Influence of CO2 signal quality on INTELLiVENT-ASV automatic MinVol management

Author: Simon Franz, Reviewer: Matthias Himmelstoss, Thomas Reimer, Sebastian Hollenberg

Incorrect positioning of the CO2 mainstream sensor may affect the quality of the signal. When using INTELLiVENT®-ASV®, an unreliable signal may in turn affect the automated adjustments, as these are dependent on the quality index of the signal from the sensor.

If a PetCO2 signal is unavailable or of poor quality for more than 30 seconds, the Ventilation adjustment OFF alarm will be generated. The %MinVol control becomes a solid red circle that is frozen and automatic adjustment of the %MinVol stops. In this case, a constant minute ventilation equal to the last valid automatic %MinVol setting will be applied.

Figure 1: Indices showing poor signal quality that will cause automated ventilation management to stop 





The poor quality of the signal is indicated by gray, red and orange bars on the display. Once a reliable PetCO2 signal is available again, the %MinVol control becomes a blue rotating circle and the bars turn green.  The alarm is reset and automated ventilation management resumes.

Therefore, correct placement and positioning of the sensor is very important.

Place the sensor/airway adapter assembly at the proximal end of the airway circuit as shown.

Figure 2: Recommended setup of the breathing circuit






  • Do not place the airway adapter between the ET tube and the elbow, as this may allow patient secretions to accumulate in the adapter.
  • Position the airway adapter with its windows in a vertical, not a horizontal, position. This helps keep patient secretions from pooling on the windows. 
Figure 3: Vertical positioning of the sensors









Relevant devices: HAMILTON-G5/S1 (SW v2.6x), HAMILTON-C6 (SW v1.x.x), HAMILTON-C3 (SW v2.0.2)