Method and apparatus for indicating the absence of a pulmonary embolism in a patient
First Claim
1. A method for determining the presence or absence of a pulmonary embolism in a patient, said method comprising the steps of:
- (a) measuring the amount of CO2 expired by the patient during the expiration of breathing gases by the patient using a breathing gas CO2 concentration sensor;
(b) measuring the volume (V) of breathing gases expired during the expiration of breathing gases by the patient using a flow sensor;
(c) determining a slope in a measurement apparatus, the slope defined by a change in the amount of expired CO2 divided by a change in breathing gas volume in an alveolar expiration phase of patient expiration;
(d) measuring an amount of CO2 in the lungs of the patient at the end of expiration using the breathing gas CO2 concentration sensor;
(e) measuring the amount of CO2 in the blood of the patient;
(f) determining the difference in the measurement apparatus between the amount of CO2 in the blood and the amount of CO2 in the lungs of the patient at the end of expiration;
(g) establishing a relationship in the measurement apparatus between the determination of step (f) and the determination of step (c) to produce a quantity for use in determining the presence or absence of a pulmonary embolism in the patient, and(h) defining the alveolar expiration phase of patient expiration as that in which the quantity produced in step (c) is reduced to a given percentage of a corresponding quantity produced for a previous phase of expiration.
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Accused Products
Abstract
A method and apparatus for determining the presence or absence of a pulmonary embolism (PE) in a patient. The breathing gas CO2 partial pressure (PCO2) during the expiration of breathing gases by the patient, the end tidal (EtCO2), CO2 partial pressure, and the CO2 partial pressure (PaCO2) of the blood are measured. The volume (V) of breathing gases expired during the expiration of breathing gases by the patient is also measured and a relationship between changes in breathing gas CO2 partial pressure (PCO2) and changes in breathing gas volume (V) in an alveolar expiration phase of patient expiration is determined. The difference between the blood CO2 partial pressure (PaCO2) and the end expiration CO2 partial pressure is divided by the relationship between PCO2 and V produce a quantity which is compared to a threshold value. If the quantity is below the threshold value, the absence of a pulmonary embolism is indicated.
12 Citations
22 Claims
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1. A method for determining the presence or absence of a pulmonary embolism in a patient, said method comprising the steps of:
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(a) measuring the amount of CO2 expired by the patient during the expiration of breathing gases by the patient using a breathing gas CO2 concentration sensor; (b) measuring the volume (V) of breathing gases expired during the expiration of breathing gases by the patient using a flow sensor; (c) determining a slope in a measurement apparatus, the slope defined by a change in the amount of expired CO2 divided by a change in breathing gas volume in an alveolar expiration phase of patient expiration; (d) measuring an amount of CO2 in the lungs of the patient at the end of expiration using the breathing gas CO2 concentration sensor; (e) measuring the amount of CO2 in the blood of the patient; (f) determining the difference in the measurement apparatus between the amount of CO2 in the blood and the amount of CO2 in the lungs of the patient at the end of expiration; (g) establishing a relationship in the measurement apparatus between the determination of step (f) and the determination of step (c) to produce a quantity for use in determining the presence or absence of a pulmonary embolism in the patient, and (h) defining the alveolar expiration phase of patient expiration as that in which the quantity produced in step (c) is reduced to a given percentage of a corresponding quantity produced for a previous phase of expiration. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method for determining the presence or absence of a pulmonary embolism in a patient, said method comprising the steps of:
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(a) measuring the amount of CO2 expired by the patient during the expiration of breathing gases by the patient using a breathing gas CO2 concentration sensor; (b) measuring the volume (V) of breathing gases expired during the expiration of breathing gases by the patient using a flow sensor; (c) determining a slope in a measurement apparatus, the slope defined by a change in the amount of expired CO2 divided by a change in breathing gas volume in an alveolar expiration phase of patient expiration; (d) measuring an amount of CO2 in the lungs of the patient at the end of expiration using the breathing gas CO2 concentration sensor; (e) measuring the amount of CO2 in the blood of the patient; (f) determining the difference in the measurement apparatus between the amount of CO2 in the blood and the amount of CO2 in the lungs of the patient at the end of expiration; (g) establishing a relationship in the measurement apparatus between the determination of step (f) and the determination of step (c) to produce a quantity for use in determining the presence or absence of a pulmonary embolism in the patient; and (h) defining the alveolar expiration phase as the concluding 10%-20% of the expiration volume.
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22. A method for determining the presence or absence of a pulmonary embolism in a patient, said method comprising the steps of:
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(a) measuring the amount of CO2 expired by the patient during the expiration of breathing gases by the patient using a breathing gas CO2 concentration sensor; (b) measuring the volume (V) of breathing gases expired during the expiration of breathing gases by the patient using a flow sensor; (c) determining a slope in a measurement apparatus, the slope defined by a change in the amount of expired CO2 divided by a change in breathing gas volume in an alveolar expiration phase of patient expiration; (d) measuring an amount of CO2 in the lungs of the patient at the end of expiration using the breathing gas CO2 concentration sensor; (e) measuring the amount of CO2 in the blood of the patient; (f) determining the difference in the measurement apparatus between the amount of CO2 in the blood and the amount of CO2 in the lungs of the patient at the end of expiration; (g) establishing a relationship in the measurement apparatus between the determination of step (f) and the determination of step (c) to produce a quantity for use in determining the presence or absence of a pulmonary embolism in the patient; (h) measuring the O2 partial pressure (EtO2) of the breathing gases at the end of expiration; (i) measuring the O2 partial pressure (PaO2) in the blood of the patient; (j) comparing EtO2 and PaO2; and (k) precluding an indication of the absence of a pulmonary embolism if the O2 difference exceeds a predetermined value.
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Specification