U.S. patent application number 12/553576 was filed with the patent office on 2010-03-04 for ventilator with controlled purge function.
This patent application is currently assigned to Nellcor Puritan Bennett LLC. Invention is credited to Daniel G. Graboi.
Application Number | 20100051026 12/553576 |
Document ID | / |
Family ID | 41213259 |
Filed Date | 2010-03-04 |
United States Patent
Application |
20100051026 |
Kind Code |
A1 |
Graboi; Daniel G. |
March 4, 2010 |
Ventilator With Controlled Purge Function
Abstract
This disclosure describes systems and methods for purging narrow
diameter sensor tubing in a ventilation system. Among other
aspects, this disclosure describes ventilation systems in which a
sensor tube purge module utilizes a ventilator-generated signal to
synchronize the purging of sensor tubes with the delivery of
respiratory therapy. Through the signal, purging is prevented from
occurring during inspiration and during events such as ventilation
maneuvers. Purging may be further improved by monitoring the
pressure of the gas used to purge the sensor tubes in order to
prevent purges being performed when the pressure is too high or too
low. One way to achieve this is by purging the sensor tubes using
gas discharged from an accumulator, in which the pressure in the
accumulator is monitored and controlled by the sensor tube purging
module.
Inventors: |
Graboi; Daniel G.;
(Encinitas, CA) |
Correspondence
Address: |
NELLCOR PURITAN BENNETT LLC;ATTN: IP LEGAL
6135 Gunbarrel Avenue
Boulder
CO
80301
US
|
Assignee: |
Nellcor Puritan Bennett LLC
Boulder
CO
|
Family ID: |
41213259 |
Appl. No.: |
12/553576 |
Filed: |
September 3, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61094377 |
Sep 4, 2008 |
|
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|
61169976 |
Apr 16, 2009 |
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Current U.S.
Class: |
128/203.12 |
Current CPC
Class: |
A61M 16/024 20170801;
A61M 16/0063 20140204; A61M 16/085 20140204; A61M 16/00 20130101;
A61M 16/0858 20140204; A61M 16/0051 20130101; A61M 16/0833
20140204; A61M 2016/0027 20130101 |
Class at
Publication: |
128/203.12 |
International
Class: |
A61M 16/00 20060101
A61M016/00 |
Claims
1. A pressure support system comprising: a pressure generating
system adapted to generate a flow of breathing gas; a ventilation
system including a patient circuit adapted to control delivery of
the flow of breathing gas; at least one circuit sensor in fluid
communication with the patient circuit via one or more sensor
tubes; and a sensor tube purge module adapted to discharge gas
through the sensor tube into the patient circuit based on a signal
received from the ventilation system.
2. The system of claim 1 wherein the signal received is a
purge-enable signal and the sensor tube purge module discharges gas
based on the purge-enable signal and one or more conditions
determined by the sensor tube purge module.
3. The system of claim 2 wherein the one or more conditions are
selected from an elapsed time since a last discharge of gas though
the sensor tube, a monitored gas pressure, an indication of a
breathing cycle of a patient connected to the patient circuit, a
user-generated command to discharge gas, and an elapsed number of
breaths since the last discharge of gas through the sensor
tube.
4. The system of claim 2 wherein when the purge-enable signal
indicates that a purge can be performed, the sensor tube purge
module discharges gas based one or more conditions determined by
the sensor tube purge module.
5. The system of claim 2 wherein when the purge-enable signal
indicates that a purge can not be performed, the sensor tube purge
module does not discharge gas.
6. The system claim 1 wherein the sensor tube purge module
transmits information to the ventilation system after each
discharge indicative of the amount of gas discharged into the
patient circuit.
7. The system of claim 6 wherein the information transmitted is
selected from one or more of a volume of gas discharged, an
indication that a discharge was performed, a discharge duration,
and a pressure associated with the discharged gas.
8. The system of claim 1 wherein the sensor tube purge module
further comprises: an accumulator from which gas is discharged
through the one or more sensor tubes; and an accumulator pressure
monitoring device.
9. The system of claim 8 wherein the sensor tube purge module
discharges gas based on the signal received from the ventilation
system and the accumulator pressure.
10. The system of claim 1 wherein the signal received is a purge
command signal directing the sensor tube purge module to discharges
gas and, in response, the sensor tube purge module discharges gas
upon a next detection of the end of patient inspiration.
11. The system of claim 1 wherein the signal received is a
recruitment maneuver signal indicating when the ventilation system
is performing a recruitment maneuver and the sensor tube purge
module does not discharge gas when the recruitment maneuver signal
indicates that a recruitment maneuver is ongoing.
12. A pressure support system comprising: a ventilation system
controlling the flow of breathing gas in a patient circuit; a
sensor in fluid communication with the patient circuit via one or
more sensor tubes; and a sensor tube purge module adapted to
discharge gas through the sensor tube into the ventilation system
based on the flow of breathing gas in the patient circuit.
13. The system of claim 12 wherein the sensor tube purge module
monitors the patient's breathing via the sensor and discharges gas
through a sensor tube only during a predetermined phase of a
patient's breathing cycle as determined by the sensor tube purge
module.
14. The system of claim 12 wherein the ventilation system monitors
the patient's breathing and the sensor tube purge module discharges
gas through a sensor tube only during a predetermined phase of a
patient's breathing cycle as determined by the ventilation
system.
15. The system of claim 14 wherein the ventilation system transmits
a signal to the sensor tube purge module indicative of the
patient's breathing cycle.
16. The system of claim 14 wherein the ventilation system transmits
a signal to the sensor tube purge module indicative of the
predetermined phase of the patient's breathing cycle.
17. A pressure support system comprising: a pressure generating
system adapted to generate a flow of breathing gas; a ventilation
system including a patient circuit; a sensor in fluid communication
with the patient circuit via a sensor tube; and a sensor tube purge
module having a controller, an accumulator from which gas is
discharged through the one or more sensor tubes, and an accumulator
pressure monitoring device, wherein the sensor tube purge module is
adapted to discharge gas from the accumulator through the sensor
tube into the patient circuit.
18. The system of claim 17 wherein the sensor tube purge module
charges the accumulator to a predetermined pressure prior to
discharging gas from accumulator through the sensor tube into the
ventilation system.
19. The system of claim 17 wherein the sensor tube purge module
monitors changes in the accumulator pressure over time.
20. The system of claim 17 wherein the sensor tube purge module
transmits an alarm notification based on the monitored changes in
pressure during a time period when the sensor tube purge module is
not actively discharging gas through the sensor tube.
21. The system of claim 17 wherein the sensor tube purge module
transmits information derived from an output the accumulator
pressure monitoring device for display by the ventilation
system.
22. The system of claim 17 wherein the sensor tube purge module
further comprises: a pump that pressurizes the accumulator.
23. The system of claim 17 wherein the sensor tube purge module
further comprises: a regulator connected to an external source of
pressurized gas that pressurizes the accumulator.
24. The system of claim 17 wherein the ventilation system monitors
a patient's breathing cycle and the sensor tube purge module
discharges gas through a sensor tube only during a predetermined
phase of a patient's breathing cycle.
25. A method of purging a sensor tube connecting a sensor to a gas
transport circuit comprising: monitoring a pressure or flow in the
gas transport circuit using the sensor; and discharging a volume of
gas through the sensor tube into the gas transport circuit based at
least in part on the monitored pressure or flow in the gas
transport circuit.
26. The method of claim 25 wherein the gas transport circuit is a
patient circuit connected to a breathing patient and the method
further comprises: determining a current phase of a breathing cycle
of the patient from the monitored pressure or flow; and discharging
the volume of gas through the sensor tube into the patient circuit
based at least in part on the current phase of the breathing cycle
of the patient.
27. The method of claim 26 wherein the discharging operation
further comprises: discharging only when the current phase of the
breathing cycle is not an inhalation phase.
28. The method of claim 26 further comprising: discharging the
volume of gas through the sensor tube into the patient circuit
based on the current phase of the breathing cycle of the patient
and a condition based on a last discharge of gas through the sensor
tube.
29. The method of claim 28 wherein the condition based on a last
discharge of gas through the sensor tube is selected from a time
period since the last discharge of gas and a number of breaths
since the last discharge of gas.
30. The method of claim 25 wherein the gas transport circuit is a
patient circuit connected to a breathing patient and the method
further comprises: monitoring a signal provided by a ventilation
system controlling the flow of gas in the patient circuit, wherein
signal is indicative of the flow of gas in the patient circuit and
generated by the ventilation system based at least in part on the
monitored pressure or flow in the gas transport circuit; and
discharging the volume of gas through the sensor tube into the
patient circuit based at least in part on the signal from the
ventilation system.
31. The method of claim 25 wherein the signal is selected from a
purge-enable signal, a recruitment maneuver signal, a signal
indicating a condition of the ventilator, and a signal indicating a
phase of a patient's breathing cycle.
32. The method of claim 25 further comprising: transmitting
information identifying the volume of gas discharged through the
sensor tube into the gas transport circuit.
33. A ventilation system adapted to generate a purge control signal
to a sensor tube purge module thereby controlling, at least in
part, when the sensor tube purge module purges the sensor
tubes.
34. The system of claim 33 wherein the purge control signal
indicates to the sensor tube purge module when a purge of the
sensor tubes can be performed.
35. The system of claim 33 wherein the purge control signal
indicates to the sensor tube purge module when to purge the sensor
tube.
36. The system of claim 33 wherein the purge control signal
indicates to the sensor tube purge module when purging of the
sensor tube is not allowed.
37. A sensor tube purge module adapted to discharge gas through a
sensor tube into a gas transport circuit comprising: a pressure
generating system adapted to discharge a volume of gas through the
sensor tube into the gas transport circuit; and a controller
controlling the discharge of gas from the pressure generating
system, the controller further adapted to communicate with a
ventilation system that controls the flow of gas in the gas
transport circuit.
38. The sensor tube purge module of claim 37 wherein the controller
is adapted to receive one or more signals from the ventilation
system, wherein the signals are selected from a signal indicating
when discharge of gas through the sensor tubes is not allowed, a
signal indicating when discharge of gas through the sensor tubes is
allowed, and a signal indicating when to discharge gas through the
sensor tubes.
39. The sensor tube purge module of claim 37 wherein the controller
is adapted to transmit information to the ventilation system based
on the discharge of gas through the sensor tubes, wherein the
information is selected from one or more of a volume of gas
discharged, an indication that a discharge was performed, a
discharge duration, and a pressure associated with the discharged
gas.
40. The sensor tube purge module of claim 37 further comprising: a
sensor attached to the sensor tubes, wherein the sensor monitors
pressure or flow in the gas transport circuit and transmits
information indicative of the pressure or flow to the
ventilator.
41. A pressure support system comprising: a ventilation system
adapted to deliver respiratory gas to a patient; and a sensor tube
purge means for synchronizing the purging of a sensor tube, with
the delivery of gas to the patient by the ventilation system.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/094,377 filed Sep. 4, 2008 and U.S. Provisional
Application No. 61/169,976 filed Apr. 16, 2009, which applications
are hereby incorporated herein by reference.
INTRODUCTION
[0002] Medical ventilators may determine when a patient takes a
breath in order to synchronize the operation of the ventilator with
the natural breathing of the patient. In some instances, detection
of the onset of inhalation and/or exhalation may be used to trigger
one or more actions on the part of the ventilator.
[0003] In order to accurately detect the onset of inhalation and/or
exhalation, and/or obtain a more accurate measurement of
inspiratory and expiratory flow/volume, a flow or pressure sensor
may be located close to the patient. For example, to achieve
accurate and timely non-invasive signal measurements,
differential-pressure flow transducers may be placed at the patient
wye proximal to the patient. However, the ventilator circuit and
particularly the patient wye is a challenging environment to make
continuously accurate measurements. The harsh environment for the
sensor is caused, at least in part, by the condensations resulting
from the passage of humidified gas through the system as well as
secretions emanating from the patient. Over time, the condensate
material can enter the sensor tubes and/or block its ports and
subsequently jeopardize the functioning of the sensor.
SUMMARY
[0004] This disclosure describes systems and methods for purging
narrow diameter sensor tubing, occasionally referred to as "sensor
lines", in a ventilation system. Among other aspects, this
disclosure describes ventilator systems in which the purging of
sensor lines is synchronized to a ventilator-generated signal.
Through the signal, purging is prevented from occurring during
inspiration and during events such as ventilation maneuvers.
Purging is further improved by monitoring the pressure of the gas
used to purge the sensor lines in order to prevent purges being
performed when the pressure is too high or too low.
[0005] There are times during ventilator operation that it would be
undesirable to purge. For example, the operator may want to perform
maneuvers such as an inspiratory pause, an expiratory pause, or a
respiratory mechanics maneuver such as NIF, P100 and Vital
Capacity. In such cases, the operator may push a button on the
ventilator user interface to initiate the maneuver. However, the
operator has requested a maneuver which should not be contaminated
with a purge.
[0006] For example, in some situations, it may be desirable to
purge only during a patient exhalation. This acts to prevent or
help prevent an inhalation of material expelled during the purge,
and reduces the maximum inflation of the lungs which would occur if
purging occurred at the end of inspiration when the lungs are at
their peak inflation point. Furthermore, it can be desirable, and
in some cases preferred to begin to purge not at the very beginning
of exhalation, but later in exhalation when the lungs are partially
deflated.
[0007] In the current Puritan Bennett 840 ventilator, the shortest
exhalation phase is about two hundred milliseconds (200 ms).
Especially in such cases, fine control over when the purge of the
proximal flow sensor package starts is desirable. Since the
ventilator is in control of when the exhalation valve opens and the
exhalation phase begins, it can know this point in time sooner and
with higher precision than does a proximal flow sensor package. Use
of a hardware "purge enable" signal sourced at the ventilator to
control the start of purging can help guarantee precision timing
for purging.
[0008] In some embodiments of the systems and methods described
herein, the possibility of a poorly timed purge may be reduced or
eliminated by adding a "purge enable" hardware signal sourced by
the ventilator and sent to the microprocessor on the proximal flow
sensor package. In some embodiments, coupling this hardware signal
with suitable software commands reduces the possibility of an
ill-timed purge, and results in negligible patient impact. Such
additional software commands may include one or more commands
directed to (1) setting target accumulator pressures and/or
pressure tolerances, (2) setting a purge delay time; (3) providing
low pressure (PEEP) information to the proximal sensor package; (4)
recording and/or transmitting purge duration; and (5) establishing
purge abort criteria.
[0009] In part, this disclosure describes a pressure support system
with means for synchronizing the purging of a sensor tube with the
delivery of gas to the patient by the ventilation system. The
system includes a pressure generating system adapted to generate a
flow of breathing gas; a ventilation system including a patient
circuit adapted to control delivery of the flow of breathing gas;
at least one circuit sensor in fluid communication with the patient
circuit via one or more sensor tubes; and a sensor tube purge
module adapted to discharge gas through the sensor tube into the
patient circuit based on a signal received from the ventilation
system. In an embodiment of the system, the signal received is a
purge-enable signal and the sensor tube purge module discharges gas
based on the purge-enable signal, that is only when the
purge-enable signal indicates that a purge is allowed by the
ventilator.
[0010] In addition, this disclosure also describes a pressure
support system having a ventilation system controlling the flow of
breathing gas in a patient circuit; a sensor in fluid communication
with the patient circuit via one or more sensor tubes; and a sensor
tube purge module adapted to discharge gas through the sensor tube
into the ventilation system based on the flow of breathing gas in
the patient circuit.
[0011] In yet another aspect of this disclosure, it describes a
pressure support system having a pressure generating system adapted
to generate a flow of breathing gas; a ventilation system including
a patient circuit; a sensor in fluid communication with the patient
circuit via a sensor tube; and a sensor tube purge module having a
controller, an accumulator from which gas is discharged through the
one or more sensor tubes, and an accumulator pressure monitoring
device, wherein the sensor tube purge module is adapted to
discharge gas from the accumulator through the sensor tube into the
patient circuit.
[0012] This disclosure further describes a method of purging a
sensor tube connecting a sensor to a gas transport circuit. The
method includes monitoring a pressure or flow in the gas transport
circuit using the sensor and discharging a volume of gas through
the sensor tube into the gas transport circuit based at least in
part on the monitored pressure or flow in the gas transport
circuit. In the event that the gas transport circuit is a patient
circuit attached to a breathing patient, the method may further
include determining a current phase of a breathing cycle of the
patient from the monitored pressure or flow and discharging the
volume of gas through the sensor tube into the patient circuit
based at least in part on the current phase of the breathing cycle
of the patient, such as discharging only when the current phase of
the breathing cycle is not an inhalation phase.
[0013] Yet another aspect, this disclosure describes a ventilation
system adapted to generate a purge control signal for use by a
sensor tube purge module thereby controlling, at least in part,
when the sensor tube purge module purges the sensor tubes. The
ventilator may allow control of purging by user's through the
ventilator's interface in which case compliance with and execution
of the user-specific purge conditions controlled by the ventilator
through the purge control signal transmitted to the purge
system.
[0014] Still a further aspect of this disclosure is the sensor tube
purge module adapted to discharge gas through a sensor tube into a
gas transport circuit. In this aspect, the sensor tube purge module
includes a pressure generating system adapted to discharge a volume
of gas through the sensor tube into the gas transport circuit; and
a controller controlling the discharge of gas from the pressure
generating system, the controller further adapted to communicate
with a ventilation system that controls the flow of gas in the gas
transport circuit.
[0015] These and various other features as well as advantages will
be apparent from a reading of the following detailed description
and a review of the associated drawings. Additional features are
set forth in the description that follows and, in part, will be
apparent from the description, or may be learned by practice of the
described embodiments. The benefits and features will be realized
and attained by the structure particularly pointed out in the
written description and claims hereof as well as the appended
drawings.
[0016] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the systems and methods for controlled purging of sensor lines.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The following drawing figures, which form a part of this
application, are illustrative of embodiments systems and methods
described below and are not meant to limit the scope of the
invention in any manner, which scope shall be based on the claims
appended hereto.
[0018] FIG. 1 illustrates an embodiment of a ventilator connected
to a human patient.
[0019] FIG. 2 illustrates an embodiment of a proximal sensor module
that includes a sensor tube purging system.
[0020] FIG. 3 illustrates an embodiment of a method of purging a
sensor tube connecting a patient circuit of a medical ventilator to
a sensor.
[0021] FIG. 4 illustrates an embodiment of a method of operating a
purge system with an accumulator.
DETAILED DESCRIPTION
[0022] Although the techniques introduced above and discussed in
detail below may be implemented for a variety of medical devices,
the present disclosure will discuss the implementation of these
techniques in the context of a medical ventilator for use in
providing ventilation support to a human patient. The reader will
understand that the technology described in the context of a
medical ventilator for human patients could be adapted for use with
other systems such as ventilators for non-human patients and
general gas transport systems in which sensor tubes in challenging
environments may require periodic or occasional purging.
[0023] Medical ventilators are used to provide a breathing gas to a
patient who may otherwise be unable to breathe sufficiently. In
modern medical facilities, pressurized air and oxygen sources are
often available from wall outlets. Accordingly, ventilators may
provide pressure regulating valves (or regulators) connected to
centralized sources of pressurized air and pressurized oxygen. The
regulating valves function to regulate flow so that respiratory gas
having a desired concentration of oxygen is supplied to the patient
at desired pressures and rates. Ventilators capable of operating
independently of external sources of pressurized air are also
available.
[0024] While operating a ventilator, it is desirable to monitor the
rate at which breathing gas is supplied to the patient.
Accordingly, systems typically have interposed flow and/or pressure
sensors. The sensors may be connected to or in communication with
the inspiratory limb and the expiratory limb of the ventilator
and/or patient circuit. In some cases, it is desirable to provide a
flow sensor and/or pressure sensor near the wye of the patient
circuit, which connects the inspiratory limb and the expiratory
limb near the patient interface (e.g., an endotracheal tube, mask,
or the like). Such a sensor package may be referred to as a
proximal sensor system, device or module.
[0025] During operation, the patient circuit can acquire exhaled
condensate from the patient and/or condensate from the action of a
humidifier in the patient circuit. For circuits containing a
proximal flow sensor package which measures flow using the
principle of differential pressure, the presence of such liquid or
viscous material in either or both of the lines used to sense
differential pressure can reduce sensor performance. One approach
to address this issue involves sending a puff, pocket, or discharge
of air down each of the differential pressure sensing tubes. Such a
discharge, which may also be referred to as a single, or
individual, purge of the tube, may help remove or prevent unwanted
condensate or the like from the tubes and/or from the proximal flow
sensor package. Depending on the embodiment, purging is performed
using a sensor tube purge system or module which may be integral
with the proximal sensor module or a separate and independent
system.
[0026] FIG. 1 illustrates an embodiment of a ventilator 20
connected to a human patient 24. Ventilator 20 includes a pneumatic
system 22 (also referred to as a pressure generating system 22) for
circulating breathing gases to and from patient 24 via the
ventilation tubing system 26, which couples the patient to the
pneumatic system via physical patient interface 28 and ventilator
circuit 30. Ventilator circuit 30 could be a two-limb or one-limb
circuit for carrying gas to and from the patient. In a two-limb
embodiment as shown, a wye fitting 36 may be provided as shown to
couple the patient interface 28 to the inspiratory limb 32 and the
expiratory limb 34 of the circuit 30.
[0027] The present systems and methods have proved particularly
advantageous in invasive settings, such as with endotracheal tubes.
However, condensation and mucus buildup do occur in a variety of
settings, and the present description contemplates that the patient
interface may be invasive or non-invasive, and of any configuration
suitable for communicating a flow of breathing gas from the patient
circuit to an airway of the patient. Examples of suitable patient
interface devices include a nasal mask, nasal/oral mask (which is
shown in FIG. 1), nasal prong, full-face mask, tracheal tube,
endotracheal tube, nasal pillow, etc.
[0028] Pneumatic system 22 may be configured in a variety of ways.
In the present example, system 22 includes an expiratory module 40
coupled with an expiratory limb 34 and an inspiratory module 42
coupled with an inspiratory limb 32. Compressor 44 or another
source or sources of pressurized gas (e.g., pressured air and/or
oxygen controlled through the use of one or more gas regulators) is
coupled with inspiratory module 42 to provide a source of
pressurized breathing gas for ventilatory support via inspiratory
limb 32.
[0029] The pneumatic system may include a variety of other
components, including sources for pressurized air and/or oxygen,
mixing modules, valves, sensors, tubing, accumulators, filters,
etc. Controller 50 is operatively coupled with pneumatic system 22,
signal measurement and acquisition systems, and an operator
interface 52 may be provided to enable an operator to interact with
the ventilator (e.g., change ventilator settings, select
operational modes, view monitored parameters, etc.). Controller 50
may include memory 54, one or more processors 56, storage 58,
and/or other components of the type commonly found in command and
control computing devices.
[0030] The memory 54 is computer-readable storage media that stores
software that is executed by the processor 56 and which controls
the operation of the ventilator 20. In an embodiment, the memory 54
comprises one or more solid-state storage devices such as flash
memory chips. In an alternative embodiment, the memory 54 may be
mass storage connected to the processor 56 through a mass storage
controller (not shown) and a communications bus (not shown).
Although the description of computer-readable media contained
herein refers to a solid-state storage, it should be appreciated by
those skilled in the art that computer-readable storage media can
be any available media that can be accessed by the processor 56.
Computer-readable storage media includes volatile and non-volatile,
removable and non-removable media implemented in any method or
technology for storage of information such as computer-readable
instructions, data structures, program modules or other data.
Computer-readable storage media includes, but is not limited to,
RAM, ROM, EPROM, EEPROM, flash memory or other solid state memory
technology, CD-ROM, DVD, or other optical storage, magnetic
cassettes, magnetic tape, magnetic disk storage or other magnetic
storage devices, or any other medium which can be used to store the
desired information and which can be accessed by the processor
56.
[0031] As described in more detail below, controller 50 issues
commands to pneumatic system 22 in order to control the breathing
assistance provided to the patient by the ventilator. The specific
commands may be based on inputs received from patient 24, pneumatic
system 22 and sensors, operator interface 52 and/or other
components of the ventilator. In the depicted example, operator
interface includes a display 59 that is touch-sensitive, enabling
the display to serve both as an input user interface device and
output device.
[0032] In addition to general control commands, the controller 50
also communicates with the proximal sensor module 66. The
information provided allows purges performed of the sensor tubes
62, 64 to be synchronized with the overall operation of the
ventilator 20. For example, the controller 50 may be programmed so
that purges will or will not occur during specific phases of the
patient's breathing cycle, during specific periods within a phase
(e.g., not at the beginning or end of a phase) or during specific
maneuvers. These specific periods may be predetermined by the
manufacturer, the hospital or adjusted by each user via the display
and ventilator's user interface. For example, in an embodiment
purge control parameters are stored in the memory of the ventilator
22 which can be revised through a user interfacing with the
controller 50. Alternatively such parameters may be transmitted to
the purge system for storage and use at a later time when
determining from a purge control signal whether purging is allowed
at any given instant. This allows an operator to control purging
through the ventilator's interface.
[0033] The ventilator 20 is also illustrated as having a proximal
sensor module (the "Prox. Module" in FIG. 1) 66. The proximal
sensor module 66 includes at least one sensor, such as a pressure
sensor, that is connected to some location in the patient circuit
30 or patient interface 28 by one or more sensor tubes 62, 64. In
the embodiment shown, two sensor tubes 62, 64 connect the proximal
sensor module 66 to a location in the wye fitting 36. As is known
in the art, for the differential pressure measurement system to
operate, a resistance to flow is placed between the flow outlets of
the two sensor tubes 62, 64. In alternative embodiments, sensor
tubes may connect to the ventilator tubing system 26 at any
location including any limb of the circuit 30 and the patient
interface 28. It should be noted that regardless of where the
sensor tubes connect to the tubing system 26, because it is assumed
that there is very little or no leakage from the tubing system 26
all gas discharged through the sensor tubes into the ventilator
tubing system 26 will ultimately be discharged from the ventilator
through the patient circuit 30 and expiratory module 40. The use of
sensor tubes as part of various different measurement systems is
known in the art.
[0034] In the embodiment shown, the proximal sensor module 66
includes a sensor tube purging system that purges the sensor tubes
by occasionally discharging gas through the sensor tubes into the
patient circuit 30. The sensor tube purging system and functions
are discussed in greater detail below.
[0035] Although FIG. 1 illustrates an embodiment have two sensor
tubes 62, 64 and one proximal sensor module 66, any number of
sensor tubes may be used depending on the number and types of
proximal sensors. For example, in some embodiments module 66
couples to three (3) tubes, with two (2) tubes used for a
differential pressure sensor function and the third tube used for
an alternative function such as gas composition analysis,
orientation or other alternative sensors, or the like. All of the
sensors may be housed in a single proximal sensor module 66 or they
may be separated into different modules 66.
[0036] Furthermore, a proximal sensor module 66 may be integrated
into the ventilator 20 as shown, or may be a completely independent
module. If independent, the proximal flow module 66 may be adapted
to detect the current phase of a patient's breathing cycle in order
to synchronize the purging of the sensor tubes with specific
breathing phases, such as the inspiratory phase or the exhalation
phase or other conditions such as respiratory maneuvers or
user-initiated purging (e.g., a user-generated "purge now"
command).
[0037] FIG. 2 illustrates an embodiment of a proximal sensor module
that includes a sensor tube purge system in addition to a proximal
sensor that prevents purges from occurring during points in the
ventilation cycle in which purges are undesirable. The proximal
sensor module 202 may be implemented as an independent, stand-alone
module, e.g., as a separate card either inside the ventilator or
within a separate housing associated with the proximal flow sensor.
Alternatively, the proximal sensor module 202 may be integrated
with components of the ventilator or another device, e.g., built
into a ventilator control board. In yet another embodiment, the
sensor tube purge system may be implemented independently from the
proximal sensor 204, for example as an in-line module between the
sensor and the patient circuit, in which case the module of FIG. 2
would not include the proximal sensor 204.
[0038] In the embodiment shown, a proximal sensor module 202 is
illustrated having a differential pressure or flow sensor 204
connected to two sensor tubes 206, 208 that are subsequently
attached to the ventilator tubing system (not shown). Sensor tubes
used in conjunction with proximal sensors may have relatively small
internal diameters. For example, tube diameters may be less than
about 10 millimeters (mm), less than about 1 mm, or even smaller.
Such sensor tubes are prone to blockage and, also because of their
small diameters, are relatively more detrimentally affected by
inner surface contamination even when not completely occluded.
[0039] In the embodiment shown, the differential pressure sensor
204 is connected to each sensor tube 206, 208 by a corresponding
valve 210, 212. The valves 210, 212 are also connected to a
pressurized vessel 214, sometimes also referred to as an
accumulator 214, and operate such that when a sensor tube 206, 208
is connected to the vessel 214 (thus allowing pressurized gas from
the vessel to be discharged through the sensor tube to the
ventilator circuit) the associated sensor tube is not connected to
the pressure sensor 204. This protects the sensor 204 from damage
due to the abrupt change in pressure caused when the sensor tube is
purged. In another embodiment, when performing an individual purge
of either sensor tube of a differential pressure sensor, the sensor
may also be disconnected from the both sensor tubes. In yet another
embodiment, the differential pressure sensor may always be
connected to the sensor tubing regardless of whether the tubes are
being purged or not. In this embodiment, the sensor 204 may or may
not be disabled (turned off) to prevent damage or the recording of
spurious pressure measurements.
[0040] In the embodiment shown, the purge module in the proximal
sensor module 202 includes the accumulator 214, a pump 216 (or
alternatively a source of pressurized gas and a regulator) for
charging the accumulator 214 with gas obtained from an external
source (e.g., ambient), a pressure sensor 218 for monitoring the
pressure in the accumulator 214, the aforementioned valves 210, 212
and a purge controller 220 that controls the functions of the purge
module. The accumulator 214 may be any appropriate size and rated
to any appropriate pressure. In an embodiment, because the volumes
and pressures necessary to purge the typically small-diameter
sensor tubes are relatively small and cost and size are always
important design factors, the accumulator 214 may have a volume
between about five (5) milliliters (ml) to about 20 milliliters. In
a specific embodiment, the accumulator 214 volume is between about
10 ml and about 12 ml. In some embodiments, accumulator 214 is
rated to hold and/or maintain pressures between about two (2)
pounds per square inch (PSI) and about thirty (30) pounds per
square inch, with ratings of up to about 3 psi, up to about 6 psi
and up to about 8 psi used in various embodiments depending on pump
size. The pump 216 may be of any type and may receive filtered air
or any other gas, including respiratory gas obtained directly from
the ventilator.
[0041] For example, in an embodiment, when power is applied to the
pump 216, gas from the gas source is pumped under pressure into the
accumulator 214. When power is removed from the pump 216, the pump
contains a suitable structure such that the pressure built up in
the accumulator 214 does not discharge back through the pump. Such
structure provides the function of a check valve without requiring
an extra component.
[0042] In the embodiment shown, the accumulator pressure sensor 218
is provided to obtain information concerning the pressure within
the vessel 214. From this information, the amount of gas used
during purging can be determined. Depending on the embodiment, the
raw pressure data may be provided to the ventilator for use in
calculating the gas flow through the patient circuit or may be
provided to the purge controller 220, which calculates the purge
volume and provides that data to the ventilator. Such a calculation
would be performed based on the pressure changes observed during
the purge cycle and previously determined data characterizing the
volume, compliance and other parameters of the purge module as is
known in the art.
[0043] In the embodiment shown, the purge controller 220 controls
the purging of the sensor tubes 206, 208 by controlling the opening
and closing of the valves 210, 212 and the pressurizing of the
accumulator 214 by the pump 216. In an embodiment, the purge
controller 220 includes a microprocessor executing software stored
either on memory within the processor or in a separate memory
cache. The purge controller 220 may or may not be involved in the
transmission of sensor data from the circuit sensor 204 to other
devices or components such as the ventilator, e.g., the circuit
sensor 204 may directly output its data signal to the
ventilator.
[0044] As discussed above, the controller 220 may also communicate
with other systems. For example, in an embodiment the controller
220 interfaces between the ventilator and the sensor tube purge
system to provide information to the ventilator such as the status
of the purge system (e.g., currently discharging, time since last
discharge, time/duration of last discharge, time until next
discharge, currently in a purge cycle, time since last purge cycle,
purge failure error due to possible occlusion of a sensor tube,
component failure, etc.) and the amount of purge gas delivered into
the patient circuit. The controller 220 may also receive
information from external sources such as modules of the
ventilator, in particular information concerning the current
breathing phase of the patient so that the purge system can
synchronize its operations with the delivery of gas to the patient,
and user interfaces. The information received may include
user-selected or predetermined values for various parameters such
as the purge cycle interval (e.g., perform a purge cycle every 10
minutes), accumulator pressure, between-discharges delay period,
individual purge/discharge interval, a purge-enable signal (e.g., a
signal indicating that the proximal sensor module 202 is free to
initiate a purge cycle), a purge-disable signal (e.g., a signal
indicating that the proximal sensor module 202 should not initiate
a purge cycle), etc. The information received may further include
directions such as a ventilator-generated purge command or an
operator command to perform a purge at the next opportunity (e.g.,
an automatic or manual purge command). The controller 220 may also
include an internal timer so that individual purges can be
performed at a user or manufacturer specified interval.
[0045] Depending on the embodiment, the controller 220 may also
monitor the pressure in the accumulator 214 (via the vessel
pressure sensor 218) when controlling the pump 216 so that
specified pressures are obtained at different points in the purge
cycle. In an alternative embodiment, the controller 220 may rely on
timing to control the operation of the purge system, for example
such as when there is no sensor 218 provided, by opening and
closing valves and operating the pump for specified lengths of
time.
[0046] In an embodiment, the proximal sensor module 202 may be
independent of the ventilator in that it determines based on its
own internal logic (which may take into account data from the
ventilator, directly from the sensor 204, the accumulator sensor
218 or other sources) when to perform purges of the sensor tubes.
In an alternative embodiment, the proximal sensor module 202 may be
less than independent of the ventilator or, even, purely a slave to
the commands provided by the ventilator and containing little or no
internal decision making or processing capabilities.
[0047] In an alternative embodiment (not shown), alternative
systems for providing pressured gas for purging may be used. For
example, in an embodiment the pump 216 and accumulator 214 may be
replaced with a regulator (not shown) and a valve that regulates
pressure from an external pressurized gas source. Many other
systems for providing pressurized gas are known in the art.
Although the systems described herein are expedient given the
current design constraints encountered by the inventors, any
suitable pressurized gas system may be used and are considered
within the scope of this disclosure.
[0048] In an alternative embodiment, the module 202 does not
include a vessel pressure sensor 218 and does not have the ability
to measure the pressure in the accumulator 214. In this case,
control of the pump 216 and knowledge of the pump's specifications
and the accumulator size may be used to determine the amount of gas
injected during an individual purge event or the full purge cycle
into the patient circuit.
[0049] As discussed above, in some embodiments of the proximal
sensor module 202, a pressure sensor 218 is added to provide
pressure readings from the accumulator 214. Additionally, in some
embodiments the repeatability of purges is improved by charging the
accumulator 214 to a fixed target pressure (measured with the
pressure sensor 218), and using a variable amount of time for
charging. In this manner, input from the pressure sensor 218 can be
used to track the accumulator pressure and adjust the pumping time
necessary to create the desired pressure. In still other
embodiments, pump performance is trended over time. In this manner,
an alert may be sent to the operator or the ventilator, may be
displayed on the ventilator graphical user interface (GUI), or the
like, to indicate the pump performance. Such a trend can be used,
for example, to schedule maintenance to replace the pump 216 in a
timely fashion.
[0050] After the accumulator 214 is charged, the accumulator 214
can discharge if left alone for a period of time due to slow
leakage through the valves and manifold seals. In an embodiment,
the extent of this leakage and the health of the system may be
determined by using the pressure sensor 218 in communication with
the accumulator circuit.
[0051] Some pumps 216 require relatively high power, and may have
problems operating at elevated temperatures. Such high temperatures
may exist, for example, in the ventilator card cage containing the
proximal flow sensor control card when the ventilator card cage is
operating under high ambient temperature conditions. In some
embodiments, a pump 216 capable of operation in such temperature
ranges is used.
[0052] FIG. 3 illustrates an embodiment of a method of purging a
sensor tube connecting a patient circuit of a medical ventilator to
a sensor. The embodiment illustrated in method 300 in simple terms
can be described as synchronizing the purging of sensor tubes with
the operation of the ventilator or, alternatively, the breathing
cycle of the patient. This is done by determining that all of the
purge system's internal conditions necessary for performing a purge
are met as well as receiving an indication from the ventilator
either that the ventilator's conditions for purging are also met or
from which that can be ascertained.
[0053] The general method 300 shown starts with an initialization
operation 302. This may take the form of a startup command or may
simply be caused by an operator turning on the ventilator or sensor
tube purge system. In yet another embodiment, the initialization
operation 302 may be caused by the receipt of a purge control
signal from the ventilator or other source or the detection of flow
in the patient circuit by the sensor tube purge system.
[0054] In the embodiment shown, upon initiation a monitoring
operation 304 is performed in which a timer or counter is utilized
to determine the elapsed time or number of breaths (depending on
the type of interval being used). During the monitoring operation
the timer counts down until the interval expires as illustrated by
the determination operation 304. Upon expiration of the interval,
this internal purge system condition is met.
[0055] The method now begins the process of determining if the
ventilator condition(s) for allowing a purge are met by performing
a check purge control signal operation 308. In the embodiment
shown, the purge control signal is received from the ventilator and
may take any number of different forms, e.g., a purge-enable signal
indicating that purges can be performed at the present time or a
purge-disable signal indicating the opposite condition, from which
the purge system can ultimately determine whether the ventilator
allows a purge at the time of the analysis.
[0056] In an alternate embodiment, the purge control signal may
need to be interpreted against some additional information to
determine if the ventilator condition is met. For example, the
ventilator may provide a signal indicative of the current phase of
the patient's breathing cycle which the purge system then must
analyze against its internally-stored setting to determine if the
current phase is one in which a purge is allowed. The purge system
may have been previously set to allow purges only when the current
phase is not the inhalation phase and, in this embodiment, if the
purge control signal indicates a phase other than inhalation, the
ventilator condition is met and a purge is performed. In yet
another embodiment, the purge control signal may be an indication
of the current flow in the patient circuit and may be compared to a
flow condition known to the purge system in order to determine if a
purge is allowed. In yet another embodiment a purge control signal
may be a signal indicating the performance of a recruitment
maneuver or a patient disconnect condition.
[0057] In an embodiment, a ventilator may transmit a variety of
different purge control signals over time. Such signals may be
transmitted to multiple different recipients including the purge
system and may conform to a standard. Furthermore, signals may be
simple analog or digital signals or may be complex signals, such as
codes indicative of different states of the ventilator or different
commands, which must be processed and identified by the purge
system before they can be interpreted and the determination made as
to whether purge is allowed by the ventilator or not.
[0058] In an embodiment, the purge control signal from the
ventilator may be a signal directly or indirectly based on the data
received from the very sensor for which the tubes will be purged.
In this embodiment, it may be of even more importance to the
ventilator when purges occur as the sensor may not be available to
provide its normal data during a purge.
[0059] A purge control signal generated by the ventilator may take
into account the expected during of a purge event and adjust the
timing of the signal accordingly to ensure that a purge does not
extend into an undesirable portion of the ventilator's operation,
e.g., the purge extends into a patient's inhalation even though
started during the previous exhalation phase. Alternatively, such
management may be performed by the purge system by tracking when
purge control signals change.
[0060] In yet another embodiment, the purge control signal may be
obtained directly from the sensor attached to the sensor tubes to
be purged or from some other sensor instead of from the
ventilator's control or communication system. In an embodiment, the
purge system may interpret the sensor data directly to determine
what the current phase is of the patient's breathing cycle or may
simply be looking for specific flow or pressure condition, e.g., a
sudden drop or rise or a stable period for a certain duration, and
when that condition is detected a purge is allowed.
[0061] The act of analyzing the information provided by the
ventilator is illustrated by the determination operation 310. In
the embodiment shown, if, after analysis, it is determined that a
purge is not allowed the system returns to the check operation 308,
thereby creating a loop that waits for the ventilator condition to
change to purge being allowed.
[0062] If the ventilator condition is met, however, a purge is
performed as illustrated in the gas discharge operation 312. This
may include discharge of gas from an accumulator or from some other
source under control of the purge system. As part of this operation
312, data may be recorded, e.g., the time of the discharge, the
duration, the volume discharged, etc. and some or all of the data
may transmitted to the ventilator.
[0063] After the purge of the tube or tubes, the timer is reset in
a reset operation 314 and the flow returns to the monitoring
operation 304 so the flow is repeated until the purge system is
shutdown, such as in response to some external command or
event.
[0064] FIG. 3 illustrates a method that checks a purge system
condition and a ventilator condition to determine when to purge
sensor lines. The ventilator is thus able to prevent purges from
being performed at inopportune times such as during inhalation and
during recruitment maneuvers. In this way, the purge system can
synchronize its operation with the ventilator and the ventilation
of the patient.
[0065] In alternative embodiments, the various operations may be
reordered or adjusted and new operations (such as checking
additional purge system conditions and/or ventilator conditions)
added so that the method's flow is altered even though the goal of
the method, synchronization and preventing purges from being
performed during specific conditions, is still achieved. For
example, in an alternative embodiment the timer may be reset if the
purge is not allowed by the ventilator.
[0066] In another embodiment of a method of purging sensor lines,
other conditions may be evaluated such as determining whether the
pressure in the accumulator is within a specific range suitable for
performing a purge.
[0067] FIG. 4 illustrates this embodiment of a method of operating
a purge system with an accumulator. In this embodiment, the
operations with like reference numbers are the same as those
described with reference to FIG. 3, with the addition of several
operations related to determining the condition of the
accumulator.
[0068] In the embodiment shown, the accumulator is pressurized in a
charge operation 407. This operation could occur at any time,
although in an embodiment it is intentional charged at or near the
time at which a purge is to be performed in order to extend the
life of valves and other equipment that degrade faster when the
accumulator is pressurized.
[0069] A determination operation 408 then tests the pressure
condition of the accumulator to determine when it has sufficient
pressure for a purge to be performed. When there is enough pressure
in the accumulator, the condition is met and, in the embodiment
shown, the pump is disabled and flow proceeds to the check purge
control signal operation 308.
[0070] In the embodiment shown, until the accumulator is fully
pressurized the charge accumulator operation 407 continues.
However, as illustrated by the determination operation 409, if
after some predetermined amount of time the desired pressure is not
reached an alarm operation 410 is performed in which an alarm or
notification is transmitted as described above. Other methods and
operations related to assessing the performance of the accumulator
may also be used or substituted in the determination operation
409.
[0071] In some embodiments, adding a pressure sensor to the
accumulator, and coupling the use of this sensor signal with
suitable new software commands, adds the ability to do one or more
of the following: (a) assess and/or guarantee that purging is
working properly; (b) monitor the health of the purge pump and
provide user feedback if pump replacement is required; (c) produce
more repeatable purges over the time, even as pump performance
degrades; and (d) confirm that leakage in the accumulator manifold
circuit is within acceptable limits.
[0072] Those skilled in the art will recognize that the methods and
systems of the present disclosure may be implemented in many
manners and as such are not to be limited by the foregoing
exemplary embodiments and examples. In other words, functional
elements being performed by a single or multiple components, in
various combinations of hardware and software or firmware, and
individual functions, can be distributed among software
applications at either the client or server level or both. In this
regard, any number of the features of the different embodiments
described herein may be combined into single or multiple
embodiments, and alternate embodiments having fewer than or more
than all of the features herein described are possible.
Functionality may also be, in whole or in part, distributed among
multiple components, in manners now known or to become known. Thus,
myriad software/hardware/firmware combinations are possible in
achieving the functions, features, interfaces and preferences
described herein. Moreover, the scope of the present disclosure
covers conventionally known manners for carrying out the described
features and functions and interfaces, and those variations and
modifications that may be made to the hardware or software or
firmware components described herein as would be understood by
those skilled in the art now and hereafter.
[0073] While various embodiments have been described, various
changes and modifications may be made which are well within the
scope of the present disclosure. For example, in an embodiment the
operation of the sensor tube purge system may be entirely
controlled by the ventilator such that the purge system performs no
logic other than to await a command to purge from the ventilator.
In addition, the methods described above could be altered in many
different ways to change the order of the operations and add
additional condition checks in order to adjust the performance of
the system to meet differing design and cost criteria. Numerous
other changes may be made which will readily suggest themselves to
those skilled in the art and which are encompassed in the spirit of
the disclosure and as defined in the appended claims.
* * * * *