Minute volume and carbon dioxide clearance as surrogates for EtCO

1. A method for automatically controlling ventilation of a patient, the method comprising:

receiving a target expiratory CO 2 concentration set by an operator as a control parameter for a ventilator to automatically maintain a constant expiratory CO 2 concentration of the patient;

measuring an actual expiratory CO 2 concentration;

comparing the actual expiratory CO 2 concentration to the target expiratory CO 2 concentration;

calculating an adjusted ventilation rate based on the comparison of the actual expiratory CO 2 concentration to the target expiratory CO 2 concentration in order to maintain the actual expiratory CO 2 concentration within a predetermined range of the target expiratory CO 2 concentration;

automatically ventilating the patient with the ventilator based on the adjusted ventilation rate so as to maintain the actual expiratory CO 2 concentration for the patient within the predetermined range of the target expiratory CO 2 concentration so as to maintain the constant expiratory CO 2 concentration of the patient; and

tracking the adjusted ventilation rate over time as an indicator of patient hemodynamic status.

2. The method of claim 1 , further comprising displaying the target expiratory CO 2 concentration and the adjusted ventilation rate over time.

3. The method of claim 2 , wherein the target expiratory CO 2 concentration and the adjusted ventilation rate over time are shown together with respect to a time axis.

4. The method of claim 1 , further comprising displaying the target expiratory CO 2 concentration and a carbon dioxide clearance value over time as an indicator of patient hemodynamic status.

5. The method of claim 1 , further comprising tracking the actual expiratory CO 2 concentration over time.

6. The method of claim 5 , further comprising displaying the adjusted ventilation rate over time and the actual expiratory CO 2 concentration over time.

7. The method of claim 6 , wherein the actual expiratory CO 2 concentration over time and the adjusted ventilation rate over time are shown together with respect to a time axis.

8. The method of claim 5 , wherein the actual expiratory CO 2 concentration over time and carbon dioxide clearance value are shown together with respect to a time axis.

9. The method of claim 1 , wherein the predetermined range is a predetermined percentage of the target expiratory CO 2 concentration.

10. The method of claim 9 , wherein the predetermined percentage is less than or equal to 0.5%.

11. The method of claim 10 , wherein the predetermined percentage is between 0.01% and 0.5%.

12. The method of claim 1 , wherein the expiratory CO 2 concentration of the patient is maintained constant based on the target expiratory CO 2 concentration set by the operator until a new target expiratory CO 2 is set by the operator.

13. The method of claim 12 , wherein, being held constant, the expiratory CO 2 concentration of the patient is not an indicator of patient hemodynamic status.

14. The method of claim 1 , wherein tracking the adjusted ventilation rate over time as an indicator of patient hemodynamic status comprises generating an alert in response to a determination that a change in an alveolar minute volume value or a carbon dioxide clearance value exceeds a predetermined change value.

15. The method of claim 1 , wherein tracking the adjusted ventilation rate over time as an indicator of patient hemodynamic status comprises generating an alert in response to a determination that a change in a carbon dioxide clearance value exceeds a predetermined rate of change value.

16. A method for automatically controlling ventilation of a patient, the method comprising:

receiving a target EtCO 2 for the patient set by an operator;

receiving an alveolar minute volume value for the patient;

measuring expiratory CO 2 in a gas expired from the patient;

calculating an actual EtCO 2 ;

comparing the actual EtCO 2 to the target EtCO 2 ; and

detecting that the actual EtCO 2 is not within a predetermined range of the target EtCO 2 , and then:

adjusting the alveolar minute volume value based on the comparison;

automatically ventilating the patient based on the adjusted alveolar minute volume value; and

displaying a carbon dioxide clearance value over time to indicate the change in patient hemodynamic status.

17. The method of claim 16 , further comprising tracking the alveolar minute volume value over time; and

displaying the target EtCO 2 and alveolar minute volume value over time together with respect to a time axis to indicate the change in patient hemodynamic status.

18. The method of claim 16 , further comprising tracking the alveolar minute volume value over time; and

displaying the actual EtCO 2 and alveolar minute volume value over time together with respect to a time axis to indicate the change in patient hemodynamic status.

19. The method of claim 16 , wherein the target EtCO 2 for the patient is received from a user input device operated by an operator.

20. The method of claim 16 , wherein the predetermined range is a predetermined percentage of the target EtCO 2 , wherein the predetermined percentage is between 0.01% and 0.5%.

21. A system for automatically ventilating a patient, the system comprising:

a ventilator;

a gas analyzer;

a controller;

a display;

wherein the controller is configured to:

receive a target EtCO 2 for the patient set by an operator;

receive an initial alveolar minute volume value for the patient;

receive from a gas analyzer an actual EtCO 2 in a gas expired from the patient;

compare the actual EtCO 2 to the target EtCO 2 ;

detect that the actual EtCO 2 is not within a predetermined range of the target EtCO 2 , and then:

calculate an adjusted alveolar minute volume value;

automatically control the ventilator to ventilate the patient based on the adjusted alveolar minute volume value so as to maintain the actual EtCO 2 concentration for the patient within the predetermined range of the target EtCO 2 concentration so as to automatically maintain a constant expiratory CO 2 concentration of the patient; and

track an adjusted ventilation rate over time as an indicator of patient hemodynamic status.

22. The system of claim 21 , wherein the controller is further configured to continually calculate the adjusted alveolar minute volume value as required to maintain the actual EtCO 2 is within the predetermined range of the target EtCO 2 .

23. The system of claim 22 , wherein the controller is further configured to operate the display to display the adjusted alveolar minute volume value with respect to time.

24. The system of claim 22 , wherein the controller is further configured to operate the display to display the adjusted alveolar minute volume value and the target EtCO 2 with respect to time.

25. The system of claim 22 , wherein the controller operates the display to display a carbon dioxide clearance value with respect to time.

26. The system of claim 21 , wherein the controller is further configured to store the adjusted alveolar minute volume value to memory.