Heart Rate as an Index of Neuroendocrine Compensation During Space Flight

Abstract : Heart rate is one of the simplest indices to record during space flight. Discovery of a significant sinusoidal arrhythmia in the first cosmonauts during weightlessness gave impetus to the development of mathematical and cybernetic heart rate analysis techniques. An algorithm facilitating automatic physiological control of the cosmonauts has been devised based on heart rhythm. The report presents data on variations in a series of mathematical and statistical indices of cardiac rhythm related to neutroendocrine regulation. Cardiac rhythm is viewed from the point of view of the theory concerning random functions in the form of a series of 100-150 values for cardiac cycle duration. Each of the values is a single manifestation of a random process which may be wholely characterized by a distributive function, by a histogram (variational pulsometry), by an autocorrelational function, or by a spectral function.