Depending upon the nature of the cardiac arrests, chest-compressions alone may be sufficient.
Some years ago, the journalists simply reported that CPR no longer included breaths. Of course, journalists get every story somewhat wrong.
If the cardiac arrest is caused by a breathing failure — as from suffocation, drowning, or opioid overdose — then breaths are needed.
If the cardiac arrest is primary — as when the victim clutches his chest and then keels over — then breaths are not needed, but won't hurt.
If you don't know which is the case, then include breaths.