Method and apparatus for detection of venous air emboli
First Claim
1. An apparatus for detecting an air embolism comprising:
- a respiratory gas nitrogen detector for detecting nitrogen in respiratory gases, said respiratory gas nitrogen detector having a signal output port which provides a nitrogen concentration signal representative of a concentration of the nitrogen detected in the respiratory gases; and
a processor having a signal input port connected to said respiratory gas nitrogen detector signal output port, said processor further comprising;
an historical data base of previously acquired nitrogen concentration signals;
a threshold analyzer having an input which receives the previously acquired nitrogen concentration signals from said historical data base and an output which provides a nitrogen concentration baseline threshold value according to a predetermined analysis criteria;
a current data register which receives and stores a current nitrogen concentration signal from said respiratory gas nitrogen detector; and
a comparator which compares the current nitrogen concentration signal with the nitrogen concentration baseline threshold value derived from said historical data base and triggers a venous air embolism alarm signal if the current nitrogen concentration signal crosses within a predetermined time window.
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Accused Products
Abstract
Concomitant measurement of EtCO2, EtN2 and (FiO2 -FeO2) concentrations are used to detect a VAE. In a respiratory gas monitoring system, continuous measurements of end-tidal carbon dioxide, end-tidal nitrogen and the difference between inspired and expired oxygen concentrations are averaged using a predetermined time period and stored as historical data. Periodically, a present value of each of these concentrations is compared to its respective historical average for a predetermined time period. If the following conditions are met, the device signals the presence of a venous air embolism: 1) a decrease in the EtCO2 concentration of 1.5 mm Hg; 2) an increase in the FeN2 concentration of 0.03 vol %; and 3) a decrease in the difference between the inspired oxygen concentration and the expired oxygen concentration of 0.20 vol %.
75 Citations
18 Claims
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1. An apparatus for detecting an air embolism comprising:
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a respiratory gas nitrogen detector for detecting nitrogen in respiratory gases, said respiratory gas nitrogen detector having a signal output port which provides a nitrogen concentration signal representative of a concentration of the nitrogen detected in the respiratory gases; and a processor having a signal input port connected to said respiratory gas nitrogen detector signal output port, said processor further comprising; an historical data base of previously acquired nitrogen concentration signals; a threshold analyzer having an input which receives the previously acquired nitrogen concentration signals from said historical data base and an output which provides a nitrogen concentration baseline threshold value according to a predetermined analysis criteria; a current data register which receives and stores a current nitrogen concentration signal from said respiratory gas nitrogen detector; and a comparator which compares the current nitrogen concentration signal with the nitrogen concentration baseline threshold value derived from said historical data base and triggers a venous air embolism alarm signal if the current nitrogen concentration signal crosses within a predetermined time window. - View Dependent Claims (2, 3, 4, 5)
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6. An apparatus for detecting an air embolism comprising:
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a respiratory gas detector which detects carbon dioxide and nitrogen in respiratory gases, said respiratory gas detector having a signal output port which provides a carbon dioxide concentration signal and a nitrogen concentration signal which are representative of a concentration of carbon dioxide and a concentration of nitrogen, respectively, in the respiratory gases; and a comparator having a signal input port connected to said respiratory gas detector signal output port wherein said comparator compares said carbon dioxide and nitrogen concentration signals with a predetermined carbon dioxide concentration threshold and a predetermined nitrogen concentration threshold, respectively, said comparator having an output which triggers an air embolism alarm when said carbon dioxide and nitrogen concentrations both cross said predetermined carbon dioxide concentration threshold and said predetermined nitrogen concentration threshold, respectively, within a predetermined time window. - View Dependent Claims (7, 8)
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9. An apparatus for detecting an air embolism comprising:
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a detector means for detecting nitrogen and carbon dioxide in respiratory gases; a gas analyzer means for determining a plurality of breath-by-breath inspired and expired concentrations of the nitrogen and carbon dioxide detected by said detector means in the respiratory gases; an end-tidal carbon dioxide analyzer means which receives the plurality of breath-by-breath inspired and expired concentrations of the carbon dioxide from said gas analyzer means and determines a plurality of breath-by-breath end-tidal carbon dioxide concentration values, EtCO2, therefrom for a plurality of breaths; an end-tidal carbon dioxide data memory means for storing the plurality of breath-by-breath end-tidal carbon dioxide concentration values, EtCO2, received from said end-tidal carbon dioxide analyzer means as a function of time; a nitrogen analyzer means which receives the plurality of breath-by-breath inspired and expired concentrations of the nitrogen from said gas analyzer means and determines a plurality of breath-by-breath expired nitrogen concentration values, FeN2, therefrom for a plurality of breaths; an expired nitrogen data memory means for storing the plurality of breath-by-breath expired nitrogen concentration values, FeN2, received from said nitrogen analyzer means as a function of time; and a processor means which
1) compares a current breath value of EtCO2 for a current breath with the plurality of breath-by-breath end-tidal carbon dioxide concentration values, EtCO2, stored in said end-tidal carbon dioxide data memory means and sets an EtCO2 TRUE flag for the current breath is a predetermined EtCO2 comparison criteria is satisfied;
2) compares a corresponding current breath value of FeN2 for the current breath with the plurality of breath-by-breath expired nitrogen concentration values, FeN2, stored in said expired nitrogen data memory means and sets an FeN2 TRUE flag for the current breath if a predetermined FeN2 comparison criteria is satisfied; and
3) signals an alarm if the EtCO2 TRUE flag for the current breath and the FeN2 TRUE flag for the current breath are both set. - View Dependent Claims (10, 11, 12, 13)
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14. A method of automatically detecting an air embolism comprising:
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detecting nitrogen in respiratory gases; determining, from the nitrogen detected in the respiratory gases, a plurality of breath-by-breath expired nitrogen concentrations for a plurality of breaths and storing the plurality of breath-by-breath expired nitrogen concentrations in a nitrogen historical data base; comparing a recent expired nitrogen concentration value of the plurality of breath-by-breath expired nitrogen concentrations with the plurality of breath-by-breath expired nitrogen concentrations stored in the nitrogen historical data base; and signalling an air embolism event when the recent expired nitrogen concentration value of the plurality of breath-by-breath expired nitrogen concentrations crosses a nitrogen baseline threshold derived from the nitrogen historical data base of breath-by-breath expired nitrogen concentrations. - View Dependent Claims (15, 16, 17, 18)
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Specification