Compliance with ethical standards: the study was approved by the Local Ethics Committee of Pirogov Russian National Research University (protocol No. 159 as of November 21, 2016) and done within a research project (Research and Technology State Registration Number НИОКТР АААА-А19-119021890068-7 as of February 18, 2019). It did not expose participants to danger and corresponded to requirements of biomedical ethics.