Rebreathing circuit to set and stabilize end tidal and arterial PCO2 despite varying levels of minute ventilation
First Claim
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1. A method of controlling partial pressure of carbon dioxide in a patient at a predetermined desired level(s), comprising drawing back an alveolar gas exhaled by the patient into a fresh gas flow for the patient to inhale when a minute ventilation of the patient is no less than the fresh gas flow.
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Abstract
A method of controlling PCO2 in a patient at a predetermined desired level(s) comprising a breathing circuit which is capable of organizing exhaled gas so as to be preferentially inhaled during re-breathing when necessary by providing alveolar gas for re-breathing in preference to dead space gas.
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Citations
20 Claims
- 1. A method of controlling partial pressure of carbon dioxide in a patient at a predetermined desired level(s), comprising drawing back an alveolar gas exhaled by the patient into a fresh gas flow for the patient to inhale when a minute ventilation of the patient is no less than the fresh gas flow.
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3. A breathing circuit, comprising:
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a port through which a patient exhales an inhalation gas and exhales an exhalation gas;
an inspiratory limb having a first end connected to the port and a second end, the inspiratory limb supplying the inhalation gas to the patient;
an expiratory limb having a first end connected to the port and a second end, the patient exhaling the exhalation gas to the expiratory limb;
a bypass conduit connecting the inspiratory limb and the expiratory limb at the second ends thereof; and
a one-way check valve disposed in the bypass conduit in a proximity of the second end of the expiratory limb, the one-way check valve being operative to direct the exhalation gas into the inspiratory limb when a pressure differential applied thereon reaches a predetermined level. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11)
a fresh gas inlet connected to the inspiratory limb for supplying a fresh gas; and
a reservoir bag connected to the second end of the inspiratory limb for storing the fresh gas.
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7. The breathing circuit of claim 3, further comprising a reservoir tube with a first end connected to the second end of the expiratory limb for retaining a predetermined part of the exhalation gas and an open second end.
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8. The breathing circuit of claim 7, wherein the reservoir tube is made of a rigid tubing material or a flexible tubing material.
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9. The breathing circuit of claim 7, wherein the reservoir tube includes a collapsible bag with a diameter larger than 22 mm.
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10. The breathing circuit of claim 7, wherein the reservoir tube has a total volume determined according to the weight of the patient.
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11. The breathing circuit of claim 7, wherein the reservoir tube has a total volume of about 3 L.
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12. A method of enhancing a diagnostic procedure or medical treatment comprising the steps of:
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providing a breathing circuit with an inspiratory path for supplying an inhalation gas to a patient and an expiratory path to which the patient exhaling an exhalation gas;
supplying a fresh gas as the inhalation gas for the patient to breathe;
drawing back a last exhalation gas exhaled by the patient in a previous breathing cycle as a part of the inhalation gas for the patient to rebreathe; and
increasing the flow of the last exhalation gas to be rebreathed by reducing the flow of the fresh gas when the patient is ventilating at a rate greater than the flow of the fresh gas and inducing hypercapnia to the patient is required.
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13. A method of treating a patient during a traumatic event characterized by hyperventilation comprising the steps of:
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providing a fresh gas to the patient, the flow of the fresh gas being equal to an alveolar ventilation of the patient;
introducing an alveolar gas exhaled by the patient into the fresh gas to prevent the alveolar ventilation from increasing due to increase of a minute ventilation of the patient; and
continuously introducing the alveolar gas into the fresh gas until the traumatic event is terminated. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A method of controlling partial pressure of carbon dioxide of a patient at a predetermined desired level, comprising the steps of:
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supplying only a fresh gas from a gas input to the patient during an inspiratory phase thereof when a minute ventilation is equal to or less than a flow rate of the fresh gas supplied by the gas input;
accumulating the fresh gas in a fresh gas reservoir during an expiratory phase of the patient;
collecting an alveolar gas exhaled from the patient at an end of the expiratory phase;
providing only the fresh has supplied from the gas input to the patient during a next inspiratory phase when the minute ventilation is equal to or less than the flow rate of the fresh has supplied by the gas input;
supplying the fresh gas accumulated in the fresh gas reservoir when the minute ventilation exceeds the flow rate of the fresh gas supplied from the gas input; and
adding the alveolar gas for the patient to rebreathe. - View Dependent Claims (20)
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Specification