Table 2.

Fault-tolerant systems

'Fault-tolerance or graceful degradation is the property that enables a system to continue operating properly in the event of the failure of some of its components. If its operating quality decreases at all, the decrease is proportional to the severity of the failure, as compared to a naively designed system in which even a small failure can cause total breakdown. Fault-tolerance is particularly sought after in high-availability or life-critical systems' [61].

Many systems must be engineered to be fault-tolerant. The same principles must be applied to critical services provided by hospitals during a disaster. The following strategies can be applied to manage demand that would otherwise prompt system failure:

• Engineered system failure – Similar to a circuit breaker, this allows system components to fail in order to prevent catastrophic damage to the system as a whole. An example might be a hospital switchboard that gives preference to internal hospital calls (rather than to calls from external sources) to preserve internal communications during an emergency.

• Redundancy – Having adequate duplicate supplies or services available in case of failure (for example, extra intravenous pumps or ventilators).

• Diversity – Having many ways of providing the same service, but via different techniques (for example, triaging patients in multiple areas of the hospital: emergency department, lobby areas, and so on).