero or positive pressure for any peak flow rate. By contrast the respirator described above will achieve zero pressure at a moderate peak flow rate: in this case approximately 55 Limin. The peak flow rate at which zero pressure is achieved can be tuned by tuning properties of the respirator, in particular the base flow rate of the fan.

Variations on the respirator system 1 described above will also be apparent to the skilled person that do not depart from the scope of the appended claims.

For example, the skilled person appreciates that other configurations of the fan-filter system 10 are possible. For example, the fan 22, the filter 20 and the junction chamber 18 need not necessarily be arranged in the same housing 11 and may instead be located in separate housings. The filter 20 may be arranged behind the fan 22.

Furthermore, it will be appreciated that the inlet valve 50 could be arranged anywhere in the second conduit 44, i.e. away from the respirator 40.

Lastly, it can be preferable to arrange two separate second conduits 44 between the fan-filter system 10 and the respirator 40. In this way, an increase in the flow of filtered air between the fan-filter system 10 and the respirator 40 can be achieved, without the use of a bulky single conduit.

Claims

Claims 1. A respirator system for delivering filtered atmospheric air to a user for inhalation, the respirator system comprising: a respirator through which a user can inhale filtered air at an inspiratory flow rate; an air filter system for filtering and drawing air from the atmosphere into the respirator system at a base flow rate and delivering filtered drawn air to the respirator; and a reservoir for storing filtered air; wherein the air filter system is arranged in fluid communication with the reservoir and the respirator such that: when the user's inspiratory flow rate is lower than the base flow rate of the filter system, at least a portion of the filtered air entering the respirator system is stored in the reservoir; and when the user's inspiratory flow rate exceeds the base flow rate of the air filter system, filtered air stored in the reservoir is drawn into the respirator for inhalation to supplement the filtered air provided by the filter system.
2. The respirator system of Claim 1, wherein the respirator system is configured such that when the user's inspiratory flow rate is less than or equal to the base flow rate of the filter system, filtered air flows from the air filter system to the respirator for inhalation by the user without supplementation from the reservoir.
3. The respirator system of Claim 1 or Claim 2, wherein the respirator and air filter system are arranged along a first airflow path, and the reservoir and the air filter system are arranged along a second airflow path, such that the air filter system is common to both airflow paths.
4. The respirator system of Claim 3, wherein the first airflow path is uni-directional from the air filter system to the respirator, and wherein the second airflow path is bidirectional from the air filter system to the reservoir and vice versa.
5. The respirator system of Claim 3 or Claim 4, wherein the air filter system comprises a junction chamber that is in fluid communication with the reservoir and the respirator, and that is configured to receive the filtered air drawn into the respirator system.
6. The respirator system of any of claims 3 to 5, wherein the respirator system comprises a first conduit arranged to fluidly connect the filter system to the respirator, and a second conduit arranged to fluidly connect the filter system to the reservoir.
7. The respirator system of any preceding claim, wherein the respirator system comprises a respirator inlet through which filtered air enters the respirator, and a respirator inlet valve configured to prevent a flow of air through the respirator inlet when the user exhales into the respirator.
8. The respirator system of Claim 7, wherein the respirator inlet comprises an opening in a body of the respirator, and the inlet valve is arranged within or adjacent to the opening.
9. The respirator system of any preceding claim, wherein the reservoir comprises an expandable air bag.
10. The respirator system of any preceding claim, comprising a support for securing the respirator to a user's face by extension around the user's head, wherein the respirator is secured to a forward portion of the support and the filter system is secured to a rearward portion of the support.
11. The respirator of Claim 10 when dependent on Claim 6, wherein the first conduit is incorporated into the support.
12. The respirator of Claim 11, or Claim 10 when dependent on Claim 6, wherein the second conduit is arranged to depend downwardly from the filter system when the respirator system is arranged for use, with the reservoir arranged at the bottom of the second conduit.
13. The respirator system of any preceding claim, wherein the respirator is configured to seal around the user's nose and/ or mouth area such that an air cavity is defined between the respirator and the user's face for receiving filtered air from the filter system and/ or reservoir.
14. The respirator system of any preceding claim, wherein the respirator comprises a respirator outlet through which exhaled air can exit the respirator, and an outlet valve arranged in or adjacent to the respirator outlet, wherein the outlet valve is configured to permit air flow out of the respirator when the user exhales and to prevent air flow into the respirator from the atmosphere.
15. The respirator system of any preceding claim, wherein the respirator system comprises a power source, preferably a battery.
16. The respirator system of any preceding claim, wherein the respirator system is for use by medical personnel
17. A method of delivering filtered atmospheric air to a user for respiration, the method comprising: drawing air from the atmosphere into the respirator system at a base flow rate, filtering the drawn air, and delivering drawn filtered air to the user for inhalation, the method further comprising when a user inspiration rate is less than the base flow rate, delivering drawn filtered air to a reservoir for storage, and when the user inspiration rate exceeds the base flow rate, supplementing the drawn filtered air delivered to the user with stored filtered air from the reservoir.
18. The method of Claim 17, for delivering filtered atmospheric air to medical personnel.
19. A respirator system configured to operate the method of Claim 17 or Claim 18.