GB2594299A - A face mask and system to remove pathogens from expired breaths, coughs, or sneezes from humans - Google Patents

Abstract

A face mask (1) with an air handling system, preferably having a low pressure resistance to breath, coughs and sneezes. The expired gas, droplets and aerosol may flow along an airway system (4,8), preferably being removed in a processing unit (9) by means of filtration, deposition or exposure to agents or methods to kill pathogens, or to exhaust them directly to an outside environment. Pressure increase within the mask, with potential escape of pathogens through mask leaks, may be avoided by having a low resistance face mask exit port (2) with a low pressure opening one-way valve (2) and an outflow chamber (4) that preferably has the ability to increase in volume rapidly with little pressure increase. The flow of gases, droplets and aerosols through the system may be controlled by a pump (10), with pressure monitoring (17) and feedback control (18).

Description

DESCRIPTION -INTRODUCTION AND BACKGROUND

A face mask and system to remove pathogens from expired breaths, coughs, or sneezes from humans The transmission of diseases from an infected person to others is frequently by the infected person releasing pathogens into their surroundings through their breath, coughs or sneezes. This route of infection is well known, and has played a major role in the annual cycle of diseases such as influenza, TB, epidemics and pandemics such as SARS and H1N1 [Tellier R, Review of Aerosol Transmission of Influenza A Virus Raymond Emerging Infectious Diseases, www.cdc.gov/eid Vol. 12, No. 11, November 2006]. Governments and bodies such as the WHO develop national and international plans and aim to advise on appropriate actions to attempt to avoid a disease spread becoming an epidemic, or a pandemic. The appropriate actions to limit spread will depend upon the specific pathogen, but a major route especially for infections involving the respiratory system, is through droplets or aerosols emitted by an uninfected person through normal breathing, talking, coughing and sneezing [Cough aerosol in healthy participants: fundamental knowledge to optimize droplet-spread infectious respiratory disease management Zayas et al. BMC Pulmonary Medicine 2012,12:11]. Healthcare workers, and others coming within close contact with the infected individual, may be advised to wear a face mask of an appropriate type, and perhaps also eye protection, other protective clothing and to ensure strict hand washing. Within the material expelled from the patient there is gas, droplets and smaller particles known as aerosols, typically defined as being under 5 pm diameter. Such aerosols may have a greater chance of infecting others since they behave more like a gas, staying in the air for a long time and potentially travelling further. Aerosols also penetrate further into the lungs of a person and more reach the alveoli of the lungs where a lower dose of pathogen is needed to infect the subject [Roy CJ, Milton DK. Airborne transmission of communicable infection-the elusive pathway. N Engl J Med 2004;350:1710-2].

Aerosols are harder to remove from the emissions from the patient since they are small and have a higher chance of penetrating a mask, and because they behave similar to a gas they can pass around a mask through any leaks caused by gaps between the mask and the patient's face. The problems of poor mask fit, for masks worn by patients and carers, are well documented [ https://www.hse.gov.uk/researchArpdfirr649.pdf, Evaluating the protection afforded by surgical masks against influenza bioaerosols Gross protection of surgical masks compared to filtering facepiece respirators, Prepared by the Health and Safety Laboratory for the Health and Safety Executive 2008, RR619]. If masks are recommended for patients then they are usually of the "surgical mask" type, which reduce pathogens significantly but which still allow release of virus or bacteria into the environment. This is particularly true when patient coughs or sneezes, since the rapid, often described as "explosive", nature of these raises the pressure behind the mask rapidly and air and expelled droplets and aerosols flow around the mask through gaps between the mask and skin [ "Violent Expiratory Events: On Coughing and Sneezing." Bourouiba et al, Journal of Fluid Mechanics 745 (March 24, 2014): 537563,], The viral or bacterial load in an environment is a major risk for healthcare workers, and others who may be in contact with the person, for example ambulance workers picking up a patient to transport them to hospital, nurses, doctors and other healthcare workers in hospitals, carers including family in the community or infected person's home, or carers in residential care homes.

Masks with higher filtration efficiency, and better facial fit, such as the N95 masks [See the HSE reference above for details and references to mask types] and the FFP2 and FFP3 masks, may be used, but only the FFP3 masks have a high efficiency for removing aerosols [ Efficacy of face masks in preventing inhalation of airborne contaminants, David J. Pippin, DDS, MS, Richard A. Verderame, DDS, Kurt K. Weber, DDSt Journal of Oral and Maxillofacial Surgery, April 1987Volume 45, Issue 4, Pages 319-323]. However, the use of FFP3 or similar masks is problematic for patients with a cough or sneeze, since the speed of the expelled air volume cannot pass sufficiently quickly through the mask and so a high pressure is built up behind the mask that then pushes air and aerosols and possibly even larger particles through gaps between the mask and the wearer's face. Also the filter on the high performance masks is in the front of the mask and is likely to get saturated quickly if worn by a patient with cough or sneeze due to the higher amount of wet droplets emitted with every cough or sneeze, and the masks are not designed to function in these conditions of dealing with hyper-secretions from an ill patient.

It is therefore clear that though high performance filtering masks may be used, they are not designed for patient use when the patient has respiratory symptoms, especially if coughing or sneezing, or if the subject needs any form of gas delivered such as nasal oxygen.

There has been no previous solution to the problem of dealing with masks being unable to contain the explosive emissions of pathogens cough and sneezes, whilst allowing good medical access to the patient. Patients who are not themselves in need of airways support through non-invasive ventilation are nevertheless capable of spreading virus and bacteria, but they also have needs in terms of eating and drinking and personal care which can be carried out with the removal of a mask to eat or drink, using good tissue cough and sneeze hygiene for the short periods when a mask cannot be worn. Though such removal of a mask increases the release of pathogens, particularly if good cough and sneeze hygiene is not performed, overall the viral or bacterial load in the room are will still be significantly reduced if there is a highly efficient pathogen removal device in use for most of the time, and it is this type of device that has previously been unavailable.

Review of the prior art shows that catching cough and sneeze expelled droplets has been the subject of a number of patents, including the use of handheld items to attempt to "catch the cough" or sneeze, such as ( US patent US 7.997.275 82, Quin, 2011, US 2014/0251349 Al, Delatorre 2014).

There have also been devices that aim to apply bacterial or viricidal agents to the cough or sneeze material as it passes through a mask ( US Patent 4,790,307, Haber et al 1988) , but none have addressed the well recognised problem that masks do not perform well in physically containing an explosive sneeze or cough, and even devices that claim to do this in a single mask do not offer any evidence that they can deal with the known factors of large volumes needing to be contained from explosive coughs or sneezes ( US US 2015/0013681 Al, APPARATUS WITH EXHAUST SPACER TO IMPROVE FILTRATION OF PATHOGENS IN RESPRATORY EMISSIONS OF SNEEZES, and WO 2018/080577 Al 2017, Bird J4.

In a healthcare context there have been attempts to address some of the issues described, and US patent US005676133A (Hickle et Al, 1997) EXPIRATORY SCAVENGING METHOD AND APPARATUS AND OXYGEN CONTROL SYSTEM FOR POST ANESTHESA CARE PATIENTS reveals an invention that is primarily aimed at scavenging anaesthetic gas but which also has the benefits of removing pathogens from the expired material. This system uses an anaesthetic face mask, and is not able to manage the high volume and pressure of coughing and sneezing, and it is not applicable in hospital ward or primary care settings.

Other highly specialised approaches include managing laminar flow of air in a room to remove pathogens by large scale air flow ( US patent US 9,310,088 B2, Melikov et al 2016), but this level of technology is not available for large scale use such as in epidemics or pandemics, nor in a domestic or primary care setting or in ambulance transport.

DESCRIPTION OF THE INVENTION

A face mask and system to remove pathogens from expired breaths, coughs, or sneezes from humans The invention is to reduce release of pathogens from an infected person's respiratory system into the air, for example into room air or air in an ambulance, achieved by a mask and system to capture oral and nasally expired gas, aerosols and particles and thereby ensuring that a very high fraction of the expelled material is not released into the environment, even when the patient is coughing or sneezing. The term "expelled material" is used to describe the gas, droplets and aerosol that the subject expels from their mouth or nose, for example during breathing, talking, coughing or sneezing. The pathogens are then removed from or killed in the captured material before the expelled material is released into the environment. The invention also allows access for medical staff to deliver oxygen or other therapy without compromising the removal of pathogens.

The device does this by providing a low resistance pathway for the expelled materials, so that even for an explosive cough or sneeze the pressure within the mask does not rise sufficiently to cause back flow around the mask edge. The expired breath, cough or sneeze passes through an outflow valve that opens at low pressure, and which then reduces the potential re-breathing of the expelled materials. The expelled material is then directed along an airway to a processing unit where pathogens are removed killed before the air flow is vented back to the room or the exhaust released to the outside environment.

Summary of the invention

The invention is a system comprising of a face mask and air handling system that captures the expired breath, from tidal breathing or from a cough or sneeze event, including gas, particles and aerosol from a human subject, and removes pathogens such as viruses and bacteria, so reducing the spread of pathogens to the surroundings and other people. The face mask captures air, aerosol and material from the nose and mouth of the wearer, or in one embodiment just the mouth. The system has a low resistance outflow from the mask such that the expelled passes into an output chamber without a significant rise in pressure under the face mask that would most probably cause backflow of gas and materials between the subject's face and the mask. The low resistance outflow is formed by having an exit port in the mask approximately in front of the wearer's mouth, with the exit port being of a large enough diameter so that the resistance to flow through the port is low. Within the exit port there is a low resistance exit valve that opens with little increase in pressure when the subject breathes or coughs or sneezes. This exit valve closes when the subject inhales, so that the subject does not re-breathe in the materials contained in their last breath or cough or sneeze. An inlet valve in the mask opens when the patient inhales, opened by the difference in pressure between the interior of the mask when the patient is inhaling and the atmospheric air pressure outside the mask. An additional piped gas inlet port is provided for the attachment of an air or oxygen delivery tube, with a blanking cap when not in use. The expired air having passed through the exit valve enters an outflow chamber which is of a relatively large volume compared to the cough or sneeze or single breath volume, and which has a wall material that presents little resistance to change in volume, and thereby there is little excess pressure resisting the flow of breath or cough or sneeze into the outflow chamber.

A suction pump at the distal end of the system draws the contents of the outflow chamber through a connecting tube and into a processing chamber, in which the pathogens in the airflow are killed, for example by UV irradiation or other toxic agents, or filtered or the droplets and aerosol are electrostatically deposited. The air flow, cleared of live pathogens, is then exhausted to the room, or may be vented to the outside of a building to obtain the benefits of dilution if, for example, there is any uncertainty about the efficiency or killing or deposition. Such uncertainty may arise if a new pathogen emerges and the system is being used to reduce spread before the sensitivity of the pathogen to toxic substances has been determined. The option to exhaust the expired air and materials to the outside environment without the process of pathogen removal, that is without the flow being filtered, killed or deposited in the processing unit, may also be taken if a risk assessment shows that the risks are acceptable given the dilution in the open environment, for the actual or suspected disease that the subject is infected with.

The efficiency of removal of pathogens will not achieve 100%, due to the imperfections of the mask-to-face seal even at low pressure, and due to the imperfections of pathogen killing and filtering methods, but the airborne pathogen load will be reduced compared to the reduction achieved with a standard face mask, and therefore the risk to healthcare workers and others will be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 Is a side view of the system, with a mask covering both nose and mouth Figure 2 Is side view of the system, with a mask covering just the and mouth Figure 3 Is a front view of part of the system, showing the mask and upper air handling system Figure 41s a side view of part of the system, device showing the mask, exit port and valve, with the person wearing the device exhaling a breath Figure 5 Is a side view of part of the system, showing the mask, exit port and valve, with the person wearing the device inhaling a breath Figure 6 is a front view of the exit port, without the exit valve shown Figure 7 is a front view of the exit port, with the exit valve shown Figure 8 is a cut through section of the processing unit, showing one possible arrangement of sub-units to remove or kill pathogens Key to the labels in the Figures (1) Mask (2) Exit Port (3) Low resistance one way valve (4) Outflow chamber (5) Inlet port (6) Gas inlet port (7) Connection (8) Connecting pipe (9) Processing Unit (10) Suction Pump (11) Exhaust pipe (12) Mouth Mask (13) Peak over Exit Port (14) Flange around Exit Port (15) Outflow chamber joint at the Exit Port (16) Mask retaining strap (17) Pressure sensor (18) Signal cable to Vacuum Pump (19) Electrostatic deposition sub-unit (20) Filter sub-unit (21) Pressure adjustment sensor and valve (22) Over-pressure line (23) Inlet pipe (24) Over-pressure line filter

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

A face mask and system to remove pathogens from expired breaths, coughs or sneezes from humans In one embodiment of the invention the capture of the expelled matter (where expelled matter is defined here as gases, droplets, particles and aerosol from a subject's mouth and nose) is enabled by having a mask and a system which has a low resistance to flow of the expelled matter from the space between the wearer's face and the mask. This low resistance is maintained even at a high rate of delivery (volume per second) of expelled matter such as occurs during cough or sneeze. In this description the person wearing the mask is referred to as "the wearer". The face mask (1) is in general construction of the type commonly used to filter the inspiration or expiration of airborne matter in medical or industrial settings, and in this embodiment the mask is of a soft material and with head straps (16) to keep it pulled close to the face. In the front of the mask there is an exit port (2) roughly at the level of the wearer's mouth, with a circular diameter of the order of the size of the opening of an adult mouth during breathing, cough or sneezing, being in this embodiment 40 mm. The exact dimensions of a particular embodiment need to be matched to the population being served, and possibly different size fittings will be used to match more closely the mask and exit port to the individual, and also considering adult or child dimensions. The expelled matter passes through a low resistance one-way valve (3), such that it opens at a pressure of around 5 mm of water, being a low pressure that will not result in a significant backflow of expelled matter through any mask-face gaps. Pressures are expressed as the height difference in a water manometer. In this embodiment the low resistance one-way valve (3) is formed by a thin flexible material, such as a thin vinyl, which is shaped like an aviation wind sock as a truncated cone of material with an open end, and it blows open when the pressure on the face side exceeds that on the outflow chamber side, and then falls closed and blocks flow when the pressure is reversed. An illustration of this is given in figures 4 and 5. In figure 4 B is the expelled breath, and E is the material escaping into the outflow chamber (4). In figure 5 the inspired breath I causes a pressure drop and the contents of the chamber cannot pass in the direction shown by arrow NP.

Further details of the exit port (2) and low pressure exit valve (3) for this embodiment are given in figures 4, Sand 6. In figures 4 and 5 it is shown that in this embodiment there is a flange (14) which is used to attach the neck of the bag-like outflow chamber (4) by use of a circular clip or '0-ring' (Figure 4, 15), or such a ring or clip formed in the neck of the outflow chamber bag. In this embodiment there is a projection (13) from the top of the exit port, much like the shape of a peak of a peaked cap, and this peak has the function of keeping the outflow chamber wall material from pressing on the material of the flexible valve which would restrict the flow of expelled matter into the outflow chamber.

The expelled matter then enters the outflow chamber (4), which is in this embodiment is formed by a very flexible thin walled plastic chamber such that its volume is at least that of 2 high volume adult coughs, where this is determined from the range of cough volume for the population being served. The essential feature of the outflow chamber is the pressure-volume relationship when a volume of air rapidly enters into it. The material is chosen so that it has little resistance to increase in internal volume, so that the pressure changes only minimally with increase in volume. The use of a thin plastic bag like material in this embodiment satisfies this requirement. If the wearer coughs, sneezes or expels a volume of air quickly then the outflow chamber fills rapidly, but because it is of sufficient volume to contain at least 2 high volume adult, and the walls are thin and flexible and easily deformed under low pressure, then the pressure remains low on the wearer's face side of the exit port. The low pressure in the mask means that there is not a significant backflow of expelled matter between the face and the mask which would result in an uncontrolled release of pathogens into the air from an infected wearer.

The exit port valve closes when the pressure on the chamber side exceeds that on the face side, for example when the wearer inhales, and the inlet port on the mask side (5) opens to let air in, and there also may be air or oxygen inflow to the mask through the piped gas inlet port (6). The inlet port (5) has a one-way valve so that it is closed when the patient breathes out, or sneezes or coughs.

The expired matter in the chamber must be removed, and this is achieved by arranging for a flow of the expelled matter through the connection (7) at the bottom of the outflow chamber (4), by applying suction through the connecting tube (8) with the suction provided by the suction pump (10) pulling air through the processing unit (9). This flow reduces the gas volume in the outflow chamber so that it is ready to receive further flow through the exit port (2), and so that the back-pressure from the outflow chamber is kept low. The flow rate of expelled matter along the connecting pipe (8) may be set by a variable control of the suction pump (10) rate, adjusted by an operator to be the correct average flow for the patient. However, breathing, coughing and sneezing are variable, and so it is preferable that a sensor (17) in the outflow chamber, or another part of the outflow airway, detects pressure and provides feedback to the suction pump (10) via an electrical signal cable (18) to increase or decrease the suction and thereby vary the flow rate and the pressure in the outflow container.

In order to ensure safety of the system in terms of not applying too negative a pressure in the outflow chamber, which may then open the valve (3) and result in a negative pressure at the patient's mouth and nose, it is preferable to have a sensor and valve triggered at low pressure by physical or electronic monitoring, to open and restore atmospheric pressure within the airway, and in this embodiment this sensor and valve is in the processing unit (Figure 8,21). The valve opens to allow air into the system if the air pressure is too low, through the inlet pipe (23) or it opens to let expelled material out along the over-pressure line (22), passing through a filter (24) in the over-pressure line if the pressure is too high. An over-pressure alarm will sound until the pressure is reduced.

When the expelled material flows into the processing unit (9) it passes through sub-systems to remove pathogens by filtration or other means of physical extraction such as electrostatic deposition, and it may also pass through other sub-systems to kill pathogens before being exhausted to the room or environment through the pump (10) and the exhaust pipe (11).

The processing unit in this embodiment, by way of example, uses two of the methods of removing pathogens from the expired material shown in Figure 8, passing the expelled material through an electrostatic deposition unit (19) and then through a filter, (20), before the cleaned gas travels on to the suction pump and is then exhausted into the local environment such, or the exhaust pipe is extended for the cleaned gas to be passed into the outdoor environment.

There are numerous other variations on the manner in which the invention may be embodied, and some of the possible variations are listed below: a) A mask covering the mouth only (Figure 2) may be appropriate for certain diseases, for certain clinical conditions and certain patients in which there is little expelled material from the nose, and also when improved access to the nose is required, for example for delivery of oxygen therapy, though oxygen therapy can also be given through the full nose and mouth mask described above.

b) The face mask may be of a rigid material, instead of fabric. This may facilitate 3D printing of the mask, and also offers the potential that a 3D scanning device could scan an individual face and print a mask made to measure. An excellent fit is not required by this invention, since the back pressure is reduced, but a good face fit increase the overall performance in containing pathogens.

c) The outflow chamber may be made of any material and construction that delivers the pressure-volume relationship described. For example a rigid material may be made into a concertina shape so that it expands and contracts with little resistance, and there are other variations possible to achieve the required performance.

d) The outflow chamber concept may be realised by having the tubing from the face mask of a relatively large diameter, say 50 mm or more, and this could then be extended to couple directly to the processing unit and thereby give a large volume, so that pressure changes on the inflow of a breath or sneeze volume are low due to the relatively low fractional increase in volume. This tubing will deliver a better pressure-volume relationship as required if it is made of a material that expands with little resistance, such as a thin flexible plastic or in a rigid material with corrugations that expand and contract with little pressure.

e) The aim of removing pathogens from the interior environment could be achieved without the processing unit if the outflow from the outflow chamber is connected to the pump via a filter and is exhausted to the outside open air. This would require a risk assessment and an understanding of the likelihood that such outside air was not likely to reenter any inhabited space, or flow where people are outside the building. Such a practice could be part of a protocol of how to deal with lack of spare filters or other supplies needed for the processing unit in times of shortage of supplies such as may occur in an epidemic or pandemic. In an ambulance transporting a patient, an outside roof vent may be used, given a risk assessment of the patient, the likely disease and the environment that the ambulance is travelling through. In any case in which high quality filtering or pathogen killing or removal is not performed, it is advisable that the best quality filter available is used to filter any such flow exhausted to the outside.

f) The processing unit may serve several mask wearers, with a suitable arrangement of piping to deliver the expelled material from each mask wearer to the common processing unit. In this embodiment there would be one pump to produce the suction for a number of masks, for example to support mask use in a hospital ward or other location where several patients with the same disease are together, such as may occur in an epidemic or pandemic.

R) The system can be made suitable for use for a wearer who is seated, in a domestic or hospital bed, and also for ambulatory subjects, or for patients undergoing transport inside a hospital, for example to go to a Radiology department for imaging, or in the community such as when ambulance staff are picking up a patient with a suspected highly infectious disease. This involves ensuring that tubing lengths are appropriate, and that system component ar of a suitable size, such as having a small battery powered processing unit that can be attached to the wearer, or placed on a wheeled unit or attached to a wheelchair or stretcher.

h) The sizes of components in the system, particularly the face mask and outflow chamber, can be adapted to different adult sizes and lung capacities, and also for children.

i) The system that draws air through from the face outflow chamber to the exhaust can be triggered by pressure changes, or other sensors, for example a breathing monitor built into the face mask, to only apply suction through the system when the wearer breathes or coughs or sneezes, or when the pressure in the outflow chamber is outside of limits set in the controlling software running on an electronic computing device that is receiving sensor inputs.

Claims (11)

1. CLAIMS1. A face mask and gas and airborne material handling system for capturing and removing or killing, a large fraction of the pathogens in expelled gases and all other materials, such as droplets and aerosols, from human subject during breathing, coughing or sneezing, or however expelled from the mouth or nose.
2. 2. A face mask and gas and airborne material handling system according to claim lin which the system offers low resistance to the collection of the expelled material and therefore has low back pressure and so keeps the pressure of gas between the mask and the wearer's face low to reduce flow of pathogens in the expelled material between the face mask and the face and into the surrounding air.
3. 3. A face mask and gas and airborne material handling system according to claim 2 in which the low resistance, and low backflow into the face mask, in ensured by the use of a low resistance exit port from the face mask to an outflow chamber, and a low resistance one-way valve in the exit port of the face mask to allow the expelled materials to leave the volume between the mask and the face at low pressure. Low resistance means that the gas pressure drop across these items is low for a wide range of flow rates relevant to the rate at which matter is expelled by the subject wearing the mask.
4. 4. A face mask and gas and airborne material handling system according to claim 2 in which the low resistance in ensured by the use of a collecting volume that has a low pressure resistance to rapid changes in volume, being made with walls of a flexible material, or made of rigid materials that are constructed to expand easily under low pressure changes.
5. 5. A face mask and gas and airborne material handling system as claimed in claim 1 in which the risk of infection of others is reduced by means of the expelled gas, droplets and aerosol from the infected person are passed through a processing unit which removes pathogens by filtration or other means of physical removal from the gas flow, and which also removes pathogens by killing them by toxic agents, such as UV radiation, chemicals or any other means.
6. 6. A face mask and gas and airborne material handling system reducing emission of pathogens as claimed in claim 5, in which the processing unit which carries out the pathogen removal handles the air from one person wearing the mask and attached to the airflow system.
7. 7. A face mask and gas and airborne material handling system reducing emission of pathogens as claimed in claim 5, in which one processing unit handles the air from several people each wearing a mask and attached to their own airflow system comprising the face mask, including the exit port and exit valve, and an outflow chamber.
8. 8. A face mask and gas and airborne material handling system as claimed in claim 5 in in which the pathogens in the expelled gases and materials from an infected person are exhausted to the outside environment with or without filtration and without the use of other devices or agents to kill or remove pathogens, thereby reducing the pathogen load in the interior building, room or ambulance where the subject is located.
9. 9. A face mask and gas and airborne material handling system as claimed in claim 1 in which there is monitoring of the pressure in key parts of the system to give electronic feedback to the vacuum pump to vary the air flow rate to ensure that the pressure and flow within the system is within the defined operating range.
10. 10. A face mask and gas and airborne material handling system as claimed in claim 1 in which there is monitoring of the wearer's breathing, coughing or sneezing, so that the pump can be operated in response to these events.
11. 11. A face mask and gas and airborne material handling system as claimed in claim 1 in which there is a physical or electronically triggered safety valve which activates when the system is outside of the system's operating range, and ensures that any over-pressure is reduced by release of gas and an alarm sounded to alert the operator to the need to investigate.