I can't understand “to your chest pressing” and "how effective you are'.
Check how effective you are seeing if his colour improves or his pulse becomes independent to your chest pressing.
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With arms straight, rock forwards, pressing down on the lower half of the breastbone. Don't be too hard or you may break a rib. Check how effective you are by seeing if his colour improves or his pulse becomes independent to your chest pressing. If this happens, stop the pressing. Otherwise continue until rescue arrives.--------------------
The question has been solved！！！！！！！！！！！！！！！！！！！！！

Question

I can't understand “to your chest pressing” and "how effective you are'.
Check how effective you are seeing if his colour improves or his pulse becomes independent to your chest pressing.
---------------------
With arms straight, rock forwards, pressing down on the lower half of the breastbone. Don't be too hard or you may break a rib. Check how effective you are by seeing if his colour improves or his pulse becomes independent to your chest pressing. If this happens, stop the pressing. Otherwise continue until rescue arrives.--------------------
The question has been solved！！！！！！！！！！！！！！！！！！！！！

Answer

"Chest pressing" is the physical act of pumping a victim's chest while performing the life-saving technique known as CPR (Cardiopulmonary resuscitation). "How effective you are" is an assessment of whether the technique is working.

In short, the sentence could be interpreted, "Check the results of your chest pumping technique by observing his colour (it should improve) or seeing if he can maintain a pulse without you continuing to pump his breast."