Claims
- 1. A rebreathing method, comprising:
evaluating at least one of a lung capacity of the patient, a size of the patient, a respiratory flow condition of the patient, and a respiratory carbon dioxide condition of the patient; and selecting a deadspace volume to be used in rebreathing based on said evaluating, said selecting being effected without substantially changing airway pressure.
- 2. The rebreathing method of claim 1, wherein said selecting comprises defining a volume of a deadspace receptacle communicating with a breathing circuit in communication with an airway of the patient.
- 3. The rebreathing method of claim 1, wherein said selecting comprises selecting a concentration of exhaled gases to remain within at least one of a breathing circuit in a communication with an airway of the patient and the airway.
- 4. The rebreathing method of claim 1, wherein said selecting comprises adjusting a deadspace within an airway of the patient.
- 5. A method for noninvasively determining at least one of a cardiac output and a pulmonary capillary blood flow of a patient, comprising:
determining a carbon dioxide elimination difference between a carbon dioxide elimination of the patient during normal breathing and a carbon dioxide elimination of the patient during rebreathing; determining an end tidal carbon dioxide difference between a partial pressure of end tidal carbon dioxide of the patient during said normal breathing and a partial pressure of end tidal carbon dioxide of the patient during said rebreathing; and compensating for functional residual capacity in lungs of the patient.
- 6. The method of claim 5, wherein said compensating comprises accounting for eliminated carbon dioxide not exhaled from the airway of the patient.
- 7. The method of claim 6, wherein said accounting comprises modifying at least one of said carbon dioxide elimination during said normal breathing and said carbon dioxide elimination during said rebreathing.
- 8. The method of claim 7, wherein said modifying comprises adding to a carbon dioxide elimination measurement a product of said functional residual capacity and a partial pressure of end tidal carbon dioxide.
- 9. The method of claim 5, comprising estimating said functional residual capacity as a function of body weight of the patient, said estimating including accounting for airway and apparatus deadspace.
- 10. The method of claim 5, further comprising:
dividing said carbon dioxide elimination difference by a product of a slope of a carbon dioxide dissociation curve and said end tidal carbon dioxide difference.
- 11. The method of claim 5, comprising measuring carbon dioxide elimination and partial pressure of end tidal carbon dioxide over a plurality of breaths.
- 12. A rebreathing method, comprising:
insufflating an airway of a patient; monitoring at least one aspect of the patient's breathing during said insufflating; reducing a volume of said insufflating; and monitoring said at least one aspect of the patient's breathing with said volume of said insufflating reduced.
- 13. The method of claim 12, wherein said insufflating is effected with gas insufflation apparatus.
- 14. The method of claim 13, wherein said reducing comprises adjusting a distance a catheter of said gas insufflation apparatus extends into the airway of the patient.
- 15. An apparatus for introducing deadspace into a breathing circuit, comprising:
a primary expiratory pathway through the breathing circuit; a deadspace portion of the breathing circuit located to receive gases exhaled by a patient upon positioning the breathing circuit in communication with an airway of the patient, said deadspace portion communicating with said primary expiratory pathway at least one junction thereof with said primary expiratory pathway; a flow restrictor positioned along said primary expiratory pathway, downstream from said junction; and a two-way valve located and positionable so as to, along with said flow restrictor, prevent gases from flowing into said deadspace portion and allow gases to flow into said deadspace portion.
- 16. The apparatus of claim 15, wherein said deadspace portion comprises at least a volume adjustable section.
- 17. The apparatus of claim 16, wherein said volume adjustable section is length expandable and length contractible.
- 18. A method for estimating the partial pressure of carbon dioxide in the alveolar blood (PSC ACO2) of an individual, comprising:
calculating a concentration of carbon dioxide in the parallel deadspace (PDSCO2) of an airway of the individual on a breath-by-breath basis; and determining an end tidal partial pressure of carbon dioxide (PetCO2) of the individual.
- 19. The method of claim 18, further comprising determining a perfusion ratio (r).
- 20. The method of claim 19, wherein:
- 21. The method of claim 18, wherein said calculating comprises:
determining the mixed inspired volume of carbon dioxide (ViCO2) inhaled by the individual; at least estimating an airway deadspace of the individual; determining a partial pressure of end tidal carbon dioxide (PetCO2) of a previous breath of the individual; and determining a tidal volume (Vt) of the individual's breathing.
- 22. The method of claim 21, wherein said calculating further comprises: at least estimating a functional residual capacity (FRC) of alveoli of the individual's lungs.
- 23. The method of claim 22, wherein
- 24. A method for estimating the cardiac output of an individual, comprising:
determining a carbon dioxide elimination (VCO2) of the individual for a before rebreathing period and for a during rebreathing period; calculating a carbon dioxide elimination difference between said carbon dioxide elimination of said before rebreathing period and said carbon dioxide elimination of said during rebreathing period; calculating a carbon dioxide content difference between said carbon dioxide content of said before rebreathing period and said carbon dioxide content of said during rebreathing period; and estimating a partial pressure of carbon dioxide in alveolar blood (PACO2) of the individual for said before rebreathing period and for said during rebreathing period respectively based on partial pressure of end tidal carbon dioxide (PetCO2) measurements of the individual during said before rebreathing period and during said during rebreathing period; converting each estimation of said partial pressure of carbon dioxide in alveolar blood to a carbon dioxide content (CCO2); dividing said carbon dioxide elimination difference by said carbon dioxide content difference.
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of application Ser. No. 09/262,510, filed Mar. 2, 1999, pending, which is a continuation-in-part of application Ser. No. 08/770,138, filed Dec. 19, 1996, now U.S. Pat. No. 5,941,242.
Continuations (1)
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Number |
Date |
Country |
Parent |
09262510 |
Mar 1999 |
US |
Child |
09777629 |
Feb 2001 |
US |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
08770138 |
Dec 1996 |
US |
Child |
09262510 |
Mar 1999 |
US |