Technical Field
[0001] The invention relates to a gas monitoring device for use with the gas cylinder and
a corresponding valve comprising suchgas monitoring device, in particular for determining
a liquid phase in a gaseous mixture.
Technological Background
[0002] Gaseous mixtures comprising one or more gaseous components are used in a variety
of fields and are often applied at remote locations and/or in varying compositions
and concentrations, such that the on-site production of such gaseous mixtures is limiting.
In order to ensure that the required amount of the gaseous mixture is provided in
a sufficient and well defined amount, such gaseous mixtures are hence commonly stored
in gas cylinders having a predefined volume and permitting a compression of the gaseous
mixture to provide the gaseous mixture in a compressed state.
[0003] Depending on the use and original fill level or filling pressure of a respective
gas cylinder, pressures of the respective gaseous mixtures may however vary between
gas cylinders. Furthermore, the gas cylinders may be stored at different locations
having distinct ambient temperatures. Since the gaseous mixtures are generally stored
in a strongly compressed state at high pressures, e.g. above 100 bar, the storage
temperature may affect the physical state of the gases mixture comprised within the
gas cylinder.
[0004] For example, a gaseous mixture may comprise two or more gaseous components having
a distinct density, wherein both gaseous components are in the gas state at the respective
pressure and within a predefined temperature range, while a reduction of the temperature
below the lower limit of said temperature range, i.e. below a critical temperature,
may result in a transition from the gas state into a liquid state for at least one
of the gaseous components. In such situation, the mixture comprised within the gas
cylinder is provided as a two-phase mixture comprising both a gas state and a liquid
or condensed state, wherein the liquid state, may e.g. adhere to the inner wall of
the gas cylinder in the form of droplets or is collected at a lower end of the respective
gas cylinder. This poses the problem that the gaseous mixture is no longer homogeneous
and is comprised at a different concentration in the gas state, such that during the
application of the gaseous mixture, i.e. by opening a valve of the gas cylinder, the
gaseous mixture comprises an incorrect concentration or even a lack of a particular
component.
[0005] Such situation is of particular concern in medical applications, wherein the gaseous
mixture is administered to a patient in the form of a breathable medicament or support
gas. For example, a medical gas may be provided as a gaseous mixture comprised of
two gaseous components, such as nitrous oxide and oxygen, which may be administered
to a patient e.g. using a demand valve downstream of a pressure regulator of the valve
of the gas cylinder. The demand valve in such case administers the appropriate volume
of gas to the patient, dependent on the patients inspiratory effort. Although these
gases are highly stable at the pressures and temperatures specified for the product,
an ambient temperature below the lower limit may result in a transition of the gaseous
nitrous oxide into a condensed or liquid state, such that the administration of the
breathing gas initially provides an oxygen-rich gaseous mixture with a low amount
of nitrous oxide or no nitrous oxide at all. Thereby, the desired therapeutic effect
may not be achieved and detrimental side effects may occur, potentially leading to
critical conditions and harming the patient.
[0006] In order to avoid the phenomena where the nitrous oxide will condense out of the
mixture, preventive techniques commonly include the provision of specific advice to
the patient or user, e.g. by providing proper instructions prior to use, a patient
information leaflet and/or by properly labeling the gas cylinder. Such preventive
techniques in particular comprise the advice to a user that the respective gas cylinder
should be stored at a temperature above 10éC for at least 24 hours before use. Where
this is not possible, the optional instructions are given to invert the gas cylinderthree
times prior to use to mix the gas before administration.
[0007] However, in case of an urgent requirement of the gaseous mixture, it may not be possible
to wait for the prescribed storage time to lapse. Furthermore, although depending
on the particular circumstances a brief storage at lower temperatures may not immediately
result in a condensation of at least one gaseous component, the useror patient may
not be capable to assess the exact state of the gaseous mixture and the necessity
of further preventive measures. In addition, even if such measures are performed,
e.g. by multiple inversions of the gas cylinder, such inversions may have been performed
incorrectly or may be insufficient to fully reduce the liquid state, even when performed
correctly. Therefore, an increased risk of administering an incorrect gaseous mixture
remains.
[0008] Accordingly, further improvements are required to e.g. determine that the gaseous
mixture has been stored correctly and has been mixed properly to ensure the safe use
of the gaseous mixture.
Summary of the invention
[0009] It is an object of the present invention to provide a device for use with a gas cylinder,
which is adapted to monitor a state of a gaseous mixture within the gas cylinder to
improve the safe use of the gaseous mixture.
[0010] Accordingly, in a first aspect, a gas monitoring device for use with a gas cylinder
device is suggested, which comprises a first temperature sensor for measuring an ambient
temperature of the gas cylinder, an indicator for indicating a status of a gaseous
mixture comprised in the gas cylinder, and an evaluation unit in communication with
the first temperature sensor and the indicator and configured to determine a status
of the gaseous mixture based on the received ambient temperature measurement and to
output a signal corresponding to said status to the indicator, when the gas monitoring
device is coupled to the gas cylinder.
[0011] By measuring an ambient temperature of the respective gas cylinder, the evaluation
unit may hence determine whether the detected temperature corresponds to a predefined
temperature or exceeds a particular threshold. For example, the evaluation unit may
be configured for a particular type of gas and/or a particular mixing ratio of various
gaseous components having a corresponding critical temperature at which a transition
from the gas state into the liquid state may occur. Accordingly, the evaluation unit
may determine the state of the gaseous mixture within the gas cylinder based on the
detected ambient temperature and depending on whether said temperature is above or
below such critical temperature, so as to indicate a probability of the presence of
a liquid state within the gaseous mixture. The type of gas, the ratio of the gaseous
components, and/or a preset critical temperature may be stored in the evaluation unit
and/or may be adjusted and provided to the evaluation unit by means of an inputting
device, such as a keyboard, touchscreen, or a selective mechanical switch or dial
provided on the device.
[0012] When the ambient temperature sensor measures a temperature that is below the critical
temperature, the evaluation unit may hence determine an increased probability of a
liquid state being present in the gaseous mixture and accordingly outputs a signal
to the indicator, such that the indicator may indicate the determined status. By the
same token, if the measured ambient temperature is above the critical temperature,
the evaluation unit may accordingly output a signal corresponding to a low probability
of a liquid state being present, such that the indicator may provide a status indicating
that the gaseous mixture may be safely used. A user, e.g. a patient or medical professional,
is hence provided with an actual status of the gaseous mixture comprised within the
gas cylinder and indicates to a user whether a use of the gas cylinder may impose
a potential risk.
[0013] In order to provide a reliable measurement of the first temperature sensor, the temperature
sensor is preferably arranged at a position, wherein the temperature sensor is not
in direct contact with the components arranged at the gas cylinder outlet, e.g. the
pressure regulator, a valve, or valve outlet, such that a temperature change during
active use of the gas cylinder caused by the expansion of the gaseous mixture does
not affect the ambient temperature measurement of the first temperature sensor. For
example, the first temperature sensor may be arranged at an outer end or outer surface
of the gas monitoring device and preferably points away from the valve components.
Alternatively, the first temperature sensor may be arranged so as to be in contact
with or parallel to a wall of the gas cylinder in the coupled state. The temperature
sensor may be formed as e.g. a thermistor, a thermocouple, or digital thermometer.
[0014] It is to be understood that the gas monitoring device may be provided as a separate
electronic module, which may be coupled to a gas cylinder, in particular to a valve
of a gas cylinder. Accordingly, the gas monitoring device is configured to be coupled
with at least one component of the gas cylinder and/or valve thereof, for example,
by the provision of attachment or fixation means, e.g. by the provision of an electromagnetic
coupling, screwing attachment, clamp or strap. Thereby, the gas monitoring device
may be coupled to any gas cylinder irrespective of the type of gas comprised within
the respective gas cylinder and/or the type of valve used with the gas cylinder. Existing
valves, pressure regulators, and/or gas cylinders may hence be retrofitted with the
gas monitoring device without requiring any invasive modifications with pressure regulating
elements being in fluid communication with the gaseous mixture and potentially being
under high pressure. The coupling may also be indirectly provided, for example, by
providing a coupling to a framework or rack of the gas cylinder. Such coupling may
hence also be provided for a plurality of gas cylinders stored and transportable in
a single rack.
[0015] The gas monitoring device may hence be coupled and securely fixed to the gas cylinder
yet provides a releasable modular unit, which may be removed, adjusted, and/or replaced.
Alternatively, the gas monitoring device may also be embedded in the valve of the
gas cylinder to form an integral unit therewith. Due to the coupling with a respective
gas cylinder, the ambient temperature measurement furthermore becomes more reliable
and specific for the respective gas cylinder.
[0016] Preferably, the evaluation unit is further configured to determine the status of
the gaseous mixture based on an evaluation of the ambient temperature measurement
over a predefined time period and/or a comparison of the ambient temperature measurement
with a predefined temperature range, wherein the outputted signal comprises an alarm,
when the determined status deviates from a predefined status stored in the evaluation
unit. In other words, the evaluation unit can record whether the gas cylinder has
been stored at the correct temperature for the correct amount of time and so is safe
for use, i.e does not comprise a gaseous mixture with separated phases.
[0017] For example, the gas cylinder may be subjected to an ambient temperature below a
critical temperature of the respective gaseous mixture for a brief period of time,
e.g., during transportation between nearby facilities after being stored at room temperature.
Although the temperature of the wall of the gas cylinder, which is generally made
of metal, may be accordingly reduced, the gaseous mixture may not fall below the critical
temperature during said period of time. Accordingly, the evaluation unit may determine
the status of the gaseous mixture based on the time in which the ambient temperature
was measured below the critical temperature. By the same token, the probability of
a transition from the gas state into the liquid state may be increased for a particular
temperature range, such that even in a case where the ambient temperature measurement
does not fall below the critical temperature or only for a brief period of time, the
evaluation unit may determine an increased probability of the presence of a liquid
state, if the ambient temperature measurement is within the predefined temperature
range. Preferably, the evaluation unit determines the status based on an evaluation
of the ambient temperature measurement over a predefined time period and a comparison
with a predefined temperature range.
[0018] Based on the determined status of the gaseous mixture, the evaluation unit accordingly
outputs a signal to the indicator so as to provide the user with information relating
to the gaseous mixture, e.g. a level of safety for using the gaseous mixture. When
the determined status deviates from a predefined status stored in or otherwise provided
to the evaluation unit, the outputted signal may comprise an alarm to indicate an
increased risk when using the gas cylinder. For example, the measured ambient temperature
may exceed a lower threshold or critical temperature for the gaseous mixture and the
evaluation unit may determine an increased probability of the presence of a liquid
state of the gaseous mixture, such that the actual status of the gaseous mixture no
longer corresponds to a safe status and instead corresponds to a risk status, which
is provided to the user in the form of an alarm, e.g. a visual warning light or acoustic
alarm, e.g. by means of a speaker or buzzer.
[0019] The determined status of the gaseous mixture and the corresponding outputted signal
may indicate e.g. whether the gaseous mixture is at a temperature which is compatible
with a medical gas application, i.e. is at a temperature suitable for being used as
a breathable medical gas. Preferably, the determined status indicates the probability
of the presence of a liquid phase within the gas cylinder, wherein the gaseous mixture
preferably comprises nitrous oxide, oxygen, helium, nitrogen, nitric oxide, carbon
monoxide, and/or carbon dioxide.
[0020] Accordingly, the gaseous mixture may be a medical gas or breathing gas for a patient,
in particular for a patient suffering from a respiratory disorder, wherein the gaseous
mixture is administered to the patient via inhalation or mechanical ventilation. The
gaseous mixture may e.g. comprise a mixture of nitrous oxide and oxygen or may comprise
a combination of helium and nitric oxide, depending on the required therapeutic effect.
[0021] For example, a combination of nitrous oxide, also known as laughing gas, and oxygen,
e.g. at equal parts, may be provided as an anesthetic, due to its pain alleviating
or analgesic effects while at the same time providing the patient with a sufficient
level of oxygen. However, while the oxygen is maintained in the gas state, the nitrous
oxide component of the gaseous mixture may at least partly transition into a liquid
state, when a particular pressure is provided and the gaseous mixture is subjected
to a temperature below the specific critical temperature, due to its larger density.
Thereby, the gaseous mixture exiting the gas cylinder upon valve actuation is comprised
of enriched oxygen, wherein the nitrous oxide is reduced or absent, thereby having
a limited therapeutic effect. By providing the measurement of the ambient temperature
of the gas cylinder, the evaluation unit may determine a probability of the presence
of a liquid state and may accordingly alert the user via the outputted signal and
the indicator.
[0022] The indicator may be provided as any means capable of visually, acoustically, and/or
electromechanically representing the outputted signal. Preferably, the indicator is
configured to present the status by activating one or more LEDs, by providing a graphical
representation or text message on a display, and/or by outputting an acoustic signal.
For example, the indicator may comprise one or more LE Ds emitting light in different
colors corresponding to a different status of the gaseous mixture, e.g. red and green,
wherein red indicates an increased risk for the user and green indicates that the
gaseous mixture is safe for use. Alternatively, or in addition, a display or screen
may be provided, which may represent the status by means of a graphical icon or pictogram
and/or by providing a text message corresponding to the status. Furthermore, an acoustic
signal may be provided by means of e.g. a speaker or buzzer, or in the acoustic signal
may be outputted as an alarm, e.g. when the determined status deviates from a predefined
status or poses a potential risk to a user.
[0023] In other words, a real time indication may be provided whether the gas cylinder has
been stored correctly and is ready for immediate use, which reduces the potential
risk of a patient using the gaseous mixture where the gas has been stored incorrectly
or not mixed properly.
[0024] Instead of continuously outputting the signal to the indicator, the indicator may
be configured to present the status on-demand by means of an actuation of a touch-sensitive
object of the indicator, preferably a button or mechanical switch, or upon actuation
due to a coupling with a remote device via NFC, Bluetooth, Zigbee, RFID, or WiFi.
[0025] By providing a retrievable status rather than a continuous status the energy consumption
of the gas monitoring device may be reduced. Furthermore, the status may be only retrievable,
when an identifier is provided to the gas monitoring device. Such identifier may be
provided by means of a touch- sensitive object or keypad, but may also be automatically
retrieved upon a successful coupling with a compatible remote device, e.g. via NFC
in case of a nearby remote device or control or via Wi-Fi, orWLAN in case of more
remote devices. Thereby, a level of security may be provided to the determined status
of the gaseous mixture in the gas monitoring device.
[0026] The gas monitoring device may furthermore comprise a valve activation sensor for
a valve of the gas cylinder, which is in communication with the evaluation unit and
wherein the evaluation unit outputs the signal based on the determined status and
the detected valve activity.
[0027] By means of the valve activation sensor an opening or closing of the valve may be
detected. Should the evaluation unit determine a status of the gaseous mixture indicating
an increased risk for a user when using the gaseous mixture and detect an activation
of the valve by means of the valve activation sensor, e.g. an opening or flow rate
setting of the valve, a signal may be outputted and be presented by the indicator
to alert the user, e.g. by means of an alarm. Such detection mechanism hence facilitates
that a further use of the gaseous mixture may be prevented. By the same token, if
no increased risk is determined, the evaluation unit may either not output a signal
or may output a signal indicating a safe use of the gaseous mixture. Accordingly,
the valve activation sensor provides an additional confirmation and level of safety
for a user or patient.
[0028] The valve activation sensor is preferably configured as a flow sensor for detecting
a flow of a gas through the valve of the gas cylinder or the gas monitoring device
comprises a second temperature sensor for measuring a temperature of a valve body
of the gas cylinder and being in communication with the evaluation unit, wherein the
evaluation unit determines an activation of the valve based on the first temperature
sensor measurement and the second temperature sensor measurement.
[0029] For example, a flow sensor may be arranged at a valve outlet of the gas cylinder
and may accordingly comprise a coupling device to provide a fluid coupling between
the valve outlet and e.g. a gas application device, for example, by means of a bayonet
or luer coupling. The use of such a flow sensor has the advantage that not only an
activation of the valve may be detected, but also a current flow rate of the gas being
applied is provided as additional information to the evaluation unit.
[0030] Alternatively, a second temperature sensor arranged at the valve body may provide
a temperature measurement of the valve body to the evaluation unit, wherein the evaluation
unit processes a compensated temperature calculated from the difference between the
measured valve body temperature and the ambient temperature overtime to determine
the flow-rate of the flow of gas from the cylinder and/or the pressure on the gas.
Such compensated temperature may be based on the fact that when a gas experiences
a rapid change in pressure, for example when it flows through a valve or regulator,
the gas experiences an iso-enthalpic process leading to a temperature change, known
as the Joule-Thomson effect. The valve body temperature can then be processed to distinguish
between the change in temperature that is attributable to the flow-rate of the gas,
and the change in temperature due to the pressure change in the cylinder. The flow-rate
of the gas and the pressure change in the cylinder can then both be determined from
the temperature and time data.
[0031] From the flow-rate it is furthermore possible to calculate the change in volume in
the gas cylinder over the time the valve was opened, and from the pressure change
it is possible to calculate the volume change based on knowing the initial or last
recorded and stored pressure and volume. Knowing the volume change hence enables the
remaining volume of gas to be calculated.
[0032] The measured compensated temperature and time information can be processed to calculate
the rate of change of temperature with time (the first temperature derivative), and
the rate of change of the first derivative with time (the second temperature derivative)
at any given time. Advantageously, information about the gas cylinder contents can
be obtained from measuring the temperature alone rather than having to rely on flow-rate
or pressure data which requires more sophisticated and invasive monitoring equipment.
[0033] Furthermore, the activation state of the valve may be factored into the temperature
measurement of the first temperature sensor. This is particularly advantageous when
the spatial arrangement between the first and second temperature sensor may not exclude
that both sensor measurements influence each other. In addition, activation of the
valve may incur a temperature change of the valve body, which may extend towards the
wall of the gas cylinder and hence to the first temperature sensor. Accordingly, the
measurement of the temperature of the valve body may be used to correct an ambient
temperature measurement. Since the activation of the valve may furthermore cause a
pressure difference within the gas cylinder, the activation state may furthermore
be used to determine the status of the gaseous mixture, such that, for example, a
low probability of the presence of a liquid state may be neglected, when a high flow
rate is indicated by the valve activation sensor.
[0034] Preferably, the indicator is configured to prompt a user to maintain the gas cylinder
within a predefined temperature range for a predefined time period and/or to invert
the gas cylinder for a predefined number of times based on the determined status.
Said time period and/or number of inversions may e.g. correspond to a probability
level of the presence of a liquid state within the gaseous mixture or generally to
an absolute ambient temperature measurement or sequence of ambient temperature measurements.
For example, a prolonged storage of a respective gas cylinder below a critical temperature
may require that the gas cylinder is maintained at e.g. room temperature for a prolonged
period of time, while a brief ambient temperature measurement just below the critical
temperature may be remedied by e.g. one to three inversions of the gas cylinder.
[0035] In order to ensure whether an inversion of the gas cylinder has taken place, the
gas monitoring device preferably comprises an accelerometer or motion sensor in communication
with the evaluation unit, wherein the evaluation unit is configured to update the
determined status based on a received measurement of said accelerometer or motion
sensor. A brief storage of a respective gas cylinder and below the critical temperature
of the gaseous mixture may e.g. be followed by one or more inversions of the gas cylinder,
such that the presence of a liquid state of the gaseous mixture may be insignificant
or may at least not pose a risk for the user. Accordingly, even if such status of
the gaseous mixture is initially determined, the status is automatically updated upon
a detection of an inversion or other movement by the accelerometer or motion sensor.
[0036] In addition, this provides a feedback mechanism to the evaluation unit in the case
where the indicator prompts a user to invert the gas cylinder for a predefined number
of times based on the determined status. In otherwords, the actual number of inversions
within a predefined period of time may be compared with the prescribed number of inversions
and the evaluation unit may accordingly output a signal based on said comparison.
If the comparison indicates that the prescribed number of inversions have occurred,
a previously determined status corresponding to an increased risk of the presence
of a liquid state within the gaseous mixture may be updated, so as to indicate to
a user that the gaseous mixture is now safe for use. If the indicator is configured
as a display or screen, the display may also indicate the temperature and the remaining
time and/or number of inversions required to ensure that the gaseous mixture is safe
for use, e.g., in the form of a countdown.
[0037] Since large institutions and facilities generally comprise a plurality of gas cylinders
for a plurality of users or patients, which may be used or stored at different and
remote locations, it is furthermore preferable that the status, for each of these
gas cylinders is remotely retrievable. Accordingly, the gas monitoring device preferably
comprises a wireless communication module in communication with the evaluation unit,
wherein the wireless communication module is configured to transmit the output signal
to a remote device, preferably a remote monitor and/or monitoring system. Thereby,
it is possible to locate and track a respective gas cylinder and it is ensured that
a required gaseous mixture is available for use. Furthermore, should the evaluation
unit of the respective gas cylinder indicate a potential risk due to the determined
status of the respective gaseous mixture, e.g. due to an undesirable storage temperature,
maintenance or relocation may be provided to ensure a proper storage of said gas cylinder.
[0038] In a medical setting, this may furthermore ensure that medical personnel is alerted,
when a status of a gaseous mixture deviates from a predefined status and use of said
gaseous mixture potentially poses a risk for a corresponding patient. If the gas monitoring
device is furthermore equipped with a valve activation sensor, an actuation or opening
of said valve may furthermore invoke an alarm in a monitoring system or in a remote
device coupled with the gas monitoring device, such that the medical personnel may
be immediately directed to the respective gas cylinder to avoid further usage.
[0039] In order to facilitate the transmission of the output signal to a remote device,
the wireless communication module is preferably configured with Bluetooth, Bluetooth
Low Energy, Zigbee, RFID, WLAN, WiFi, and/or similar communication standards to facilitate
a nearby or remote communication.
[0040] To facilitate transportation and for ease of implementation of the gas monitoring
device, the gas monitoring device is preferably configured as a stand-alone unit comprising
an electrical energy storage medium and/or comprises an electrical coupling. For example,
the gas monitoring device may be powered by a battery, such as half an AA, an AA or
an AAA standard battery, which provides a sufficient longevity to maintain the gas
monitoring device between one to five years in standby or low activity mode. Such
battery power has the advantage that no further implementations are required other
than a correct coupling of the gas monitoring device to the gas cylinder and that
the gas monitoring device may be used with a gas cylinder at an arbitrary location.
Alternatively, or in addition, the gas monitoring device may be provided with an electric
coupling device, such that the gas monitoring device may be charged or powered by
an external electrical energy source. Furthermore, the gas monitoring device may be
electrically coupled to a powered integrated valve by means of a corresponding interface.
[0041] According to a further aspect of the invention, a valve for a gas cylinder is suggested,
comprising a gas monitoring device as described in the above. For example, the gas
monitoring device may be coupled to the valve via an attachment or fixation means,
such as a screwing attachment, or alternatively via an electromagnetic coupling. Preferably,
the gas monitoring device is integrated in the valve, e.g. embedded or otherwise securely
fixed to the valve. Accordingly, the gas monitoring device may be provided as a releasable
module, which is secured to the valve, e.g., for retrofitting purposes of existing
valves, or may be formed as an integral part.
[0042] The valve may furthermore comprise a pressure sensor, which is in communication with
the evaluation unit, wherein the evaluation unit is configured to determine the status
based on the received ambient temperature measurement and the detected pressure of
the gaseous mixture in the gas cylinder. As described in the above, the state of each
gaseous component in the gaseous mixture may be dependent on both the pressure and
the temperature within the gas cylinder. Although most gaseous components are in a
gas state at ambient temperature and even at high pressure, gaseous components may
transition into the liquid state below a particular temperature, known as the critical
temperature. Accordingly, including the pressure of the gaseous mixture within the
gas cylinder in the determining of the status of the gaseous mixture further increases
the validity of a determined probability of the presence of a liquid state within
the gaseous mixture. For this purpose the evaluation unit may be in direct communication
with the pressure sensor or may communicate with said pressure sensorvia an interface
provided in the valve.
[0043] The evaluation unit, as described in the above may comprise any computing means,
such as a processor or microprocessor to process the various measurements and may
furthermore comprise a data storage, storing e.g. lists of critical temperatures for
particular gaseous components, and may be configured to compare said measurements
with available data, e.g. thresholds or temperature ranges, stored in said storage.
In addition, and inputting means may be provided, such that relevant data for determining
the status of the gaseous mixture may be manually or automatically inputted.
[0044] The evaluation unit may furthermore be in communication with or be configured as
a control unit of the valve, wherein the control unit is configured to control the
valve actuation based on the determined status. The evaluation unit may hence be coupled
with an existing control unit, e.g. via an interface, or may form an integral part
of a control unit.
[0045] The evaluation unit may hence also be configured as being part of a controller or
as controller itself and may accordingly be operatively coupled with various actuation
components of a valve, e.g. a pressure regulator and/or a valve actuation wheel or
knob, either directly or via an interface of the valve.
[0046] Accordingly, based on the determined status of the gaseous mixture, the evaluation
unit may actively prevent an activation or actuation of the valve, for example, when
the determined status indicates a risk for a user. The control function of the activation
may furthermore be provided by a remote device, e.g. a coupled remote device or central
monitoring device, by means of a corresponding coupling, e.g. by means of a wireless
communication module.
Brief description of the drawings
[0047] The present disclosure will be more readily appreciated by reference to the following
detailed description when being considered in connection with the accompanying drawings
in which:
Figure 1 is a graphical representation of the physical state of nitrous oxide at different
pressures and temperatures;
Figure 2 is a schematic view of a gas monitoring device coupled to a gas cylinder;
Figure 3 is another schematic view of a gas monitoring device securely attached to
a valve and gas cylinder wall of a gas cylinder;
Figure 4 is another schematic view of the gas monitoring device according to Figure
3 with further functional features;
Figure 5 is a schematic view of the gas monitoring device according to Figure 4 in
communication with a remote device; and
Figure 6 is a perspective view of a valve with an attached gas monitoring device.
Detailed description of preferred embodiments
[0048] In the following, the invention will be explained in more detail with reference to
the accompanying Figures. In the Figures, like elements are denoted by identical reference
numerals and repeated description thereof may be omitted in order to avoid redundancies.
[0049] In Figure 1 a graph is shown indicating the physical state of nitrous oxide, which
may be used in a gas mixture together with oxygen, e.g. at equal parts, and is normally
administered to a patient for therapeutic purposes. The physical behavior of nitrous
oxide is depicted for the respective pressure (P) and temperature (T) ranges. As shown
by curve A and rectangular elements, nitrous oxide may be in a gas state or phase
even at high pressures yet reaches a critical point, as indicated by C. Provided that
the pressure and temperature of the gas mixture remain to the left of curve A, there
will be no separation of the gas mixture, i.e. the nitrous oxide will remain in the
gas state. Furthermore, at pressures above the critical point C on the curve, the
gas mixture will remain as a gas. However, if the pressure is maintained and the temperature
is reduced to below -6éC, the nitrous oxide component of the mixture will start to
condense out of the gas mixture, as indicated by curve B and triangular elements.
By the same token, if the temperature is further reduced, nitrous oxide will transition
into the liquid phase even at lower pressures. Accordingly, with low temperatures,
stability of the gaseous mixture is reduced, increasing the probability of a gas separation,
which may pose a risk to a patient when using the gaseous mixture.
[0050] Figure 2 is a schematic view of a gas monitoring device 10 coupled to a gas cylinder
12 having a valve 14. As indicated by the dashed line, the gas monitoring device 10
is not required to be in direct contact with the gas cylinder 12 or valve 14. For
example, the gas monitoring device 10 may also be coupled to the gas cylinder 12 by
means of an attachment to a holder or rack of the gas cylinder 12, such that the gas
monitoring device 10 may be associated with a particular gas cylinder.
[0051] The gas monitoring device 10 comprises a first temperature sensor 16, which is configured
and arranged to detect an ambient temperature so as to provide a corresponding measurement
to the evaluation unit 20. The evaluation unit 20 comprises a computing means in the
form of a processor as well as a data storage to compare the measured ambient temperatures
with a predefined temperature range stored in the evaluation unit20. Said temperature
range corresponds to a dew point or critical temperature for a given pressure and
specific component, e.g. nitrous oxygen, which is comprised in the gaseous mixture
in the gas cylinder 12.
[0052] Accordingly, a provided ambient temperature below said temperature range may indicate
that said gaseous component in the gaseous mixture may transition into the liquid
phase, e.g. condense, such that the gaseous mixture is at least partly separated and
the required concentration of the respective components within the gaseous mixture
does not correspond to a prescribed concentration. In order to alert a user handling
the gas cylinder 12, the gas monitoring device 10 comprises an indicator 18, which
is configured in the form of a display and which is in communication with the evaluation
unit 20 to receive an output signal corresponding to a determined status of the gaseous
mixture. The display may hence present a text message or graphical icon indicating
whether the gaseous mixture and gas cylinder 12 is safe for use based on the received
signal. However, alternatively, or in addition, the indicator 18 may also provide
an indication of the determined status by means of a light or LE D and/or acoustic
signal, such as an alarm via a buzzer.
[0053] The embodiment depicted in Figure 3 essentially corresponds to the embodiment of
Figure 2, wherein in addition to the first temperature sensor 16 a valve activation
sensor 24 is comprised in the gas monitoring device 10. The gas monitoring device
10 is directly coupled to the gas cylinder 12 and the valve 14, e.g. to a wall of
the gas cylinder 12, by means of an attachment means, e.g. a screwing fixation, Velcro,
or an adhesive. Accordingly, the gas monitoring device 10 is specific for the gas
cylinder 12 even in the case of a separation of the gas cylinder 12 from a holder.
[0054] Furthermore, such arrangement facilitates the measurement of an actuation of the
valve 14 due to the direct coupling. The valve activation sensor 24 may e.g. be configured
as a sensor to detect an opening and closing of the valve 14, but is preferably configured
to determine a flow rate of the gaseous mixture exiting the valve 14. In order to
avoid any necessary further implementations and to provide a non-invasive measurement
of the flow rate, the valve activation sensor 24 may be formed as a second temperature
sensor, which measures a temperature of the valve body.
[0055] The valve comprises a primary on-off valve, a flow-regulator valve, and an outlet
connection (not shown). The second temperature sensor of the gas monitoring device
is in direct contact with the valve body of the valve 14 and is configured as a thermistor,
which is mechanically biased via a resilient member such that the thermistor engages
the valve body, when the gas monitoring device 10 is assembled onto the valve body.
[0056] The processor of the evaluation unit 20 is operable to calculate a compensated temperature
over time, the compensated temperature being the difference between the measured valve
body temperature and the measured ambient temperature, and then determines the first
temperature derivate (dCT/Dt) and the second temperature derivate (d2CT/dt2), which
together may be used during operation of the valve to determine the flow rate and
pressure change in the cylinder. From the determined flow rates and/or pressure changes,
the volume change in the gas cylinder 12, and hence the remaining volume, can be calculated.
[0057] To facilitate the determining of the flow rate the processor of the evaluation unit
20 can store reference data associated with the gas cylinder 12 to which it is attached.
The reference data may include valve calibration data which equates temperature change
of the valve body to gas flow-rate through the valve body when the flow-regulator
valve is opened. The valve calibration data is specific and selected according to
the valve 14 and gas cylinder 12 to which the valve 14 is attached, and may include
valve material, valve size, filling pressure of the cylinder 12, cylinder volume,
and cylinder material.
[0058] The evaluation unit 20 may hence not only indicate a potential risk of using the
gaseous mixture below a predefined ambient temperature, but may also provide further
information derived from the determined flow rate to indicate a calculated remaining
time, provide a warning to user that a flow rate does not correspond to a prescribed
flow rate, and/or alert a user that the remaining amount of the gaseous mixture is
insufficient for a prescribed treatment and a replacement or refill of the gas cylinder
12 will be required. Said information may be provided by means of the outputted signal
to the indicator 18.
[0059] In addition, in order to reduce the energy consumption, the indicator 18 may be configured
to present the determined status information by means of a button 22, such that the
status is only retrievable upon activation of said button. Therefore, a continuous
indication is avoided by the provision of on-demand retrieval. Furthermore, such retrieval
may require an identifier, such that a level of security is provided and e.g. only
medical personnel is capable to perform the status reading.
[0060] The embodiment according to Figure 4 comprises a wireless communication module 28,
which is in communication with the evaluation unit 20 and is configured to transmit
the determined status to a remote device, e.g. via Bluetooth or Low E nergy Bluetooth.
This ensures that a user or medical personnel that is not in direct vicinity of the
gas cylinder 12 may monitor the gaseous mixture comprised in the gas cylinder 12 and
may be alerted, if the risk of a gas separation is determined based on the measured
ambient temperature. To be able to transmit such information the wireless communication
module 28 may require a coupling with the remote device, e.g. by providing an identifier
or by requiring an initial physical proximity to the gas monitoring device 10, e.g.
via NFC or RFID, to ensure that the transmitted information is only receivable by
an authorized remote device.
[0061] The gas monitoring device 10 furthermore comprises an accelerometer 26, which is
securely attached and is configured to measure a movement and acceleration of the
gas monitoring device 10. The accelerometer 26 is in direct communication with the
evaluation unit 20 and may be used to ensure that a prescribed number of inversions
is performed, as indicated by the indicator 18 or in outputted signal corresponding
to the determined status, when the determined status indicates a potential risk for
the use of the gaseous mixture.
[0062] For example, the gas cylinder 12 may have been stored at a temperature, which causes
a particular gaseous component to separate from the gaseous mixture due to a transition
into the liquid state, e.g. due to condensation. In such case, the indicator 18 may
present information based on the determined status to maintain the gas cylinder 12
at above a particular temperature for a predefined period of time a nd/or to invert
the gas cylinder 12 a predefined number of times prior to use. While the first temperature
sensor 16 measures the ambient temperature and hence provides feedback to the evaluation
unit 20 as to whether the gas cylinder 12 is stored at a required temperature, the
accelerometer 26 provides feedback to the evaluation unit 20 as to the number of inversions
and whether said inversions have been performed correctly. Accordingly, the evaluation
unit 20 may periodically or continuously update the determined status and may provide
such update via the outputted signal to the indicator 18.
[0063] The wireless communication module 28 may furthermore be in communication with a remote
device 30, as indicated in Figure 5 by means of the dashed line, wherein the remote
device 30 may be configured as a central monitoring unit or remote central computer
system. The transmitter of the wireless communication module 28 may hence transmit
the signal corresponding to the determined status to the remote device 30 to alert
the operator of the remote device 30, if the determined status poses a risk for a
user. In addition, the transmitter may be capable of transmitting data, which in addition
to the determined status and depending on the configuration of the evaluation unit
20 may include the gas cylinder 12 details and the remaining volume left in the gas
cylinder 12 to the remote device 30 to make the operator of the remote device 30 aware
if the cylinder needs changing.
[0064] Although the processor of the evaluation unit 20 processes the ambient temperature,
the flow rate data, and the movement data over time and updates the determined status,
said processing steps may also be performed by the remote device 30, i.e. when the
level of required independency and remoteness is low, such that there is no need for
any processing to be done in the gas monitoring device 10. This may furthermore reduce
the energy consumption of the gas monitoring device 10.
[0065] The remote device 30 or plurality of remote devices 30 may be positioned e.g. in
a ward, surgery, filling station, and/or storage station and may be either stationary
or configured as a mobile and/or handheld device. Furthermore, to facilitate the communication
between the gas monitoring device 10 and the remote device 30, the communication may
be provided via one or more hubs, wherein the hubs can then communicate with e.g.
the central computer using wireless transmission protocols more suitable for longer
distances, such as Wi-Fi.
[0066] The evaluation unit 20 is furthermore configured as a controller being in communication
with the actuation components of the valve 14, as indicated by the dashed line. Accordingly,
the evaluation unit 20 may control an opening and/or closing of the valve and is furthermore
preferably configured to seta particular flow rate. For example, when the determined
status indicates a potential risk for the use of the gaseous mixture due to an inhomogeneous
phase separation of the gaseous mixture, the evaluation unit 20 may control the valve
14 so as to close the valve 14 and may at the same time output an alert to the user
via the outputted signal. By the same token, the remote device 30 may be configured
to not only receive the information from the wireless communication module, but to
also transmit input data for the evaluation unit 20, e.g. by comprising a transceiver,
including control commands for the valve 14. Thereby, a medical professional or operator
may ensure that only a safe to use gaseous mixture is administered to a patient.
[0067] A more detailed embodiment of the various optional features of the valve 14 including
a gas monitoring device 10 is depicted in the perspective view of a valve 14 in Figure
6. The valve 14 is attached to a gas cylinder 12 (only part of which is shown) and
is mechanically and fluidly connected via connector 32. The valve 14 comprises a valve
body 34 which has a primary on-off valve 36, a flow-regulator valve 38, and an outlet
connection 40. Accordingly, using the flow-regulator valve, a flow rate may be set
ranging from 0 to 0,5 and from 1 to about 25 L per minute. The gaseous mixture is
then administered to a patient via a patient interface, arranged downstream of the
outlet connection 40, e.g. via tubing. The valve 14 also has a mechanical pressure
gauge 21 to indicate the pressure in the gas cylinder 12, a filling port 44, and a
medical quick connector 46.
[0068] Accordingly, the gas monitoring device 10 is coupled to the gas cylinder 12 by means
of an attachment to the valve 14. Although said valve 14 may be configured as an analog
valve, the gas monitoring device 10 may optionally also be coupled to a digital valve,
wherein the gas monitoring device 10 is preferably integrated in the valve as an embedded
feature.
[0069] It will be obvious for a person skilled in the art that these embodiments and items
only depict examples of a plurality of possibilities. Hence, the embodiments shown
here should not be understood to form a limitation of these features and configurations.
Any possible combination and configuration of the described features can be chosen
according to the scope of the invention.
List of reference numerals
[0070]
- 10
- Gas monitoring device
- 12
- Gas cylinder
- 14
- Valve
- 16
- First temperature sensor
- 18
- Indicator
- 20
- Evaluation unit
- 22
- Button
- 24
- Valve activation sensor
- 26
- Accelerometer
- 28
- Wireless communication module
- 30
- Remote device
- 32
- Connector
- 34
- Valve body
- 36
- Primary on-off valve
- 38
- Flow-regulatorvalve
- 40
- Outlet connection
- 42
- Filling port
- 44
- Medical quick connector
- A
- Gas phase
- B
- Liquid phase
- C
- Critical temperature
1. Gas monitoring device (10) for use with a gas cylinder(12), comprising:
a first temperature sensor(16) for measuring an ambient temperature of the gas cylinder
(12),
an indicator (18) for indicating a status of a gaseous mixture comprised in the gas
cylinder(12), and
an evaluation unit (20) in communication with the first temperature sensor (16) and
the indicator (18) and configured to determine a status of the gaseous mixture based
on the received ambient temperature measurement and to output a signal corresponding
to said status to the indicator (18), when the gas monitoring device (10) is coupled
to the gas cylinder(12).
2. Gas monitoring device (10) according to claim 1, wherein the evaluation unit(20) is
further configured to determine the status of the gaseous mixture based on an evaluation
of the ambient temperature measurement over a predefined time period and/or a comparison
of the ambient temperature measurement with a predefined temperature range, and wherein
the outputted signal comprises an alarm, when the determined status deviates from
a predefined status stored in the evaluation unit (20).
3. Gas monitoring device (10) according to claim 1 or 2, wherein the determined status
indicates the probability of the presence of a liquid phase within the gas cylinder
(12), wherein the gaseous mixture preferably comprises nitrous oxide, oxygen, helium,
nitrogen, nitric oxide, carbon monoxide, and/or carbon dioxide.
4. Gas monitoring device (10) according to any of the preceding claims, wherein the indicator
(18) is configured to present the status by activating one or more LEDs, by providing
a graphical representation or text message on a display, and/or by outputting an acoustic
signal.
5. Gas monitoring device (10) according to claim 4, wherein the indicator(18) is configured
to present the status on-demand by means of an actuation of a touch-sensitive object
of the indicator (18), preferably a button (22) or mechanical switch, or upon actuation
due to a coupling with a remote device (30) via NFC, Bluetooth, Zigbee, RFID, WLAN
orWiFi.
6. Gas monitoring device (10) according to any of the preceding claims, further comprising
a valve activation sensor(24) fora valve (14) of the gas cylinder(12) being in communication
with the evaluation unit (20), wherein the evaluation unit (20) outputs the signal
based on the determined status and the detected valve activity.
7. Gas monitoring device (10) according to claim 6, wherein the valve activation sensor
(24) is configured as a flow sensor for detecting a flow of a gas through the valve
(14) of the gas cylinder (12) or wherein the gas monitoring device (10) comprises
a second temperature sensor for measuring a temperature of a valve body (34) of the
gas cylinder (12) and being in communication with the evaluation unit (20), wherein
the evaluation unit (20) determines an activation of the valve (14) based on the first
temperature sensor measurement and the second temperature sensor measurement.
8. Gas monitoring device (10) according to claim 6 or 7, wherein the activation state
of the valve (14) is factored into the temperature measurement of the first temperature
sensor (16).
9. Gas monitoring device (10) according to any of the preceding claims, wherein the indicator
(18) is configured to prompt a user to maintain the gas cylinder(12) within a predefined
temperature range for a predefined time period and/or to invert the gas cylinder (12)
for a predefined number of times based on the determined status.
10. Gas monitoring device (10) according to any of the preceding claims, further comprising
an accelerometer (26) or motion sensor in communication with the evaluation unit (20),
wherein the evaluation unit (20) is configured to update the determined status based
on a received measurement of said accelerometer (26) or motion sensor.
11. Gas monitoring device (10) according to any of the preceding claims, further comprising
a wireless communication module (28) in communication with the evaluation unit (20),
wherein the wireless communication module (28) is configured to transmit the output
signal to a remote device (30), preferably a remote monitor and/or monitoring system,
preferably via Bluetooth, Bluetooth Low Energy, Zigbee, RFID, WLAN, and/or WiFi.
12. Gas monitoring device (10) according to any of the preceding claims, configured as
a stand-alone unit comprising an electrical energy storage medium and/or comprising
an electrical coupling.
13. Valve (14) for a gas cylinder (12), comprising a gas monitoring device (10) according
to any of the preceding claims, wherein the gas monitoring device (10) is preferably
integrated in the valve.
14. Valve (14) according to claim 13, further comprising a pressure sensor in communication
with the evaluation unit (20), wherein the evaluation unit (20) is configured to determine
the status based on the received ambient temperature measurement and the detected
pressure of the gaseous mixture in the gas cylinder (12).
15. Valve (14) according to claim 13 or 14, wherein the evaluation unit (20) is in communication
with or is configured as a control unit of the valve (14), wherein the control unit
is configured to control the valve actuation based on the determined status.