Minute volume as a surrogate for EtCO

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

receiving a target EtCO 2 for the patient at a controller associated with a ventilator;

receiving an alveolar minute volume value for the patient at the controller;

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

calculating with the controller an actual EtCO 2 ;

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

if the actual EtCO 2 is not within a predetermined range of the target EtCO 2 ,

adjusting the alveolar minute volume value based on a difference between the actual E t CO 2 and the target E t CO 2 ;

operating the ventilator to automatically ventilate the patient based on the adjusted alveolar minute volume value; and

operating a display to indicate a change in patient status.

2. The method of claim 1 wherein the indicating the change in patient status comprises displaying the actual EtCO 2 and the target EtCO 2 on the display.

3. The method of claim 1 wherein the indicating the change in patient status comprises displaying the alveolar minute volume value and the adjusted alveolar minute volume value on the display.

4. The method of claim 3 further comprising storing the alveolar minute volume value over time; and

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

5. The method of claim 3 further comprising storing the alveolar minute volume value over time; and

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

6. The method of claim 1 wherein the target EtCO 2 for the patient is received from a user input device operated by a operator.

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

a ventilator;

a gas analyzer;

a controller; and

a display

wherein the controller automatically controls the ventilator to ventilate the patient by

receiving a target EtCO 2 for the patient;

receiving an initial alveolar minute volume value for the patient;

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

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

determining that the actual EtCO 2 is not within a predetermined range of the target EtCO 2 ,

calculating an adjusted alveolar minute volume value based on a difference between the actual E t CO 2 and the target E t CO 2 ; and

automatically ventilating the patient based on the adjusted alveolar minute volume value.

8. The system of claim 7 wherein, if the actual EtCO 2 is not within a predetermined range of the target EtCO 2 , the controller operates the display to indicate a change in patient status.

9. The system of claim 7 wherein the controller continually calculates the adjusted alveolar minute volume value as required to maintain the actual EtCO 2 within the predetermined range of the target EtCO 2 .

10. The system of claim 7 wherein the controller stores the adjusted alveolar minute volume value to memory.

11. The system of claim 9 wherein the controller operates the display to display the adjusted alveolar minute volume value with respect to time.

12. The system of claim 9 wherein the controller operates the display to display the adjusted alveolar minute volume value and the target EtCO 2 with respect to time.

13. The system of claim 7 wherein the target EtCO 2 for the patient and the initial alveolar minute volume value for the patient are set by an operator via a user input device.