The behaviour of a set of statistical and dynamical characteristics, used in chaotic dynamics, is analysed as it applies to the electrocardiograms of human under the influence of different types of stress.  
A new quantitative electrocardiogram characteristic is introduced as a distribution entropy, normalized by the signal variance. A perspective of this parametre application as a diagnostic criterion is proved by series of test experiments. By comparison with traditional medico—biological characteristics the higher sensitivity and stability of this criterion is proved. A number of test experiments has been conducted that confirm the validity of the above two conclusions and prove the applicability of the proposed method under the conditions of stress influence varied over a wide range. The stability of the proposed method in respect is proved. 
On the basis of this method, a special diagnostic instrument for analysis and топ initoring of the being of a living organism can be developed. To measure the above parametres no sophisticated instrumentation, nor preliminary surgical intervention is required.