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

Not Applicable

Completed

• Conditions: Healthy
• Interventions: Other: Head-down tilt and immersion

• Registration Number: NCT00515645
• Lead Sponsor: Centre Hospitalier Universitaire de Saint Etienne

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°.

Detailed Description

Not available

Study Timeline

• Study First Submitted: 2007-08-13
• Study First Submitted QC: 2007-08-13
• Study First Posted: 2007-08-14
• Study Start: 2008-04
• Primary Completion: 2011-07
• Study Completion: 2011-07
• Status Verified: 2020-05
• Last Update Submitted: 2020-05-07
• Last Update Posted: 2020-05-11

Recruitment & Eligibility

• Status: COMPLETED
• Sex: Male
• Target Recruitment: 15

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

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: SINGLE_GROUP

Arm && Interventions

Group	Intervention	Description
1	Head-down tilt and immersion	-

Primary Outcome Measures

Name	Time	Method
heart rate variability	inclusion, one week, two weeks

Secondary Outcome Measures

Name	Time	Method
Blood pressure variability	inclusion, one week, two weeks
Spontaneous baroreflex activity	inclusion, one week, two weeks
Pulmonary diffusion	inclusion, one week, two weeks
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
Cardiac haemodynamic	Inclusion, one week, two weeks

Trial Locations

Locations (1)

Centre Hospitalier de Saint-Etienne; 🇫🇷 Saint-Etienne, France