Natural Death:

Death caused by natural processes such as old age, organ failure or disease, as opposed to external factors such as accident, injury, or homicide.

Euthanasia:

A third party decides that a person’s life is no longer worth living and takes direct action, such as giving the person a substance, with the intention of ending the person’s life. Can be further broken down into “voluntary” and “involutary”. Currently not legal in the U.S.

Physician Assisted Suicide:

Also known as medical aid in dying (MAiD) or death with dignity. An individual requests a life-ending drug prescription from his physician. The physician prescribes the drug, individual has the prescription filled and administers to himself to end his life. This is currently legal in 10 states in the US and being considered in 7 others. [1]

Suicide:

An individual takes action to end his own life.

Feeding Tubes and Fluid IVs:

These are delivery methods of essential substances for a person who can no longer nourish himself without aid. The person is still responsible for the bodily tasks that integrate these substances into his system as needed to sustain health and life. A feeding tube doesn’t digest and deliver nutrients for a person, it only makes them available. An IV doesn’t integrate fluids into tissues and cells, it only makes them available for the person to do that.

EWTN provides a helpful summary:

1. Food and water are natural means of sustaining life, not medical acts, even if delivered artificially.
2. Nutrition and hydration are ordinary and proportionate means of care.
3. Food and water are morally obligatory unless or until they cannot achieve their finality, which is providing nutrition and hydrating and alleviating suffering.
4. The length of time they are, or will be, used is not grounds for withholding or withdrawing artificially delivered nutrition and hydration.
5. If the result of withholding or withdrawing nutrition and hydration is death by starvation and dehydration, as opposed to an undying disease or dysfunction, it is gravely immoral.

In summary, nutrition and hydration, like bathing and changing the patient's position to avoid bedsores, is ordinary care that is owed to the patient. This is true even if it is delivered artificially, as when a baby is bottle-fed or a sick person is tube-fed. [2]

Ventilator:

Ventilators are often defined as replacing breathing/respiration but they only replace inhalation. [3] This is considered extraordinary care in part because of the burden it puts on the patient.

Quality of Life:

As defined by Oxford Dictionary, quality of life is the standard of health, comfort, and happiness experienced by an individual or group.

Suffering:

Enduring situations which cause pain physically or emotionally. Our hedonistic culture currently sees suffering as the ultimate experience to be avoided because it seems to be the opposite of happiness/pleasure. Christians take a very different view. While suffering is a result of corrupt human nature, and so not good in and of itself, God uses it for our good. When we suffer well, suffering produces perseverance, which produces character, which produces hope. [4] Suffering well draws us closer to God because we cannot manage alone. Suffering strips away the facade and makes us honest about our ultimate dependency on God.

Refusing care, except nutrition and hydration, is morally permissible:

Do Not Resuscitate Orders and refusal of treatment for disease are always ethical. In these cases, it is the disease or internal issue that is ending the life of the person which makes it a natural death.

“We must, therefore, ask the question ‘will the withdrawal of nutrition and hydration allow the person to die, or kill the person?’ When it allows a person to die from an underlying condition, rather than unnecessarily prolonging their suffering, it may be removed. So, for example, in the last hours, even days, of a cancer patient's life, or if a sick person's body is no longer able to process food and water, there is no moral obligation to provide nutrition and hydration. The patient will die of their disease or their organ failure before starvation or dehydration could kill them. However, when the withdrawal of nutrition and hydration is intended to kill the person, or will be the immediate and direct cause of doing so―quite apart from any disease or failure of their bodies, then to withdraw food and water would be an act of euthanasia...” [5]