Limitations of Rechtschaffen and Kales.

The guidelines of Rechtschaffen and Kales (R&K) were meant as a reference method. However, it became, unintentionally, a gold standard. The rules have never been appropriately validated. It is used for the scoring of recordings of, for instance, pathological sleep, for which it was not designed. Today R&K is an insufficient description of sleep processes. In practice, the rules are often difficult or impossible to follow and deviations are common, although not reported. The major drawbacks are: low temporal resolution, ignorance of spatial information, insufficient number of stages, low correspondence between electrophysiological activity and stages, and ignorance of other physiological parameters such as autonomous nervous system activity and body motility. The original idea of the committee should be followed; the guidelines should be revised with the accumulation of new knowledge and development of technology. This is especially true for the analysis of delta waves, which should replace visual scoring of the NREM sleep stages. Many of the problems related to the use of the manual are not due to the system itself but the way it has been applied. This has evidently had a serious impact on the way of thinking and the development of the field in general.