Stop funding dialysis after age 70. Then stop the practice of admitting terminally ill patients to the intensive care unit. Understand these and you begin to get insight into the system. Changing them is another story. Physicians have a few directives- Do no harm.
Every human life is of equal, incalcuable value.
The contraints are people, time and money. There are some rules on spending money, but in the end, when life is at stake, we spend money. As the money runs out, the people and their time become constrained. You live or die because you came to the ER at a slack time or a busy time. You live or die because of whether a nurse had time to brief another nurse at shift change.