Journal of Nursing Administration:
Letter To The Editor

Chaos Theory

Diggs, Walter W. LFACHE

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Memphis, Tennessee

Dear Editor:

This is to support the very important article, "Chaos Theory: Learning a New Science,"1 by Elaine McGuire, in which she equates chaos with nonlinear variation. McGuire's nursing example of nonlinear chaos is census variation. Another example is acuity or nursing workload. Acuity may vary more than the census and may be independent of diagnosis or severity. Acuity may be defined as the degree of psychosocial risk of health treatment or the degree of dependency or functional status of the patient.

Severity may have nonlinear cost attributes also. Severity may be defined as the degree of biomedical risk, morbidity, or mortality of medical treatment.

Nursing workload or acuity in a suburban hospital may vary 30% (plus or minus 15%) from day to day. This nonlinear variation may be replicated by multiplying census by nurse:patient ratios, resulting in a nonlinear curve. It appears that nurse staffing costs increase with a nonlinear doubling factor of 1-2-4-8-16, not a linear 1-2-3-4. If this nonlinear nursing cost curve is true, the average patient may not be an average patient!

There are other examples of nonlinear cost phenomena in medical care: the cost of capitating elderly patients compared to other patients, the relative costs of primary, secondary, and quaternary care, and the cost of outliers. Chaos theory and linear variation as defined by McGuire can be used to explain difficulties in case mix risk adjustment and performance measurement. In medical care there appears to be nonlinear cost phenomena involving acuity, severity, and technology-a triple whammy!

Walter W. Diggs, LFACHE

Memphis, Tennessee

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1. McGuire E. Chaos Theory: Learning a New Science. J Nurs Adm. 1999;29(2):8-9.

© 1999 Lippincott Williams & Wilkins, Inc.