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Cardiac Autonomic Functions During Head-out Immersion and During Head Down Tilt (IMMERSION)

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ClinicalTrials.gov Identifier: NCT00515645
Recruitment Status : Completed
First Posted : August 14, 2007
Last Update Posted : July 19, 2011
Information provided by:

Study Description
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°.

Condition or disease Intervention/treatment
Healthy Other: Head-down tilt and immersion

Study Design

Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 15 participants
Allocation: Non-Randomized
Intervention Model: Single Group Assignment
Masking: None (Open Label)
Primary Purpose: Basic Science
Official Title: Cardiac Autonomic Functions During Head-out Immersion and During Head Down Tilt
Study Start Date : April 2008
Primary Completion Date : July 2011
Study Completion Date : July 2011
Arms and Interventions

Arm Intervention/treatment
Experimental: 1 Other: Head-down tilt and immersion
Head-down tilt -6° at inclusion, head-down tilt -15° at week one and Water Immersion at week two

Outcome Measures

Primary Outcome Measures :
  1. heart rate variability [ Time Frame: inclusion, one week, two weeks ]

Secondary Outcome Measures :
  1. Blood pressure variability [ Time Frame: inclusion, one week, two weeks ]
  2. Spontaneous baroreflex activity [ Time Frame: inclusion, one week, two weeks ]
  3. Pulmonary diffusion [ Time Frame: inclusion, one week, two weeks ]
  4. Upper limbs vascular resistance [ Time Frame: inclusion, one week, two weeks ]
  5. post ischemic forearm hyperemia [ Time Frame: inclusion, one week, two weeks ]
  6. Hematocrit rate [ Time Frame: Inclusion, one week, two weeks ]
  7. Cardiac haemodynamic [ Time Frame: Inclusion, one week, two weeks ]

Eligibility Criteria

Information from the National Library of Medicine

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Ages Eligible for Study:   18 Years to 40 Years   (Adult)
Sexes Eligible for Study:   Male
Accepts 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
Contacts and Locations

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT00515645

Centre Hospitalier de Saint-Etienne
Saint-Etienne, France, 42055
Sponsors and Collaborators
Centre Hospitalier Universitaire de Saint Etienne
Ministry of Health, France
Principal Investigator: Frédéric Roche, MD PhD Centre Hospitalier de Saint-Etienne