PaCO2 - PetCO2 gradient and target shift

Author: Clinical Experts Group, Hamilton Medical, Reviewer: N/A

INTELLiVENT®-ASV® uses partial pressure of end tidal CO2 (PetCO2) measured by the CO2 sensor as monitoring input for the regulation of ventilation. The measured PetCO2 value is used to track partial CO2 pressure in the arteries (PaCO2).

​In general, PetCO2 value represents a reliable index of CO2 partial pressure in the arterial blood (PaCO2) (measured using blood gas analysis (BGA)). To get the most accurate approximation of PaCO2, the second highest PetCO2 value out of 8 breaths is used.

Under common conditions, PaCO2 is approximately 3–5 mmHg higher than PetCO2 — the difference between the values is referred to as the PaCO2-PetCO2 gradient.  Under special clinical conditions (including ventilation/perfusion problems or presence of a shunt), the PaCO2-PetCO2 gradient can increase, requiring adjustment of the ventilation targets. The Target Shift control (INTELLiVENT-ASV window) allows you to move the PetCO2 target range to the left (lower values) or to the right (higher values) within the limits defined.

PaCO2 (BGA):                           60 mmHg
PaCO2 target (physician):      40–50 mmHg
PetCO2 patient (measured):  38 mmHg

Because the measured PetCO2 is in the PetCO2 target range, INTELLiVENT-ASV does not see a need to increase %MinVol.

Target shift of -15 mmHg

However, the target range for PetCO2 needs to be lower because of the PaCO2-PetCO2 gradient.

Where PaCO2 (BGA) is too high, shift the target range 10–15 mmHg  to the left.

The %MinVol will increase resulting in a decrease in patient CO2.

Please note:    

- Record the measured patient PetCO2 value just before BGA
- To proceed as described, the measured patient PetCO2 needs to be in the target range for PetCO2
- If the patient is not within the set target PetCO2 range just before BGA, you can still adjust the target range as above.

Remember that INTELLiVENT-ASV will always try to bring the patient into the middle of the target range. This is particularly important when adjusting the target range where the patient is not in the set range just before BGA.

Relevant devices and software*: HAMILTON-G5/S1 - v2.6x; HAMILTON-C3 - v2.0x; HAMILTON-C6 - v1.0x

* Some features are options. Not all devices and features are available in all markets.

Target shift, PetCO2, PaCO2, BGA, blood gas, target range, measured PetCO2 INTELLiVENT

Date of Printing: 16.08.2018
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