GB2596835A - Microbial filtering and humidifying mask system - Google Patents

Abstract

A microbial filtering and humidifying system comprising a face mask 1 which provides a heat and moisture exchanger (HME/HMX), a filter and an oxygen supply inlet 7. In a preferred arrangement, each of the HME/HMX, filter and oxygen supply inlet are provided within/on a casing 6 which is attached to the body of the mask, preferably on a front surface thereof. The casing may also provide a female connector 14 for connecting with an anaesthetic breathing circuit. The system is able to supply anaesthetic gases and oxygen to a patient at the same time as providing viral and bacterial filtration. A Luer port 8 may also be provided on the casing, to allow for sampling. The mask is preferably held to the face of a user by means of a T-shaped harness (10, Fig 3) connected to the mask by means of hooks 9.

Description

MICROBIAL FILTERING AND HUMIDIFYING MASK SYSTEM

This invention relates to a microbial filtering and humidifying mask system.

There is currently a global coronavirus pandemic, COVID-19, and efforts to prevent infecting healthcare personnel have concentrated on using Personal Protective Equipment (PPE) for workers who make direct or close contact with infectious patients. Viral or bacterial infectious respiratory diseases can be spread through droplet or aerosol released during coughing, sneezing or speaking by an infected or infectious person. Inhalation or ingestion of these droplets or aerosol containing the micro-organisms or fomites can cause infection. Thus far, over six million recorded cases of coronavirus infection have been recorded worldwide, with approximately three hundred and eighty thousand deaths. COV1D-19 is highly infectious and causes significant mortality which is still rising. It has devastated the world economy by lockdown measures designed to curtain the spread of the pandemic. There is, thus, a need to reduce the spread of coronavirus infection and help to reduce the incidents of COVID-19.

During the coronavirus pandemic, spread of the virus to healthcare workers can be significantly reduced by limiting the spread from infectious patients being treated by the healthcare workers. A study has shown that covering the face of an infectious person with a surgical face mask significantly reduces the viral particles contained in the droplets or aerosol in the patient's exhaled air. However, it is problematic to administer oxygen to patients who are wearing a surgical face mask and who require continuous supplemental oxygen.

Airway devices used to administer oxygen and anaesthetic are removed from patients at the end of general anaesthesia. Extubation and intubati on processes are critical periods in aerosol generation. At these periods, infectious droplets or aerosols can be spread from the patient's mouth and nostrils into their immediate environment. The attending anaesthetist and recovery personnel are thereby exposed to inhalation of these infectious droplets and aerosol generated during these periods. The patient requires supplemental oxygen during the emergence period and wearing an ordinary surgical mask makes supplemental oxygen delivery to the patient very difficult and ineffective. Ward staff caring for an infectious patient may be exposed to infectious droplets or aerosol.

After weaning a patient from a ventilator in an intensive therapy unit (ITU), the endotracheal tube placed in the patient's trachea is removed. During this intermediate period, supplemental oxygen is delivered via face masks or other devices. This means that if a patient is infectious they can spread micro-organisms and place the healthcare workers at risk of infection. Wearing ordinary surgical face masks at this juncture can reduce the microorganism load on the exhaled air, but this also makes oxygen administration difficult.

Efforts to prevent infecting healthcare personnel have concentrated on using PPE for the workers who make direct or close contact with the infectious patient. Attempts made to reduce infection of healthcare workers include the following: PPE -face masks, hazmat suit, goggles/vizor, gloves.

Attempting to prevent the spread of coronavirus in the population has included isolating the infectious patients, social distancing of two metres and public partial or complete lockdown.

Healthcare workers are responsible for caring for infected patients and it is critical to protect those workers so that they can continue to deliver care to patients. Previous efforts have assisted, but not completely prevented healthcare workers from being infected with COVID-I 9. At the early stage of the COVID-19 pandemic, it is believed that healthcare workers accounted for 41% of those infected by the disease in Wuhan. In Spain, 13.6% of the infected population have been healthcare workers, and as at 16th April, 2020, 16.2% of the infected population of the United Kingdom have been critical key workers in the NHS.

Prior art anaesthetic masks are commonly in use and some have been designed to protect the wearer from inhaling infectious substances. Some masks have been made to prevent the patient from infecting healthcare workers and one example is an oxygen mask filter system disclosed in US 6659102B1. Other measures have included a filtering and humidifying face mask in US 20070044802A1, a disposable anaesthesia face mask in USD 6582845 I, an anaesthesia mask in CN 20247836311 Also known is a filtering anti-slip anaesthetic mask (CN 204050598E) used to administer anaesthetic gases and oxygen with the provision to filter inhaled impurities in gases. This Canadian reference uses two small filtered openings for oxygen and gastric tubes as well as a larger gas delivery opening similar to existing anaesthesia masks, albeit filtered. There is also known a gas delivery mask with expiratory, inspiratory, and dilution valves in EP 140915B1. This European reference is a complex mask used to deliver constant oxygen concentration using sequential oxygen dilution with room air irrespective of the respiratory rate. This prior art mask is bulky and contains three valves as well as a reservoir bag.

Anaesthetic masks are in existence and widely known and used for the administration of anaesthetic gases and oxygen during general anaesthesia or during induction of sedation in ITU. Filters have been used to protect the anaesthetic machine, ventilators and patients from infection or cross-infection. Heat and moisture exchangers exist in practice and are used in combination with filters to humidify oxygen and anaesthetic gases during general anaesthesia and sedation in ITU.

Public Health England has recommended patients that are infected with COVID19 to wear surgical masks so as to reduce the viral load on the droplets from the patient's nostrils and mouth when coughing, sneezing and speaking. As noted by Public Health England, delivery of supplemental oxygen to such patients becomes problematic.

It is an object of this invention to provide a microbial filtering and humidifying mask system which at least partially mitigates the foregoing difficulties.

According to this invention there is provided microbial filtering and humidifying mask system including a face mask locating a heat and moisture exchanger and a breathing system filter, in combination with an oxygen supply inlet, whereby anaesthetic gases and oxygen are suppled to a patient at the same time as providing viral and bacterial filtration.

Preferably, the heat and moisture exchanger, breathing system filter and oxygen supply inlet are mounted in a casing attached to a front, in use, portion of the face mask.

Conveniently, a Liter port is also provided to said casing.

The breathing system filter may he either a pleated hydrophobic high efficiency particulate filler or an electrostatic filter employing electrets.

Advantageously, the face mask has a body which is substantially conically-shaped, with the casing being mounted at the apex of the cone.

Conveniently, hooks are provided on the body for attachment of a harness for holding the mask on the face of a user.

Advantageously, said hooks are provided at opposing sides and at the top, in use, of the body.

Conveniently, the harness is an elasticated T-shaped member with at least one securing aperture in each limb for securement of the harness to said hooks.

Advantageously, a peripheral cuff is provided around the periphery of the body to provide an interface between the body and the face of a wearer, in use.

Preferably, the body and the cuff are made of transparent material.

Preferably, the casing also contains a female connector for anaesthesia breathing circuit connection when anaesthetic gas and oxygen are administered.

Advantageously, the cuff is made of silica material containing an air pocket. It will, thus, be understood that the present invention is a combination of an anaesthesia mask with integral heat and moisture exchanger and microbial filter re-designed for induction of anaesthesia, after anaesthesia in theatres and ITU and on hospital wards. It is composed of a mask body and integral heat and moisture exchanger with a microbial filter. Supplemental oxygen is administered through an oxygen inlet on the filter. The mask of the system of this invention prevents infectious droplets and aerosol of infected patients from being spread to the immediate environment. Thus, the risk to healthcare workers from being infected is reduced.

The microbial filtering and humidifying mask system of this invention is intended to be used for induction of anaesthesia, during the emergence from general anaesthesia and during the entire recovery phase from the anaesthetic. It can be worn by the patient on hospital wards. An advantage of the present invention is that an infectious patient can wear the mask on the ward and be taken to the operating theatre whilst protecting healthcare workers and may be used after their operation or any other procedure when the patient is returned to the ward without compromising oxygen delivery. The mask of the invention may also he used after weaning a patient from an ITU ventilator and can he used to administer humidified oxygen to a patient on the ward while protecting immunocompromised patients at risk of infection.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a front view of a microbial filtering and humidifying mask system in accordance with this invention, Figure 2 shows a right-hand side view of the system shown in Figure 1.

Figure 3 shows a top view of a harness for the system shown in Figures 1 and 2. In the Figures, like reference numerals denote like parts.

The microbial filtering and humidifying mask system shown in Figures 1 and 2 has a generally oval-shaped, approximately conical body 1 that is worn over a person's nose and mouth with a top portion 2 resting on the bridge of the nose of the person, but below their eyes. A lower portion 3 is arranged to rest on a person's chin The body may be made of transparent material, such as plastics, and by being transparent it is made less claustrophobic to patients while enabling visualization of any secretions or vomitus from a person's mouth. Circumferentially surrounding the body I is a cuff 4 made of transparent soft silicon material that may contain an air pocket so as to provide a comfortable snug fit to the wearer.

A heat and moisture exchanger and filter (HMEF) 5 is mounted in a casing 6 affixed to a forwardly facing part of the body I, approximately at the apex of the body.

The casing 6 has an oblong shape which enables exhaled air from both the mouth and nostrils to make contact with the HMEF. Such an arrangement increases filtration and reduces misting that occurs during heat and moisture exchange. A larger exhalation surface is provided to minimize resistance to breathing. The casing contains a 22mm female connector 14 for connecting with an anaesthetic breathing circuit. Also connected to the casing 6 is an oxygen inlet 7 comprising a connector through which oxygen tubing from an oxygen source, e.g. a cylinder or oxygen wall outlet, may be connected to the mash, thereby delivering supplemental oxygen to a patient. A cap is tethered to the base of the oxygen inlet connector to close off the inlet when oxygen is not being delivered to the patient through the inlet. It is to be understood that instead of the oxygen inlet connector being connected on a side of the casing 6 it may be located at any convenient point around the casing.

Also mounted on the casing 6 is a Luer port 8 which is a gas-sampling port. This port is used to sample carbon dioxide for respiratory monitoring and has a cap tethered to the base of the port to cover the port when not in use. The Luer port cap may be distinctly coloured with a contrasting colour to make it visible in the event that it should fall into the HMEF filter.

The HMEF is a heat and moisture exchanger (HME) and a highly efficient breathing system filter (BSF). Filtering of viral and bacterial particles is achieved using either a pleated hydrophobic high efficiency particulate air filter or an electrostatic filter using electrets. A high efficiency particulate air filter uses randomly woven fiberglass and is pleated to increase the filtering surface and this also reduces the resistance to breathing. Particles less than 0.1pm (viruses) are filtered by diffusion (Brownian motion), while those greater than 0.4pm are filtered by interception and an impaction mechanism. The filter should not impose more resistance to breathing than an anaesthetic heat and moisture exchange and filter. To provide humidified inhaled gas, the filter is incorporated with a heat and moisture exchanger The air that is breathed by a person contains some water vapour, the amount depending on the temperature. As the air passes through an individual air passage it is warmed up to body temperature and collects moisture from the mucus lining of the trachea. The trachea mucosa contains mucus consisting of viscous gel and a watery low viscosity sol layer. The sol layer is used to humidify inhaled air or gases. Just below the level of the carina, the inhaled gas becomes fully saturated with water vapour ( 100% relative humidity) at 37'C. This leaves the lower respiratory tract with moist gases.

When dry gases are inhaled over a long period, the sol layer is depleted leaving viscous mucous that can plug off alveoli and cause atelectasis and other respiratory complications. In a patient whose trachea is intubated, the mucus humidification is bypassed at the trachea level. This function delivers dry gas to the bronchi causing respiratory complications. Thus, humidified oxygen is given to patients with respiratory infection. The filters are coated with hydroscopic material, e.g. calcium or lithium chloride, to enable them to function as a heat and moisture exchanger and filter. When cold, dry gas passes into a person's lungs it is warmed and humidified and the exhaled air is warm and fully saturated with water vapour. When the exhaled air conies into contact with the colder heat and moisture exchanger, which is at room temperature, the water vapour in the exhaled air condenses within the heat and moisture exchanger. The condensed water is now available to humidify the gas at the next inhalation, and so the cycle continues.

A harness 10, shown in Figure 3, is attached to the casing 6 by three hooks 9 attached to the casing. The hooks are positioned at each side and the top of the mask.

The hooks enable the, preferably, elasticated harness to be fastened to the mask to hold it on a person's face.

As shown in Figure 3, the harness 10 is generally T-shaped having, by way of example, four holes Ii at the extremity of each limb of the T-shape so as to permit adjustment of tension of the elastic when the harness is attached to the hooks.

Thus, the present invention, while filtering microorganisms also overcomes the problem of dry oxygen damaging the mucus membrane of the respiratory tract by providing a simple, passive and inexpensive way of providing humidification and heat conservation through the HMEF.

The microbial filtering and humidifying mask system of this invention incorporates a heat mid moisture exchanger with a viral and bacterial filter and a type of.tnaesthetic face mask into a single unit. The mask of this system is designed to be worn by patients who have respiratory infection during their infectious phase whilst in a hospital environment so as to protect healthcare workers. Respiratory infections can be spread when droplet and aerosols released from the environment during sneezing, coughing or speech are inhaled by other people. The mask is also intended to be worn by an infected and infectious patient while on a hospital ward or during transport to various departments of the hospital, in an operating theatre after general anaesthetic, in the theatre's recovery area, in ITU after weaning a patient off a ventilator to protect healthcare workers from infected patients. The mask can be used for induction of anaesthesia immediately after endotracheal extubation, at the end of anaesthetic or after weaning a patient from a ventilator in an ITU setting. The mask system is also used when humidified oxygen is required by a patient.

The mask system of this invention delivers variable oxygen concentration depending on a patient's respiratory minute volume and oxygen flow rate and filters exhaled gases from the patient.

Claims (12)

1. CLAIMSA microbial filtering and humidifying mask system including a face mask locating a heat and moisture exchanger and a breathing system filter, in combination with an oxygen supply inlet, whereby anaesthetic gases and oxygen are suppled to a patient at the same time as providing viral and bacterial filtration.
2. 2. A system as claimed in claim 1, wherein the heat and moisture exchanger, breathing system filter and oxygen supply inlet are mounted in a casing attached to a front, in use, portion of the face mask.
3. 3. A system as claimed in claim 2, wherein a Luer port is also provided to said casing.
4. 4. A system as claimed in any preceding claim, wherein the breathing system filter is either a pleated hydrophobic high efficiency particulate filter or an electrostatic filter employing electrets.
5. 5. A system as claimed in claim 2, wherein the face mask has a body which is substantially conically-shaped, with the casing being mounted at approximately the apex of the cone.
6. 6. A system as claimed in claim 5, wherein hooks are provided on the body for attachment of a harness for holding the mask on the face of a user.
7. 7. A system as claimed in claim 6, wherein said hooks are provided at opposing sides and at the top, in use, of the body.
8. 8. A system as claimed in claim 6 or 7, wherein the harness is an elasticated T-shaped member with at least one securing aperture in each limb for securement of the harness to said hooks.
9. 9. A system as claimed in claim 2, wherein a peripheral cuff is provided around the periphery of the body to provide an interface between the body and the face of a wearer, in use.
10. 10. A system as claimed in claim 9, wherein the body and the cuff are made of transparent material.
11. 11. A system as claimed in claim 9 or 10, wherein the cuff is made of silica material containing an air pocket.
12. 12. A system as claimed in claim 2, wherein the casing also contains a female connector for anaesthesia breathing circuit connection when anaesthetic gas and oxygen are administered.