1. Kotelnikov Institute of Radioengineering and Electronics of Russian Academy of Sciences, Saratov Branch, Zelyonaya Street, 38, Saratov 410019, Russia
2. Institute of Physics, Saratov State University, Astrakhanskaya Street, 83, Saratov 410012, Russia
3. Institute of Cardiological Research, Saratov State Medical University, B. Kazachaya Street, 112, Saratov 410012, Russia
4. National Medical Research Center for Therapy and Preventive Medicine, Petroverigsky Lane, 10, Moscow 101000, Russia
5. Interdisciplinary Sleep Medicine Center, Charité—Universitätsmedizin, Charitéplatz 1, Berlin 10117, Germany