Method and system for determining a scaled respiratory flow rate and volume during respiration of a patient
A method for determining a scaled respiratory flow rate and volume during respiration of a patient includes a) successively determining a plurality of values for a difference between a pressure in at least a first location in an upper respiratory tract of the patient and a reference pressure, b) deriving the scaled respiratory flow rate from the plurality of values for the pressure difference by using a first relationship, c) deriving the scaled respiratory volume from the plurality of values for the pressure difference by using a second relationship, and d) displaying the scaled respiratory flow rate derived in step b) and the scaled respiratory volume derived in step c) or a further variable derived from the scaled respiratory flow rate and volume in a graphical representation. Step a) is performed during tidal breathing of the patient. A system for performing the aforementioned method.
1 . A method for determining a scaled respiratory flow rate and volume during respiration of a patient, comprising the steps of:
a) using a pressure sensor located in or near a nasal cannula in fluid communication with the patient's nostril to collect pressure measurements in at least a first location in an upper respiratory tract of the patient, and successively determining a plurality of values for a difference between a pressure in at least the first location in the upper respiratory tract of the patient and a reference pressure, wherein the first location in the upper respiratory tract is in a nostril of the patient and wherein the reference pressure is ambient pressure;
b) deriving the scaled respiratory flow rate from the plurality of values for the pressure difference by using a first relationship;
c) deriving the scaled respiratory volume from the plurality of values for the pressure difference by using a second relationship; and
d) displaying the scaled respiratory flow rate derived in step b) and the scaled respiratory volume derived in step c) or a further variable derived from the scaled respiratory flow rate and volume in a graphical representation;
wherein step a) is performed during tidal breathing of the patient; and
wherein an end of a prong of a nasal cannula is arranged in the upper respiratory tract before step a) is performed, the end of the cannula prong being arranged in the nostril between the first location and a nostril entry to create aerodynamic resistance or cause a local narrowing of the respiratory tract to increase the pressure differences.
2 . The method of claim 1 , wherein the scaled respiratory flow rate and scaled respiratory volume are displayed in a single graph, and optionally
wherein the first and second relationships used in steps b) and c) are each generalized relationships which are substantially independent of the patient.
3 . The method of claim 1 , wherein there is a first location in each of the patient's nostrils and wherein a first plurality of values for the pressure difference is determined in one of the patient's nostrils and a second plurality of values for the pressure difference is determined in the other nostril.
4 . The method of claim 1 , wherein the pressure sensor is arranged in a collective tube connected to a proximal end of the nasal cannula, the nasal cannula also having a distal end inserted into the patient's nostrils.
5 . The method of claim 1 , wherein at least one of:
steps b) and c) are performed at a location that is remote from the patient, and wherein the plurality of values for the pressure difference is transmitted to the remote location; and
step a) is performed for a plurality of breathing cycles during tidal breathing of the patient, and wherein derivation of the scaled respiratory flow rate in step b) and derivation of the scaled respiratory volume in step c) for each separate cycle include the use of the values for the pressure difference determined during the plurality of breathing cycles.
6 . The method of claim 2 , wherein the first generalized relationship used in step b) to derive the scaled respiratory flow rate is:
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and I ex =I ex (T)/K, I in =I in (T)/K, and T =T/K, with K the number of breathing cycles taken into account, T the time needed to complete these breathing cycles, and in which Δp is the pressure difference and b is a constant which depends on the sign of Δp.
7 . The method of claim 2 , wherein the second generalized relationship used in step c) to derive the scaled respiratory volume is:
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with I ex =I ex (T)/K, I in =I in (T)/K, and T =T/K with K the number of cycles taken into account, and T the time needed to complete these breathing cycles.
8 . The method of claim 1 , wherein the derivations in steps b) and c) and/or the displaying in step d) are/is performed by a computer.
9 . A system for determining a scaled respiratory flow rate and volume during respiration of a patient, comprising:
a determination module comprising a pressure sensor located in or near a nasal cannula in fluid communication with the patient's nostril to collect pressure measurements in at least a first location in an upper respiratory tract of the patient, the determination module configured for successively determining a plurality of values for a difference between a pressure in at least the first location in the upper respiratory tract of the patient and a reference pressure, the determination module being configured for determining the pressure differences between a first location in a nostril of the patient and ambient pressure;
a first derivation module comprising a first processing circuit configured for deriving the scaled respiratory flow rate from the plurality of values for the pressure difference by using a first relationship;
a second derivation module comprising a second processing circuit configured for deriving the scaled respiratory volume from the plurality of values for the pressure difference by using a second relationship; and
a display module comprising a display configured for displaying the scaled respiratory flow rate and the scaled respiratory volume or a further variable derived from the scaled respiratory flow rate and volume in a graphical representation;
wherein the determination module is configured to be operative during tidal breathing of the patient, and
wherein the determination module comprises an end of a prong of a nasal cannula configured to be arranged in the upper respiratory tract, the end of the cannula prong being configured to be arranged in the nostril between the first location and a nostril entry to create aerodynamic resistance or cause a local narrowing of the respiratory tract to increase the pressure differences.
10 . The system of claim 9 , wherein the display module is configured to display the scaled respiratory flow rate and scaled respiratory volume in a single graph, and optionally
wherein the first and second determination modules are each configured for using generalized relationships which are substantially independent of the patient.
11 . The system of claim 9 , wherein there is a first location in each of the patient's nostrils and wherein the determination module is configured for determining a first plurality of values for the pressure difference in one of the patient's nostrils and a second plurality of values for the pressure difference in the other nostril.
12 . The system of claim 9 , wherein the pressure sensor is arranged in a collective tube connected to a proximal end of the nasal cannula, the nasal cannula also having a distal end inserted into the patient's nostrils.
13 . The system of claim 9 , wherein at least one of:
the first and second derivation modules are at a location that is remote from the patient and are connected to the determination module for receiving the plurality of values for the pressure difference; and
the determination module is configured for determining the plurality of values for the pressure difference for a plurality of breathing cycles during tidal breathing of the patient, and wherein the first and second derivation modules are each configured for using, for each separate cycle, the values for the pressure difference determined during the plurality of breathing cycles.
14 . The system of claim 10 , wherein the first derivation module is configured to use the following relationship to derive the scaled respiratory flow rate:
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and I ex =I ex (T)/K, I in =I in (T)/K, and T =T/K, with K the number of breathing cycles taken into account, T the time needed to complete these breathing cycles, and in which Δp is the pressure difference and b is a constant which depends on the sign of Δp.
15 . The system of claim 10 , wherein the second derivation module is configured to use the following relationship to derive the scaled respiratory volume:
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in which:
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and I ex =I ex (T)/K, I in =I in (T)/K, and T =T/K, with K the number of breathing cycles taken into account, T the time needed to complete these breathing cycles, and in which Δp is the pressure difference and b is a constant which depends on the sign of Δp.
16 . The system of claim 9 , wherein the first and second derivation modules and/or the display module form(s) part of a computer.
17 . A method for determining a scaled respiratory flow rate and volume during respiration of a patient, comprising the steps of:
a) using a pressure sensor located in the patient's nostril to collect pressure measurements in at least a first location in an upper respiratory tract of the patient, and successively determining a plurality of values for a difference between a pressure in at least the first location in the upper respiratory tract of the patient and a reference pressure, wherein the first location in the upper respiratory tract is in a nostril of the patient and wherein the reference pressure is ambient pressure;
b) deriving the scaled respiratory flow rate from the plurality of values for the pressure difference by using a first relationship;
c) deriving the scaled respiratory volume from the plurality of values for the pressure difference by using a second relationship; and
d) displaying the scaled respiratory flow rate derived in step b) and the scaled respiratory volume derived in step c) or a further variable derived from the scaled respiratory flow rate and volume in a graphical representation
wherein step a) is performed during tidal breathing of the patient, and
wherein an obstacle is arranged in the upper respiratory tract before step a) is performed, the obstacle being arranged in the nostril between the first location and a nostril entry to cause a local narrowing of the respiratory tract to increase the pressure differences.
18 . The method of claim 17 , wherein the pressure sensor is carried by the obstacle.
19 . A system for determining a scaled respiratory flow rate and volume during respiration of a patient, comprising:
a determination module comprising a pressure sensor located in the patient's nostril to collect pressure measurements in at least a first location in an upper respiratory tract of the patient, the determination module configured for successively determining a plurality of values for a difference between a pressure in at least the first location in the upper respiratory tract of the patient and a reference pressure, the determination module being configured for determining the pressure differences between the first location in the nostril of the patient and ambient pressure;
a first derivation module comprising a first processing circuit configured for deriving the scaled respiratory flow rate from the plurality of values for the pressure difference by using a first relationship;
a second derivation module comprising a second processing circuit configured for deriving the scaled respiratory volume from the plurality of values for the pressure difference by using a second relationship; and
a display module comprising a display configured for displaying the scaled respiratory flow rate and the scaled respiratory volume or a further variable derived from the scaled respiratory flow rate and volume in a graphical representation;
wherein the determination module is configured to be operative during tidal breathing of the patient, and
wherein the determination module comprises an obstacle configured to be arranged in the upper respiratory tract, the obstacle being configured to be arranged in the nostril between the first location and a nostril entry to cause a local narrowing of the respiratory tract to increase the pressure differences.
20 . The system of claim 19 , wherein the obstacle carries the pressure sensor.