The invention relates to a method and a device for removing respiratory artefacts in invasive blood pressure measurements. The level of CO2 in the expired air is monitored during blood pressure measurement and used to approximate and remove the respiratory artifacts. In one embodiment, the respiratory frequency from the respiratory signal is extracted by identifying the end-tidal CO2 level for each breath. A model is derived for the respiratory artifacts using the respiratory frequency, and the model is subtracted from the measured blood pressure data.