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

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°.

Study Overview

• Status: Completed
• Conditions: Healthy
• Intervention / Treatment: Other: Head-down tilt and immersion

• Study Type: Interventional
• Enrollment (Actual): 15
• Phase: Not Applicable

Contacts and Locations

Study Locations

• France
  • Saint-Etienne, France, 42055
    • CENTRE HOSPITALIER DE SAINT-ETIENNE

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 40 years (ADULT)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: Male

Description

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 Plan

How is the study designed?

Design Details

• Primary Purpose: BASIC_SCIENCE
• Allocation: NA
• Interventional Model: SINGLE_GROUP
• Masking: NONE

Number of Arms

1

Arms and Interventions

Participant Group / 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

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
heart rate variability	inclusion, one week, two weeks

Secondary Outcome Measures

Outcome Measure	Time Frame
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

Collaborators and Investigators

• Sponsor: Centre Hospitalier Universitaire de Saint Etienne
• Collaborators: Ministry of Health, France
• Investigators: Principal Investigator: Frédéric Roche, MD PhD, CENTRE HOSPITALIER DE SAINT-ETIENNE

Publications and helpful links

General Publications

• Gabrielsen A, Johansen LB, Norsk P. Central cardiovascular pressures during graded water immersion in humans. J Appl Physiol (1985). 1993 Aug;75(2):581-5. doi: 10.1152/jappl.1993.75.2.581.
• Shiraishi M, Schou M, Gybel M, Christensen NJ, Norsk P. Comparison of acute cardiovascular responses to water immersion and head-down tilt in humans. J Appl Physiol (1985). 2002 Jan;92(1):264-8. doi: 10.1152/jappl.2002.92.1.264.
• Ueno LM, Miyachi M, Matsui T, Takahashi K, Yamazaki K, Hayashi K, Onodera S, Moritani T. Effect of aging on carotid artery stiffness and baroreflex sensitivity during head-out water immersion in man. Braz J Med Biol Res. 2005 Apr;38(4):629-37. doi: 10.1590/s0100-879x2005000400018. Epub 2005 Apr 13.

Study record dates

Study Major Dates

• Study Start: April 1, 2008
• Primary Completion (ACTUAL): July 1, 2011
• Study Completion (ACTUAL): July 1, 2011

Study Registration Dates

• First Submitted: August 13, 2007
• First Submitted That Met QC Criteria: August 13, 2007
• First Posted (ESTIMATE): August 14, 2007

Study Record Updates

• Last Update Posted (ACTUAL): May 11, 2020
• Last Update Submitted That Met QC Criteria: May 7, 2020
• Last Verified: May 1, 2020

More Information

Terms related to this study

• Keywords: Healthy volunteers; Autonomic nervous system; Heart rate variability; Immersion; Head-down tilt
• Other Study ID Numbers: 0708061; 2007-A00727-46 (OTHER: AFSSAPS)