US2013340756A1PendingUtilityA1
Method and apparatus to attain and maintain target end tidal gas concentrations
Est. expiryJul 28, 2025(expired)· nominal 20-yr term from priority
Inventors:Marat SlessarevJoseph FisherGeorge VolgyesiEitan PrismanDavid MikulusChristopher HudsonCliff Ansel
A61M 2230/202A61M 16/0078A61M 16/085A61B 5/0833A61B 5/055A61M 2230/435A61M 16/024A61M 2230/43A61B 5/0836A61M 16/12A61M 2016/0039A61M 2016/0021A61M 2202/0225A61M 2230/432A61M 16/08A61M 16/0045A61M 2230/205A61M 16/0051
43
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Claims
Abstract
In a first aspect, the invention relates to an apparatus for inducing or maintaining a target end tidal concentration of a gas in a subject comprising a breathing circuit, a source of gas flow into the circuit, means for controlling the rate of the source of gas flow into the circuit and means for controlling the concentration of gases in the source gas flow independently from each other. In another aspect, the invention relates to a method of preparing an apparatus for inducing or maintaining a target end tidal concentration of a gas X in a subject comprising selecting a rate of a source gas flow into a breathing circuit, selecting the concentration of at least one constituent gas of a component gas making up the source gas to a level corresponding to the end tidal concentration of the gas X, whereby the apparatus is adapted to administer a source gas having a first gas composition.
Claims
exact text as granted — not AI-modified1 - 110 . (canceled)
111 . A method for inducing or maintaining a target end tidal concentration of at least one gas X in a subject comprising:
a) selecting a rate of a source gas flow into a re-breathing circuit used by the subject, the rate projected to be less than the minute ventilation of the subject such that the subject in-hales the source gas for the first portion of a breath and a neutral gas for a remainder of a breath; b) selecting the concentration of at least one constituent gas X of at least one component gas making up the source gas, wherein the concentration of the constituent gas X in the source gas is computed from:
A) the target end tidal concentrations of gas X;
B) the flow rate of the source gas into the breathing circuit; and
C) if X is a gas consumed by the patient gas, the minute consumption of gas X, or if gas X is produced by the patient, the minute production of gas X.
c) providing the source gas for inhalation by the subject for the first portion of a breath and providing a neutral gas for inhalation for the remainder of the breath.
112 . A method according to claim 111 , wherein the end tidal concentration of two constituent gases are targeted independently.
113 . A method according to claim 111 , wherein the requisite concentration of a constituent gas X in the source gas is approximated using one of the following computations:
i
)
F
G
1
X
=
F
T
ET
X
-
V
.
X
V
.
G
1
,
where {dot over (V)}X is the patient's minute production of gas X, F T ET X is the target end tidal concentration of gas X, and {dot over (V)}G 1 is the flow rate of the source gas;
ii
)
F
G
1
X
=
F
T
ET
X
+
V
.
X
V
.
G
1
,
where {dot over (V)}X is the patient's minute consumption of gas X, F T ET X is the target end tidal concentration of gas X and {dot over (V)}G 1 is the flow rate of the source gas.
114 . A method according to claim 111 , wherein the concentration of each constituent gas X in the source gas is approximated using one of the following computations:
i
)
F
G
1
X
=
F
T
ET
X
-
V
.
X
V
.
G
1
,
where {dot over (V)}X is the patient's minute production of gas X, F T ET X is the target end tidal concentration of gas X, and {dot over (V)}G 1 is the flow rate of the source gas;
ii
)
F
G
1
X
=
F
T
ET
X
+
V
.
X
V
.
G
1
,
where {dot over (V)}X is the patient's minute consumption of gas X, F T ET X is the target end tidal concentration of gas X and {dot over (V)}G 1 is the flow rate of the source gas.
115 . A method according to claim 111 , wherein the source gas is constituted from at least one component gas, and wherein a subject is prepared for administration of a diagnostic test by allowing a subject to inhale the source gas for a time period at least sufficient to attain the target end tidal concentrations of the constituent gas.
116 . A method according to claim 115 , wherein said at least sufficient time period is no greater than 30 seconds at a rate corresponding to a minute ventilation which is greater than the rate of flow of the source gas.
117 . A method according to claim 115 , wherein said at least sufficient time period is no greater than the duration of a single breath and wherein the rate of flow of the source gas is between 5 and 20 liters per minute.
118 . A method according to claim 111 , further comprising the step of selecting a different concentration of the at least one constituent gas in the source gas, the concentration of the at least one constituent gas selected to be at a predetermined level corresponding to a second different target end tidal concentration of gas X.
119 . A method according to claim 118 , further comprising the step of allowing a subject to inhale said source gas having different concentration of the at least one constituent gas for a time period at least sufficient to attain the second target end tidal concentration of gas X.
120 . A method according to claim 119 , further comprising the step of measuring a physiological variable in a subject at least at one respective time point corresponding to a period of maintaining each of said first and second end tidal concentrations of gas X.
121 . A method according to claim 120 , wherein said physiological variable is vascular reactivity.
122 . A method according to claim 115 , wherein said diagnostic test comprises measuring cerebrovascular reactivity (CVR) by MRI.
123 . A method according to claim 121 , wherein cerebrovascular reactivity (CVR) is measured by MRI.
124 . A method according to claim 111 , wherein the source gas has a minimum safe concentration of O 2 .
125 . The method of claim 124 wherein each component gas has a minimum safe O 2 concentration of 10%.
126 . The method of claim 111 , wherein the partial re-breathing circuit is a sequential gas delivery circuit.
127 . The method of claim 111 , wherein the constituent gas whose end tidal concentration target is being induced is O 2 .
128 . The method of claim 111 , wherein the constituent gas whose end tidal concentration target is being induced is CO 2 .
129 . The method of claim 121 , wherein the constituent gas whose end tidal concentration target is being induced is CO 2 .
130 . The method of claim 112 , wherein the end tidal CO 2 level is changed while the end tidal O 2 level is kept constant or wherein the end tidal PO 2 level is changed while the end tidal PCO 2 level is kept constant or wherein the end tidal PO 2 level and the end tidal PCO 2 level are changed simultaneously.
131 . A method according to claim 111 , using at least three component gases in which respective constituent gases concentrations have the following composition ranges:
i) GAS A: 85-100% oxygen i) Gas B: 85-100% carbon dioxide ii) Gas C: 85-100% nitrogen.
or
a) Gas A: 50-100% O 2 , 0-20% CO 2
b) Gas B: 10-30% O 2 , 20-80% CO 2
c) Gas C: 10-30% O 2 , 0-20% CO 2 ;
or
d) Gas A: 100% O 2 , 0% CO 2
e) Gas B: 10% O 2 , 20-80% CO 2
f) Gas C: at least 10% O 2 , 0% CO 2 .
132 . A method according to claim 112 , comprising the step of measuring occulovascular reactivity by controlling the end tidal CO 2 and O 2 levels of a subject and monitoring occulovascular blood flow.
133 . A method according to claim 112 , comprising the step of measuring a beneficial level of oxygenation to tissues for the purpose of radiotherapy or chemotherapy by independently controlling the end tidal CO 2 and O 2 levels of a subject and monitoring oxygenation or blood flow in the tumor.Cited by (0)
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