Such means of preserving human life as cannot be obtained or used without extreme difficulty in terms of pain, expense, or other burdening factors. The burden applies either to the person whose life is at stake or to those on whom his or her welfare depends. In addition, means should be considered extraordinary if, when used, they do not offer a reasonable hope of benefit to the one for whom they are intended.
There is no general obligation to use extraordinary means to keep alive, on the premise that God does not exact what is beyond the ordinary power of humans in general. At times, however, one may be bound to employ extraordinary means to preserve life. The two conditions under which such an obligation becomes binding are that a person is necessary to one's family, to the Church, or to society, and the success of the extraordinary means is very probable.