TABLE 5-3 Nurse Staffing Estimates Derived from Staffing Studiesa

Estimated RN:Patient Ratio

Source of Estimates



Estimates derived from authors’ report of average hppd for all nursing staff and % RN nursing staff. Data from 1994 New York and California state databases. Authors note poor quality of these data.

Lichtig et al. (1999)


Authors estimated 6.2 RN hppd (adjusted)b from national 1996 American Hospital Association (AHA) data.

Kovner et al. (2000)


Authors estimated 6.56 RN hppd (adjusted) from 1996 AHA data for hospitals in 13 states.

Kovner et al. (2002)


Authors estimated average RN (administrative and direct-care) hppd of 7.8 from 11 states that collected 1997 nurse staffing data from state hospital data sets across all hospital inpatient units.

Needleman et al. (2002)


Authors estimated 6.3 RN hppd across medical–surgical, ICU, and coronary care units in 232 California hospitals.

Cho et al. (2003)

aEstimates calculated by dividing 24 hours by the number of hppd.

bAHA data were adjusted to account for differences between hospital inpatient and outpatient services.

Intensive care units A 1988–1990 study of 42 hospital ICUs, including a combination of volunteer hospitals and a geographically stratified random sample of nonfederal U.S. hospitals with at least 200 beds (the vast majority of all hospitals with ICUs), obtained nurse staffing data on each shift from a questionnaire completed by the director of the nursing unit. In that study, the mean number of patients cared for by an ICU nurse was 1.5 (range of 0.7 to 3.3). Hospitals falling one standard deviation below the mean had staffing ratios of one nurse for every 2.1 patients (Shortell et al., 1994). This average of 1.5 patients per nurse is identical to average ICU staffing levels calculated from hours of ICU nursing care (18 hppd) and the proportion of that care delivered by RNs (90 percent) reported in a 2.5-year study (1993–1995) of nurse staffing and adverse events in eight ICUs in 11 hospitals7 (Blegen and Vaughn, 1998), and is similar to that observed more recently in California. OSHPD data for 1998–1999 show average nurse-to-patient ICU staffing levels of 1.0:1.5 (medical–surgical), 1.0:1.8 (coronary), 1.0:1.2 (pediatric), and 1.0:2.1 (neonatal) (Spetz et al., 2000).


Ninety percent of 18 hppd = 16.2 RN hppd; 24 hours/day/patient divided by 16.2 RN hppd = 1.48 patients per RN.

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