Instead of using the highest level, try adjusting the settings until you find you maximum comfortable suction level. This means the highest level where you can pump without experiencing pain or discomfort, which encourages efficient milk expression.
Learn more about finding your maximum comfortable suction level below.
For reference, your Philips Avent electric breast pump can be set to a max level of 16 on the motor unit, which is equal to 360 mbar/270 mmHg.