Determining critical values of calculated parameters within a physiologic model

To determine the critical value of calculated but not readily measurable variables of a physiologic model, we examine clinical studies of similar variables and establish the critical values. The calculated variables considered in this study are the partial pressure of oxygen in the myocardium and in the gray matter of the brain. Partial pressure target values of 29 mmHg for cerebral tissue and 23 mmHg for myocardial tissue were determined to be suitable for a critical threshold. We validated these with a physiologic model test by ensuring that these corresponded to a reasonable value of cardiac output, vital sign commonly used to evaluate patient well being. These values can be used for future analysis of physiologic monitors´ alarm systems when using physiologic models.