Healthy
Conditions
Keywords
Autonomic nervous system, Immersion, Heart rate variability, Head-down tilt, Healthy volunteers
Brief summary
Head down tilt (HDT) was widely used to simulate microgravity effects on cardiovascular system. HDT could be a suitable model of water immersion (WI) which is also used to simulate the cardiovascular effects of microgravity and which is not easy to study in laboratory. To define the possibility to simulate immersion by HDT, a comparison between these models is required. A comparison between WI and few angles during HDT seems necessary to understand which angle is more adapt. The immersion induces an increase of the central blood volume. This increase is caused by a redistribution of blood from peripheral portions of the body to the intrathoracic circulation. It seems to load cardiopulmonary and arterial baroreceptors. These baroreceptors bring into play autonomic nervous system (ANS) activation and induce a bradycardia. HDT induces an increase in central blood volume as supported by the central venous pressure and cardiac volume increase and in return, MSNA and heart rate decrease. These cardiovascular effects seem to be the same as the thermoneutral immersion and suggest that the ANS activation is the same during HDT and WI. Nevertheless, a few previous studies about ANS in HDT indicate some discordant results: a sympathetic decrease was reported but several results show an increase of parasympathetic activity linked with a trend of increase of arterial baroreflex. The aim of this study is to assess ANS activity in HDT on different angles (-6° and -15°) and WI. The investigators suppose an increase of parasympathetic activity during WI corresponding to parasympathetic activation during HDT especially at -6°.
Interventions
OTHERHead-down tilt and immersion
Head-down tilt -6° at inclusion, head-down tilt -15° at week one and Water Immersion at week two
Sponsors
Ministry of Health, France
Centre Hospitalier Universitaire de Saint Etienne
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
BASIC_SCIENCE
Masking
NONE
Eligibility
Sex/Gender
MALE
Age
18 Years to 40 Years
Healthy volunteers
Yes
Inclusion criteria
* Sportsman * None coffee, alcohol, cigarettes 6 hours before the start of each visit * Each meal must have been taken 4 hours before each visit * No intensive sport 48 hours before ech visit * Written inform consent
Exclusion criteria
* Subject with cardiovascular,renal disease or with metabolic syndrome * Subject with medication * Subject who participated to an other medical research
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| heart rate variability | inclusion, one week, two weeks |
Secondary
| Measure | Time frame |
|---|---|
| Upper limbs vascular resistance | inclusion, one week, two weeks |
| post ischemic forearm hyperemia | inclusion, one week, two weeks |
| Hematocrit rate | Inclusion, one week, two weeks |
| Pulmonary diffusion | inclusion, one week, two weeks |
| Blood pressure variability | inclusion, one week, two weeks |
| Spontaneous baroreflex activity | inclusion, one week, two weeks |
| Cardiac haemodynamic | Inclusion, one week, two weeks |
Countries
France
Outcome results
None listed