addition impedance measurements of the chest for indicating the air volume in the lungs may be used as described in the next section other setups of the system may also be viable the ventilation measuring means may for example be integrated into the mask and there may or may not be a ventilation bag instead the rescuer can use his her mouth to ventilate the patient in addition or instead of flow measurements end tidal co 2 etco 2 measurements may also be implemented etco 2 may be used as an indicator as to how good the treatment is and thus if the cpr can be improved advanced life support als personnel may intubate a cardiac arrest victim and perform compressions and ventilations at the same time as the compressions will compress the lungs thus pushing air out of them compressions may influence the ventilation measurements low pass filtering or adaptive filtering of the ventilation measurements may therefore be necessary adaptive filtering may use any single or combination of force acceleration velocity and or depth as additional inputs as they all relate to compression activity how to do this is per se known to a person skilled in the art of.