METHODS AND SYSTEMS FOR MONITORING VOLUMETRIC CARBON DIOXIDE

• US 20130006134A1
• Filed: 06/30/2011
• Published: 01/03/2013
• Est. Priority Date: 06/30/2011
• Status: Abandoned Application

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Doyle, Peter R., Kimm, Gardner, Jafari, Mehdi M.
• Application Number:
  US13/174,240
• Publication Number:
  US 20130006134A1
• Time in Patent Office: Days
• US Class Current: 600/532
• CPC Class Codes: A61B 5/0836 Measuring rate of CO2 production
• CPC Class Codes: A61M 16/0063 Compressors
• CPC Class Codes: A61M 16/026 specially adapted for predicting, e.g. for determining an information representative of a flow limitation during a ventilation cycle by using a root square technique or a regression analysis
• CPC Class Codes: A61M 16/0833 T- or Y-type connectors, e.g. Y-piece
• CPC Class Codes: A61M 2016/0027 pressure meter
• CPC Class Codes: A61M 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase
• CPC Class Codes: A61M 2205/502 User interfaces, e.g. screens or keyboards
• CPC Class Codes: A61M 2230/432 partial CO2 pressure (P-CO2)

Abstract

This disclosure describes novel systems and methods for monitoring volumetric CO₂ during ventilation of a patient being ventilated by a medical ventilator. The disclosure describes more accurate, more cost effective, and/or less burdensome non-invasive methods and systems for calculating volumetric CO₂ than previously utilized methods and systems. The disclosure describes estimating a flow rate in a breathing circuit to calculate a volumetric CO₂. Further, the disclosure describes synchronizing the estimated flow rate with a measured CO₂ to calculate a volumetric CO₂. Additionally, the disclosure describes synchronizing a measured flow rate from within the breathing circuit with a measured CO₂ to calculate a volumetric CO₂.

Claims

1. A method for monitoring volumetric CO₂ during ventilation of a patient being ventilated by a medical ventilator, the method comprising:

estimating at least one flow rate at a first location in a breathing circuit by monitoring at least one respiratory parameter with at least one sensor located outside of the breathing circuit;

monitoring CO₂ concentrations with a capnometer at a second location in the breathing circuit; and

calculating a volumetric CO₂ passing through at least one of the first and second locations for at least one breath based at least on an algorithm, the monitored CO₂ concentrations taken by the capnometer, and the at least one estimated flow rate.

2. The method of claim 1, wherein the at least one monitored respiratory parameter is at least one of flow and pressure.

3. The method of claim 1, wherein the first location and the second location are the same location.

4. The method of claim 1, wherein the algorithm is

5. The method of claim 1, further comprising synchronizing at least one CO₂ measurement taken by the capnometer with the at least one estimated flow rate from a same sampling period.

6. The method of claim 5, further comprising monitoring an amount of oxygen exhaled by the patient with an oxygen sensor at a third location in the breathing circuit.

7. The method of claim 6, wherein the step of synchronizing is at least based on at least one oxygen measurement taken by the oxygen sensor.

8. The method of claim 5, wherein the step of calculating the volumetric CO₂ for each breath has an accuracy of at least 90%.

9. The method of claim 5, wherein the step of synchronizing comprises:

selecting a common event; and

aligning the at least one measurement of CO₂ and the at least one estimated flow rate based at least on timing of the common event.

10. The method of claim 9, wherein the step of aligning further comprises utilizing the common event is to determine a delay between the at least one CO₂ measurement and the at least one estimated parameter.

11. The method of claim 10, wherein the step of aligning further comprises accounting for the delay to synchronize the at least one CO₂ measurement with the at least one estimated parameter.

12. The method of claim 11, wherein the common event is at least one of a start of inspiration, a start of exhalation, and a transition point between inspiration and exhalation.

13. The method of claim 11, wherein the step of aligning is further based on at least one of inspiratory status, expiratory status, response time of ventilator delivery valves, response time of ventilator exhalation valves, compliance of the breathing circuit, and estimates of anatomic dead-space.

14. The method of claim 5, further comprising utilizing the calculated volumetric CO₂ to adjust the at least one estimated parameter.

15. A medical ventilator system, comprising:

a pneumatic gas delivery system, the pneumatic gas delivery system adapted to control a flow of gas from a gas supply to a patient via a breathing circuit;

a sensor estimator, the sensor estimator estimates at least one flow rate at a first location in the breathing circuit based at least on measurements taken by at least one sensor located outside of the breathing circuit;

a capnometer, the capnometer monitors an amount of carbon dioxide in respiration gas at a second location in the breathing circuit; and

a processor in communication with the pneumatic gas delivery system, the sensor estimator, and the capnometer, the processor is configured to calculate a volumetric CO₂ passing through at least one of the first and second locations for at least one breath based at least on an algorithm, the monitored CO₂ concentrations taken by the capnometer, and the at least one estimated flow rate.

16. The medical ventilator system of claim 15, wherein the at least one sensor is at least one of a flow sensor and a pressure sensor.

17. The medical ventilator system of claim 15, wherein the first location and the second location are the same location.

18. The medical ventilator system of claim 15, further comprising a synchronization module, the synchronization module synchronizes at least one CO₂ measurement taken by the capnometer with the at least one estimated parameter from a same sampling period.

19. The medical ventilator system of claim 18, further comprising an oxygen sensor, the oxygen sensor monitors the amount of oxygen in the respiration gas at a third location in the breathing circuit.

20. The medical ventilator system of claim 19, wherein the synchronization module further synchronizes the at least one CO₂ measurement with the at least one estimated flow rate from the same sampling period based at least on at least one oxygen measurement taken by the oxygen sensor.

21. The medical ventilator system of claim 19, wherein the sampling period is determined by a timing of a common event.

22. The medical ventilator system of claim 21, wherein the common event is at least one of a start of inspiration, a start of exhalation, and a transition point between inspiration and exhalation.

23. A computer-readable medium having computer-executable instructions for monitoring volumetric CO₂ during ventilation of a patient being ventilated by a medical ventilator, the method comprising:

repeatedly estimating at least one flow rate at a first location in a breathing circuit by monitoring at least one respiratory parameter with at least one sensor located outside of the breathing circuit;

repeatedly monitoring CO₂ concentrations with a capnometer at a second location in the breathing circuit; and

repeatedly calculating a volumetric CO₂ passing through at least one of the first and second locations for at least one breath based at least on an algorithm, the monitored CO₂ concentrations taken by the capnometer, and the at least one estimated flow rate.

24. A medical ventilator system, comprising:

means for estimating at least one flow rate at a first location in a breathing circuit by monitoring at least one respiratory parameter with at least one sensor located outside of the breathing circuit;

means for monitoring CO₂ concentrations with a capnometer at a second location in the breathing circuit; and

means for calculating a volumetric CO₂ passing through at least one of the first and second locations for at least one breath based at least on an algorithm, the monitored CO₂ concentrations taken by the capnometer, and the at least one estimated flow rate.