JP7402870B2 - Contamination mask and its control method - Google Patents

Description

The present invention relates to a contamination mask for providing filtered air to a wearer of the mask using fan-assisted flow.

The World Health Organization (WHO) estimates that 4 million people die each year due to air pollution. Part of the problem is the quality of outside air in cities. The worst class are Indian cities like Delhi, which have annual pollution levels more than 10 times the recommended levels. Beijing is well known for its annual average of 8.5 times the recommended safety level. However, even European cities such as London, Paris and Berlin are higher than the levels recommended by the WHO.

The only way to deal with this problem is to wear a mask that provides cleaner air through filtration, as this problem does not improve much in the short term. One or two fans are added to the mask to improve comfort and effectiveness. These fans are turned on during use and are typically used at a constant voltage. For reasons of efficiency and longevity, these fans are typically electrically commutated brushless DC fans.

The advantage for the wearer of using a motorized mask is that the lungs are relieved of the slight strain caused by inhalation against the resistance of the filter in conventional non-motorized masks.

Furthermore, in traditional non-motorized masks, inhalation also creates a slight negative pressure inside the mask, and this negative pressure can lead to contaminants leaking into the mask, and if these are toxic substances, this leakage can be dangerous. . A powered mask delivers a steady stream of air to the face, providing a slight positive pressure determined by, for example, the resistance of the exhalation valve, ensuring that any leakage is directed outward rather than inward.

There are several advantages when fan operation or speed is adjusted. This can be used to improve comfort by better ventilation during inhalation and exhalation sequences, or can be used to improve electrical efficiency. The latter can lead to longer battery life or enhanced ventilation. Both of these aspects require improvements in current designs.

To adjust the speed of the fan, the pressure within the mask is measured and both the pressure fluctuation and the pressure are used to control the fan.

For example, the pressure within the mask is measured by a pressure sensor, and the fan speed can be varied depending on the sensor reading. Because pressure sensors are costly, it is desirable to provide an alternative method of monitoring pressure within the mask.

The applicant has proposed a solution, which has not yet been published, of using the rotational speed of the fan as a proxy for the pressure measurement. The pressure or change in pressure is determined based on the rotational speed of the fan. This pressure information can also be used to track a user's breathing patterns and determine if a mask is being worn. This technique is described in WO2018/215225.

The applicant has also proposed a solution, which has not yet been published, in which the inner mask environment (temperature and relative humidity) is used as an indicator for use in controlling the speed of the fan. However, sensors within the mask chamber are susceptible to errors due to condensation, which can degrade sensor response. Similarly, temperature and humidity sensors typically have slow responses and may not be able to track changes as quickly as necessary. In hot weather conditions, the change between the temperature detected when breathing in and the temperature detected when breathing out is also small.

Known control methods also do not easily take into account user activity, such as the user's exercise level.

Therefore, there is a need for a fan speed control method and apparatus that can be implemented at low cost and that can provide fan speed control that takes into account a user's activity level.

WO 2016/157159 discloses a respiratory mask comprising a fan, an outlet valve, and a sensor for detecting parameters indicative of the user's breathing cycle. Optionally other parameters are measured, such as humidity, temperature and pressure. The outlet valve is controlled according to the sensed parameters.

The invention is defined by the claims.

According to an example according to one aspect of the invention:
air chamber,
a filter forming a boundary between the air chamber and the ambient environment outside the air chamber;
a fan for sucking air into the air chamber from outside the air chamber and/or sucking air out of the air chamber from the inside of the air chamber;
means for determining the rotational speed of the fan;
providing a contamination mask having: a temperature sensor for measuring ambient temperature outside the air chamber; and a controller;
obtaining from the determined fan rotational speed or a change in the fan rotational speed a first value related to breathing depth and a second value related to breathing rate; and the first value, the second value 2 and depending on the ambient temperature, the fan speed is adapted to set a fan speed, said fan speed being set to a selected one of a plurality of non-zero fan speeds.

The mask includes automatic adjustment of fan speed based on fan rotation speed and external temperature. By considering the outside temperature, an estimation of the user's comfort is made. Fan speed adjustment can provide different airflow under different environmental conditions (temperature) and for different activity levels of the user. For example, during the summer months, when walking quickly, the user requires a large amount of airflow to help manage the intramask environment, while during the winter months, walking quickly requires a relatively large amount of airflow to avoid making the wearer cold. A small amount of airflow is required. Measurement of ambient temperature, i.e., use outside the mask chamber, avoids the problem of water condensation.

This provides a low cost solution, eg the required external sensing, which can be easily integrated on a PCB board.

The first and second values allow user activity to be taken into account. The first value relates, for example, to the depth of breathing, which means that there is a positive correlation between the first value and the depth of breathing. More generally, the first value is related to (i.e. correlated with) the magnitude of the fan pressure fluctuation, for example. Pressure fluctuations are caused by breathing when the mask is worn and during normal use. The second value has a positive correlation with respiration rate. This may be used as another indicator of the user's activity level in addition to the depth of breathing as indicated by the first value.

The present invention relates to a contamination mask. This refers to devices whose primary purpose is to filter the ambient air that the user breathes. Masks do not provide any form of patient treatment. In particular, the pressure levels and flows resulting from fan operation may assist in providing comfort (by influencing the temperature or relative humidity within the air chamber) and/or require significant additional breathing effort by the user. It is merely intended to assist in providing flow across the filter without having to do so. The mask provides no overall respiratory support compared to the situation where the user does not wear a mask.

In this system, instead of taking pressure measurements, fan speed monitoring is also used. To measure the speed of the fan, the fan itself may be used so that no additional sensor is required. Since the chamber is closed during normal use, pressure fluctuations within the chamber affect the load conditions of the fan and thus change the electrical characteristics of the fan. Similarly, the electrical characteristics of the fan determine the nature of the chamber, such as the volume of the chamber and whether it is an open or closed volume.

The first value is based, for example, on the maximum swing in fan rotational speed during the sampling window. This swing represents the degree of pressure fluctuation and therefore it is related to the depth of breathing. The second value is, for example, a frequency based on the time between consecutive maximum and minimum values of the rotational speed of the fan. This time period corresponds to half the breathing period, so the frequency directly derived from this value corresponds to twice the breathing rate (ie, the frequency).

The sampling window is selected to be sufficient to capture at least one full breathing cycle, for example 6 seconds to capture one full breathing cycle, with a minimum breathing rate of 10 breaths/min.

The filter directly forms a boundary between the air chamber and the surrounding environment outside this air chamber. This provides a compact configuration that avoids the need for flow carrying passages. This means that the user can breathe through the filter. A filter may have multiple layers. For example, an outer layer (eg, a fabric layer) may form the body of the mask, and an inner layer for removing finer contaminants. The inner layer may be removable for cleaning or replacement, but both layers filter together in that air can pass through the structure and this structure performs the filtration function. may be considered as configuring.

The filter therefore preferably comprises an outer wall of the air chamber and optionally one or more other filter layers. This provides a particularly compact construction and allows for a larger filter area, since the body of the mask performs the filtering function. Thus, when the user inhales, ambient air is supplied directly to the user through the filter.

For exhaust fans, the pressure can be positive or negative (compared to ambient pressure), eg, when the fan is off, there is a negative pressure caused by inhalation and a positive pressure caused by exhalation. When the exhaust fan is on, negative or positive pressure is possible during breathing, depending on fan speed and breathing characteristics. Negative pressure occurs when you are not breathing.

If the fan is intended to provide an increase in the pressure within the air chamber (e.g. the flow entering the air chamber during inhalation), it may provide a slightly increased pressure, e.g. to assist the user's inhalation. That is all that is required.

In any case, the maximum pressure within the air chamber during use is, for example less than 4 cm H ₂ O, such as less than 2 cm H ₂ O, such as less than 1 cm H ₂ O, and is higher than the pressure outside the air chamber.

The mask may further include a humidity sensor for measuring an ambient humidity level outside the air chamber, and the controller is configured to set the fan speed in further dependence on the humidity level. Therefore, both external ambient temperature and humidity are taken into account. This provides increased accuracy with respect to determining environmental conditions.

For example, the controller may determine from the ambient temperature and ambient humidity level,
The apparatus is configured to obtain a thermal index value related to a measure of comfort.

This thermal index value is representative of typical ambient environmental conditions and is used to ensure fan speeds are set to account for expected user comfort in these specific conditions. .

The value of the thermal index has a polynomial function consisting of ambient temperature, ambient humidity level, and one or more powers of ambient temperature and/or ambient humidity level. For example, it can include a function of ambient temperature, ambient temperature squared, ambient humidity level, and ambient humidity level squared.

The controller is
From the current fan rotational speed and the first and second values, the fan is configured to generate instructions to increase the fan speed, decrease the fan speed, or keep the fan speed the same.

Therefore, the breathing depth and breathing rate are used to control whether a change in fan speed is necessary, taking into account the current fan speed.

From the ambient temperature and ambient humidity level, the controller
The fan is configured to determine an amount to increase or decrease the speed of the fan.

Accordingly, the environmental conditions determine the amount by which fan speed adjustment is required.

The controller is configured to determine from the rotational speed of the fan or a change in the rotational speed of the fan that the mask is not being worn, and to turn off the fan if it is determined that the mask is not being worn. Ru.

The fan rotation signal is analyzed to detect whether a mask is being worn. This takes into account both a first value indicating the depth of breathing (when a breath is detected) and a second value indicating the rate of breathing (when a breath is detected).

By determining whether the mask is being worn, the mask design allows power to be saved when the mask is not being worn, without the need for any additional sensors. In particular, if no pressure difference across the mask is detected, this indicates that both sides are at atmospheric pressure and the mask is not being worn. In reality, there is no longer a closed or partially closed chamber, so the air chamber is open to the atmosphere. If a mask is detected not being worn, the fan is turned off.

The fan is driven by an electronically commutated brushless motor and the means for determining the rotational speed consists of an internal sensor in the motor. Instead, the means for determining the rotational speed consist of a circuit for detecting ripples on the electrical supply to the motor driving the fan.

Internal sensors are already provided in the motor to enable rotation of the motor. The motor may have an output port to which the output of the internal sensor is supplied. There is therefore a port carrying a signal suitable for determining the rotational speed. Instead, the ripple caused by switching the current through the motor's coils is detected, which causes an induced change in the supply voltage as a result of the finite impedance of the input voltage source.

The fan is a two-wire fan, and the ripple detection circuit includes a high-pass filter. Additional circuitry required for motors that do not already have adequate fan speed output can be minimized.

The controller is
configured to determine the breathing cycle from the rotational speed of the fan or a change in the rotational speed of the fan, and to control the outlet valve depending on the phase of the breathing cycle and/or to turn off the fan during the inhalation time. Ru.

Monitoring the rotation thus provides a simple method to determine the inhalation phase, and this method can be used to control the timing of the mask's vent valve, or whether the mask is being worn and therefore in use. used to determine whether

The controller may be configured to turn off the fan during the inhalation period. This is used to save power. Turning off the fan during inhalation, when so configured, saves power and is therefore desirable for users who do not have difficulty breathing through the filter.

The fan may only be used to draw air from inside the air chamber to the outside. In this way, the fan can facilitate supplying fresh filtered air to the air chamber at the same time, even during exhalation, which improves user comfort. In this case, the pressure in the air chamber may be lower than the external pressure (atmospheric pressure) so that fresh air is always supplied to the face.

The outlet valve comprises a passive pressure regulating check valve or an actively actuated electrically controllable valve. This is used to make the mask more comfortable. During inhalation, closing the valve (actively or passively) prevents unfiltered air from being inhaled. During exhalation, the valve is opened so that exhaled air is released.

The present invention also provides a non-therapeutic method of controlling a contamination mask, where the contamination mask is not a mask for administering treatment to a patient, and the method comprises:
drawing gas into and/or drawing gas out of the air chamber of the mask using a fan forming a boundary between the air chamber and the ambient environment outside the air chamber;
determining a rotational speed of the fan;
From the determined fan rotation speed or a change in the fan rotation speed,
obtaining a first value related to the depth of breathing and a second value related to the rate of breathing;
measuring an ambient temperature outside the air chamber; and depending on the first value, the second value and the ambient temperature, setting a fan speed, the fan speed comprising: having a step set to a selected one of a plurality of non-zero fan speeds.

The method further includes measuring an ambient humidity level outside the air chamber, and setting the fan speed is further dependent on the humidity level. Thermal index values are obtained from temperature and humidity measurements, which are related to comfort measures.

The method includes:
generating an instruction to increase fan speed, decrease fan speed, or keep fan speed the same from the current fan rotational speed and the first value; and from the ambient temperature and ambient humidity level, determining the amount by which the speed of the method should be increased or decreased.

Examples of the invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a pressure monitoring system implemented as part of a face mask. FIG. 2 shows an example of the components of a pressure monitoring system. FIG. 3 shows an example of a combined temperature and humidity sensor. FIG. 4A shows rotation signals during inspiration and expiration. FIG. 4B shows how the rotational speed of the fan changes over time. FIG. 5 shows a circuit for controlling the current flowing through one of the stators of a brushless DC motor. FIG. 6 is a diagram used to explain the thermal index scale. FIG. 7 shows how the mask is operated.

The invention will be explained with reference to the drawings.

The detailed description and specific examples, while indicating exemplary embodiments of apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. I hope you understand that. These and other features, aspects, and advantages of the devices, systems, and methods of the present invention will be better understood from the following description, appended claims, and accompanying drawings. It is to be understood that the drawings are only schematic and are not drawn to scale. It is also to be understood that the same reference numbers are used throughout the drawings to indicate the same or similar parts.

The present invention provides a contamination mask with a driven fan, in which the rotational speed of the fan as well as the external temperature and optionally the humidity level are also monitored. The rotational speed of the fan or a change in the rotational speed of the fan is used to obtain a first value related to the depth of breathing and a second value related to the rate of breathing. These are used in combination with ambient temperature and optionally ambient humidity level to set the fan speed. Therefore, the fan speed is set taking into account the user's breathing characteristics and ambient environmental conditions.

FIG. 1 shows a face mask with automatic fan speed control.

A subject 10 is shown wearing a face mask 12 that covers the subject's nose and mouth. The purpose of the mask is to filter the air before it is breathed into the subject. For this purpose, the mask body itself acts as an air filter 16. Upon inhalation, air is drawn into the air chamber 18 formed by the mask. During inhalation, the outlet valve 22, such as a check valve, is closed by the low pressure in the air chamber 18.

The sensing device 24 is provided to measure at least the ambient temperature, preferably both the ambient temperature and the humidity (eg, relative or absolute humidity) outside the air chamber 18.

The filter 16 may be formed by only the main body of the mask, or there may be multiple layers. For example, the mask body may have an outer cover formed from a porous textile material that acts as a pre-filter. Inside this outer cover, a finer filter layer is reversibly attached to the outer cover. The finer filter layer may then be removed for cleaning and replacement, while the outer cover may be cleaned, for example by wiping. The outer cover also performs a filtration function, for example protecting the finer filter from large debris (e.g. mud), while the finer filter filters fine particulate matter. There may be more than two layers. The multiple layers together act as the overall filter of the mask.

When the subject exhales, air is expelled through the outlet valve 22. This valve is opened to allow easy exhalation, but closed during inhalation. Fan 20 assists in removing air through outlet valve 22. Preferably, more air is expelled than exhaled air so that additional air is supplied to the face. This reduces relative humidity and provides cooling, thereby increasing comfort. During inhalation, closing the valve prevents unfiltered air from being inhaled. The timing of the outlet valve 22 is therefore dependent on the subject's breathing cycle. The outlet valve may be a simple passive check valve actuated by a pressure differential across the filter 16. However, the outlet valve may alternatively be an electronically controlled valve.

When the mask is worn and the user is breathing, the pressure within the chamber changes. In particular, the chamber is closed by the user's face. The pressure within the closed chamber when wearing the mask also changes as a function of the subject's breathing cycle. When the subject exhales, the pressure increases slightly, and when the subject inhales, the pressure decreases slightly.

If the fan is driven at a constant drive level (ie, voltage), different prevailing pressures will themselves appear as different loads on the fan because there will be different pressure drops across the fan. This changed load then results in different fan speeds. Therefore, fan rotation speed may be used as a proxy for measuring fan pressure.

For a known pressure (eg, atmospheric pressure) on one side of the fan, monitoring the pressure allows determination of the pressure, or at least a change in pressure, on the other side of the fan. This other side is a closed chamber with a pressure different from atmospheric pressure, for example.

The pressure fluctuations detected based on monitoring the rotational speed of the fan may be used to obtain information regarding the user's breathing. In particular, the first value represents the depth of respiration and the second value represents the rate of respiration. According to the invention, the first and second values, as well as the ambient temperature and ambient humidity level, are used to set the speed of the fan. Moreover, by detecting equal pressure (or other conditions related to the first and second values) on both sides of the fan, it can be determined that the chamber is not closed and both sides are connected to atmospheric pressure. is also possible.

This results in a variation in fan speed below the threshold. Therefore, this situation is used to determine that the mask is not being worn and therefore not being used. This information can be used to switch off the fan to save power.

The means for determining the rotational speed may comprise an already existing output signal from the fan's motor, or a separate simple detection circuit may be provided as an additional part of the fan. However, in both cases no additional sensors are needed as the fan itself is used.

FIG. 2 shows an example of the components of the system. Components that are the same as in FIG. 1 are given the same reference numerals. The sensing devices are shown as separate temperature and humidity sensors 24a and 24b.

In addition to the components shown in FIG. 1, FIG. 2 shows a controller 30, a local battery 32, and means 36 for determining the rotational speed of the fan.

Fan 20 has fan blades 20a and fan motor 20b. In one example, fan motor 20b is an electronically commutated brushless motor and the means for determining rotational speed comprises an internal sensor of said motor. Electronically commutated brushless DC fans have internal sensors that measure the position of the rotor and switch the current through the coils so that the rotor rotates. Internal sensors are therefore already provided in such motors to enable feedback control of the speed of the motor.

The motor may have an output port to which the output 34 of the internal sensor is supplied. There is therefore a port carrying a signal suitable for determining the rotational speed.

Alternatively, the means for determining the rotational speed may consist of a circuit 36 for detecting ripples on the power supply to the motor 20b. This ripple is caused by switching the current through the motor coils, which causes an induced change in the supply voltage as a result of the finite impedance of the battery 32. The circuit 36 includes, for example, a high-pass filter so that only signals in the frequency band in which the fan rotates are processed. This provides very simple additional circuitry and is much lower cost than traditional pressure sensors.

This includes a two-wire fan whose motor does not have an integrated sensor output terminal.
This means that it can be of any design. It also works with a brushed DC motor.

If the outlet valve 22 is an electronically switched valve, breathing cycle timing information may be used to control the outlet valve 22 depending on the phase of the breathing cycle. Therefore, monitoring the fan speed provides a simple method to determine the inhalation phase, which can then be used to control the timing of the mask outlet valve 22.

In addition to controlling the outlet valve, the controller can turn off the fan during inhalation or exhalation times. This gives the mask different modes of operation, which can be used to save power.

For a given drive level (or voltage), the load on the fan blades is reduced, resulting in lower fan pressure and higher fan speed. This causes an increase in flow. Therefore, there is an inverse relationship between fan speed and pressure differential.

This inverse relationship may be obtained during a calibration process or provided by the fan manufacturer. The calibration process includes, for example, analyzing fan speed information over a period in which the subject is instructed to inhale and exhale regularly with normal breathing. The captured fan speed information is then matched to the breathing cycle, thereby setting a threshold for distinguishing between inspiration and expiration.

FIG. 3 shows one possible design of a module incorporating a fan, check valve and detection device 24. This module has a printed circuit board 34 carrying a battery 32 and a sensing device 24 on one side, and a fan 20 and valve 22 mounted on the other side. A cover 36 is provided on the upper surface side. The detection device faces outward from the mask.

FIG. 4A schematically shows the rotor position versus time (as measured sensor voltage).

The rotational speed is measured from the frequency of the alternating current (AC) component (caused by switching events in the motor) of the direct current (DC) voltage to the fan. This AC component results from variations in the current drawn by the fan imposed on the impedance of the power supply.

FIG. 4A shows the signal during inhalation as plot 40 and the signal during exhalation as plot 42. There is a decrease in frequency during exhalation caused by the increased load on the fan due to the increased pressure gradient. Therefore, the observed frequency changes are due to different fan performance during the breathing cycle.

FIG. 4B shows the variation in frequency over time by plotting the rotational speed of the fan versus time. Between successive maximum and minimum values, there is a maximum difference in fan rotational speed Δfan, which correlates with the depth of breathing. This is the first value obtained from the fan rotation signal. The time between these points in time is used to obtain a second value, for example the frequency corresponding to this time period (in this case twice the respiratory rate).

It should also be noted that the first value may be obtained from the raw fan rotation signal or a smoothing may be performed first. Therefore, there are at least two different ways to calculate maximum swing based on unprocessed real-time velocity or processed velocity. In reality, there is noise or other fluctuations that add to the real-time signal. A smoothing algorithm may be used to process the real-time signal and calculate a first value from the smoothed signal.

During exhalation, the operation of the fan forces air out of the area between the face and the mask. This improves comfort as exhalation becomes easier. It can also draw additional air into the face, which reduces temperature and relative humidity. During inspiration and exhalation, operation of the fan improves comfort as fresh air is drawn into the space between the face and the mask, thereby cooling said space.

During inhalation, the outlet valve is closed (either actively or passively) and the fan is switched off to save power. This provides a mode of operation based on detection of breathing cycles.

If the fan is turned off during part of the breathing cycle and therefore does not provide pressure information, the exact timing of the inspiratory and expiratory phases is inferred from previous breathing cycles.

For fan-assisted exhalation, power needs to be restored just before the outlet valve reopens. This also ensures that the next inspiratory-expiratory cycle is maintained at the appropriate time and that sufficient pressure and flow are available.

Power savings of approximately 30% are easily achievable using this approach, resulting in extended battery life. Alternatively, the power to the fan could be increased by 30% to increase effectiveness.

When using different fan and valve configurations, measurement of fan rotational speed allows control to achieve improved comfort.

In fan configurations where the filter is in series with the fan, pressure monitoring is specifically used to measure the flow resistance of the filter based on the pressure drop across the fan and filter. This can be switched on when the mask is not on the face for a certain period of time. This resistance can be used as a proxy for filter age.

As mentioned above, fans that use electronically commutated brushless DC motors have internal sensors that measure the position of the rotor and switch the current through the coils so that the rotor rotates.

FIG. 5 shows an H-bridge circuit functioning as an inverter to generate an alternating voltage from the DC supply VDD, GND to the motor stator coil 50. The inverter has a set of switches S1-S4 for generating an alternating voltage across the coil 50. These switches are controlled by signals that depend on rotor position, and these rotor position signals may be used to monitor rotation of the fan.

As mentioned above, the system preferably measures both ambient temperature and humidity. These two measurements are combined to provide a measure of comfort level, such as a measure known as the Heat Index. Figure 6 shows a diagram of relative humidity (%RH) versus temperature (°C). Different regions are shaded differently to indicate different heat index values.

The thermal index is a function of ambient temperature (T), ambient temperature squared (T ² ), ambient humidity level (rh), and ambient humidity level squared (rh ² ). An example is
Index _heat = -42.379 + (2.04901523 x T) + (10.14333127 x rh) - (0.22475541 x T x rh) - (6.83783 x 10 ^-3 x T ² ) - (5.481717 ×10 ^-2 ×rh ² ) + (1.22874 × 10 ^-3 ×T ² ×rh) + (8.5282 × 10 ^-4 ×T × rh ² ) - (1.99 × 10 ^-6 ×T ² × ^rh2 )
It is.

The thermal index gives a measure of the degree of comfort under conditions of different temperature and relative humidity. For example, less than 29 is classified as no discomfort, 29 to 34.5 is classified as acceptable, 34.5 to 39 is classified as having some discomfort, and 39 to 45 is classified as having some discomfort. A rating of 45 to 54 is classified as very uncomfortable, a rating of 45 to 54 is classified as dangerous, and a rating above 54 corresponds to imminent heat stroke. Therefore, the higher the index value, the more uncomfortable the person feels. A thermal index is available if T>10°C. If T<10°C, other cooling parameters should be considered.

The controller sets the initial fan rotation speed using Table 1 below.

When T>10° C., the initial fan rotation speed increases with increasing thermal index. Relatively low fan rotation is provided while T<10°C. This low fan rotation ensures that the user does not feel too cold.

The rotational speeds given in the table are of course only examples.

The fan rotation signal is obtained in real time, and a first value representing the depth of respiration and a second value representing the respiration rate are continuously monitored. The normal breathing rate for adults at rest is 12-18 bpm (breaths per minute), and it increases when people engage in activities such as running, walking briskly or biking.

The sampling window should include at least one respiratory cycle, otherwise no respiratory rate can be obtained.

The first value representing the depth of breathing is the maximum swing in rotational speed captured within a sampling window (of at least one breath, e.g. 5 seconds), as shown in Figure 4B: Δfan=Fan(max) -Fan (min)
Based on.

The second value representing the respiration rate is the frequency f=1/|t _Fan(max) −t _Fan(min) | corresponding to the timing difference for these maximum and minimum values.
is given by

The second value is therefore the frequency based on the time between successive maximum and minimum values in the rotational speed of the fan. Again, the second value may be obtained from the raw fan rotation signal, or a smoothing may be performed first.

The respiratory rate may be defined as 0.5f. Another way to calculate f is to identify the inflection point from a drop (rise) to a rise (fall).

To adjust the rotation speed of the fan in real time, one example utilizes a lookup table 2 as shown below.

The lookup table has the following four subtables. Each sub-table is for a different range of breathing rates (i.e., a different range for a second value), and each sub-table is for a different range of breathing rates (i.e., a different range for a second value), and each sub-table is for a different range of breathing rates (i.e., a different range for a second value), and each sub-table is for varying the fan speed by changing the breathing depth (i.e., the first value Δfan). shows how things need to change.

In each sub-table, "-" means that the fan speed will keep running at the current level, "Fan+, Fan-, Fan++ and Fan--" will change how the fan speed is changed. It shows that.

The desired change to the fan speed depends on the current level of the fan speed (as indicated by the "-", it points towards the desired value), the breathing rate (breaths/min), and the breathing depth. It can be seen that it depends on Δfan.

The meaning of Fan+, Fan-, Fan++ and Fan-- is clarified by Table 3 below.

The value n represents the number of times a step change in fan speed is made, such as between fan speed settings 1-5 in the table above.

For example, if the current fan level is level 1 and n=3 (eg, in this scenario, "Fan+" AND heat index > 45), the fan should be changed to level 4 (1+3).

To determine the initial fan speed, the appropriate initial fan speed is required, not necessarily from the lowest speed when the fan is turned on by the user. Since the thermal index can approximately reflect the user's comfort level under different environmental conditions, the thermal index is used to set the initial speed as shown above.

When adapting the fan speed in real time, the breathing rate and volume changes with the user's activity. For example, sitting normally with a breathing rate of 12 bpm and a tidal volume of 0.5 L will probably result in a fan speed change (Δfan) of less than 350 rpm if the fan level is ~5500 rpm (see Table 2 above). arise. If the activity increases, for example from sitting to walking (eg, 20 bpm, 1 L volume), Δfan increases above 350 rpm, which requires an increase in fan level. Thermal index is used to help determine what level the fan should be changed to.

The above table only provides one detailed implementation, and of course different versions are possible for different fan designs, etc.

The mask may be intended to cover only the nose and mouth (as shown in Figure 1), or it may be a full face mask. Masks are meant to filter the air around you.

The mask design described above has a main air chamber formed by a filter material through which the user breathes air.

Another mask design has a filter in series with the fan, as described above. In this case, the fan helps the user to draw air through the filter, thus reducing the user's breathing effort. An outlet valve allows exhaled air to be discharged, and an inlet valve may be provided at the intake port.

The invention of detecting pressure fluctuations caused by breathing may again be used to control the inlet and/or outlet valves. The fan in this example needs to be turned on during inhalation to assist the user in drawing air through the filter in series, but may be turned off during exhalation when the outlet valve is open. Thus, the obtained pressure information may be used again to control the fan to conserve power when fan operation is not required. Detection of whether a mask is worn may be performed.

It will be appreciated that the invention may be utilized in many different mask designs, with fan-assisted inhalation or exhalation, and air chambers formed by filter membranes or sealed airtight air chambers.

One option, as mentioned above, is therefore the use of a fan only to draw air from inside the air chamber to the outside, for example when the exhaust valve is open. In such cases, the pressure within the mask volume may be maintained below external atmospheric pressure by the fan so that there is a net flow of clean, filtered air into the mask volume during exhalation. Thus, the lower pressure may be caused by the fan during exhalation and by the user during inspiration (when the fan is turned off).

An alternative option is the use of a fan only to draw air into the air chamber from the surroundings. In such cases, the fan operates to increase the pressure within the air chamber, but the highest pressure within the air chamber during use is outside the air chamber, since it is not specifically intended for high-pressure assisted breathing. The pressure remains below 4 cm H ₂ O. Therefore, low power fans may be used.

In all cases, the pressure within the air chamber preferably remains below 2 cm H ₂ O, below 1 cm H ₂ O or below 0.5 cm H ₂ O, and above the external atmospheric pressure. Therefore, a contamination mask is not intended for use in providing continuous positive airway pressure and is not a mask for administering therapy to a patient.

Since the mask is particularly interesting for low power operation, it is preferably battery operated.

In the above example, the first value related to the depth of breathing is obtained based on the maximum swing of the rotational speed of the fan during the sampling window. Other analyzes of fan rotational speed may be used. For example, a maximum positive deviation from the average fan speed or a maximum negative deviation from the average fan speed may be used. The fan speed swing may be the maximum value of any one breathing cycle within the sampling window, or may be the difference between the lowest and highest fan speed observed over the entire sampling window. . Before the first value is obtained, other statistical measures may be obtained first, such as, for example, an average or a moving average. For example, extreme values may be filtered out to exclude events such as sneezing or coughing.

Therefore, there may be different ways to obtain the first value and more complex signal processing than described above may be performed. However, there is generally a correlation between the amplitude of variations in fan rotational speed and the depth of breathing.

In the above example, the second value related to the respiration rate is obtained based on the time between successive maximum and minimum values of the rotational speed of the fan. Other analyzes of fan rotational speed may be used. For example, the time may be between consecutive maximum values (without using the minimum time) or between consecutive minimum values (without using the maximum time). Averaging may be performed over a time window, and other processing may be performed, for example to exclude events such as sneezes or coughs as described above. Therefore, more complex signal processing may be performed, again for example averaging or moving averages, to determine the respiratory rate.

Therefore, there are different ways to obtain the second value. However, there is generally a correlation between the timing between variations in fan rotational speed and breathing rate.

Fan speed is controlled using multiple possible fan speed values. Thus, the fan speed is not only controlled between an operating fan speed and a zero (off) fan speed. There may be three, four, five or more separate fan speed settings. The example above has five fan speed settings, but there may be more than five.

Accordingly, the fan speed is set to a selected one of a plurality of non-zero fan speeds. The mask has the ability to drive the fan to any one of these fan speeds. As mentioned above, there may be a set of discrete fan speeds that the fan can be set to, or there may be a range of continuous fan speeds, where the algorithm determines the possible Any desired fan speed within the range may be selected.

FIG. 7 shows how the mask is operated.

This method is
in step 70, using a fan to draw gas into and/or draw gas out of the air chamber of the mask;
In step 72, determining the rotational speed of the fan;
in step 74, obtaining a first value related to breathing depth and a second value related to breathing rate from the determined fan rotational speed or change in fan rotational speed;
in step 76, measuring an ambient temperature outside the air chamber and an ambient humidity level outside the air chamber; and in step 78, depending on the first value, the second value, the ambient temperature and the ambient humidity level. The step includes setting the speed of the fan.

The method includes determining in step 80 that the mask is not worn, based on the first value or the first value and the second value, and then turning off the fan.

As mentioned above, embodiments utilize controllers implemented in a number of ways, along with software and/or hardware, to perform the various functions required. A processor is an example of a controller that uses one or more microprocessors that are programmed using software (eg, microcode) to perform the required functions. However, a controller may be implemented with or without a processor, or with dedicated hardware to perform some functions and a processor (e.g. one or more processors) to perform other functions. (a programmed microprocessor and associated circuitry).

Examples of controller components used in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field programmable gate arrays (FPGAs).

In various implementations, a processor or controller may be associated with one or more storage media, such as volatile and nonvolatile computer memory, such as RAM, PROM, EPROM, and EEPROM. The storage medium may be encoded with one or more programs that, when executed on one or more processors and/or controllers, perform the required functions. Various storage media may be mounted within the processor and/or controller, or may be transportable such that one or more programs stored on the storage media are loaded into the processor or controller. .

Other variations to the disclosed embodiments can be understood and implemented by those skilled in the art in practicing the invention from a consideration of the drawings, this disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and does not exclude the presence of a plurality of an element, even if it does not state that there is a plurality of the element. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims shall not be construed as limiting the scope.

Claims (15)

air chamber,
a filter forming a boundary between the air chamber and the ambient environment outside the air chamber;
a fan for sucking air into the air chamber from outside the air chamber and/or sucking air out of the air chamber from the inside of the air chamber;
means for determining the rotational speed of the fan;
a temperature sensor for measuring ambient temperature outside the air chamber, and a contamination mask having a controller, the controller comprising:
obtaining from the determined fan rotational speed or a change in the fan rotational speed a first value related to breathing depth and a second value related to breathing rate; 2 and the ambient temperature, the fan speed is set to a selected one of a plurality of non-zero fan speeds, and the fan speed is set to a selected one of a plurality of non-zero fan speeds at different ambient temperatures. A pollution mask, wherein different airflows are provided for conditions and different activity levels of the user of the pollution mask. 2. The mask of claim 1, wherein the first value is based on a maximum swing in fan rotational speed during a sampling window. The mask according to claim 1 or 2, wherein the second value is a frequency based on the time between consecutive maximum and minimum rotational speeds of the fan. Claim 1, further comprising a humidity sensor for measuring an ambient humidity level outside the air chamber, and wherein the controller is configured to set a fan speed further depending on the humidity level. The mask according to any one of items 3 to 3. 5. The mask of claim 4, wherein the controller is configured to obtain a thermal index value related to a measure of comfort from the ambient temperature and the ambient humidity level. 6. The mask of claim 5, wherein the thermal index value has a polynomial function consisting of the ambient temperature, the ambient humidity level, and one or more powers of the ambient temperature and/or the ambient humidity level. The controller is
configured to generate an instruction to increase the fan speed, decrease the fan speed, or keep the fan speed the same from the current fan rotational speed and the first and second values. The mask according to any one of items 4 to 6. The controller is
8. The mask of claim 7, configured to determine from the ambient temperature and the ambient humidity level the amount by which the fan speed should be increased or decreased. The controller is
configured to determine from the rotational speed of the fan or a change in the rotational speed of the fan that the mask is not being worn, and to turn off the fan if it is determined that the mask is not being worn; The mask according to any one of claims 1 to 8. The fan is driven by an electronically commutated brushless motor, and the means for determining the rotational speed comprises an internal sensor of the motor, or the means for determining the rotational speed drives the fan. Consists of a circuit for detecting ripples on the electrical supply to the motor,
A mask according to any one of claims 1 to 9. The controller is
determining a breathing cycle from the rotational speed of the fan or a change in the rotational speed of the fan, and controlling an outlet valve depending on the phase of the breathing cycle and/or turning off the fan during the inhalation period; The mask according to any one of claims 1 to 10, configured to. A non-therapeutic method of controlling a contamination mask, wherein the contamination mask is not a mask for administering treatment to a patient, the method comprising:
drawing gas into and/or drawing gas out of the air chamber of the mask using a fan forming a boundary between the air chamber and the ambient environment outside the air chamber;
determining a rotational speed of the fan;
obtaining a first value related to breathing depth and a second value related to breathing rate from the determined fan rotational speed or change in fan rotational speed;
measuring an ambient temperature outside the air chamber; and depending on the first value, the second value and the ambient temperature, setting a fan speed, the fan speed being , a contamination mask configured to one of a plurality of non-zero fan speeds, wherein different airflows are provided for different environmental temperature conditions and for different activity levels of a user of the contamination mask; Non-therapeutic methods. 13. The method of claim 12, comprising measuring an ambient humidity level outside the air chamber, and setting the fan speed further dependent on the humidity level. 14. The method of claim 13, comprising the step of obtaining a thermal index value related to a measure of comfort from the ambient temperature and the ambient humidity level. generating an instruction to increase the fan speed, decrease the fan speed, or keep the fan speed the same from the current fan rotation speed and the first value;
15. A method according to claim 13 or 14, comprising determining from the ambient temperature and the ambient humidity level the amount by which the speed of the fan should be increased or decreased.

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