Cardiac Autonomic Functions During Head-out Immersion and During Head Down Tilt

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

COMPLETED

Clinical Phase

NA

Total Enrollment

15 participants

Study Classification

INTERVENTIONAL

Study Start Date

2008-04-30

Study Completion Date

2011-07-31

Brief Summary

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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°.

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Detailed Description

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Conditions

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Healthy

Study Design

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Allocation Method

NA

Intervention Model

SINGLE_GROUP

Primary Study Purpose

BASIC_SCIENCE

Blinding Strategy

NONE

Study Groups

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1

Group Type EXPERIMENTAL

Head-down tilt and immersion

Intervention Type OTHER

Head-down tilt -6° at inclusion, head-down tilt -15° at week one and Water Immersion at week two

Interventions

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Head-down tilt and immersion

Head-down tilt -6° at inclusion, head-down tilt -15° at week one and Water Immersion at week two

Intervention Type OTHER

Eligibility Criteria

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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

Minimum Eligible Age

18 Years

Maximum Eligible Age

40 Years

Eligible Sex

MALE

Accepts Healthy Volunteers

Yes