Pressure support system with a low leak alarm and method of using same
First Claim
1. A pressure support system comprising:
- a pressure generator adapted to provide a gas flow;
a conduit operatively coupled to said pressure generator to deliver a gas flow to a patient;
an interface device operatively coupled to said conduit to communicate a gas flow to an airway of a patient, wherein at least one of said conduit and said interface device includes an exhaust vent that provides a flow of exhaust gas to atmosphere from a respective one of said conduit and said interface device;
flow sensing means for determining a rate at which gas flows in said conduit and for providing flow signal indicative thereof;
pressure sensing means for determining a pressure of gas at a patient and for providing a pressure signal indicative thereof; and
processing means, receiving said flow signal and said pressure signal, for determining whether a current flow of exhaust gas passing through said exhaust vent is below an alarm threshold based on said flow signal and said pressure signal and for providing an output indicative of said determination.
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Accused Products
Abstract
A pressure support system and method of using same that includes a pressure generator adapted to provide a gas flow, a conduit coupled to the pressure generator to deliver a gas flow to a patient, an interface device coupled to the conduit to communicate the gas flow to an airway of the patient. An exhaust vent that provides a flow of exhaust gas to atmosphere is provided in the conduit or the interface device. A flow sensor detects a rate at which gas flows in the conduit and provides a first output indicative thereof, and a pressure sensor detects a pressure of gas at the patient and provides a second output indicative thereof. A control system receives the first and second outputs and determines whether a current flow of exhaust gas passing through the exhaust vent is below an alarm threshold based on the first and second outputs and provides a third output indicative of this determination.
204 Citations
25 Claims
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1. A pressure support system comprising:
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a pressure generator adapted to provide a gas flow;
a conduit operatively coupled to said pressure generator to deliver a gas flow to a patient;
an interface device operatively coupled to said conduit to communicate a gas flow to an airway of a patient, wherein at least one of said conduit and said interface device includes an exhaust vent that provides a flow of exhaust gas to atmosphere from a respective one of said conduit and said interface device;
flow sensing means for determining a rate at which gas flows in said conduit and for providing flow signal indicative thereof;
pressure sensing means for determining a pressure of gas at a patient and for providing a pressure signal indicative thereof; and
processing means, receiving said flow signal and said pressure signal, for determining whether a current flow of exhaust gas passing through said exhaust vent is below an alarm threshold based on said flow signal and said pressure signal and for providing an output indicative of said determination. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
during said learn period, where Qc is a current flow of gas within said conduit, Qknown is a predetermined flow of exhaust gas passing through said exhaust vent, and Tbreath is an integral number of breathing cycles, and (2) sets said alarm threshold based on a first set of criteria responsive to said first relationship being negative and based on a second set of criteria responsive to said first relationship not being negative.
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6. A pressure support system according to claim 5, wherein said processing means calculates a second relationship, Rleak, defined as:
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and wherein said processing means sets said alarm threshold as one of (1) a predetermined percentage less than a sum of Qknown, and Rleak and (2) a predetermined amount less than a sum of Qknown, and Rleak, responsive to said first relationship determined during said learn period being negative.
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7. A pressure support system according to claim 5, wherein said processing means also monitors said first relationship during nominal operation of said pressure support system and changes from said first set of criteria to said second set of criteria by which said alarm threshold is set responsive to said first relationship not being negative for a predetermined period of time and thereafter adjusts said alarm threshold according to said second set of criteria.
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8. A pressure support system according to claim 5, wherein Qknown is determined by one of:
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(1) performing an exhaust vent test that includes;
(a) providing a plurality of pressures to a patient via said pressure generator, (b) measuring a current flow of gas within said conduit associated with each of said plurality of pressures, (c) establishing a pressure versus flow relationship for said exhaust vent based on said plurality of pressures and flow associated therewith, and (d) setting Qknown based on said pressure versus flow relationship;
(2) recalling Qknown from a database based on said exhaust vent being used with said pressure support system, wherein said data base contains a plurality of pressure verses flow relationships associated with various types of exhaust vents; and
(3) setting Qknown to zero if both steps (1) and (2) are not performed.
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9. A pressure support system according to claim 8, wherein said processing means sets said alarm threshold as one of (1) a predetermined percentage of Qknown and (2) a predetermined amount less than Qknown, responsive to said first relationship determined during said learn period not being negative and one of (1) said exhaust vent test having been performed and (2) Qknown having been recalled from said database, and wherein said processing means sets said alarm threshold as one of (1) a predetermined percentage of a predetermined minimum exhaust vent leakage rate and (2) a predetermined amount less than said predetermined minimum exhaust vent leakage rate responsive to said first relationship determined during said learn period not being negative and said exhaust vent test and recalling of Qknown from said database having not been performed.
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10. A pressure support system according to claim 9, wherein said processing means determines, during normal operation of said pressure support system, whether a current flow of exhaust gas passing through said exhaust vent is below said alarm threshold by repeatedly determining whether said first relationship is negative, and
wherein said processing means calculates, during normal operation, a constant Rleak according to a second relationship defined as: -
if said first relationship is not negative, wherein Pp is a pressure at an airway of a patient, and according to a third relationship defined as;
if said first relationship is negative, and wherein said processing means, during normal operation, provides said third output based on whether a fourth relationship defined as Qknown+Rleak{square root over (Pp+L )} is less than said alarm threshold for a first predetermined period of time, responsive to Rleak not being negative, and wherein said processing means provides said third output based on whether a fifth relationship defined as Qknown+Rleak is less than said alarm threshold for a second predetermined period of time, responsive to Rleak being negative.
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11. A pressure support system according to claim 1, wherein said processing means determines, during normal operation of said pressure support system, whether a current flow of exhaust gas passing through said exhaust vent is below said alarm threshold by repeatedly determining whether a first relationship defined as:
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is negative, where Qc is a flow of gas within said conduit, Qknown is a predetermined rate of flow of exhaust gas passing through said exhaust vent, and Tbreath is an integral number of breathing cycles.
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12. A pressure support system according to claim 11, wherein said processing means determines whether said current rate of flow of exhaust gas passing through said exhaust vent is below said alarm threshold by calculating a constant Rleak according to a second relationship defined as:
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if said first relationship is not negative, wherein Pp is a pressure at an airway of a patient, and according to a third relationship defined as;
if said first relationship is negative.
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13. A pressure support system according to claim 12, wherein said processing means, during normal operation, provides said third output based on whether a fourth relationship defined as Qknown+Rleak{square root over (Pp+L )} is less than said alarm threshold for a first predetermined period of time, responsive to Rleak not being negative, and wherein said processing means provides said third output based on whether a fifth relationship defined as Qknown+Rleak is less than said alarm threshold for a second predetermined period of time, responsive to Rleak being negative.
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14. A method of providing pressure support including a low leak alarm comprising the steps of:
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providing a gas flow from a pressure generator to a patient via a conduit operatively coupled to said pressure generator, wherein an interface device is also coupled to said conduit to communicate a gas flow from said conduit to an airway of a patient, and wherein an exhaust vent in disposed in one of said interface device and a portion of said conduit proximate to said interface device to communicate a flow of exhaust gas to atmosphere from a respective one of said conduit and said interface device;
detecting a rate at which gas flows in said conduit and providing a first output indicative thereof;
detecting a pressure of gas at a patient and providing a second output indicative thereof;
determining whether a current flow of exhaust gas passing through said exhaust vent is below an alarm threshold based on said first output and said second output; and
providing a third output indicative of a result of said determining step. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
monitoring said rate at which gas flows in said conduit and said pressure of gas at a patient during a learn period; and
setting said alarm threshold based on said monitored gas flow in said conduit and said pressure of gas at a patient during said learn period.
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17. A method according to claim 16, wherein said monitoring step includes determining a first relationship defined as:
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during said learn period, where Qc is a current flow of gas within said conduit, Qknown is a predetermined flow of exhaust gas passing through said exhaust vent, and Tbreath is an integral number of breathing cycles; and wherein said alarm threshold setting step includes setting said alarm threshold based on a first set of criteria responsive to said first relationship being negative and setting said alarm threshold based on a second set of criteria responsive to said first relationship not being negative.
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18. A method according to claim 17, further comprising a step of calculating a second relationship, Rleak, defined as:
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and wherein said setting step includes setting said alarm threshold as one of (1) a predetermined percentage less than a sum of Qknown, and Rleak and (2) a predetermined amount less than a sum of Qknown, and Rleak, responsive to said first relationship determined during said learn period being negative.
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19. A method according to claim 17, further comprising the steps of:
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monitoring said first relationship during normal operation of said pressure support system;
changing from said first set of criteria to said second set of criteria by which said alarm threshold is set responsive to said first relationship not being negative for a predetermined period of time; and
adjusting said alarm threshold based on said second set of criteria.
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20. A method according to claim 17, further comprising the step of determining Qknown by performing the following steps:
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(1) performing an exhaust vent test by performing the following steps;
(a) providing a plurality of pressures to a patient via said pressure generator, (b) measuring a current flow of gas within said conduit associated with each of said plurality of pressures, (c) establishing a pressure versus flow relationship for said exhaust vent based on said plurality of pressures and rates of flow associated therewith, and (d) setting Qknown based on said pressure versus flow relationship;
(2) recalling Qknown from a database based on said exhaust vent being used with said pressure support system, wherein said database contains a plurality of pressure verses flow relationships associated with various types of exhaust vents; and
(3) setting Qknown to zero if both steps (1) and (2) are not performed.
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21. A method according to claim 20, wherein said alarm threshold setting step includes setting said alarm threshold as one of (1) a predetermined percentage of Qknown and (2) a predetermined amount less than Qknown, responsive to said first relationship determined during said learn period not being negative and one of (1) said exhaust vent test having been performed and (2) Qknown having been recalled from said database, and wherein said alarm threshold is set as one of (1) a predetermined percentage of a predetermined minimum exhaust vent leakage rate and (2) a predetermined amount less than said predetermined minimum exhaust vent leakage rate responsive to said first relationship determined during said learn period not being negative and said exhaust vent test and recalling Qknown from said database having not been performed.
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22. A method according to claim 21, wherein said determining step includes determining, during normal operation, whether a current rate of flow of exhaust gas passing through said exhaust vent is below said alarm threshold by repeatedly determining whether a first relationship defined as:
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is negative, where Qc is a flow of gas within said conduit, Qknown is a predetermined flow of exhaust gas passing through said exhaust vent, and Tbreath is an integral number of breathing cycles, further comprising; calculating a constant Rleak according to a second relationship defined as;
if said first relationship is not negative, wherein Pp is a pressure at an airway of a patient; and calculating a constant Rleak according to a third relationship defined as;
if said first relationship is negative; outputting a low leak alarm responsive to a fourth relationship defined as Qknown+Rleak{square root over (Pp+L )} being less than said alarm threshold for a first predetermined period of time, responsive to Rleak not being negative; and
outputting a low leak alarm responsive to a fifth relationship defined as Qknown+Rleak being less than said alarm threshold for a second predetermined period of time, responsive to Rleak being negative.
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23. A method according to claim 14, wherein said determining step includes determining, during normal operation, whether a current flow of exhaust gas passing through said exhaust vent is below said alarm threshold by repeatedly determining whether a first relationship defined as:
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is negative, where Qc is a flow of gas within said conduit, Qknown is a predetermined rate of flow of exhaust gas passing through said exhaust vent, and Tbreath is an integral number of breathing cycles.
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24. A method according to claim 23, further comprising the steps of
calculating a system constant Rleak according to a second relationship defined as: -
if said first relationship is not negative, wherein Pp is a pressure at an airway of a patient; and calculating a system constant Rleak according to a third relationship defined as;
if said first relationship is negative.
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25. A method according to claim 24, further comprising the steps of:
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determining whether Rleak not being positive;
outputting a low leak alarm responsive to a fourth relationship defined as Qknown+Rleak{square root over (Pp+L )} being less than said alarm threshold for a first predetermined period of time, responsive to Rleak not being negative; and
outputting a low leak alarm responsive to a fifth relationship defined as Qknown+Rleak being less than said alarm threshold for a second predetermined period of time, responsive to Rleak being negative.
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Specification