Compressions are done to cause the blood to circulate when the heart is not beating. So first, check for a pulse. If there is no pulse, then yes, you do CPR even in the case of a severe chest injury, since the person will certainly die (and indeed, is already clinically dead) without this treatment. If you have a defibrillator, that might get the heart to start beating again, but you may still have to use CPR. Of course, for such a terribly injured person, you must get real medical help as soon as possible, but you can use CPR to keep the person alive until the ambulance arrives.
Look in the mouth, sweep if you see the object; attempt to ventilate, 30 compressions if breaths don't go in; repeat sweep, breaths, compressions, until breaths go in.
Speed, rhythm and degree of compression begin to fail.
If an adult is unconscious and has not responded after five abdominal thrusts (Heimlich maneuver), call emergency services immediately. Begin CPR if trained, starting with chest compressions, and continue until help arrives or the person begins to show signs of life. If trained and able, you can also check the mouth for any visible obstruction and remove it if safe to do so. Always prioritize calling for professional assistance in such emergencies.
In the recovery position
Current UK guidelines recommends 30 rapid chest compressions followed by 2 rescue breaths in adults during CPR. After rescue breaths, it is recommended to begin compressions as soon as possible thereafter. Therefore, working with two people is always preferable. For kids, i think it's split in half or something, like 15:1
immediately
This depends on the underlying law and circumstances. Many times a statute of limitations will begin when the relevant injury occurs or when a reasonable person would have discovered the relevant injury.
If a choking victim is unresponsive and has no pulse, call emergency services immediately. Begin CPR by performing chest compressions at a rate of 100-120 compressions per minute. After every 30 compressions, open the airway and give 2 rescue breaths; then continue the cycle. If you can, check the mouth for any visible obstruction and remove it if it's safe to do so.
If you find an unresponsive adult victim with no evidence of injury, first ensure the scene is safe before approaching. Check for responsiveness by gently shaking the person and calling out to them. If there is no response, call emergency services immediately and begin CPR if you are trained, ensuring to provide chest compressions and rescue breaths until help arrives. Monitor the victim's condition and be prepared to use an AED if available.
If someone stops breathing, immediately call for emergency medical help. Begin CPR by performing chest compressions at a rate of 100 to 120 compressions per minute, and if trained, provide rescue breaths after every 30 compressions. Continue CPR until emergency personnel arrive or the person starts breathing again. If an Automated External Defibrillator (AED) is available, use it as soon as possible.
It causes healing to begin at the injury site.
You should contact 911 if you have not already. Also check for a pulse, if there is not one present begin CPR.