Systems theory
One theory that is useful in understanding family and health provider interactions in critical care is family system theory. A key concept in family systems theory is that a Chang in one part of the system(for example,the hospitalization of a critically ill parent ) affects the entire family system,resulting in a strain on coping resources and possibly family distress .one way that systems,such as families,attempt to maintain or restore equilibrium and thereby reduce distress is by controlling "inputs and outputs"; for exemple,controlling what is allowed to enter or leave the system.a major input and output that is very relevant to critical care nurse is the two-way communication of information.