Since agonal breathing will not support life, when agonal breathing occurs it is the same as no breathing; so immediately proceed with care.
Agonal sounds is an official medical term for what would unscientifically be called the "death rattle". While the sound is entirely different in both timing and form with each person and situation, there is a distinct commonality acknowledged by those who are exposed to it regularly. There are both academic and professional conversations on what actions if any should be attempted once the sound has been heard.
Agonal breathing will not support life; rescue breathing (or CPR if no pulse) is required.
Because cardiac arrest means heart is not beating, which means brain is not getting blood. It is the brain that signals body to breath, however the brain needs blood and will die without it. However, there are some cases of cardiac arrest where person will have whats called agonal respirations. This is where they are gasping for air, this type of breathing is abnormal and inadequate to sustain life and is a sign of near death. Even though a person may be in cardiac arrest the brainstem is still functioning enough to realize the body doesn't have enough oxygen and is signalling body to breath. This is actually a good sign during a cardiac arrest because patients with agonal breathing have higher resuscitation rates.
open the airway and give two breath/check the victim pulse
Yes
Agonal respiration is an abnormal pattern of breathing characterised by gasping, laboured breathing, accompanied by strange vocalisations and myoclonus.
Give rescue breaths as agonal breathing will not support life.
Tip the head to open the airway. Check for signs of life (look, listen, feel for breathing & movement). Since agonal gasps fails the breathing criteria, you would immediately begin CPR for an adult.
ventilation
Continue or begin CPR. Agonal respirations do not indicate that the victim is breathing on his own. They are also known as the "death rattle".
It is called agonal breaths. Since agonal breaths will not support life, assuming an adult, you would immediately begin CPR.