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Effects of negative inclination of the head on intracranial pressure and cardiovascular control in healthy individuals: perspectives for spatial travels

Description: Increased intracranial pressure (ICP) in microgravity environment may reduce brain compliance and impair compensatory brain mechanisms, causing decreased cerebral blood flow (CBF). Thus, brain functions may be affected, making this phenomenon worrisome to astronauts, especially in interplanetary and long-duration missions. The ICP elevation is usually due to fluid displacement from the lower limbs and trunk to the head. Changes in hemodynamic control can also be observed as increased sympathetic autonomic nervous system activity, perpetuating this cycle of elevated ICP and decreased brain functions. The gold standard for measuring ICP is an invasive method, but this method has important disadvantages, and therefore, non-invasive measurement devices have been developed and studied. Objective: to investigate hemodynamic effects in a microgravity model (head-down tilt); characterize the immediate changes in the ICP waveform morphology during and after the test; to relate these changes to the autonomic nervous system behavior through the evaluation of heart rate variability (HRV) and baroreflex sensitivity (BRS). Methodology: a cross-sectional study with 50 healthy and active individuals, determined by biochemical tests, questionnaires, body composition, clinical examination and cardiopulmonary exercise test (CPET). Five meetings will be held: the first to clarify the nature of the project, to complete the sociodemographic questionnaire and the consent term. In the second one, a blood test will be done, and on the third day, the dual-energy X-ray absorptiometry (DXA) and CPET will be done. On the other days, the ICP and ANS function will be evaluated by the HRV and BRS before, during and after the head-down tilt test, which will consist of the subject inclination on the tilt table by -6 ° and -15 °. Statistics: Tests of normality (Kolmogorov-Smirnov) and homogeneity (Levene) will be applied. To verify the relationship between the postures and the ICP and cardiovascular variables, the ANOVA tests of repeated measures or Friedman will be performed, for parametric or non-parametric cases, respectively. For all analyzes, will be considered a significance level of 5% and a confidence interval of 95%. (AU)

Funder: Fundação de Amparo à Pesquisa do Estado de São Paulo

Funding type: grant

Funder scheme: Auxílio à Pesquisa - Regular

Start date: 2020-05-01

End date: 2023-02-28

Investigator: Thiago Luiz de Russo

Institution: Universidade Federal de São Carlos (UFSCAR). Centro de Ciências Biológicas e da Saúde (CCBS)

Topic: Spaceflight effects on biology

Subfield: Physiology

Field: Medicine

Domain: Health Sciences

Funded outputs count: 2