The intensive care unit (ICU) and the operating room are two of the clinical environments in which the use of computer systems is becoming a necessity. The authors discuss some of the particular aspects of: classical monitoring systems and ICU expert systems. A semantic-based method is proposed for the management and interpretation of clinical measurements in the ICU. This approach allows the user to define the major characteristics of the clinical use under consideration. These characteristics are used to elaborate specific ranges that take into account the differential characteristics of the clinical case under consideration. Those patient-adapted ranges will serve to perform the symbolic processing of the numerical data. The resulting literals will be used by the inferential engine to obtain conclusions and define therapeutic guidelines. Since the inferential process is based on the meaning of the numerical information the knowledge engineering task is considerably simplified.