Note: Descriptions are shown in the official language in which they were submitted.
CA 02789613 2012-09-12
SURGICAL HUMIDIFIER CONTROL
BACKGROUND
Field
[0001] This disclosure relates generally to heating and humidifying gases, and
more particularly to heating and humidifying insufflation gases for use in
surgery.
Description of Related Art
[0002]
Insufflation gases can be used in surgery for a variety of purposes. In
open surgery, gas can be insuffiated into a body cavity for de-airing, as in
cardiac
surgery. In laparoscopic surgery, the abdominal wall can be distended using
gas to
provide room for instrument insertion and tissue dissection. The insufflation
gas can be
inert or non-toxic, such as air or carbon dioxide (CO2). Medical grade CO2 can
be
supplied in cylinders and delivered to a patient at room temperature (e.g.,
between
about 19 and 21 degrees Celsius), with a relative humidity approaching 0%.
This gas is
colder and drier than the environment inside the patient (e.g., about 37
degrees Celsius
and a relative humidity of about 100%, respectively). Temperature and humidity
of an
insufflation gas can be adjusted to more closely approximate the environment
inside the
patient prior to delivery. Heating and humidifying the insufflation gas can
decrease
cellular damage or desiccation, limit adhesion formation, or reduce other
deleterious
effects.
[0003] It is therefore an object of the present invention to provide a
surgical
humidifier and/or a method of controlling a surgical humidification and/or
which will go
at least some way towards addressing the foregoing problems or which will at
least
provide the public with a useful choice.
[0004] In this specification where reference has been made to patent
specifications, other external documents, or other sources of information,
this is
generally for the purpose of providing a context for discussing the features
of the
invention. Unless specifically stated otherwise, reference to such external
documents is
not to be construed as an admission that such documents, or such sources of
information, in any jurisdiction, are prior art, or form part of the common
general
knowledge in the art.
[0005] Further aspects and advantages of the present invention will become
apparent from the ensuing description which is given by way of example only.
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SUMMARY
[0006] The systems, methods and devices described herein have innovative
aspects, no single one of which is indispensable or solely responsible for
their desirable
attributes. Without limiting the scope of the claims, some of the advantageous
features
will now be summarized.
[0007] According to some embodiments, a method is provided that allows the
humidifier to adjust power to a heater plate to account for changes in flow
rate to
provide a consistent output. The method can include receiving a flow rate
reading from
a flow sensor configured to sense a flow rate of an insufflation gas exiting a
chamber of
the surgical humidifier. The method can include determining a power
requirement
corresponding to the received flow rate reading, wherein the power requirement
is one of
a plurality of set points which correspond to ranges of flow rates. The method
can
include providing electrical energy to a heater plate in the surgical
humidifier according
to the power requirement.
[0008] According to some embodiments, a method is provided for use with a
surgical humidifier that uses other sensors in addition to a chamber outlet
sensor to
control power to a heater plate at relatively low flows. The method can
include receiving
a flow rate reading from a flow probe configured to sense a flow rate of an
insufflation
gas exiting a chamber of the surgical humidifier. The method can include
selecting a low
flow mode based on the flow rate reading wherein the low flow mode is selected
when
the received flow rate reading is less than a low flow threshold. The method
can include
providing electrical energy to a heater plate in the surgical humidifier to
achieve a
defined temperature set point corresponding to the low flow mode.
[0009] According to some embodiments, a method is provided for use with a
surgical humidifier that allows the humidifier to be switched on, and to stay
warm and
ready before gas flow starts. The method can include detecting a pre-heat
mode. The
method can include determining a heater plate temperature set point. The
method can
include receiving a heater plate temperature reading from a heater plate
sensor. The
method can include providing electrical energy to a heater plate in the
surgical
humidifier to achieve the heater plate temperature set point.
[0010] According to some embodiments, a method is provided for use with a
surgical humidifier that allows the humidifier to detect a mode of use, and to
change the
humidifier control algorithm accordingly. The method can include receiving a
flow rate
reading from a flow probe configured to sense a flow rate of an insufflation
gas exiting a
chamber of the surgical humidifier. The method can include starting a timer
when the
flow rate reading exceeds a flow rate threshold. The method can include
switching to a
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high flow mode when the flow rate exceeds the flow rate threshold for a
defined
duration. The method can include providing electrical energy to a heater plate
in the
surgical humidifier to achieve a chamber outlet temperature set point
corresponding to
the high flow mode.
[0011] According to some embodiments, a surgical humidifier is provided
wherein the humidifier is configured to respond to varying flow rates of an
insufflation
gas. The humidifier can include a humidifier body and a chamber configured to
removably engageable with the humidifier body and hold a volume of water. The
chamber can include an inlet port configured to receive an insufflation gas
from an
insufflator conduit and an outlet port configured to direct a humidified
insufflation gas to
a patient conduit. The humidifier can include a chamber outlet temperature
sensor
configured to measure a temperature of the humidified insufflation gas. The
humidifier
can include a flow probe configured to measure a flow rate of the humidified
insufflation
gas. The humidifier can include a heater plate coupled to the humidifier body
and
configured to deliver heat to the chamber. The humidifier can include a
humidifier
control system electrically coupled to the heater plate, the humidifier
control system
being configured to control an amount of electrical power to the heater plate.
The
humidifier can be configured to receive a temperature measurement from the
chamber
outlet temperature sensor, to receive a flow rate reading from the flow probe,
to
determine a chamber outlet temperature set point in response to the received
flow rate
reading, and to adjust the amount of electrical power to the heater plate
based on a
difference between the chamber outlet temperature set point and the
temperature
measurement.
[0012] The term "comprising" as used in this specification means "consisting
at least in part of". When interpreting each statement in this specification
that includes
the term "comprising", features other than that or those prefaced by the term
may also
be present. Related terms such as "comprise" and "comprises" are to be
interpreted in
the same manner.
[0013] This invention may also be said broadly to consist in the parts,
elements and features referred to or indicated in the specification of the
application,
individually or collectively, and any or all combinations of any two or more
said parts,
elements or features, and where specific integers are mentioned herein which
have
known equivalents in the art to which this invention relates, such known
equivalents are
deemed to be incorporated herein as if individually set forth.
[0014] The invention consists in the foregoing and also envisages
constructions of which the following gives examples only.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Throughout the drawings, reference numbers can be reused to indicate
general correspondence between reference elements. The drawings are provided
to
illustrate example embodiments described herein and are not intended to limit
the scope
of the disclosure.
[0016] FIG. 1 illustrates an example surgical humidification system for
delivering temperature-controlled and humidity-controlled gas to a patient,
the surgical
humidification system having a humidifier incorporating a humidifier control
system.
[0017] FIG. 2 illustrates a block diagram of an embodiment of a
humidifier
control system.
[0018] FIG. 3 illustrates a flow chart of an example method of
controlling a
humidifier to provide for a consistent output by accounting for changes in
flow rate.
[0019] FIG. 4 illustrates a flow chart of an example method of
controlling a
humidifier in a low flow mode.
[0020] FIG. 5 illustrates a flow chart of an example method of
controlling a
humidifier in a pre-heat mode.
[0021] FIG. 6 illustrates a flow chart of an example method of
controlling a
humidifier to adjust control properties according to a mode of operation.
[0022] FIGs. 7A-C illustrate a flow chart of an example method for
controlling
a humidifier.
[0023] FIG. 8 illustrates a state chart corresponding to a method of
determining a control state that can be implemented in an example embodiment
of a
control module.
DETAILED DESCRIPTION
[0024] Described herein are methods and systems that increase control,
consistency, and/or efficiency of humidifiers across a range of flow rates and
in a variety
of usage scenarios. It will be understood that although much of the
description herein is
in the context of open or laparoscopic surgery, one or more features of the
present
disclosure can also be implemented in other scenarios where it is desirable to
output a
gas having a defined temperature and/or humidity, such as during minimally
invasive
procedures, endoscopic surgery, and respiratory applications.
[0025] Insufflation gases can be used in a variety of surgical
procedures. In
laparoscopic surgery, insufflation gases can be used to create a viewing space
for a
surgeon to operate and manipulate instruments within a patient. In open
surgery,
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insufflation gases can be used in a body cavity for de-airing. These
environments can
include cells that are susceptible to damage when exposed to relatively dry
and cold
gases. For example, the peritoneum is a delicate single layer structure and
may be
damaged when exposed to climatic change. Insufflation gases can be relatively
cold and
dry and may cause damage to the peritoneum, damage that can be reduced or
avoided
through humidifying and warming the insufflation gas. Relatively large volumes
of gas
can be used in some laparoscopic operations (e.g., up to about 500 L in some
cases).
An effect of this continuous flow of cold, dry gas on the lining of the
abdominal cavity
can be significant, causing structural changes that may contribute to post-
operative pain
and scarring (e.g., adhesions).
[0026] It can be desirable to prevent damage that could lead to downstream
problems. For example, cold, dry gas can cause evaporative cooling and
desiccation
inside a patient's peritoneum. Warming and humidifying the insufflation gas
can reduce
or prevent this desiccation and sequential cooling and cellular desiccation,
which in turn
can limit adhesion formation. This can have a positive effect on post-
operative pain that
not only increases quality of care but reduces recovery time and increase
department
throughput. Warming and humidifying insufflation gases may reduce intra-
operative
hypothermia, reduce post-operative pain, and improve post-operative recovery.
[0027] Some embodiments described herein provide for a humidification
system that is configured to deliver warm, humidified gas to a patient
undergoing a
surgical procedure. The gas is passed through a water chamber which is filled
with
water that is heated using a heater plate. Water evaporates in the chamber and
combines with the gas which flows over it, thereby heating and/or humidifying
the gas.
The temperature of the gas can be maintained as it travels along a heated tube
to an
outlet port for delivery to the patient. The humidification system can monitor
the
temperature and flow rate of the gas at a chamber outlet, and control an
amount of
electrical power delivered to the heater plate to provide a gas having a
desired
temperature and humidity. Thus, surgical gas from a gas source (e.g., an
insufflator, a
gas bottle, or the like) can be humidified and heated and delivered to the
patient,
enabling the patient's peritoneum or other targeted area to remain moist and
warm.
[0028] Some embodiments described herein provide for a surgical
humidification system that includes a humidifier control system configured to
determine
a mode of operation, a mode of control, a heater plate set point, or any
combination of
these. The humidifier control system can base this determination at least in
part on
feedback from components of the humidification system. The components of the
humidification system can provide feedback through sensors or other electrical
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1
components, and feedback can include, for example, outlet gas temperature,
heater
plate temperature, heater plate power, gas flow rate, user input through user
interface
elements, duration of operation, and the like. Some embodiments of the
humidifier
control system can improve efficiency of the humidification system, provide an
output
gas with relatively consistent humidity and temperature, and provide greater
control
over temperature and humidity of the gas compared to control systems that do
not
incorporate system component feedback. The humidifier control system can
provide at
least some of these improvements through modules configured to process system
component feedback and adjust output settings according to a control loop
feedback
mechanism.
Example Surgical Humidification System
[0029]
FIG. 1 illustrates an example surgical humidification system 100 for
delivering temperature- and humidity-controlled gas to a patient 102, the
surgical
humidification system 100 having a humidifier 104 incorporating a humidifier
control
system 106. The humidifier 104 is connected to an insufflator 108 through an
insufflator
conduit 110. The humidifier 104 delivers humidified gas to the patient 102
through a
patient conduit 112. The conduits 110, 112 can be made of flexible plastic
tubing.
[0030] The humidifier 104 receives gas from the insufflator 108 through the
insufflator conduit 110. The gas can be filtered through a filter 111 and
delivered to the
humidifier 104 through a humidifier inlet 114. The gas is humidified as it
passes
through a humidifying chamber 116, which is effectively a water bath, and the
gas flows
out through a humidifier outlet 118 and into the patient conduit 112. The gas
then
moves through the patient conduit 112 to the patient 102. In some embodiments,
a
filter can be disposed between the humidifier outlet 118 and the patient 102.
[0031] The humidifier 104 comprises a body 124 removably engageable with
the humidification chamber 116. The humidification chamber 116 has a metal
base 121
and is adapted to hold a volume of water 120, which can be heated by a heater
plate
122. The heater plate 122 can be in thermal contact with the metal base 121 of
the
humidification chamber 116. Providing power to the heater plate 122 can cause
heat to
flow from the heater plate 122 to the water 120 through the metal base 121. As
the
water 120 within the humidification chamber 116 is heated it can evaporate and
the
evaporated water can mix with gases flowing through the humidification chamber
116
from the filter 111 and insufflator 108. Accordingly, the humidified gases
leave the
humidification chamber 116 via outlet 118 and are passed to the patient via
the patient
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conduit 112 and into the surgical site to insufflate and/or expand the
surgical site or
peritoneal cavity.
[0032] The humidifier 104 includes the humidifier control system 106
configured to control a temperature and/or humidity of the gas being delivered
to the
patient 102. The humidifier control system 106 can be configured to regulate
an amount
of humidity supplied to the gases by controlling an electrical power supplied
to the
heater base 122. The humidifier control system 106 can control operation of
the
humidification system 104 in accordance with instructions set in software and
in
response to system inputs. System inputs can include a heater plate sensor
126, an
outlet chamber temperature sensor 128, and a chamber outlet flow probe 130.
For
example, the humidifier control system 106 can receive temperature information
from
the heater plate sensor 126 which it can use as an input to a control module
used to
control the power or temperature set point of the heater plate 122. The
humidifier
control system 106 can be provided with inputs of temperature and/or flow
rates of the
gases. For example, the chamber outlet temperature sensor 128 can be provided
to
indicate to the humidifier control system 106 the temperature of the
humidified gas as it
leaves the outlet 118 of the humidification chamber 116. The temperature of
the gases
exiting the chamber can be measured using any suitable temperature sensor 128,
such
as a wire-based temperature sensor. The chamber outlet flow probe 130 can be
provided to indicate to the humidifier control system 106 the flow rate of the
humidified
gas. The flow rate of the gases through the chamber 116 can be measured using
any
suitable flow probe 130, such as a hot wire anemometer. In some embodiments,
the
temperature sensor 128 and flow probe 130 are in the same sensor housing. The
temperature sensor 128 and flow probe 130 can be connected to the humidifier
104 via
connector 132. Additional sensors may be incorporated into the surgical
humidification
system 100, for example, for sensing parameters at the patient end of the
patient
conduit 112.
[0033] The humidifier control system 106 can be in communication with the
heater plate 122 such that the humidifier control system 106 can control a
power
delivered to the heater plate 122 and/or control a temperature set point of
the heater
plate 122. As described further herein, the humidifier control system 106 can
determine
an amount of power to deliver to the heater plate 122, or a heater plate set
point, based
at least in part on a flow condition, an operation mode, a flow reading, an
outlet
temperature reading, a heater plate sensor reading, or any combination of
these or other
factors.
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[0034] The surgical humidification system 100 can include a conduit heating
wire 134 configured to provide heat to the gases traveling along the patient
conduit 112.
Gases leaving the outlet 118 of the humidification chamber 116 can have a high
relative
humidity (e.g., about 100%). As the gases travel along the patient conduit 112
there is
a chance that water vapor may condense on the conduit wall, reducing the water
content
of the gases. To reduce condensation of the gases within the conduit, the
conduit
heating wire 134 can be provided within, throughout, and/or around the patient
conduit
112. Power can be supplied to the conduit heating wire 134 from the humidifier
104 and
can be controlled through the humidifier control system 106. In some
embodiments, the
heating wire 134 is configured to maintain the temperature of the gas flowing
through
the patient conduit 112. In some embodiments, the conduit heating wire 134 can
be
configured to provide additional heating of the gas to elevate the gases
temperature to
maintain the humidity generated by the heated water bath in the humidifier
104.
Example Humidifier Control System
[0035] FIG. 2
illustrates a block diagram of an example humidifier control
system 106. The humidifier control system 106 can include hardware, software,
and/or
firmware components used to control the humidifier 104. The humidifier control
system
106 can be configured to receive information from various sensors or systems,
determine a mode of operation based at least in part on the received
information,
determine a heater plate set point based at least in part on the received
information,
and control the heater plate 122 to achieve a defined temperature and/or power
output.
The humidifier control system 106 can include a control module 205, a heater
plate
feedback module 210, a chamber temperature feedback module 215, a controller
220,
and data storage 225.
Components of the humidifier control system 106 can
communicate with one another, with external systems, and with other components
of
the humidifier 104 over communication bus 230.
[0036] The humidifier control system 106 includes the control module 205
configured to determine a control mode based at least in part on information
received
regarding the temperature sensor 128, the heater plate 126, the flow probe
130, user
interface elements, or any combination of these. The control module 205 can
use the
received information to select an appropriate or desired control mode, such as
a pre-
heat mode, a warm-up mode, an on mode, or other control mode. Based at least
in part
on the selected control mode, the control module 205 can provide the heater
plate
feedback module 210 or the chamber temperature feedback module 215 with a set
point
corresponding to a chamber set point, a heater plate set point, or some
combination of
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these. The set point can be selected based at least in part on the received
information
and the control mode. For example, the control module 205 can receive a flow
rate
reading from the flow probe 130. Based at least in part on the flow rate
reading, the
control module 205 can determine to control the heater plate 122 using the
heater plate
feedback module 210 or the chamber temperature feedback module 215. Similarly,
the
control module 205 can use a variety of conditions to determine a method of
control. In
some embodiments, the control module 205 uses a flow rate, a chamber outlet
temperature, a heater plate reading, a duration of any of a flow condition, a
duration of
a control mode, or any combination of these to determine an appropriate
control mode.
For example, the control module 205 can determine that the humidifier is in a
high flow
state in an open surgery setting when a flow rate exceeds a defined threshold
for a
defined duration. If the flow rate exceeds the flow rate threshold for the
defined
duration, the control module 205 can use the chamber temperature feedback
module
215 with an input chamber set point to control the heater plate 122. As
another
example, if the flow rate is below a threshold, the control module 205 can
determine to
use the heater plate feedback module 210 with a heater plate temperature
setting to
control the heater plate 122. As another example, if the flow rate is
determined to be
above a threshold, the control module 205 can use the chamber temperature
feedback
module 215 to control the heater plate setting, wherein the control module 205
provides
the chamber temperature feedback module 215 with a chamber set point
corresponding
to the flow rate. The received information used by the control module 205 can
be used
without any additional processing or the information can be processed prior to
use. For
example, the received information can represent instantaneous values or time-
averaged
values. The received information can be converted into different units, such
as from a
received voltage to a corresponding temperature.
[0037] The humidifier control system 106 includes the heater plate feedback
module 210 configured to control the heater plate 122 in response to input
from the
heater plate sensor 126. The heater plate feedback module 210 can receive a
heater
plate temperature set point and control power to the heater plate 122 to
achieve the
heater plate temperature set point. The heater plate feedback module 210 can
be used
to control the heater plate 122 when in a defined operation mode or under
defined flow
conditions, as determined by the control module 205. For example, the heater
plate
feedback module 210 can receive a heater plate temperature setting from the
control
module 205, receive a heater plate sensor reading from the heater plate sensor
126 or
from the control module 205, and determine a heater plate setting 235 (e.g.,
whether to
apply power to the heater plate 122) based at least in part on a difference
between the
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heater plate temperature setting and the heater plate sensor reading. The
heater plate
feedback module 210 can use a control loop feedback mechanism to adjust the
heater
plate setting 235 to achieve a desired set point. The control module 205 can
use the
heater plate feedback module 210 to control the heater plate 122 until it
determines that
input from system components (e.g., the chamber temperature sensor 128, heater
plate
sensor 126, and/or flow probe 130) warrant using the chamber temperature
feedback
module 215.
[0038] The humidifier control system 106 includes the chamber temperature
feedback module 215 configured to control the heater plate 122 in response to
input
from the chamber outlet temperature sensor 128. The chamber temperature
feedback
module 215 can be configured to use a feedback control loop that incorporates
information from the chamber outlet temperature sensor 128, the heater plate
reading
126, the flow probe 130, or any combination of these to determine a heater
plate setting
235. Similar to the heater plate feedback module 210, the control module 205
can use
the chamber temperature feedback module 215 to determine a heater plate
setting 235
until it determines that input from system components warrant using the heater
plate
feedback module 210. The chamber temperature feedback module 215 can use a
control loop feedback mechanism to adjust the heater plate setting 235 to
achieve a
desired set point. Adjustments can be made based at least in part on input
received
from the temperature sensor 128, the flow probe 130, the heater plate reading
126, or
any combination of these.
[0039] The heater plate feedback module 210 and the chamber temperature
feedback module 215 can use control loop feedback mechanisms to determine a
heater
plate setting 235 to control the heater plate 122. Parameters of the control
loop
feedback mechanism can be adjusted to achieve desired results, including, for
example,
reducing or minimizing gas temperature overshoots or undershoots, increasing
efficiency
of humidification, providing a consistent humidifier output, decreasing start-
up times for
humidification, accommodate for varying flow rates, or any combination of
these. In
some embodiments, the control loop feedback mechanism is a PID controller. In
some
embodiments, parameters of the PID controller can be selected according to a
heater
plate setting, a control mode, a flow rate, a user setting, an outlet
temperature, a heater
plate set point, or any combination of these.
[0040] The humidifier control system 106 includes the controller 220
configured to interact with the modules, data storage 225, and external
systems of the
humidifier 104. The controller 220 can include one or more physical processors
and can
be used by any of the other components, such as the control module 205, to
process
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information. The humidifier control system 106 includes data storage 225. Data
storage
225 can include physical memory configured to store digital information and
can be
coupled to the other components of the humidifier control system 106, such as
the
controller 220, the control module 205, the heater plate feedback module 210,
and the
chamber temperature feedback module 215.
[0041] The humidifier control system 106 having the control module 205, the
heater plate feedback module 210, and the chamber temperature feedback module
215
can provide flow-dependent control such that heating control can be based on a
current
flow rate and can be adaptable to changing flow rates during use (e.g., during
surgery).
For example, the temperature of the gases exiting the chamber 116 can drop if
the flow
rate of the gases entering and flowing through the chamber 116 increases. The
increased flow rate can cause a larger volume of insufflation gas to pass
through the
chamber 116. The larger volume of gases can use more energy from the water
vapor,
hence leading to a temperature drop as the gases exit. A larger flow rate of
gases can
use a larger amount of water vapor for the gases to be humidified to a
suitable level.
The humidifier control system 106 can be configured to compensate for the
increased
gas flow by increasing the power to the heater base in order to cause more
water in the
chamber 116 to evaporate such that the gases are humidified to a suitable
level. The
feedback modules 210 and 215 can be configured to avoid adding an undesirable
amount of heat to the chamber 116 through the use of control loop feedback
mechanisms, as described herein. This can reduce temperature overshoots which
can be
undesirable.
[0042] The control system 106 can provide control when the chamber 116
contains relatively large volumes of water or when the chamber 116 is an auto-
fill
chamber, which can be desirable for long-duration surgeries or procedures. The
control
system 106 can provide therapy specific control through an auto-detect mode or
through
a user interface element such as a mode button. For example, the control
system 106
can be configured to detect whether the humidifier 104 is being used for open
surgery or
laparoscopic surgery based at least in part on a duration of a high flow rate,
and control
the heater plate 122 accordingly. The control system 106 can be configured to
deliver a
desired or defined level of humidity through the use of feedback from the
chamber outlet
temperature sensor 128, the heater plate sensor 126, and/or the flow probe
130. By
controlling the humidifier 104 using this feedback, the risk of undesirable
heat being
delivered to the patient can be reduced or eliminated.
[0043] The
following sections provide non-limiting examples of humidification
controls:
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Variable Flow Rates
[0044] FIG. 3
illustrates a flow chart of an example method 300 for controlling
a humidifier to provide for a consistent output by accounting for changes in
flow rate.
The humidifier 104 can adjust heater plate settings to account for changes in
the flow
rate which can cause inefficiencies in the humidification process. For
example, at flow
ranges typical in a laparoscopic procedure (e.g., between about 0 and 15
liters per
minute (Lpm)), the efficiency of the humidifier 104 can vary across the flow
range. In
some embodiments, for a given water temperature inside the chamber 116, the
output
temperature and humidity of the gas will decrease as flow rate increases. The
method
300 can be used to provide a consistent output humidity and/or temperature by
controlling the heater plate such that an amount of power delivered to the
heater plate
122 is based at least in part on the flow rate of the gas. For ease of
description, the
steps in the method 300 are described as being performed by the humidifier
control
system 106. However, any step or combination of steps in the method 300 can be
performed by any component of the humidifier control system 106, any
combination of
components of the humidifier control system 106, or any component or
combination of
components of the humidifier 104 or surgical humidification system 100.
[0045] In block
305, the humidifier control system 106 receives a flow rate
reading from the flow probe 130. The flow rate reading can be processed
according to
processing instructions in the humidifier control system 106. In some
embodiments, the
humidifier control system 106 monitors the flow sensor, receiving multiple
flow rate
readings. The frequency of readings can depend at least in part on the
humidifier
control system 106, the flow probe 130, or other factors or combination of
factors. In
some embodiments, the flow rate reading corresponds to an average of multiple
flow
probe values over time. Using the time-averaged flow rate can reduce or
eliminate
fluctuations in power supplied to the heater plate 122 by the humidifier
control system
106 in response to the flow rate readings. The time over which the average
flow rate
reading is taken can be configured to reduce or eliminate small-scale
fluctuations and to
be responsive to changes in flow rates.
[0046] In block
310, the humidifier control system 106 determines a chamber
temperature set point based at least in part on the flow rate reading. The
chamber
temperature set point can correspond to a range of flow rates such that there
is a single,
defined chamber temperature set point corresponding to any flow rate between a
lower
flow rate and an upper flow rate. There
can be multiple chamber set points
corresponding to multiple flow rate ranges. In some embodiments, the chamber
temperature set point is an output of a real-valued function of the flow rate.
In some
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CA 02789613 2012-09-12
embodiments, the chamber temperature set point is an output of a discrete-
valued
function of the flow rate. In some embodiments, the chamber temperature set
point is a
function of the flow rate and other variables. By determining the chamber
temperature
set point based at least in part on the flow rate reading, the humidifier 104
can be
configured to experience a slowed response to rapidly changing flows where
fluctuations
in flow result in little or no fluctuations in power output to the heater
plate 122.
Temperature overshoots may happen in a case where the flow rate temporarily
increases
and the humidifier control system 106 responds to the increase by increasing
the heater
plate power. The humidifier 104 can be configured to reduce or eliminate
temperature
overshoots when a flow rate subsequently reduces by limiting an amount of
added power
at higher flows. Avoiding temperature overshoots can be desirable because
cooling the
water in the humidifier 104 can be difficult and/or time intensive.
[0047] In block 315, the humidifier control system 106 determines an amount
of power to be applied to the heater plate 122 based at least in part on a
difference
between a chamber outlet temperature reading and the chamber temperature set
point.
As described above, the humidifier control system 106 can use a control loop
feedback
mechanism to determine a chamber temperature set point. The control loop
feedback
mechanism can accept as input the chamber temperature set point, the chamber
temperature reading, and the heater plate power and output a new heater plate
power
setting based at least in part on a difference between the chamber temperature
set point
and the chamber temperature reading. The control loop feedback mechanism can
incorporate current measurements in addition to previous measurements to
improve or
optimize control of the temperature and/or humidity of the gas.
[0048] In block 320, the humidifier control system 106 determines a mode of
use. The mode of use can correspond to, for example, use in conjunction with
open
surgery, a laparoscopic procedure, an endoscopic procedure, or the like. The
chamber
temperature set point can be altered based on the mode of use. For example,
the
humidifier control system 106 can have different sets of chamber temperature
set points
for laparoscopic and open surgery.
[0049] In block 325, the humidifier control system 106 provides an amount of
electrical power to the heater plate 122, the amount of power based at least
in part on
the flow rate reading and the mode of operation. The humidifier control system
106 can
update the amount of electrical power provided to the heater plate 122 based
at least in
part on an updated flow rate reading, an updated mode of use, or a combination
of both
of these.
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CA 02789613 2012-09-12
Low Flow Rates
[0050] FIG. 4 illustrates a flow chart of an example method 400 of
controlling
a humidifier 104 when a flow rate of the insufflation gas is relatively low
(e.g., less than
or equal to about 3 Lpm, less than or equal to about 2 Lpm, less than or equal
to about
1 Lpm, or less than or equal to about 0.5 Lpm). The method 400 can compensate
for
difficulties in acquiring accurate temperature information in the chamber
outlet 118 of
the humidifier 104 arising from relatively small amounts of gas passing over
the
chamber outlet temperature sensor 128. The method 400 can use other sensors in
addition to the chamber outlet temperature sensor 128 to control the
humidifier 104 at
relatively low flows or at flows where the chamber outlet temperature sensor
128 may
provide temperature information that is less accurate than desired.
[0051] At relatively low flow rates, the chamber temperature sensor 128 can
return inaccurate temperature readings that tend to be lower than the actual
temperature of the gas. This can cause the humidifier control system 106 to
increase
power to the heater plate 122 to compensate for this apparent drop in
temperature. To
reduce or avoid undesirable increases in power delivered to the heater plate
122, the
humidifier control system 106 can use the method 400 to switch the humidifier
104 into
a low-flow state where the chamber outlet temperature is not used to control
the heater
plate 122. The humidifier control system 106 can use, for example, the output
from a
temperature sensor located at the heater plate to control the heater plate 122
to
maintain the heater plate 122 at a particular temperature. As a result, when
flow
increases over a defined flow threshold, the humidifier control system 106 can
again use
the chamber outlet temperature sensor 128 to control the humidifier 104
thereby
reducing or eliminating excessive temperature over-shoot. For ease of
description, the
steps in the method 400 are described as being performed by the humidifier
control
system 106. However, any step or combination of steps in the method 400 can be
performed by any component of the humidifier control system 106, any
combination of
components of the humidifier control system 106, or any component or
combination of
components of the humidifier 104 or surgical humidification system 100.
[0052] In block 405, the humidifier control system 106 receives a flow
rate
reading. Similar to the description corresponding to block 305 in FIG. 3, the
humidifier
control system 106 can monitor the flow sensor and use an instantaneous or a
time-
averaged value of the flow rate. The flow rate reading can be processed prior
to use by
the humidifier control system 106.
[0053] In block 410, the humidifier control system 106 determines a low
flow
mode based at least in part on the flow rate reading. The low flow mode can be
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determined where the flow rate reading is less than or equal to a defined
threshold. The
defined threshold can be less than or equal to about 3 Lpm, less than or equal
to
about 2 Lpm, less than or equal to about 1 Lpm, less than or equal to about
0.5 Lpm.
The humidifier control system 106 can determine a normal mode when the flow
rate
reading exceeds the defined threshold.
[0054] In block 415, the humidifier control system 106 determines a
heater
plate temperature set point. In some embodiments, the humidifier control
system 106
uses a heater plate temperature set point in the low flow mode rather than a
chamber
temperature set point because at low flow rates the chamber outlet temperature
produces unstable results and/or produces readings that have an accuracy that
is less
than desirable. The humidifier control system 106 can use a control loop
feedback
mechanism to determine a heater plate power based at least in part on a
difference
between the heater plate temperature set point and a heater plate temperature
reading.
For example, if the heater plate temperature reading is less than the heater
plate set
point, power can be applied to the heater plate 122. If the heater plate
temperature is
greater than or equal to the heater plate set point, power can be removed from
the
heater plate 122. In some embodiments, the heater plate temperature set point
can be
at least about 36 degrees and/or less than or equal to about 60 degrees, at
least about
36 degrees and/or less than or equal to about 50 degrees, at least about 36.5
degrees
and/or less than or equal to about 40 degrees, or about 37 degrees.
[0055] In block 420, the humidifier control system 106 provides
electrical
power to the heater plate 122 based on the low-flow mode. The power provided
to the
heater plate 122 can change if the flow rate reading exceeds the defined
threshold and
the humidifier 104 enters a normal mode of operation.
Pre-Heat Mode
[0056] FIG. 5 illustrates a flow chart of an example method 500 of
controlling
a humidifier in a pre-heat mode. In some surgical procedures, there can be a
relatively
long delay between a time at which the humidifier 104 is set up and a time
that gas flow
to the patient 102 commences. If the humidifier 104 is left off until gas flow
starts, the
humidifier 104 can output a low temperature until the humidifier 104 warms up.
If the
humidifier 104 is left on until gas flow starts, the humidifier 104 can output
a gas having
an elevated temperature due at least in part to the chamber output temperature
sensor
128 being unable to read the gas flow temperature when there is no gas flow.
The
humidifier control system 106 can use the method 500 to determine a heater
plate set
point to power the heater plate 122 when the humidifier 104 is turned on,
thereby
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enabling the humidifier to stay warm and ready for gas flow to start. For ease
of
description, the steps in the method 500 are described as being performed by
the
humidifier control system 106. However, any step or combination of steps in
the
method 500 can be performed by any component of the humidifier control system
106,
any combination of components of the humidifier control system 106, or any
component
or combination of components of the humidifier 104 or surgical humidification
system
100.
[0057] The pre-heat mode can be used with the humidifier 104 that is
configured to be used in conjunction with laparoscopic procedures as well as
open
surgery. Due at least in part to the constant high gas flow used in open
surgery, the
humidifier control system 106 can use a relatively aggressive control
algorithm to
achieve an desirable warm-up time. However, this type of algorithm can result
in
excessive instability during laparoscopic procedures which may lead to
unwanted
temperature overshoots. Thus, to avoid using the aggressive algorithm and
still achieve
a desirable warm-up time during open surgery, the humidifier control system
106 can
use the method 500 to operate the humidifier 104 according to the pre-heat
mode. The
pre-heat mode allows the humidifier 104 to be partially set up with only the
chamber
116 filled with water attached and without the conduits 110, 112 attached.
When the
humidifier 104 is switched on in this partially set up state, the humidifier
control system
106 can detect this and automatically enter the pre-heat mode. In the pre-heat
mode,
the humidifier control system 106 uses the heater plate temperature instead of
the
chamber outlet temperature to control power to the heater plate 122 to achieve
a heater
plate temperature set point. As such, the pre-heat mode allows the heater
plate to
receive power and to be switched on prior to commencement of the open or
laparoscopic
procedure to allow time for the chamber to warm up. Once the procedure is
ready to
commence, set up of the surgical humidification system 100 can be completed
(e.g.,
connecting the patient conduit 112 from the patient 102 to the outlet port 118
and/or
connecting the insuffiator conduit 110 from the insufflator 108 to the inlet
port 114).
The humidifier control system can automatically detect the completed set up at
which
point the humidifier control system 106 can switch out of pre-heat mode and
enter a
normal run mode. In some embodiments, warm-up time is reduced to less than 10
minutes for both open and laparoscopic procedures when utilizing the pre-heat
mode for
about 5 minutes.
[0058] In block
505, the humidifier control system 106 detects a pre-heat
mode. The pre-heat mode can be where the chamber 116 is coupled to the
humidifier
body 124 such that the heater plate 122 is in contact with the metal base 121.
The pre-
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CA 02789613 2012-09-12
heat mode can be where the chamber 116 is coupled to the humidifier body 124
and the
chamber contains a defined amount of water. The pre-heat mode can be where the
chamber 116 is at least partially filled with water and is coupled to the
humidifier body
124 and the insufflator conduit 110, the patient conduit 112, or both are
disconnected
from the chamber 116. In some embodiments, the pre-heat mode can be selected
by a
user using a user interface element.
[0059] In block 510, the humidifier control system 106 determines a
heater
plate temperature set point. In some embodiments, the heater plate temperature
set
point is a constant value in the pre-heat mode. In block 515, the humidifier
control
system 106 receives a heater plate temperature from the heater plate sensor
126. In
block 520, the humidifier control system 106 determines a power to apply to
the heater
plate 122 based at least in part on the heater plate temperature set point and
the heater
plate temperature reading. In some embodiments, the humidifier control system
106
uses a control loop feedback mechanism to determine a power to apply to the
heater
plate 122. For example, the humidifier control system 106 can determine to
apply
power to the heater plate 122 when the heater plate temperature reading is
less than
the heater plate temperature set point. In some embodiments, the amount of
power
applied is proportional to the difference between the heater plate temperature
set point
and the heater plate temperature reading.
[0060] In block 520, the humidifier control system 106 provides
electrical
power to the heater plate 122. In some embodiments, the humidifier control
system
106 is configured to detect when the pre-heat mode no longer applies and to
operate in
a normal mode. The pre-heat mode can be terminated where the insufflator
conduit 110
and the patient conduit 112 are connected to the chamber 116 and the chamber
is
coupled to the humidifier body 124. In the normal mode, the humidifier control
system
106 can control the amount of power to the heater plate 122 based at least in
part on a
flow rate reading, a mode of use, a chamber outlet temperature, a heater plate
temperature, or any combination of these as described herein with reference to
FIGs 3 or
4.
Procedure Mode of Use
[0061] FIG. 6 illustrates a flow chart of an example method 600 of
controlling
a humidifier to adjust control properties according to a mode of use. The
humidifier 104
can be used in laparoscopic procedures, endoscopic procedures, open surgery,
and the
like. Open surgery can use a relatively high, constant flow rate (e.g.,
greater than about
15 Lpm) compared to laparoscopic surgery flow rates (e.g., varying between
about 0 and
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CA 02789613 2012-09-12
=
15 Lpm). Differing control modes can be used for the different procedures due
at least
in part to this difference in consistency and magnitude of flow rates. The
humidifier
control system 106 can use the method 600 to detect which mode of use is being
employed and change control algorithms accordingly. The humidifier control
system 106
can detect an open surgery mode of use when the flow rate reading exceeds a
defined
threshold for a defined duration. The defined threshold and duration can be
selected
such that it is improbable that a laparoscopic procedure would use a flow rate
exceeding
the defined threshold for the defined duration.
[0062] In block 605, the humidifier control system 106 receives a flow
rate
reading. Similar to the description corresponding to block 305 in FIG. 3, the
humidifier
control system 106 can monitor the flow sensor and use an instantaneous or a
time-
averaged value of the flow rate. The flow rate reading can be processed prior
to use by
the humidifier control system 106. In some embodiments, the humidifier control
system
106 can receive flow rate readings on a nearly continuous basis. This can
enable the
humidifier control system 106 to monitor the flow rate readings over time.
[0063] In block 610, the humidifier control system 106 times a duration
of a
flow rate above a high flow threshold. In some embodiments, to distinguish
between
open and laparoscopic procedures automatically, the humidifier control system
106 can
begin a timer once a high flow state is detected. Detecting a high flow state
can
comprise receiving a flow rate reading that exceeds the high flow threshold.
In some
embodiments, the high flow threshold is at least about 7 Lpm, at least about
10 Lpm, at
least about 12 Lpm, at least about 15 Lpm, or at least about 20 Lpm. The timer
can
continue to run as long as the flow remains above the high flow threshold. If
the flow
reduces below the high flow threshold, the timer can be reset. The timer can
restart if
the flow rate reading once again exceeds the high flow threshold.
[0064] In block 615, the humidifier control system 106 controls the
heater
plate 122 according to a high flow mode when the flow rate exceeds the high
flow
threshold for a duration threshold. In some embodiments, the duration
threshold is at
least about 1 minute, at least about 2 minutes, at least about 3 minutes, or
at least
about 5 minutes. Because flow rates temporarily exceeding the high flow
threshold can
be used in laparoscopic procedures, the duration threshold can be configured
to be long
enough to exclude typical temporary increases in flow rate in laparoscopic
procedures.
To reduce or avoid temperature overshoots that may occur after high flow
periods during
laparoscopic surgery, the chamber temperature set point can be reduced
compared to
the chamber temperature set point for open surgery. As a result, short periods
of high
flow in laparoscopic surgery may not result in the humidifier control system
106
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CA 02789613 2012-09-12
=
=
providing undesirable power to the heater plate that may result in temperature
overshoots when the flow reduces again. However, for open surgery the
humidifier
control system 106 can be configured to automatically provide a desirable
quantity of
power to the heater plate 122 to sustain a desired temperature and/or humidity
for the
high flow rates used. In some embodiments, the chamber temperature set point
is set
to a value of at least about 36 degrees and/or less than or equal to about 60
degrees, at
least about 36 degrees and/or less than or equal to about 50 degrees, at least
about
36.5 degrees and/or less than or equal to about 40 degrees, at least about
36.5 degrees
and/or less than or equal to about 37.5 degrees, or about 37 degrees. If after
switching
to the high flow mode the flow rate readings drop below the high flow
threshold, the
humidifier control system switches to a normal mode of operation and the timer
can be
reset. The normal mode of operation can be similar to the modes of operation
described
herein with reference to FIGs. 3 and 4.
[0065] In
block 620, the humidifier control system 106 controls the humidifier
104 using a chamber temperature set point when in the high flow mode. In some
embodiments, the chamber temperature set point in the high flow mode is
different from
the chamber temperature set point in the normal flow mode. The humidifier
control
system 106 can be configured to apply an amount of power to the heater plate
122
based at least in part on a difference between a chamber temperature set point
and a
chamber temperature reading, similar to the methods described herein with
reference to
FIG. 3. When not in the high flow mode, the humidifier control system 106 can
control
the humidifier 104 using a chamber temperature set point or a heater plate
temperature
set point, as described herein with reference to FIGs. 3 and 4. In some
embodiments, a
high flow mode and/or a normal mode can be selected by a user using a user
interface
element.
[0066] In some embodiments, the mode of use can be automatically detected
without using a flow rate. The automatic detection can comprise utilizing a
timer to time
how long it takes to reach a temperature set point based on a heating energy
delivered
to the heater plate 122. It can take longer to reach the temperature set point
at
relatively constant high flow rates (e.g., similar to flow rates used for open
surgery) than
at variable low flow rates (e.g., similar to flow rates used for laparoscopic
surgery).
Example of a Control System and Method
[0067] FIGs. 7A-C illustrate a flow chart of an example method 700 for
controlling a humidifier 104. The example method 700 incorporates elements
from the
example control methods described herein with reference to FIGs. 3-6. The
example
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a
method 700 illustrated in the flow charts in FIGs. 7A-C represents an example
embodiment of a method 700 to be implemented in the humidifier control system
106 to
control the humidifier 104.
[0068] As illustrated in FIG. 7A, the method 700 begins in block 702 with
detecting a mode of operation. The mode of operation can be a pre-heat mode or
an on
mode. The pre-heat mode is similar to the method described herein with
reference to
FIG. 5 and can be automatically detected based at least in part on a
configuration of the
humidifier and/or through a user selection. If the humidifier control system
106 detects
a pre-heat mode, the system 106 sets a heater plate temperature set point
(HPTs) in
block 704. In block 706, the humidifier control system 106 measures a heater
plate
temperature (HPTm). In block 708, the humidifier control system 106 compares
the
measured temperature to the set point and determines whether to apply power to
the
heater plate 122 in block 710, or to apply no power to the heater plate 122 in
block 712.
In some embodiments, the humidifier control system 106 can determine an amount
of
power to apply to the heater plate 122 based at least in part on a difference
between the
set point and the measurement, where the amount of power is proportional to
the
difference (represented by the "(P)" in block 710). In
some embodiments, the
humidifier control system 106 determines the amount of power using a PID
controller.
In block 714, the humidifier control system 106 detects whether the humidifier
104
remains in a pre-heat mode. If so, the humidifier control system 106 returns
to block
706 to measure the heater plate temperature. If the humidifier control system
106
detects that the humidifier 104 is in an on mode in block 702, it moves to
block 716 to
detect if the humidifier 104 warrants a warm-up mode.
[0069] In block 716 the humidifier control system 106 detects whether the
humidifier 104 warrants a warm-up mode. If the humidifier warrants a warm-up
mode,
the humidifier control system 106 moves to block 718 and controls power to the
heater
plate 122 according to the warm-up mode. If no warm-up mode is warranted, the
humidifier control system 106 moves to block 720 to sense a flow rate of gases
through
the humidifier 104.
[0070]
FIG. 7B illustrates a second portion of the method 700 for controlling
the humidifier 104. In block 720, the humidifier control system 106 detects
flow rate
readings from the flow probe 130. Based at least in part on the flow probe
readings, the
humidifier control system 106 enters a defined control state. In a first
control state,
identified in FIG. 7B as the "Zero Flow State," the humidifier control system
106 resets a
timer in block 722, the timer corresponding to a high flow mode timer
described with
reference to FIG. 6. In block 724, the humidifier control system sets a heater
plate
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CA 02789613 2012-09-12
temperature set point and in block 726 it measures a heater plate temperature.
In block
728 the humidifier control system 106 compares the heater plate temperature
set point
to the heater plate temperature measurement. If the measurement is less than
the set
point, the humidifier control system 106 applies power to the heater plate 122
in block
730. In some embodiments, the amount of power applied to the heater plate 122
is
determined using a PID feedback controller (identified as "PID" in block 730).
If the
measurement is greater than or equal to the set point, the humidifier control
system 106
removes power from the heater plate 122 in block 732. The humidifier control
system
106 then returns to block 720 to detect the flow rate.
[0071] In a
second control state, identified in FIG. 7B as the "Low Flow State,"
the humidifier control system 106 resets a timer in block 734, the timer
corresponding to
a high flow mode timer described with reference to FIG. 6. In block 736, the
humidifier
control system sets a chamber outlet temperature set point (ChTs) and in block
738 it
measures a chamber outlet temperature (ChTm). In block 740 the humidifier
control
system 106 compares the chamber outlet temperature set point to the chamber
outlet
temperature measurement. If the
measurement is less than the set point, the
humidifier control system 106 applies power to the heater plate 122 in block
742. In
some embodiments, the amount of power applied to the heater plate 122 is
determined
using a PID feedback controller (identified as "PID" in block 742). If the
measurement is
greater than or equal to the set point, the humidifier control system 106
removes power
from the heater plate 122 in block 744. The humidifier control system 106 then
returns
to block 720 to detect the flow rate.
[0072] In a
third control state, identified in FIG. 7B as the "Med Flow State,"
the humidifier control system 106 follows the same sequence of events
described for the
"Low Flow State," except the chamber outlet temperature set point may be
different, as
described herein with reference to Table 1. Furthermore, as described herein,
the "Med
Flow State" and the "Low Flow State" can differ with regard to the conditions
for entering
the control states, as described herein with reference to FIG. 8.
[0073] FIG. 7C
illustrates flow charts for a fourth and fifth control state. The
fourth control state is identified as "High 1 Flow State" in FIG. 7C. If the
humidifier
control system 106 enters the fourth control state in response to the flow
rate readings,
it checks whether the high flow timer has started in block 758. If the timer
has already
started, the humidifier control system 106 reads the timer in block 760. If
the timer has
not already started (e.g., it has been previously reset in other control
states), the timer
is started in block 762. The timer starts when a flow rate reading exceeds the
high flow
threshold, as described herein with reference to FIG. 6. If the timer is read
and it has a
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CA 02789613 2012-09-12
value less than the duration threshold, the humidifier control system moves to
block 764
to set a chamber outlet temperature set point. If the timer is greater than or
equal to
the duration threshold, the humidifier control system 106 changes control
states in block
766, from "High 1 Flow State" to "High 2 Flow State." The "High 2 Flow State"
can
correspond to a control state used in conjunction with open surgery, where
flow rates
are relatively constant and exceed the high flow threshold for times longer
than the high
flow duration. Upon changing the control state, the humidifier control system
106
moves to block 764 to set a chamber outlet temperature set point. The chamber
outlet
temperature set points can be different for the different states, as described
herein with
reference to Table 1. Once the chamber outlet temperature set point is set,
the
humidifier control system 106 controls the heater plate 122 according to the
methods
described in the second and third control states corresponding to the "Low
Flow State"
and the "Med Flow State" described with reference to FIG. 76. The humidifier
control
system 106 then returns to block 720 to receive a flow rate reading.
[0074] FIG. 8
illustrates a state chart 800 corresponding to a method of
determining a control state that can be implemented in an example embodiment
of a
control module 205. The control module 205 of the humidifier control system
106 can
use flow rate readings to determine a control state or mode, examples of which
are
described with reference to FIGs. 3, 4, and 7A-C. For example, the state chart
800 is
initiated in the "Zero Flow State" 802. If the flow rate exceeds flow Fl while
in the "Zero
Flow State" 802, the control module 205 moves to the "Low Flow State" 804. In
some
embodiments, the flow Fl can be about 1 Lpm. If the flow rate drops below flow
F2 or
exceeds flow F3 while in the "Low Flow State" 804, the control module 205
moves to the
"Zero Flow State" 802 or the "Med Flow State" 806, respectively. In some
embodiments,
the flow F2 can be about 1 Lpm and flow F3 can be about 3 Lpm. If the flow
rate drops
below flow F4 or exceeds flow F5 while in the "Med Flow State" 806, the
control module
205 moves to the "Zero Flow State" 802 or the "High 1 Flow State" 808,
respectively. In
some embodiments, the flow F4 can be about 2 Lpm and flow F5 can be about 5.5
Lpm.
If the flow rate drops below flow F6 while in the "High 1 Flow State" 808 or
if the control
module 205 is in the "High 1 Flow State" 808 for a time that exceeds time LT,
the control
module 205 moves to the "Zero Flow State" 802 or the "High 2 Flow State" 810,
respectively. In some embodiments, the flow F6 can be about 4.5 Lpm. In some
embodiments, the time ti can be about 3 minutes. If the flow rate drops below
flow F7
while in the "High 2 Flow State" 810, the control module 205 moves to the
"Zero Flow
State" 802. In some embodiments, the flow F7 can be about 7 Lpm.
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CA 02789613 2012-09-12
[0075] In some embodiments, the control module 205 controls the
humidifier
104 through the heater plate feedback module 210 when in the "Zero Flow State"
802.
As described herein, the heater plate feedback module 210 uses a heater plate
temperature set point and a heater plate temperature reading to control power
to the
heater plate 122. In some embodiments, the control module 205 controls the
humidifier
104 through the chamber temperature feedback module 215 when in any state
besides
the "Zero Flow State" 802. As described herein, the chamber temperature
feedback
module 215 uses a chamber outlet temperature set point and a chamber outlet
temperature reading to control power to the heater plate 122.
[0076] Table 1 lists example chamber set points corresponding to different
control states. For example, when the humidifier control system 106 is in the
"Zero Flow
State" there is no chamber set point and the humidifier control system 106
controls the
heater plate 122 using a fixed heater plate temperature TO, as described
herein. In
some embodiments, the fixed heater plate temperature TO can be about 37
degrees.
When the humidifier control system 106 is in the "Low Flow State," the "Med
Flow
State," the "High 1 Flow State," or the "High 2 Flow State" the humidifier
control system
106 can use PID feedback control to achieve a chamber set point corresponding
to a
temperature Ti, T2, T3, or T4, respectively. In some embodiments, the chamber
outlet
temperature set points Ti, T2, T3, and T4 are about 37 degrees, about 35
degrees,
about 33 degrees, and about 37 degrees, respectively. The "High 2 Flow State"
can be
used in conjunction with open surgery and the other control states can be used
in
conjunction with laparoscopic procedures, for example.
Table 1
Chamber Heater Plate Therapy
Setpoint
Zero Flow State No set point Fixed heater plate temperature Laparoscopic
TO
Low Flow State Temperature Ti PID feedback controlled heater
Med Flow State Temperature T2 plate to achieve set point
High 1 Flow State Temperature T3
High 2 Flow State Temperature T4 Open
surgery
[0077] Examples of humidifier control systems and associated components
and methods have been described with reference to the figures. The figures
show
various systems and modules and connections between them. The various modules
and
systems can be combined in various configurations and connections between the
various
CA 02789613 2012-09-12
modules and systems can represent physical or logical links. The
representations in the
figures have been presented to clearly illustrate principles controlling a
surgical
humidifier, and details regarding divisions of modules or systems have been
provided for
ease of description rather than attempting to delineate separate physical
embodiments.
The examples and figures are intended to illustrate and not to limit the scope
of the
inventions described herein. For example, the principles herein may be applied
to a
surgical humidifier as well as other types of humidification systems,
including respiratory
humidifiers. The principles herein may be applied in laparoscopic surgery or
open
surgery as well as in other scenarios, such as endoscopic procedures and/or
other
minimally invasive surgical procedures.
[0078] As used herein, the term "processor" refers broadly to any suitable
device, logical block, module, circuit, or combination of elements for
executing
instructions. For example, the controller 220 can be any conventional general
purpose
single- or multi-chip microprocessor such as a Pentium processor, a MIPS
processor,
a Power PC processor, AMDC) processor, or an ALPHA processor. In addition,
the
controller 220 can be any conventional special purpose microprocessor such as
a digital
signal processor. The various illustrative logical blocks, modules, and
circuits described
in connection with the embodiments disclosed herein can be implemented or
performed
with a general purpose processor, a digital signal processor (DSP), an
application specific
integrated circuit (ASIC), a field programmable gate array (FPGA), or other
programmable logic device, discrete gate or transistor logic, discrete
hardware
components, or any combination thereof designed to perform the functions
described
herein. A general purpose processor, such as controller 220, can be a
conventional
microprocessor, but the controller 220 can also be any conventional processor,
controller, microcontroller, or state machine. Controller 220 can also be
implemented as
a combination of computing devices, e.g., a combination of a DSP and a
microprocessor,
a plurality of microprocessors, one or more microprocessors in conjunction
with a DSP
core, or any other such configuration.
[0079] Data
storage can refer to electronic circuitry that allows information,
typically computer or digital data, to be stored and retrieved. Data storage
can refer to
external devices or systems, for example, disk drives or solid state drives.
Data storage
can also refer to fast semiconductor storage (chips), for example, Random
Access
Memory (RAM) or various forms of Read Only Memory (ROM), which are directly
connected to the communication bus or one or more processors of the humidifier
control
system 106. Other types of memory include bubble memory and core memory. Data
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CA 02789613 2012-09-12
storage can be physical hardware configured to store information in a non-
transitory
medium.
[0080] Although certain preferred embodiments and examples are disclosed
herein, inventive subject matter extends beyond the specifically disclosed
embodiments
to other alternative embodiments and/or uses, and to modifications and
equivalents
thereof. Thus, the scope of the claims or embodiments appended hereto is not
limited
by any of the particular embodiments described herein. For example, in any
method or
process disclosed herein, the acts or operations of the method or process can
be
performed in any suitable sequence and are not necessarily limited to any
particular
disclosed sequence. Various operations can be described as multiple discrete
operations
in turn, in a manner that can be helpful in understanding certain embodiments;
however, the order of description should not be construed to imply that these
operations
are order dependent. Additionally, the structures described herein can be
embodied as
integrated components or as separate components. For purposes of comparing
various
embodiments, certain aspects and advantages of these embodiments are
described. Not
necessarily all such aspects or advantages are achieved by any particular
embodiment.
Thus, for example, various embodiments can be carried out in a manner that
achieves or
optimizes one advantage or group of advantages as taught herein without
necessarily
achieving other aspects or advantages as can also be taught or suggested
herein.
[0081] Conditional language used herein, such as, among others, "can,"
"could," "might," "may," "e.g.," and the like, unless specifically stated
otherwise, or
otherwise understood within the context as used, is generally intended to
convey that
certain embodiments include, while other embodiments do not include, certain
features,
elements and/or states. Thus, such conditional language is not generally
intended to
imply that features, elements and/or states are in any way required for one or
more
embodiments. As used
herein, the terms "comprises," "comprising," "includes,"
"including," "has," "having" or any other variation thereof, are intended to
cover a non-
exclusive inclusion. For example, a process, method, article, or apparatus
that comprises
a list of elements is not necessarily limited to only those elements but may
include other
elements not expressly listed or inherent to such process, method, article, or
apparatus.
Also, the term "or" is used in its inclusive sense (and not in its exclusive
sense) so that
when used, for example, to connect a list of elements, the term "or" means
one, some,
or all of the elements in the list. Conjunctive language such as the phrase
"at least one
of X, Y and Z," unless specifically stated otherwise, is otherwise understood
with the
context as used in general to convey that an item, term, etc. may be either X,
Y or Z.
Thus, such conjunctive language is not generally intended to imply that
certain
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CA 02789613 2012-09-12
embodiments require at least one of X, at least one of Y and at least one of Z
each to be
present.
[0082] Methods and processes described herein may be embodied in, and
partially or fully automated via, software code modules executed by one or
more general
and/or special purpose computers. The word "module" refers to logic embodied
in
hardware and/or firmware, or to a collection of software instructions,
possibly having
entry and exit points, written in a programming language, such as, for
example, C or
C++. A software module may be compiled and linked into an executable program,
installed in a dynamically linked library, or may be written in an interpreted
programming language such as, for example, BASIC, Peri, or Python. It will
be
appreciated that software modules may be callable from other modules or from
themselves, and/or may be invoked in response to detected events or
interrupts.
Software instructions may be embedded in firmware, such as an erasable
programmable
read-only memory (EPROM). It will be further appreciated that hardware modules
may
comprise connected logic units, such as gates and flip-flops, and/or may be
comprised of
programmable units, such as programmable gate arrays, application specific
integrated
circuits, and/or processors. The modules described herein can be implemented
as
software modules, but also may be represented in hardware and/or firmware.
Moreover,
although in some embodiments a module may be separately compiled, in other
embodiments a module may represent a subset of instructions of a separately
compiled
program, and may not have an interface available to other logical program
units.
[0083] In certain embodiments, code modules may be implemented and/or
stored in any type of computer-readable medium or other computer storage
device. In
some systems, data (and/or metadata) input to the system, data generated by
the
system, and/or data used by the system can be stored in any type of computer
data
repository, such as a relational database and/or flat file system. Any of the
systems,
methods, and processes described herein may include an interface configured to
permit
interaction with users, operators, other systems, components, programs, and so
forth.
[0084] It should be emphasized that many variations and modifications may
be made to the above-described embodiments, the elements of which are to be
understood as being among other acceptable examples. All such modifications
and
variations are intended to be included herein within the scope of this
disclosure and
protected by the following claims. Further,
nothing in the foregoing disclosure is
intended to imply that any particular component, characteristic or process
step is
necessary or essential.
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