If you don't have an automatic defibrillator then you don't stop and check for signs of life. The chances of reviving simply due to chest compressions is a joke. What they need is electricity to restart the heart.
If you have an AED then you check after you get a "No Shock Advised" from the AED.
You should check for signs of life every two minutes while performing rescue breathing on an adult or child
Once CPR is started for an adult, don't stop to check for signs of life. Continue CPR until EMS arrives to take over.
About how often should you stop and check for signs of life when performing rescue breathing on a child?
Check about every 2 minutes.
Every 2 minutes check for signs of life when performing RB.
Check for signs of life on a child every 2 minutes.
Check for signs of life about every 2 minutes.
Check for a pulse about every 2 minutes.
Do not stop CPR to check for signs of life in Adult CPR. Continue CPR until help (EMS) arrives or someone takes over.
In the initial assessment, check for signs of life. During rescue breathing, check for signs of life every 2 minutes. During CPR, don't check for signs of life any more. Unless you see obvious signs of life once CPR is started, continue doing CPR.
Check every 2 minutes.
Check for signs of life when performing rescue breathing on a child every 2 minutes.