Untangling function: measuring the severity, type and meaning of disabilities.

In this commentary, we argue that the current biomedical and psychosocial models of illness that form the basis of medicine are insufficient to describe this interface. We offer a biopsycho-ecological model of illness and disability referred to as health environmental integration (HEI) as a framework intended to encourage a more complete understanding of disability as arising at the interface between the person's internal and external worlds. By this model, person-level functional abilities as well as the subjective meaning of those functions result in part from interactions created by the exchange of energy and information between the person and his environment. Three components are essential in measuring function: severity of deficit, type of deficit, and meaning. We present functional status staging as an approach to measuring severity and type of deficit, and recovery preference exploration as a way to measure meaning. Rehabilitation medicine can come closer to bridging the gap between biological and the subjectively-based aspects of human function, by measuring all three concepts.