It is my understanding of the laws in the U.S., though, that we are not allowed to use poor quality of life as a reason for withholding or withdrawing care. We cannot discriminate against people with impairments; withholding life support would constitute discrimination.
We are allowed to stop support, however, when continued treatment is futile or prolongs suffering. And there is the rub: how do we determine futility? And do we sometimes say we are stopping support because of futility when we are really stopping it because of quality of life issues?
For example, we are not allowed to withhold life saving treatment from a child with Down's syndrome, a chromosomal defect that causes mental retardation and other birth defects. However, we are allowed to - and usually do - withhold treatment from children with Trisomy 13 or 18, which are also chromosomal defects that cause mental retardation - a much more severe retardation than that of Down's syndrome kids - as well as other birth defects.
Eighty or ninety per cent of babies with Trisomy 13 or 18 die by age one year. They often die because they simply stop breathing; the respiratory center of their brain, responsible for regulating their breathing, doesn't work properly. They can also die because of other birth defects, such as serious heart problems. If a normal child were to stop breathing, we would begin support with a ventilator. This is not usually offered Trisomy 13 or 18 patients. We say we don't offer it because it would be futile; the baby would eventually die from another problem caused by the Trisomy. But the truth is, many of the Trisomy 13 and 18 children if put on a ventilator, if their heart defect were repaired, and a feeding tube placed, and anti-reflux surgery done, could possibly live for years. It would not, in my opinion, be a life of high quality (and I am not advocating it be done.) Most of these patients cannot even smile, let alone walk or talk or indicate their desires, but they would be alive. So when we withhold life support from them, are we really doing it because it would be futile, or because the quality of life would be so poor?
In reality, the distinction between futility and poor quality of life is not so clear.