National and statewide assessments of hospital nurse staffing frequently utilize a measure that averages counts of the number of nurses or hours of nursing care given the number of patients or patient days of care per hospital (Aiken, Sochalski, and Anderson 1996; Anderson and Kohn 1996; Spetz 1998; Buerhaus and Staiger 1999; Kovner, Jones, and Gergen 2000; Unruh 2002). These calculations provide a rough measure of nursing staff resources given patient volume, but they do not consider the intensity of nursing care that must be provided for that patient volume.

Intensity of nursing care, or the intensive effort spent at work (Green 2001), is important to consider because staffing needs vary not only with the number of patients being cared for, but also with the type of care provided for each of those patients. As nursing care intensity increases, the amount of nursing staff required to properly care for patients will increase (Moores 1970).

Factors that contribute to the level of intensity include: (1) other human resources, such as support staff; (2) physical resources, such as unit layout; (3) the work design and technology, such as the level of computerization and model of nursing care; (4) administrative practices; (5) the severity of the patients being cared for; and (6) the turnaround time to produce the product (patient turnover or throughput) (Cooper and Zaske 1987; Nichols 1991; Shamian et al. 1994; O’Brien-Pallas et al. 1997; Allan 1998; Cavouras 2002; Seago 2002).