Method and system for continuously monitoring cardiac output

• US 6,186,956 B1
• Filed: 05/25/1999
• Issued: 02/13/2001
• Est. Priority Date: 05/28/1998
• Status: Expired due to Fees

• Current Assignee: University of South Carolina
• Original Assignee: University of South Carolina
• Inventors: McNamee, James E
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US09/318,594
• Time in Patent Office: 630 Days
• Field of Search: 600/529, 600/534, 600/538, 600/526, 600/504, 600/505
• US Class Current: 600/526
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/083 Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption

Abstract

The present invention is a method and system for continuously monitoring cardiac output. In a preferred embodiment, the method and system of the present invention comprises a pneumotachograph, differential pressure transducer, and a signal amplifier/conditioner interconnected to a programmed digital computer. A patient, preferably, inserts the pneumotachograph in his mouth or, alternatively, the pneumotachograph is connected to a patient'"'"'s tracheal cannula. As the patient exhales and inhales the differential pressure transducer measures the drop in pressure as air flows through the pneumotachograph thereby producing a weak electrical signal non-linearly proportional to flow. Next, the weak signal is directed through the amplifier/signal conditioner which increases the amplitude and removes some of the noise contained in the transducer output. A digital computer is then utilized to convert the analog time varying electrical signal into a stream of digital data, store it on disk, display it in real time and processes the signal using an experimentally determined correlation factor and mathematical equations relating the fluctuations in air flow with stroke volume to obtain the cardiac output.

Claims

1. A system for continuously monitoring cardiac output of a patient, said system comprising:

measuring means for measuring air flowing through the throat of a patent;

generating means in operational connection with said measuring means for generating an electrical output signal proportional to the air flow measured by said measuring means; and

processing means in operational connection with said generating means for processing said electrical output signal to extract cardiogenic oscillations, to monitor cardiac output.

2. The system as recited in claim 1, wherein said measuring means is a pneumotachograph having a tube that is capable of insertion into the mouth of a patient.

3. The system as recited in claim 1, wherein said measuring means is a pneumotachograph having a tube that is capable of insertion into the tracheal cannula of a patient.

4. The system as recited in claim 1, wherein said processing means amplifies said electrical output signal in order to extract cardiogenic oscillations.

5. The system as recited in claim 1, further comprising conversion means in operational connection with said processing means for converting said electrical output signal into a stream of digital data.

6. The system as recited in claim 1, further comprising calculation means in operational connection with said processing means for calculating cardiac output based on said extracted cardiogenic oscillations.

7. A system for continuously monitoring cardiac output of a patient, said system comprising:

measuring means for measuring air flowing through the throat of a patent;

generating means in operational connection with said measuring means for generating an electrical output signal proportional to the air flow measured by said measuring means;

amplification means in operational connection with said generating means for amplifying said electrical output signal; and

processing means in operational connection with said amplification means for processing said electrical output signal to extract cardiogenic oscillations, to monitor cardiac output.

8. The system as recited in claim 7, wherein said measuring means is a pneumotachograph having a tube that is capable of insertion into the mouth of a patient.

9. The system as recited in claim 7, wherein said measuring means is a pneumotachograph having a tube that is capable of insertion into the tracheal cannula of a patient.

10. The system as recited in claim 7, further comprising conversion means in operational connection with said processing means for converting said electrical output signal into digital data.

11. The system as recited in claim 7, further comprising calculation means in operational connection with said processing means for calculating cardiac output based on said extracted cardiogenic oscillations.

12. A method for continuously monitoring the cardiac output of a patient comprising the steps of:

measuring the air flow in the throat of a patient; and

extracting monitoring cardiac output by cardiogenic oscillations from the measured air flow.

13. The method as recited in claim 12, wherein said measuring step is performed during periods of apnea.

14. The system as recited in claim 12, wherein said measuring step is performed by a pneumotachograph having a tube that is capable of insertion into the mouth of a patient.

15. The system as recited in claim 12, wherein said measuring step is performed by a pneumotachograph having a tube that is capable of insertion into the tracheal cannula of a patient.

16. The method as recited in claim 12, further comprising the step of converting the cardiogenic oscillations to an electrical output signal.

17. The method as recited in claim 16, further comprising the step of converting said electrical output signal to a stream of digital data.

18. The method as recited in claim 17, further comprising the step of displaying said stream of digital data.

19. The method as recited in claim 12, further comprising the step of inferring cardiac output from said extracted cardiogenic oscillations.

20. The method as recited in claim 12, further comprising the step of continuously calculating cardiac output based upon said cardiogenic oscillations.