A.V. Demin – Research Scientist, Laboratory of Cardiorespiratory System Physiology and Baromedicine, State Research Center RF – Institute of Biomedical Problems of RAS (Moscow)  E-mail: a_demin2005@mail.ru

Yu.A. Popova – Ph.D. (Med.), Leading Research Scientist, Laboratory of Cardiorespiratory System Physiology and Baromedicine, State Research Center RF – Institute of Biomedical Problems of RAS (Moscow) E-mail: julija.popova@gmail.com

A.V. Suvorov – Dr. Sc. (Med.), Corresponding Member of Tsiolkovsky Russian Academy of Cosmonautics, 

Head of the Department of Physiology and Biomechanics of Cardiorespiratory System in Extreme Conditions,

State Research Center RF – Institute of Biomedical Problems of RAS (Moscow),

E-mail: suvalex@inbox.ru

Statement of the problem. To control and evaluate recovery during sleep in cosmonauts, it is important to use an affordable method for quantifying sleep quality, based on measuring a small number of physiological parameters.

Aim of the work – to quantify the individual restorative properties of sleep in healthy people when modeling the effects of microgravity (on the model of «dry» immersion).

Research tasks: comparison of the average values of the Kerdo’s autonomous index (KAI) during sleep under normal conditions and on the 5th day of «dry» immersion; search for analytical expressions of changes in KAI depending on sleep duration in the conditions of «dry» immersion; determination of maxima and minima of recovery during sleep of healthy volunteers; development of a method for individual assessment of recovery during sleep based on the dependence of KAI on the duration of sleep, and estimation of this method of sleep restoration in healthy volunteers on the 5th day of stay in «dry» immersion.

Results. A study of the recovery of the human body during sleep, based on an analysis of the time series of KAIs at night, was conducted in five practically healthy men. For the study, the portable somnological device SomnoWatch (SomnoMedics, Germany) was used, which allows recording ECG, systolic and diastolic blood pressure for each heart cycle, and heart rate. The study of KAI during the night sleep of each volunteer was carried out twice: under normal sleep conditions (under controlled laboratory conditions, control) and on the 5th night of stay in an immersion bath. The duration of sleep was established on the basis of diary entries and visual observation of the testers. The value of blood pressure for each heart cycle was automatically calculated using a mathematical algorithm for the speed of the pulse wave propagation from the heart to the finger of the hand based on measuring the time of the R-waves of the ECG and the time of their corresponding peaks of the photoplethysmogram, individual anthropometric data of volunteers and calibration measurements of blood pressure using an oscillometric tonometer. KAI was calculated by measuring heart rate and diastolic blood pressure without taking into account the uninformative factor of 100%. The time series of the KAI measurements were approximated by polynomials, then the areas between the curves and the abscissa were calculated, and then the areas obtained under different sleep conditions were compared. Sleep recovery was considered the better, the larger the area above the curve obtained as a result of integration. Practical significance. It was found that the recovery of the body during night sleep in all volunteers in the conditions of «dry» immersion decreased compared to normal conditions. The studies and their analysis allow us to recommend a new method based on the measurement of two cardiological parameters and the calculation of the integrated characteristics of the KAI to quantify the body's recovery during physiological sleep, in particular when in extreme conditions.

Demin A.V., Popova Yu.A., Suvorov A.V. Quantitative assessment of a body recovery during sleeping healthy men under «dry» immersion conditions. Technologies of living systems. 2020. V. 17. № 2. P. 46 - DOI: 10.18127/j20700997-202002-05 (In Russian)

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