U.S. patent application number 10/188778 was filed with the patent office on 2003-09-04 for automatic fever abatement applications.
Invention is credited to Balding, David P..
Application Number | 20030167034 10/188778 |
Document ID | / |
Family ID | 23566269 |
Filed Date | 2003-09-04 |
United States Patent
Application |
20030167034 |
Kind Code |
A1 |
Balding, David P. |
September 4, 2003 |
Automatic fever abatement applications
Abstract
A method for treating fever by establishing a closed loop
pathway to flow a treatment substance through a patient's body
without the substance entering the patient's bloodstream, by
engaging a fever characteristic sensor with the patient, by
receiving a signal from such sensor and using the controller to
control temperature and/or flow of the treatment substance.
Inventors: |
Balding, David P.; (Mission
Viejo, CA) |
Correspondence
Address: |
Arlyn L. Alonzo, Esq.
ALSIUS CORPORATION
Suite 150
15770 Laguna Canyon Road
Irvine
CA
92618
US
|
Family ID: |
23566269 |
Appl. No.: |
10/188778 |
Filed: |
July 3, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10188778 |
Jul 3, 2002 |
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09396200 |
Sep 15, 1999 |
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6447474 |
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Current U.S.
Class: |
604/66 |
Current CPC
Class: |
A61M 2205/3606 20130101;
A61M 25/00 20130101; A61M 2205/3368 20130101 |
Class at
Publication: |
604/66 |
International
Class: |
A61M 031/00 |
Claims
What is claimed is:
1. A method for treating fever comprising: establishing a pathway
for fluid communication for a treatment substance to flow in a
closed loop through a patient's body without entering the
bloodstream; engaging at least one fever characteristic sensor with
the patient; receiving signals from the sensor at a controller;
using the controller to control at least one of: temperature, and
flow, of the treatment substance to counter fever in the
patient.
2. The method of claim 1, wherein the controller counters fever by
alleviating fever once the sensor indicates that the patient is
febrile.
3. The method of claim 1, wherein the controller counters fever by
prophylactically preventing a febrile episode.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation of U.S. patent
application Ser. No. 09/396,200 entitled Automatic Fever Abatement
System, filed on Sep. 15, 1999, the disclosures of which are
incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a system that abates fever
in hospital patients by administering medication, coolant, or other
treatment substance.
[0004] 2. Description of the Related Art
[0005] In warm blooded creatures, temperature regulation is one of
the most important functions of the body. The human body seeks to
maintain a core temperature of 37 degrees Celsius, and functions
optimally when this temperature is achieved. Excessive temperatures
cause various health problems, one of the most serious being brain
damage. For patients with brain injury, fever can exacerbate
neuronal outcomes.
[0006] To treat fever, a number of different techniques are known.
For example, patients often receive medication such as
acetaminophen (Tylenol) or acetylsalicylic acid (aspirin). In one
extreme technique, physicians cool the patient's entire body by
packing it in ice. In another technique, the patient is covered
with a cooling blanket, such as an inflatable cushion that is
filled with a coolant such as air or water. There are also other
traditional approaches such a gastric lavage with ice water,
infusing cold solution, etc.
[0007] One newly developed approach treats fever by circulating a
coolant through a catheter placed inside a patient's body. The
catheter may be inserted into veins, arteries, cavities, or other
internal regions of the body. The present assignee has pioneered a
number of different cooling catheters and techniques in this area.
Several different examples are shown in U.S. application Ser. No.
09/133,813, which was filed on Aug. 13, 1998 and is hereby
incorporated into the present application by reference.
[0008] Regardless of which technique is ultimately used to treat a
patient's fever, each of these techniques is manually activated by
medical staff when they initially detect fever. Accordingly, some
attention is required of medical staff in order to initially detect
the onset of fever. This approach is therefore subject to some
delay from the time medical staff recognize the start of fever
until treatment is initiated. Importantly, the delay in applying
treatment is a missed opportunity to prevent the fever in the first
place. Moreover, during this delay, the fever may proceed into more
serious stages. Thus, this delay can represent some health risk to
the patient. As the science of medicine is interested in minimizing
or reducing health risks wherever possible, the present Assignee
realizes that known fever abatement approaches may not be
completely satisfactory.
SUMMARY OF THE INVENTION
[0009] Broadly, the present invention concerns a machine-driven
system to treat or even prevent fever in hospital patients by
administering medication, coolant, or other treatment substance.
One exemplary system includes a treatment substance administration
path ("path"), a flow device, a source, one or more fever
characteristic sensors, and a controller. The path may be an
open-ended structure, such as a tube, or a closed-ended structure
such as a catheter with a sealed, internal conduit. The treatment
substance administration path is coupled to regions of the
patient's body that will contain or absorb the treatment substance,
as appropriate to the particular substance being used. The path is
coupled to the flow device, which is itself attached to the source.
The flow device comprises a pump, valve, or other suitable
mechanism to regulate flow of the treatment substance from the
source through the path. The source contains a treatment substance
such as medication (in the case of an open-ended path) or a coolant
(in the case of a closed-ended path). One or more fever
characteristic sensors are attached to various sites on the
patient. In the case of a closed-ended path, the system may also
include a return vessel to receive treatment substance returning
from the patient's body.
[0010] The fever characteristic sensors repeatedly measure
temperature, metabolic rate, and/or other bodily properties that
are affected by fever, and provide representative machine-readable
outputs. Concurrently, the controller repeatedly computes a supply
strategy to regulate the patient's temperature according to
pre-programmed specifications. Then, according to the computed
strategy, the controller directs the flow device to deliver
treatment substance to the path, and ultimately to the patient's
body. In addition to administering coolant, medication, or other
treatment substance to treat fever, the controller may activate
other antipyretic means by (1) starting, adjusting, or redirecting
a fan, (2) adjusting an air conditioning thermostat, (3) issuing
visual or audible warning signals to hospital staff, etc.
[0011] In one embodiment, the invention may be implemented to
provide a method to automatically treat or prevent fever in
hospital patients by administering medication, coolant, or other
antipyretic treatment substance. In another embodiment, the
invention may be implemented to provide an apparatus, such as fever
abatement system, for automatically treating or preventing fever in
hospital patients. In still another embodiment, the invention may
be implemented to provide a signal-bearing medium tangibly
embodying a program of machine-readable instructions executable by
a digital data processing apparatus to perform operations to manage
components of an automatic fever abatement system. Another
embodiment concerns logic circuitry having multiple interconnected
electrically conductive elements configured to perform operations
to manage components of an automatic fever abatement system.
[0012] The invention affords its users with a number of distinct
advantages. In addition to quickly recognizing the presence or
future onset of fever, the invention automatically initiates a
procedure to cool the patient. Unlike the prior art, there is no
delay before medical staff recognize the start of fever. In fact,
actions may be taken before the body even exhibits any temperature
rise. With the invention, rapid delivery of a therapeutic drug can
begin within minutes from fever recognition. As another benefit,
the invention utilizes machine control to minimize operator
supervision, and thereby reduces operating costs and frees medical
staff for other duties. Accordingly, the prompt recognition and
treatment of fever no longer requires twenty-four hour,
minute-by-minute attention from hospital staff and doctors. As
still another advantage, fever detection characteristics may be
customized for each patient to ensure early and accurate fever
detection. The invention also provides a number of other advantages
and benefits, which should be apparent from the following
description of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1A is a schematic diagram of a fever abatement system
according to the invention.
[0014] FIG. 1B is a diagram of a closed-end treatment substance
administration path according to the invention.
[0015] FIG. 1C is a diagram of an open-end treatment substance
administration path according to the invention.
[0016] FIG. 2 is a diagram of a digital data processing apparatus
according to the invention.
[0017] FIG. 3 shows an exemplary signal-bearing medium according to
the invention.
[0018] FIG. 4 is a flowchart of an operating sequence for automated
fever abatement according to the invention.
DETAILED DESCRIPTION
[0019] The nature, objectives, and advantages of the invention will
become more apparent to those skilled in the art after considering
the following detailed description in connection with the
accompanying drawings.
[0020] Hardware Components & Interconnections
[0021] Automatic Fever Abatement System
[0022] Introduction
[0023] One aspect of the invention concerns a machine-driven system
to treat or prevent fever in hospital patients by administering
medication, coolant, or other antipyretic means. This system may be
implemented in various ways, one example being shown by the
hardware components and interconnections shown by the system 100 of
FIG. 1. The system 100 includes a controller 104, one or more fever
characteristic sensors 106, a flow device 110, a treatment
substance administration path 108, and a source 112. The system 100
is utilized to automatically treat or even prevent fever in the
patient 102.
[0024] Fever Characteristic Sensor(s)
[0025] As mentioned above, the system 100 includes one or more
fever characteristic sensor(s) 106. As used herein, "fever" is
defined as bodily temperature that is above normal due to pathogens
or other stimuli. The system of this invention may be configured to
detect fever; more advantageously from the standpoint of preventing
fever, the invention may be configured to predictively detect the
future onset of fever. Utilizing the foregoing definition of fever,
the presence of fever is easily determined by detecting an elevated
body temperature. In this respect, the fever characteristic sensors
106 may include one or more temperature sensors, deployed in
various regions of the body that accurately represent the
temperature of the entire body, the body core, or a particular
region. As an example, a single temperature sensor may be deployed
at the esophagus, bladder, tympanic membrane, rectum, or another
local site that is representative of the body's core temperature.
With multiple temperature sensors, the sensors may be distributed
at various sites, and the resulting measurements averaged to
provide a more accurate representation of the patient's
temperature.
[0026] Advantageously, the fever characteristic sensors 106 may
also include other sensors to detect the onset of fever. Since
fever is preceded by increased metabolic rate, the sensors 106 may
also include devices to detect increased oxygen consumption,
increased carbon dioxide in exhaled air, decreased venous
hemoglobin oxygen saturation, and the like. In the case of oxygen
consumption or carbon dioxide measurement, the sensors 106 may
comprise a gas analyzer coupled to automatic ventilation equipment
or an open mask apparatus. In the case of venous hemoglobin oxygen
measurement, relevant sensors 106 may comprise optical light
reflectance and/or transmission devices, such as commercially
available devices for detecting blood saturation.
[0027] Treatment Substance Administration Path
[0028] The treatment substance administration path 108 ("path")
provides a means to administer a treatment substance to the
patient. The path 108 may be open-end or closed-end. With an
open-end path, the treatment substance takes a one-way trip into a
region of the patient's body that is likely to absorb, distribute,
or effectively process the treatment substance. The open-end
treatment substance administration path, for example, may be routed
to the patient's stomach, veins, arteries, esophagus, or rectum.
The open-end path is advantageous for treatment substances that
comprise medication, such as acetaminophen, in which case an
exemplary treatment substance administration path may comprise a
device such as nasogastric tube. FIG. 1C shows an exemplary
open-end path 140. The path 140 comprises a conduit having a body
146 with an inlet 142 and an outlet 144. The open-end treatment
substance administration path 140 is deployed by inserting the
outlet 144 into an artery, vein, stomach, rectum, skin, lungs or
other suitable body access point. Other examples of open-end path
include a nasogastric tube, open-end catheter, intravenous needle,
syringe, suppository, perforated tube for "drip" irrigation,
transdermal patch, aerosol or other inhalant, etc.
[0029] In contrast to the open-end path, treatment substance
circulates within the closed-end path without actually contacting
the patient's body. This is beneficial if the treatment substance
comprises a coolant such as saline. FIG. 1B shows an exemplary
closed-end path 120, which is embodied by a cooling catheter. The
catheter 120 includes a housing 122 having distal 128 and proximal
130 ends. The housing 122 contains a conduit 123 that runs from the
catheter's proximal end 130 to the distal end 128 and back again.
The conduit 123 has a supply opening 126 and a return opening 124.
The conduit 123 therefore provides a round-trip path internal to
the catheter 120, where this path is sealed from any contact with
the patient's body. The closed-end path 120 is deployed by
inserting the distal end 128 into a suitable blood vessel such as
the inferior vena cava. A number of exemplary catheters and their
use are described in U.S. application Ser. No. 09/321,515, which
was filed on May 27, 1999 and is hereby incorporated by reference
into the present application.
[0030] Flow Device, Source, Return Vessel
[0031] The flow device 110 controls flow of the treatment substance
from a source 112 to the patient to help prevent or abate the
patient's fever. In one embodiment, the flow device 110 may
comprise a pump or other structure that actively causes the
treatment substance to flow through the path from the source 112,
where the source comprises an intravenous bag, vial, jar, carton,
box, or other storage facility. In another embodiment, the
treatment substance flows by gravity and the flow device 110
comprises a valve, on-off switch, or other mechanism to regulate
treatment substance flowing from the source 112. Here, the source
112 may comprise any intravenous bag, vial, jar, carton, box, or
other storage facility, whether compressible or not. In still
another embodiment, the source 112 has a dynamic volume and the
treatment substance flows by reduction of the source's volume.
Namely, the source 112 may be a self-compressed vessel (e.g.,
distended elastic container), or a compressible vessel whose volume
decreases under external force (e.g., syringe, hydraulic vessel,
compressible intravenous bag, chamber with piston-driven lid,
etc.). In the case of a self-compressed source 112, the flow device
110 comprises a solenoid or other suitable device to regulate the
amount of flow through the path; in the case of an externally
compressed source 112, the flow device 110 comprises a compression
mechanism such as a hydraulic pump, motor, piston, pinchers,
screw-driven vise, etc. Ordinarily skilled artisans (having the
benefit of this disclosure) will recognize a variety of other
options to implement the flow device 110 and source 112.
[0032] In the case of an open-end path, the flow device 110
regulates flow of the treatment substance directly into the
patient's body. In the case of a closed-end path, the flow device
110 regulates flow of the treatment substance into the supply
opening (e.g., 126, FIG. 1B), and also collects spent treatment
substance from the catheter's return opening (e.g., 124, FIGURE
1B). The flow device 110 deposits returned treatment substance into
the return vessel 114. The return vessel 114 may be omitted when an
open-end path is used, or if the return vessel 114 leads to, or is
combined with, the source 112. When a closed-end path is used,
equipment for cooling the treatment substance may be implemented at
the source 112, the flow device 110, return vessel 114, or other
suitable location. If desired, the path 108 may be configured to
incorporate one or more fever characteristic sensors 106. For
instance, a rectal temperature probe may be combined with a path
designed for exposure or insertion of an antipyretic drug or
suppository.
[0033] Other Antipyretic Apparatus(es)
[0034] In addition to the foregoing components, the controller 104
may be coupled to one or more additional controller-activated
antipyretic apparatuses, whether related to the administration of
treatment substance or not. Some examples include inflatable
cooling blankets, oscillating or fixed fans, air conditioning
thermostats for room air or bath water, etc.
[0035] Controller-Generally
[0036] The controller 104 receives measurements from the sensor(s)
106, and serves to regulate operation of the flow device 110
according to predetermined specifications. To implement this
automatic control feature, the controller 104 comprises an
electronic module such as logic circuitry, discrete circuit
elements, or a digital data processing apparatus (computer) that
executes a program of machine-readable instructions.
[0037] When implemented in logic circuitry or a computer, the
controller 104 analyzes the patient's temperature and/or other
fever characteristic signals utilizing the controller's own
programming, and provides the resultant output signal to regulate
the flow device 110. When implemented in discrete circuitry, the
circuitry or the controller 104 processes the patient's fever
characteristics with circuitry to provide a resultant output signal
that regulates the flow device 110.
[0038] Controller-Digital Data Processing Apparatus
[0039] As mentioned above, one embodiment of the controller 104 is
a digital data processing apparatus. This apparatus may be embodied
by various hardware components and interconnections, one example
appearing in FIG. 2. The apparatus 200 includes a processor 202,
such as a microprocessor or other processing machine, coupled to a
storage 204. In the present example, the storage 204 includes a
fast-access storage 206, as well as nonvolatile storage 208. The
fast-access storage 206 may comprise random access memory (RAM),
and may be used to store the programming instructions executed by
the processor 202. The nonvolatile storage 208 may comprise, for
example, one or more magnetic data storage disks such as a "hard
drive", a tape drive, or any other suitable storage device. The
apparatus 200 also includes an input/output 210, such as a line,
bus, cable, electromagnetic link, or other means for the processor
202 to exchange data with other hardware external to the apparatus
200.
[0040] Despite the specific foregoing description, ordinarily
skilled artisans (having the benefit of this disclosure) will
recognize that the apparatus discussed above maybe implemented in a
machine of different construction, without departing from the scope
of the invention. As a specific example, one of the components 206,
208 may be eliminated; furthermore, the storage 204 may be provided
on-board the processor 202, or even provided externally to the
apparatus 200.
[0041] Controller-Logic Circuitry
[0042] In contrast to the digital data storage apparatus discussed
previously, a different embodiment of the invention implements the
controller 104 with logic circuitry instead of computer-executed
instructions. Depending upon the particular requirements of the
application in the areas of speed, expense, tooling costs, and the
like, this logic may be implemented by constructing an
application-specific integrated circuit (ASIC) having thousands of
tiny integrated transistors. Such an ASIC may be implemented using
CMOS, TTL, VLSI, or another suitable construction. Other
alternatives include a digital signal processing chip (DSP),
discrete circuitry (such as resistors, capacitors, diodes,
inductors, and transistors), field programmable gate array (FPGA),
programmable logic array (PLA), and the like.
[0043] Operation
[0044] In addition to the structure described above, a different
aspect of the invention concerns a process for automated fever
abatement. As illustrated below, this process includes steps that
are manually performed, such as preparing the patient for
treatment. The process also includes automatic, machine-activated
steps that treat or even prevent the patient's fever.
[0045] Signal-Bearing Medium
[0046] In the context of FIGS. 1-2, the automated fever abatement
process may be implemented, for example, by operating the
controller 104, as embodied by a digital data processing apparatus
200, to execute a sequence of machine-readable instructions. These
instructions may reside in various types of signal-bearing media.
In this respect, one aspect of the present invention concerns a
programmed product, comprising signal-bearing media tangibly
embodying a program of machine-readable instructions executable by
a digital data processor to operate the system 100 to perform
automated fever abatement.
[0047] This signal-bearing media may comprise, for example, RAM
(not shown) contained within the controller 104, as represented by
the fast-access storage 206, for example. Alternatively, the
instructions may be contained in another signal-bearing media, such
as a magnetic data storage diskette 300 (FIG. 3), directly or
indirectly accessible by the processor 202. Whether contained in
the diskette 300, storage 204, or elsewhere, the instructions may
be stored on a variety of machine-readable data storage media, such
as direct access storage (e.g., a conventional "hard drive,"
redundant array of inexpensive disks (RAID), or another direct
access storage device (DASD)), magnetic tape, electronic read-only
memory (e.g., ROM, EPROM, or EEPROM), optical storage (e.g.,
CD-ROM, WORM, DVD, digital optical tape), paper "punch" cards, or
other suitable signal-bearing media including transmission media
such as digital and analog and communication links and wireless. In
an illustrative embodiment of the invention, the machine-readable
instructions may comprise software object code, compiled from a
language such as "C," etc.
[0048] Logic Circuitry
[0049] In contrast to the signal-bearing medium discussed above,
the method of automated fever abatement may be implemented using
logic circuitry, without using a processor to execute instructions.
In this embodiment, the logic circuitry is implemented in the
controller 104, and serves to perform an operational sequence
according to this invention as described below. The logic circuitry
may be implemented using many different types of circuitry, as
discussed above.
[0050] Overall Sequence of Operation
[0051] FIG. 4 shows a sequence 400 that illustrates one example of
the method aspect of the present invention. For ease of
explanation, but without any intended limitation, the example of
FIG. 4 is described in the context of FIGS. 1-2, as described
above. After the sequence 400 is initiated in step 402, medical
staff prepare the patient for treatment (step 404). As an example,
such preparation may involve bathing, shaving, dressing, and other
activities. Next, medical staff interconnect the components of the
system 100 and deploy the path 108 to the appropriate bodily
site(s) (step 406). Alternatively, if the system 100 components are
pre-assembled, the assembly steps are omitted. After step 406,
medical staff deploy the fever characteristic sensor(s) 106 at
target regions of the patient's body. Upon completion of step 406,
the sensors begin to measure the relevant physiological
characteristics and provide representative machine-readable
outputs.
[0052] As illustrated, steps 404,406, and 408 are performed
manually. As described below, however, steps 409, 410, 412, and 414
are performed by the controller 104 and serve to implement an
automated method of fever abatement. In step 409, the controller
104 collects input for use in deciding how to operate the flow
device 110 and thereby regulate the patient's temperature. Among
other possible input, the input of step 409 includes input from the
sensor(s) 106, such as body temperature, metabolic rate, and other
bodily characteristics affected by fever. The input may also
include other information such as (1) whether the path 108 is
closed-end or open-end, (2) if the path 108 is open-end, the
strength of the medication that constitutes the treatment
substance, (3) the volume output of the flow device 110, (4) the
patient's temperature history, (5) the history of treatment
substance application with the current patient, (6) any
post-delivery time delay required for treatment substance to take
effect, and (7) other such factors.
[0053] After step 409, the controller computes a supply strategy in
step 410. The supply strategy specifies a volume, timing, and rate
of treatment substance supply that is calculated to regulate the
patient's temperature according to predetermined specifications.
These predetermined specifications are pre-programmed into the
controller 104. As an example, the predetermined specifications may
dictate keeping the patient's core temperature at or below 37.5
degrees Celsius, limiting any temperature excursions to a maximum
time or temperature, etc.
[0054] Thus, the supply strategy constitutes the manner of
treatment substance delivery that will achieve the predetermined
specifications. To compute the supply strategy, the controller 104
considers the input from step 409 and applies a predetermined
analysis to this data. The predetermined analysis may be specified
by one or more equations, lookup tables, or other machine-readable
information available to the controller 104 by software
programming, hardware configuration, etc.
[0055] To illustrate step 410 in greater detail some examples are
provided. In a first example, the path 108 is closed-end and the
treatment substance comprise room temperature or cooled saline, and
the predetermined specifications require keeping the patient's core
temperature below 37.5 degrees Celsius. Here, one example of the
controller's strategy is (1) operating the flow device 110 to
circulate coolant if the patient's temperature reaches 37.5 degrees
Celsius, and (2) ceasing operation of the flow device 110 whenever
the patient's temperature is below 37.5 degrees Celsius.
[0056] In a second example, the path 108 is open-end and the
treatment substance comprises one or more antipyretic drugs such as
acetaminophen, aspirin, naproxen, ibuprofen, etc. In this example,
the controller 104 may compute a strategy that activates the flow
device 110 to administer a bolus of the treatment substance upon
detecting fever or febral onset. Bolus may be especially desirable
because fever tends to occur in spikes with rapid onset, and rapid
initial delivery in a bolus may rapidly establish a meaningful
blood concentration of the antipyretic treatment substance.
[0057] As an alternative strategy, an initial bolus of one drug may
be administered, and if fever persists, a second larger bolus of
the same drug or a bolus of a second antipyretic drug is
administered. Furthermore, once fever is detected (or febral inset
predicted), the treatment substance may be administered with an
increasing rate if a preset body temperature is reached or if a
predetermined rate of temperature increase is detected.
[0058] After the supply strategy is computed in step 410, the
controller 104 directs the administration equipment 100 to
implement this strategy in step 412. Namely, the controller 104
directs the flow device 110 to begin delivering the treatment
substance to the path 108 according to the computed supply
strategy. Where the flow device 110 comprises a valve, step 412
involves opening, closing, or adjusting constriction of the valve.
Where the flow device 110 is a pump, the flow rate may be
controlled by varying pump speed or repeatedly turning a
constant-speed pump on and off. Also in step 412, the controller
104 may record the time that treatment began for subsequent
documentation by nurses, etc.
[0059] In step 414, the controller 104 determines whether it has
received an "off" command. The "off" command may be received by
keyboard entry, manual activation of a switch (not shown) coupled
to the controller 104, expiration of a pre-programmed treatment
period, etc. If the "off" command has not been received, the
sequence 400 returns to step 409, whereupon the controller 104
receives further input from the sensors 106, adjusts the supply
strategy if necessary (step 410), and directs the components of the
system 100 accordingly (step 412). When step 414 receives the "off"
command, the routine 400 ends in step 416.
[0060] Other Embodiments
[0061] While the foregoing disclosure shows a number of
illustrative embodiments of the invention, it will be apparent to
those skilled in the art that various changes and modifications can
be made herein without departing from the scope of the invention as
defined by the appended claims. Furthermore, although elements of
the invention may be described or claimed in the singular, the
plural is contemplated unless limitation to the singular is
explicitly stated.
* * * * *