Publishing rate of /fmu/out/sensor_combined

Hello! I want to use the IMU-data of my pixhawk4. I successfully set up a UXRCE-client/agent bridge over the telem1 port on the pixhawk. However, the publishing rate is approx. 100Hz and I want to increase it as much as possible. Setting the param IMU_INTEG_RATE to 400Hz and running uorb top sensor_combined in the MAVLink-shell, tells me that the uORB-topic is published at 400Hz. What is limiting the publishing rate onto ROS2 then? How can I increase this publishing rate?