4-5 min. Brain cannot function more than 4-5 minutes of lack of oxygen.
Not very long. The brain is extremely sensitive to anoxia (being without oxygen). Depending on other medical issues, after approx 5 minutes brain damage can occur, which is why it is so important to begin CPR immediately.
2-4 minutes. It depends on age, temperature, cause of cardiac arrest, whether or not CPR is done and other factors but 2-4 minutes is about it.
Possibly. Any time your heart stops pumping, the blood in your arteries and veins stops flowing. Therefore all of the organs are not getting the blood they need to function. The brain is a very sensitive organ and can get damaged if it is not receiving proper blood flow. There are ways to check the brain for such damage. Talk to your doctor about seeing a neurologist.
Yes. The brain only tolerates a brief loss of oxygen delivery. A cardiac arrest of 2 minutes is long enough to cause permanent, even profound, brain damage.
Could a pacemaker keep an individuals heart beating after a cardiac arrest. If the answer to the above question is yes, then how long would it continue to assist the heart in beating and would it help to prevent brain damage until medical help arrives.
Yes.. Yes. A pacemaker is placed in the heart to prevent the heart from beating too slow. As an example a pacemaker may be set to ensure the heart beats 70 times a minute. If your intrinsic heart beats slower than 70, or if your heart stops beating (as in a cardiac arrest), then the pacemaker will send an electrical impulse to the heart to keep beating at 70 beats per minute. To avoid brain damage, the person must also be breathing normally. If the person is not breathing normally (10-20 breaths per minute), call 911 and initate cpr.
Generally no. In most circumstances the term cardiac arrest refers to a rhythm problem called ventricular fibrillation. Eventually there is no electrical activity at all and even a pacemaker cannot stimulate the heart.