People usually code for one or two reasons. They have either a cardiac or respiratory arrest. Preceding this events, respiratory or cardiac failure occurs due to a number of reasons. In either case, you need respiration and circulation to survive. Other than the obvious terminal patient, intubation after a code and mechanical ventilation is often crucial and necessary in sustaining life.
When your heart slows beating, beats to fast, or more importantly not at all, then your blood enriched with oxygen is not properly circulating to vital organs. Carbon dioxide, or what you blow out, is not being eliminating and is actually increasing in the bloodstream. This increase in carbon dioxide causes the body to become more acidic and throws the ph out of whack. Oxygen can be given during a code with an ambu bag, but often restoration of a normal ph takes a little longer than restoration of a normal heartbeat. Often a shock can restore a normal heart rate within seconds. It usually takes at least 20 minutes or more to restore normal blood ph. When a patient is intubated and placed on a ventilator this task can usually be accomplished very quickly. The patient is sedated and allowed to rest while this is occurring. When all values have returned to normal sedation is decreased and weaning from life support begins. The patient is then removed from life support by means of the respiratory therapist deflating the cuff on the tube and having the patient cough. It is simple and it doesn't take but a minute.
There are certain circumstance where life support shouldn't be pursued such as when someone has been down to long or if someone is very old and doesn't want their life prolonged, and when someone has a poor quality of life and is very sick. For everyone else, careful consideration should be made when considering a DNI status unless you truly know what that entails. Some people do not realize that if they have had a surgical procedure under anesthesia, that they have more than likely had a tube placed when they went to sleep, and it is usually removed before they ever get to the recovery room. A code status is something that should be discussed with a physician and the decision made long before an event has a chance to occur. Just know the facts before making the decision to forgo intubation after a code.