US2014311491A1PendingUtilityA1
Apparatus to attain and maintain target end tidal partial pressure of a gas
Est. expiryDec 5, 2031(~5.4 yrs left)· nominal 20-yr term from priority
A61M 16/0069A61B 5/0833A61M 16/0883A61B 5/4836A61M 16/0051A61M 16/1005A61B 5/0836A61M 16/0003A61M 16/122A61M 2230/205A61M 2230/202A61M 2230/20A61M 16/026A61M 2230/432A61M 2016/0021A61M 16/085A61M 2016/102A61M 2230/43A61M 2016/0027A61B 5/083A61M 2016/1025A61M 2016/103A61M 2205/502A61M 16/12A61M 2230/435
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Claims
Abstract
A processor obtains input of a logistically attainable end tidal partial pressure of gas X (PetX[i] T ) for one or more respective breaths [i] and input of a prospective computation of an amount of gas X required to be inspired by the subject in an inspired gas to target the PetX[i] T for a respective breath [i] using inputs required to utilize a mass balance relationship, wherein one or more values required to control the amount of gas X in a volume of gas delivered to the subject is output from an expression of the mass balance relationship. The mass balance relationship is expressed in a form which takes into account (prospectively), for a respective breath [i], the amount of gas X in the capillaries surrounding the alveoli and the amount of gas X in the alveoli, optionally based on a model of the lung which accounts for those sub-volumes of gas in the lung which substantially affect the alveolar gas X concentration affecting mass transfer.
Claims
exact text as granted — not AI-modified1 . A method of controlling a gas delivery device to target or attain a target end tidal partial pressure of gas X in a subject, wherein a signal processor operatively associated with a gas delivery device controls the amount of gas X contained in a volume of inspiratory gas delivered to a subject in a respective breath [i], using inputs and outputs processed by the signal processor for a respective breath [i], the method comprising:
(a) Obtaining input of one or more values sufficient to compute the concentration of gas X in the mixed venous blood entering the subject's pulmonary circulation for gas exchange in one or more respective breaths [i] (C MV X[i]); (b) Obtaining input of a logistically attainable end tidal partial pressure of gas X (PetX[i] T ) for a respective breath [i]; (c) Utilizing a prospective computation to determine an amount of gas X required to be inspired by the subject to target the PetX[i] T for a respective breath [i], the prospective computation using inputs sufficient to compute a mass balance equation for a respective breath [i], the inputs including values, for a respective breath [i], from which C MV X[i] and the concentration of gas X in the subject's lung affecting mass transfer can be determined, wherein one or more values required to control the amount of gas X in a volume of gas delivered to the subject is output from the mass balance equation; and (d) Outputting control signals to the gas delivery device to control the amount gas X in a volume of gas delivered to the subject in a respective breath [i] to target the respective PetX[i] T based on the prospective computation.
2 . A method according to claim 1 , wherein the mass balance equation is formulated in terms of discrete respective breaths [i] taking into account one or more discrete volumes corresponding to a subject's FRC, anatomic dead space, a volume of gas transferred between the subject's lung and pulmonary circulation in the respective breath [i] and an individual tidal volume of the respective breath [i].
3 . A method according to claim 1 , wherein the inspired gas comprises a first inspired gas and a second inspired gas, wherein the first inspired gas is delivered in the first part of a respective breath [i] followed by the second inspired gas for the remainder of the respective breath [i], the volume of the first inspired gas preferably selected so that intake of the second inspired gas at least fills the entirety of the anatomic dead space.
4 . A method according to claim 1 , wherein a concentration of gas X (F I X) in the first inspired gas is computed from the mass balance equation to target or attain a PetX[i] T in a respective breath [i].
5 . A method according to claim 1 , wherein the mass balance equation is solved for F I X.
6 . A method according to claim 1 , comprising the step of obtaining inputs required to compute F I X prospectively to target PetX[i] T for a respective breath [i], wherein F I X is computed using a mass balance equation which comprises terms corresponding to all or an application-specific subset of the terms in:
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7 . A method according to claim 6 , wherein F I X is computed prospectively from a mass balance equation expressed in terms which correspond to all or an application-specific subset of the terms in equation 1 and the first inspired gas has a concentration of gas X which corresponds to F I X for the respective breath [i].
8 . A method according to claim 1 , wherein the gas inspired by the subject in each respective breath [i] comprises a first inspired gas and a second inspired neutral gas, wherein the first inspired gas is delivered in the first part of a respective breath [i] followed by a second inspired neutral gas for the remainder of the respective breath [i], the volume of the first inspired gas selected so that intake of the second inspired neutral gas at least fills the entirety of the anatomic dead space; wherein F I X is computed prospectively using a mass balance equation which comprises all or a functional subset of the terms in equation 1 and wherein the first inspired gas has a concentration of gas X which corresponds to F I X for the respective breath [i].
9 . A method according to claim 1 , comprising ascertaining the volume of inspired gas entering the subject's alveoli by fixing a tidal volume of an inspired gas containing gas X using a ventilator and subtracting a volume of gas corresponding to an estimated or measured value for the subject's anatomic dead space volume.
10 . A method according to claim 1 , wherein the gas inspired by the subject is inspired via a sequential gas delivery circuit; and wherein the rate of flow of gas into the sequential gas delivery circuit is used to compute the volume of inspired gas entering the subject's alveoli in a respective breath [i].
11 . A method according to claim 1 , further comprising tuning one or more parameters required for computation of F I X including at least one parameter selected from the group consisting of the subject's functional residual capacity (FRC) and the subject's total metabolic production or consumption of gas X.
12 - 13 . (canceled)
14 . A method according to claim 11 , wherein FRC is tuned in a series of tuning breaths by:
(a) changing the targeted end tidal concentration of gas X between a tuning breath [i+x] and a previous tuning breath [i+x−1]; (b) comparing the magnitude of the difference between the targeted end tidal concentration of gas X for said tuning breaths [i+x] and [i+x−1] with the magnitude of the difference between the measured end tidal concentration of gas X for the same tuning breaths to quantify any discrepancy in relative magnitude; and (c) adjusting the value of FRC in proportion to the discrepancy to reduce the discrepancy in any subsequent prospective computation of F I X.
15 . A method according to claim 11 , wherein the total metabolic production or consumption of gas X is tuned in a series of tuning breaths by comparing a targeted end tidal concentration of gas X (PetX[i+x] T ) for the at least one tuning breath [i+x] with a corresponding measured end tidal concentration of gas X for the corresponding breath [i+x] to quantify any discrepancy and adjusting the value of the total metabolic production or consumption of gas X in proportion to any discrepancy to reduce the discrepancy in any subsequent prospective computation of F I X.
16 . A method according to claim 15 , wherein FRC is tuned in a series of tuning breaths in which a sequence of end tidal concentrations of gas X is targeted at least once by:
(a) obtaining input of a measured baseline steady state value for PetX[i] for computing F I X at start of a sequence; (b) selecting a target end tidal concentration of gas X (PetX[i] T ) for at least one tuning breath [i+x] wherein PetX[i+x] T differs from PetX[i+x−1] T ; and (c) comparing the magnitude of the difference between the targeted end tidal concentration of gas X for said tuning breaths [i+x] and [i+x−1] with the magnitude of the difference between the measured end tidal concentration of gas X for the same tuning breaths to quantify any discrepancy in relative magnitude; (d) adjusting the value of FRC in proportion to any discrepancy in magnitude to reduce the discrepancy in a subsequent prospective computation of F I X including in any subsequent corresponding tuning breaths [i+x−1] and [i+x] forming part of an iteration of the sequence.
17 . A method according to claim 14 , wherein the total metabolic consumption or production of gas X is tuned in a series of tuning breaths in which a sequence of end tidal concentrations of gas X is targeted at least once by:
(a) obtaining input of a measured baseline steady state value for PetX[i] for computing F I X at start of a sequence; (b) targeting a selected target end tidal concentration of gas X (PetX[i] T ) for each of a series of tuning breaths [i+1 . . . i+n], wherein PetX[i] T differs from the baseline steady state value for PetX[i]; (c) comparing the targeted end tidal concentration of gas X (PetX[i+x] T ) for at least one tuning breath [i+x] in which the targeted end tidal gas concentration of gas X has been achieved without drift in a plurality of prior breaths [1+x−1, 1+x−2 . . . ] with a corresponding measured end tidal concentration of gas X for a corresponding breath [i+x] to quantify any discrepancy and adjusting the value of the total metabolic consumption or production of gas X in proportion to the discrepancy to reduce the discrepancy in a subsequent prospective computation of F I X including in any subsequent corresponding tuning breath [i+x] forming part of an iteration of the sequence.
18 . A method according to claim 1 , wherein input of a concentration of gas X in the mixed venous blood entering the subject's pulmonary circulation for gas exchange in a respective breath [i] (C MV X[i]) is determined by a compartmental model of gas dynamics.
19 . A method according to claim 16 , wherein the compartmental model of gas dynamics accounts for the total and compartmental metabolic production or consumption of gas X, the total and compartmental storage capacity for gas X and the total cardiac output and compartmental contribution to total cardiac output.
20 - 29 . (canceled)
30 . A method according to claim 1 , wherein gas X is carbon dioxide.
31 - 32 . (canceled)
33 . An apparatus for controlling an amount of at least one gas X in a subject's lung to attain a targeted end tidal partial pressure of the at least one gas X, comprising:
(1) a gas delivery device; (2) a control system for controlling the gas delivery device, the control system configured for:
(a) Obtaining input of a concentration of gas X in the mixed venous blood entering the subject's pulmonary circulation for gas exchange in one or more respective breaths [i] (C MV X[i]);
(b) Obtaining input of a logistically attainable end tidal partial pressure of gas X (PetX[i] T ) for a respective breath [i];
(c) Obtaining input of a prospective computation of an amount of gas X required to be inspired by the subject in an inspired gas to target the PetX[i] T for a respective breath [i] using inputs required to compute a mass balance equation including C MV X[i], wherein one or more values required to control the amount of gas X in the volume of gas delivered to the subject is output from the mass balance equation; and
(d) Controlling the amount of gas X in the volume of gas delivered to the subject in a respective breath [i] to target the respective PetX[i] T based on the prospective computation.
34 . An apparatus according to claim 33 , wherein the mass balance equation is computed based on a tidal model of the lung.
35 . An apparatus according to claim 33 , wherein the mass balance equation is computed in terms of discrete respective breaths [i] including one or more discrete volumes comprising or corresponding to a subject's FRC, anatomic dead space, a volume of gas transferred between the subject's lung and pulmonary circulation in the respective breath [i] and an individual tidal volume of the respective breath [i].
36 . An apparatus according to claim 33 , wherein the inspired gas comprises a first inspired gas and a second inspired gas, wherein the first inspired gas is delivered in a first part of a respective breath [i] followed by the second inspired gas for a remainder of the respective breath [i], a volume of the first inspired gas selected so that intake of the second inspired gas at least fills the entirety of the anatomic dead space; and wherein for a respective breath [i], the volume of the first inspired gas and a concentration of gas X in the second inspired gas are selected to attain PetX[i] T ; and wherein, optionally, for a respective breath [i], the concentration of gas X in the second inspired gas corresponds to PetX[i] T for a respective breath [i].
37 - 38 . (canceled)
39 . An apparatus according to claim 33 , comprising the step of obtaining inputs required to compute an F I X to target PetX[i] T for a respective breath [i], wherein F I X is computed using a mass balance equation which comprises terms corresponding to all or an application-specific subset of the terms in:
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40 . (canceled)
41 . An apparatus according to claim 33 , wherein the control system is implemented by a computer.
42 . An apparatus according to claim 41 , wherein the computer provides output signals to one or more rapid flow controllers.
43 . An apparatus according to claim 41 , wherein the computer receives input from a gas analyzer and an input device adapted for providing input of one or more logistically attainable target end tidal concentration of gas X (PetX[i] T ) for a series of respective breaths [i].
44 . An apparatus according to claim 33 , wherein the control system, in each respective breath [i], controls the delivery of at least a first inspired gas and wherein delivery of the first inspired gas is coordinated with delivery a second inspired neutral gas, such that a selected volume of the first inspired gas is delivered in a first part of a respective breath [i] followed by the second inspired neutral gas for a remainder of the respective breath [i].
45 - 89 . (canceled)Cited by (0)
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