FIELD OF THE DISCLOSURE
[1] The present disclosure relates to breathing assistance apparatuses. In
particular, the present disclosure relates to the detection of bubbling in a breathing assistance
apparatus and/or estimating flow and/or pressure in a gases flow pathway.
BACKGROUND
[2] Breathing assistance apparatuses are used in various environments such as
hospital, medical facility, residential care, or home environments to deliver a flow of gases to
users or patients. A breathing assistance or respiratory therapy apparatus (collectively,
"respiratory apparatus" or "respiratory devices") may be used to deliver a flow of gases and
optionally additionally or alternatively deliver supplementary oxygen or other gases. The
breathing assistance apparatus may also comprise a humidification apparatus to deliver heated
and humidified gases. As discussed in more detail below the humidification apparatus may be
separate to, or part of the breathing assistance apparatus. A breathing assistance apparatus may
allow adjustment and control over characteristics of the gases flow, including flow rate,
temperature, gases concentration, humidity, pressure, etc. Sensors, such as flow sensors and/or
pressure sensors, are used to measure characteristics of the gases flow.
SUMMARY
[3] In an aspect of the disclosure there is provided a breathing assistance
apparatus for providing respiratory therapy, the breathing assistance apparatus comprising:
a flow generator, the flow generator configured to provide a flow of
gases to an inspiratory conduit at a target flow rate,
at least one gases property sensor, the at least one gases property sensor
configured to measure a flow rate and/or a pressure of the gases in a gases flow
pathway,
wherein the gases flow pathway compnses at least the inspiratory
conduit configured to be connected to a patient interface, and an expiratory
conduit configured to be connected to a patient interface and a pressure
regulator, the pressure regulator comprising a chamber with a column of a liquid
into which an end portion of the expiratory conduit is submerged,
a controller, the controller configured to:
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determine at least one waveform characteristic based on a
waveform of the measured flow and/or pressure, and
based on the at least one waveform characteristic, determine
whether bubbling is occurring in the pressure regulator.
[4] Determination of whether bubbling is occurring may be based on
determining pressure and/or flow oscillations in the waveform indicative of bubbling in the
pressure regulator.
[5] The controller may be configured to display whether bubbling is occurring
in the pressure regulator on a display.
[6] The controller may be configured to generate an alarm based on whether
bubbling is occurring in the pressure regulator.
[7] The controller may be configured to generate the alarm if it is determined
bubbling is not occurring in the pressure regulator.
[8] The controller may be configured to generate the alarm if it is determined:
the percentage of time bubbling is occurring over a time period is below a threshold, or the
percentage of time bubbling is not occurring over a time period is above a threshold.
[9] The alarm may comprise one or more of:
an audio alarm,
a visual alarm.
[10] The apparatus may comprise a display, optionally the display comprises one
or more of: a touchscreen and/or one or more mechanical input devices.
[11] The controller may automatically select a respiratory therapy mode based
on whether bubbling is occurring in the pressure regulator.
[12] The respiratory therapy mode may comprise a bubble CPAP therapy mode
and a high flow therapy mode.
[13] Detection of bubbling may be occurring constantly or intermittently while
the apparatus is operating in a non-bubble CPAP mode.
[14] The controller is configured to generate an alarm when bubbling is detected
in a non-bubble CPAP mode.
[15] The determination of whether bubbling is occurring may be based on at least
one waveform characteristic exceeding an associated threshold.
[16] The determination of whether bubbling is occurring may be based on a
model, the model comprising one or more waveform characteristic factors associated with each
waveform characteristic.
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[17] The model may be a regression model.
[18] The one or more waveform characteristic factors may be determined
experimentally.
[19] The determination of whether bubbling IS occumng m the pressure
regulator may be over a time period.
[20] The at least one waveform characteristic may comprise or be based on one
or more of:
an amplitude of the waveform,
a distance between positive peaks of the waveform,
a magnitude of the amplitude difference between consecutive positive and
negative peaks of the waveform.
[21] The at least one waveform characteristic may compnse at least one
amplitude characteristic, and wherein the amplitude characteristic comprises one or more of:
an average of the amplitude of the positive peaks of the waveform, optionally
over a time window,
a standard deviation of the amplitude of the positive peaks of the waveform,
optionally over a time window.
[22] The at least one waveform characteristic may comprise at least one peak
distance characteristic, and wherein the peak distance characteristic comprises one or more of:
an average distance between positive peaks of the waveform, optionally over a
time window,
a standard deviation of the distance between positive peaks of the waveform
optionally over a time window.
[23] The at least one waveform characteristic may comprise at least one peak
difference characteristic, and wherein the peak difference characteristic comprises one or more
of:
an average of the magnitude of the amplitude difference between consecutive
positive and negative peaks of the waveform, optionally over a time window,
a standard deviation of the magnitude of the amplitude difference between
consecutive positive and negative peaks of the waveform, optionally over a time
window.
[24] The controller may be configured to apply a high pass and/or a low pass
filter to the measurement of the flow rate or pressure and/or the waveform.
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[25] The waveform may be configured to be divided into a one or more time
windows, and optionally wherein the determination of whether bubbling is occurring is made
for each time window.
[26] Each time window may be approximately two seconds.
[27] Each time window may overlap with a preceding time window, and/or a
subsequent time window.
[28] The time window overlap may be approximately 1.5 seconds.
[29] The determination of whether bubbling is occurring may be a probability of
bubbling occurring between 0 and 1.
[30] Bubbling may be determined to be occurrmg when the probability of
bubbling occurring is greater than 0.5.

CLAIMS:
1. A breathing assistance apparatus for providing respiratory therapy, the breathing
assistance apparatus comprising:
a flow generator, the flow generator configured to provide a flow of
gases to an inspiratory conduit at a target flow rate,
at least one gases property sensor, the at least one gases property sensor
configured to measure a flow rate and/or a pressure of the gases in a gases flow
pathway,
wherein the gases flow pathway compnses at least the inspiratory
conduit configured to be connected to a patient interface, and an expiratory
conduit configured to be connected to a patient interface and a pressure
regulator, the pressure regulator comprising a chamber with a column of a liquid
into which an end portion of the expiratory conduit is submerged,
a controller, the controller configured to:
determine at least one waveform characteristic based on a
waveform of the measured flow and/or pressure, and
based on the at least one waveform characteristic, determine
whether bubbling is occurring in the pressure regulator.
2. The breathing assistance apparatus of claim 1, wherein determination of whether
bubbling is occurring is based on determining pressure and/or flow oscillations in the
waveform indicative of bubbling in the pressure regulator.
3. The breathing assistance apparatus of claim 1 or claim 2, wherein the controller is
configured to display whether bubbling is occurring in the pressure regulator on a
display.
4. The breathing assistance apparatus of any one of claims 1 to 3, wherein the controller
is configured to generate an alarm based on whether bubbling is occurring in the
pressure regulator.
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5. The breathing assistance apparatus of claim 4, wherein the controller is configured to
generate the alarm if it is determined bubbling is not occurring in the pressure
regulator.
6. The breathing assistance apparatus of claim 4 or claim 5, wherein the controller is
configured to generate the alarm if it is determined: the percentage of time bubbling is
occurring over a time period is below a threshold, or the percentage of time bubbling
is not occurring over a time period is above a threshold.
7. The breathing assistance apparatus of any one of claims 4 to 6, wherein the alarm
comprises one or more of:
an audio alarm,
a visual alarm.
8. The breathing assistance apparatus of any one of claims 1 to 7, wherein the apparatus
comprises a display, optionally the display comprises one or more of: a touchscreen
and/or one or more mechanical input devices.
9. The breathing assistance apparatus of any one of claims 1 to 8, wherein the controller
automatically selects a respiratory therapy mode based on whether bubbling is
occurring in the pressure regulator.
10. The breathing assistance apparatus of claim 8, wherein the respiratory therapy mode
comprises a bubble CP AP therapy mode and a high flow therapy mode.
11. The breathing assistance apparatus of any one of claims 1 to 10, wherein detection of
bubbling is occurring constantly or intermittently while the apparatus is operating in a
non-bubble CPAP mode.
12. The breathing assistance apparatus of any one of claims 1 to 11, wherein the
controller is configured to generate an alarm when bubbling is detected in a nonbubble
CP AP mode.
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13. The breathing assistance apparatus of any one of claims 1 to 12, wherein the
determination of whether bubbling is occurring is based on at least one waveform
characteristic exceeding an associated threshold.
14. The breathing assistance apparatus of any one of claims 1 to 13, wherein the
determination of whether bubbling is occurring is based on a model, the model
comprising one or more waveform characteristic factors associated with each
waveform characteristic.
15. The breathing assistance apparatus of claim 14, wherein the model is a regression
model.
16. The breathing assistance apparatus of any one of claims 1 to 15, wherein the
determination of whether bubbling is occurring in the pressure regulator is over a time
period.
17. The breathing assistance apparatus of any one of claims 1 to 16, wherein the at least
one waveform characteristic comprises or is based on one or more of:
an amplitude of the waveform,
a distance between positive peaks of the waveform,
a magnitude of the amplitude difference between consecutive positive and
negative peaks of the waveform.
18. The breathing assistance apparatus of any one of claims 1 to 17, wherein the at least
one waveform characteristic comprises at least one amplitude characteristic, and
wherein the amplitude characteristic comprises one or more of:
an average of the amplitude of the positive peaks of the waveform, optionally
over a time window,
a standard deviation of the amplitude of the positive peaks of the waveform,
optionally over a time window.
19. The breathing assistance apparatus of any one of claims 1 to 18, wherein the at least
one waveform characteristic comprises at least one peak distance characteristic, and
wherein the peak distance characteristic comprises one or more of:
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an average distance between positive peaks of the waveform, optionally over a
time window,
a standard deviation of the distance between positive peaks of the waveform
optionally over a time window.
20. The breathing assistance apparatus of any one of claims 1 to 19, wherein the at least
one waveform characteristic comprises at least one peak difference characteristic, and
wherein the peak difference characteristic comprises one or more of:
an average of the magnitude of the amplitude difference between consecutive
positive and negative peaks of the waveform, optionally over a time window,
a standard deviation of the magnitude of the amplitude difference between
consecutive positive and negative peaks of the waveform, optionally over a time
window.
21. The breathing assistance apparatus of any one of claims 1 to 20, wherein the
controller is configured to apply a high pass and/or a low pass filter to the
measurement of the flow rate or pressure and/or the waveform.
22. The breathing assistance apparatus of any one of claims 1 to 21, wherein the
waveform is configured to be divided into a one or more time windows, and
optionally wherein the determination of whether bubbling is occurring is made for
each time window.
23. The breathing assistance apparatus of claim of 22, wherein each time window
overlaps with a preceding time window, and/or a subsequent time window.
24. The breathing assistance apparatus of any one of claims 1 to 23, wherein the at least
one gases property sensor is located at one or more of:
in the breathing assistance apparatus, optionally within the flow generator,
in a patient interface,
in the pressure regulator,
in the inspiratory conduit and/or expiratory conduit.
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25. The breathing assistance apparatus of any one of claims 1 to 24, wherein the at least
one gases property sensor is located within the gases flow pathway.
26. The breathing assistance apparatus of any one of claims 1 to 25, wherein the flow
generator configured to provide a flow of gases to an inspiratory conduit at a target
flow rate.
27. The breathing assistance apparatus of any one of claims 1 to 26, wherein the
controller is configured to determine a waveform based on the measurement of the
flow rate and/or pressure of the gases in the gases flow path.
28. The breathing assistance apparatus of any one of claims 1 to 27, wherein the liquid is
water, or a saline solution.
29. The breathing assistance apparatus of any one of claims 1 to 28, wherein the
controller is configured to determine that bubbling is intermittent based on the ratio of
time bubbling is occurring to time bubbling is not occurring over a time period.
30. The breathing assistance apparatus of any one of claims 1 to 29, wherein the
controller is configured to determine that bubbling is intermittent when a ratio of the
time bubbling is occurring to time bubbling is not occurring is within a range.
31. The breathing assistance apparatus of any one of claims 1 to 32, wherein detection of
bubbling is occurring in the pressure regulator during a therapy session indicates that
therapy is being provided.
32. The breathing assistance apparatus of any one of claims 1 to31, wherein the controller
is configured to determine one or more indicators of bubbling time metrics based on
detection of bubbling during one or more therapy sessions.
33. The breathing assistance apparatus of any one of claims 31, wherein the one or more
indicators of bubbling time metrics is one or more of:
a bubbling index, wherein the bubbling index, wherein the bubbling index is a
percentage of the total therapy time for which bubbling is occurring,
a no bubbling time for which bubbling is not occurring,
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a bubbling time for which bubbling is occurring.
34. The breathing assistance apparatus of any one of claims 32 to 34, wherein the
controller is configured to upload one or more bubbling time metrics to a server.
35. The breathing assistance apparatus of any one of claims 32 to 34, wherein the
controller is configured to generate an alarm when one or more indicators of bubbling
time metrics falls below a threshold.
36. The breathing assistance apparatus of any one of claims 32 to 35, wherein the
controller is configured to indicate that therapy is being provided when one or more
bubbling time metrics are above a threshold.
37. A breathing assistance apparatus for providing respiratory therapy, the breathing
assistance apparatus comprising:
a flow generator, the flow generator configured to provide a flow of
gases to an inspiratory conduit,
a controller, the controller configured to automatically select a
respiratory therapy mode based on whether bubbling is occurring in the pressure
regulator.
38. The breathing assistance apparatus of claim 37, wherein the breathing assistance
apparatus comprises at least one gases property sensor, the at least one gases property
sensor configured to measure a flow rate and/or a pressure of the gases in a gases flow
pathway.
39. The breathing assistance apparatus of claim 37 or claim 38, wherein the controller is
configured to:
determine a waveform based on the measurement of the flow rate and/or
pressure of the gases in the gases flow path, and
determine at least one waveform characteristic based on the flow and/or
pressure waveform, and
based on the at least one waveform characteristic, determine whether bubbling
is occurring in a pressure regulator
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40. The breathing assistance apparatus of any one of claims 37 to 39, wherein the
controller automatically selects a bubble CPAP mode if bubbling is occurring in the
pressure regulator.
41. The breathing assistance apparatus of any one of claims 37 to 40, wherein the
respiratory therapy mode comprises a bubble CPAP therapy mode or a high flow
therapy mode.
42. A breathing assistance apparatus for providing respiratory therapy, the breathing
assistance apparatus comprising:
a flow generator, the flow generator configured to provide a flow of
gases to an inspiratory conduit,
wherein the gases flow pathway compnses at least the inspiratory
conduit configured to be connected to a patient interface, and an expiratory
conduit configured to be connected to a pressure regulator the pressure regulator
comprising a chamber with a column of a liquid into which an end portion of
the expiratory conduit is submerged,
a controller, the controller configured to:
measure at least one characteristic of bubbling in the
pressure regulator,
determine at least one waveform characteristic based on
a waveform of the measured characteristic of bubbling in the
pressure regulator, and
based on the at least one waveform characteristic,
estimate a flow rate and/or pressure in the gases flow pathway.
43. The breathing assistance apparatus of claim 42, wherein the at least one characteristic
of bubbling in the pressure regulator is based on one or more of:
a signal indicative of an image of the bubbler as an output of a visual sensor,
a signal indicative of the surface of the water in the bubbler as an output of
a water level sensor,
a signal indicative of the sound generated by the bubbler as an output of a
microphone,
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a signal indicative of the optical properties of the liquid in the bubbler as an
output of an optical sensor,
a signal indicative of a gas flow characteristic, as an output of a gas flow
characteristic sensor.
44. The breathing assistance apparatus of claim 42 or claim 43, wherein the at least one
characteristic of bubbling in the pressure regulator is based on a signal indicative of a
gases flow rate in the gases flow pathway as an output of a flow sensor, optionally the
signal is based on a measured flow rate and/or a pressure of the gases in the gases
flow pathway.
45. The breathing assistance apparatus of any one of claims 42 to 44, wherein the at least
one characteristic of bubbling in the pressure regulator is based on a signal indicative
of a gases pressure in the gases flow pathway as an output of a pressure sensor
(optionally the signal is based on a measured pressure of the gases in the gases flow
pathway).
46. The breathing assistance apparatus of any one of claims 42 to 45, wherein the estimated
flow rate in the gases flow pathway is a flow rate of gases at an end of the expiratory
conduit.
47. The breathing assistance apparatus of claim 46, wherein the flow rate of gases at the
end of the expiratory conduit is at the pressure regulator.
48. The breathing assistance apparatus of any one of claims 42 to 47, wherein the
pressure in the gases flow pathway is a pressure at the patient interface.
49. The breathing assistance apparatus of any one of claims 46 to 48, wherein the controller
is configured to generate one or more alarms based on the estimated flow rate of gases
at an end of the expiratory conduit and/or the estimated pressure at a patient interface.
50. The breathing assistance apparatus of claim 49, wherein the controller is configured to
generate one or more alarms if the estimated flow rate of gases at an end of the
expiratory conduit (and optionally at the pressure regulator) is above a threshold.
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51. The breathing assistance apparatus of claim 49 or claim 50, wherein the controller is
configured to generate one or more alarms if the estimated pressure at the patient
interface is above a threshold.
52. The breathing assistance apparatus of any one of claims 49 to 51, wherein the one or
more alarms comprises one or more of:
an audio alarm,
a visual alarm.
53. The breathing assistance apparatus of any one of claims 48 to 52, wherein the
controller is configured to estimate the pressure at the patient interface additionally
based on a relationship between the flow rate of the gases in a gases flow pathway and
a pressure of the gases in a gases flow pathway.
54. The breathing assistance apparatus of any one of claims 42 to 53, wherein the
apparatus comprises at least one gases property sensor configured to measure a flow
rate of the gases in a gases flow pathway and/or a pressure of the gases in a gases flow
pathway.
55. The breathing assistance apparatus of claims 54 wherein the controller is configured
to estimate a leak flow rate of the system, the leak flow rate based on the difference
between the measured flow rate of the gases in a gases flow pathway and the
estimated flow rate of gases through the pressure regulator.
56. The breathing assistance apparatus of claim 55, wherein the controller is configured to
generate an alarm when the estimated leak flow rate is above a leak threshold
57. The breathing assistance apparatus of claim 55 or claim 56, wherein the controller is
configured to generate an alarm when the estimated leak flow rate increases by more
than a leak increase threshold over a predetermined period of time.
58. The breathing assistance apparatus of any one of claims 48 to 57, wherein the
controller is configured to estimate a set point of the pressure regulator based on the
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estimated flow rate of gases through the pressure regulator and the estimated pressure
at a patient interface.
59. The breathing assistance apparatus of any one of claims 48 to 58, wherein the
controller is configured to display the estimated pressure at the patient interface on at
least one display.
60. The breathing assistance apparatus of any one of claims 42 to 59, wherein the
apparatus comprises a display, optionally the display comprises one or more of: a
touchscreen and/or one or more mechanical input devices.
61. The breathing assistance apparatus any one of claims 42 to 60, wherein the respiratory
therapy mode comprises a bubble CPAP therapy mode and a high flow therapy mode.
62. The breathing assistance apparatus of any one of claims 42 to 61, wherein the
estimated flow rate and/or pressure in the gases flow pathway (optionally, the flow
rate of gases through the pressure regulator and/or a pressure at a patient interface) is
based on a model, the model comprising one or more waveform characteristic factors
associated with each waveform characteristic.
63. The breathing assistance apparatus of claim of 62, wherein the model is a regression
model.
64. The breathing assistance apparatus of claim of 62 or claim 63, wherein the one or
more waveform characteristic factors are determined experimentally.
65. The breathing assistance apparatus of any one of claims 42to 64, wherein the at least
one waveform characteristic comprises or is based on one or more of:
an amplitude of the waveform,
a distance between positive peaks of the waveform,
a number of times the waveform crosses a threshold,
a time between positive peaks of the waveform,
a time between negative peaks of the waveform,
an amplitude of positive peaks of the waveform,
an amplitude of negative peaks of the waveform,
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a magnitude of the amplitude difference between consecutive positive and
negative peaks of the waveform.
66. The breathing assistance apparatus of any one of claims 42 to 65, wherein the at least
one waveform characteristic comprises at least one amplitude characteristic.
67. The breathing assistance apparatus of any one of claims 42 to 66, wherein the
amplitude characteristic comprises one or more of:
an average of the amplitude of the positive peaks of the waveform, optionally
over a time window,
a standard deviation of the amplitude of the positive peaks of the waveform,
optionally over a time window,
an average of the amplitude of the negative peaks of the waveform, optionally
over a time window,
a standard deviation of the amplitude of the negative peaks of the waveform,
optionally over a time window,
an average of the amplitude of the waveform, optionally over a time window,
a standard deviation of the amplitude of the waveform, optionally over a time
window.
68. The breathing assistance apparatus of any one of claims 42 to 67, wherein the at least
one waveform characteristic comprises at least one peak distance characteristic.
69. The breathing assistance apparatus of any one of claims 42 to 68, wherein the peak
distance characteristic comprises one or more of:
an average distance between positive peaks of the waveform, optionally over a
time window,
a standard deviation of an average distance between positive peaks of the
waveform, optionally over a time window.,
a standard deviation of the distance between positive peaks of the waveform
optionally over a time window
an average distance between negative peaks of the waveform, optionally over a
time window,
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a standard deviation of the negative between positive peaks of the waveform
optionally over a time window.
70. The breathing assistance apparatus of any one of claims 42 to 69, wherein the at least
one waveform characteristic comprises at least one peak difference characteristic.
71. The breathing assistance apparatus of any one of claims 42 to 70, wherein the peak
difference characteristic comprises one or more of:
an average of the magnitude of the amplitude difference between consecutive
positive and negative peaks of the waveform, optionally over a time window,
a standard deviation of the magnitude of the amplitude difference between
consecutive positive and negative peaks of the waveform, optionally over a time
window.
72. The breathing assistance apparatus of any one of claims 42 to 71, wherein the at least
one waveform characteristic comprises at least one crossing characteristic.
73. The breathing assistance apparatus of any one of claims 42 to 72, wherein the
crossing characteristic comprises one or more of:
a number of times the waveform crosses zero,
a number of times the waveform crosses an average amplitude of the waveform.
74. The breathing assistance apparatus of any one of claims 42 to 73, wherein the
controller is configured to apply a high pass and/or a low pass filter to the
measurement of the characteristic of bubbling in the pressure regulator.
75. The breathing assistance apparatus of any one of claims 42 to 74, wherein the
waveform is configured to be divided into one or more time windows, and optionally
wherein the determination of the flow rate of gases through the pressure regulator
and/or the pressure at a patient interface is made for each time window,
76. A breathing assistance system comprising the breathing assistance apparatus of any
one of claims 1 to 7 5.
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77. A controller for a breathing assistance apparatus for providing respiratory therapy, the
controller configured to:
determine at least one waveform characteristic based on a waveform of a
measured flow and/or pressure, and
based on the at least one waveform characteristic, determine whether bubbling
is occurring in a pressure regulator.
78. A method of detecting bubbling in a pressure regulator of a breathing assistance
system, the method comprising:
determining at least one waveform characteristic based on a waveform of a
measured flow and/or pressure, and
based on the at least one waveform characteristic, determining whether
bubbling is occurring in a pressure regulator.
79. A controller for a breathing assistance apparatus for providing respiratory therapy, the
controller configured to automatically select a respiratory therapy mode based on
whether bubbling is occurring in the pressure regulator.
80. A method for selecting a therapy mode for a breathing assistance apparatus, the
method comprising:
automatically selecting a respiratory therapy mode based on whether bubbling
is occurring in the pressure regulator.
81. A controller for a breathing assistance apparatus for providing respiratory therapy, the
controller configured to:
determine at least one waveform characteristic based on a waveform of a
measured characteristic of bubbling in the pressure regulator, and
based on the at least one waveform characteristic, estimate an estimated flow
rate and/or pressure in a gases flow pathway.
82. A method for estimating a flow rate and/or a pressure in a gases flow path of a
breathing assistance system, the method comprising:
determining at least one waveform characteristic based on a waveform of a
measured characteristic of bubbling in a pressure regulator, and
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based on the at least one waveform characteristic, estimating an estimated flow
rate and/or pressure in a gases flow pathway.
83. A breathing assistance apparatus for providing respiratory therapy, the breathing
assistance apparatus comprising:
a flow generator, the flow generator configured to provide a flow of
gases to an inspiratory conduit at a target flow rate,
wherein the gases flow pathway comprises at least the inspiratory
conduit configured to be connected to a patient interface, and an expiratory
conduit configured to be connected to a pressure regulator the pressure regulator
comprising a chamber with a column of water into which an end portion of the
expiratory conduit is submerged,
at least one sensor, the sensor configured to measure at least one
characteristic indicative of bubbling in the pressure regulator,
a controller, the controller configured to:
determine at least one waveform characteristic based on a
waveform of the measurement of at least one characteristic indicative of
bubbling in the pressure regulator, and
based on the at least one waveform characteristic, determine
whether bubbling is occurring in the pressure regulator.
84. A controller for a breathing assistance apparatus for providing respiratory therapy, the
controller configured to:
based on a measurement of at least one characteristic indicative of bubbling in
the pressure regulator, determine whether bubbling is occurring in a pressure regulator.
85. A method of detecting bubbling in a pressure regulator of a breathing assistance
system, the method comprising:
determining at least one waveform characteristic based on a waveform of a
measurement of at least one characteristic indicative of bubbling in the pressure
regulator, and
based on the at least one waveform characteristic, determining whether
bubbling is occurring in the pressure regulator.