ADAPTIVE RESPONSES OF THE CARDIOVASCULAR-SYSTEM TO PROLONGED SPACEFLIGHT CONDITIONS - ASSESSMENT WITH HOLTER MONITORING

This article presents selected findings obtained with Holter monitorin g from two crew members of the expedition, performed during a 175-day space mission on board orbital space station ''MIR.'' Using mathematic al processing of daily cardiointervals files, 5-minute sections of rec ords were analyzed consecutively. Then, the average daily values of in dices, the average-per-every-eight-hours values (morning, evening, nig ht) and mean values per hour were computed. The results of analysis sh owed that prolonged exposure of man to microgravity conditions leads t o important functional alteration in human neuroautonomic regulatory m echanisms. Both crew members had significant increase of heart rate, t he rise of stress index, the decrease in power of the spectrum in the range of respiratory sinus arrhythmia. These marked signs of activatio n of the sympathetic section of the vegetative nervous system showed i ndividual variations. The analysis of the daily collection of cardioin tervals with Holter monitoring allows us to understand and forecast th e functional feasibilities of the human organism under a variety of st ress conditions associated with acute and chronic microgravity exposur e.