Integrative Study of Physiological Changes Induced by a 5-Day Dry Immersion on 20 Healthy Female Volunteers (DI5-Women)
Condition: Weightlessness; Weightlessness; Adverse Effect
Study type: Interventional

Summary: 
      Dry immersion (DI) is a ground-based model of prolonged conditions of simulated microgravity.
      Dry immersion involves immersing the subject in water covered with an elastic waterproof
      fabric. As a result, the immersed subject, who is freely suspended in the water mass, remains
      dry. Within a relatively short duration, the model can faithfully reproduce most
      physiological effects of actual microgravity, including centralization of body fluids,
      support unloading, and hypokinesia.

      The objective of the study is to evaluate the physiological changes induced by 5 days of dry
      immersion in the female organism. The main physiological systems will be explored before,
      during and after the 5 days of immersion through a battery of specific tests and
      measurements. The results will be analyzed by scientists specializing in each field in order
      to better understand the dry immersion model, to compare its effects with those of the
      bedrest model and those of spaceflight. The clinical (adverse effects, comfort of subjects)
      and operational aspects are also part of the secondary objectives of the study.
    

Detailed description: 
      The space agencies are actively engaged in studying the physiological adaptation to space
      environment through studies on board the International Space Station (ISS) but also on the
      ground. Ground-based experiments simulating the effects of weightlessness are used to better
      understand the mechanisms of physiological adaptation, design and validate the
      countermeasures. Dry immersion (DI) is a ground-based model of prolonged conditions of
      simulated microgravity, which has been mainly used in Russia. The past years however, the
      model has been implemented as well in Europe and expertise in conducting DI studies has been
      gained in particular in France where a few DI studies have been conducted in the MEDES Space
      Clinic in Toulouse for CNES (French Space Agency). Dry immersion involves immersing the
      subject in water covered with an elastic waterproof fabric. As a result, the immersed
      subject, who is freely suspended in the water mass, remains dry. Within a relatively short
      duration, the model can faithfully reproduce most physiological effects of actual
      microgravity, including centralization of body fluids, support unloading, and hypokinesia.
      Furthermore, physiological changes have been reported in the neuromuscular, skeletal and
      sensorimotor systems, in fluid electrolyte regulation, in the cardiovascular system,
      metabolism, blood and immunity, respiration, and thermoregulation. Dry immersion provides a
      unique opportunity to study the physiological effects of the lack of a supporting structure
      for the body (a phenomenon called 'supportlessness'). As such, dry immersion is proposed to
      mimic actual spaceflight in terms of the monotonous environment, posture-motion limitations,
      hemodynamic changes and hypokinetic effects, support unloading, and decreased proprioceptive
      input. Immersion studies have so far only been conducted in men and a minority of studies
      using the bedrest model have included women. Likewise, few studies conducted to date have
      investigated gender differences in the astronaut population. The small number of female
      astronauts may be part of the reason why scientific data are lacking to draw valid
      conclusions about possible gender differences. However, if women currently constitute only
      about 10% of astronauts, women are and will be more and more represented in crews. Women now
      constitute 30% of American crews and NASA (US space agency) has announced gender parity for
      crews on future lunar missions. It is therefore essential to study the physiological changes
      induced by weightlessness in women, to compare them with those observed in men and to develop
      efficient countermeasures for preventing them. The main physiological systems will be
      explored before, during and after the 5 days of immersion through a battery of specific
      standardized tests and measurements. The objective of the study is to evaluate the
      physiological changes induced by 5 days of dry immersion in the female organism. The study
      conditions such as patient recruitment, nutrition, data collection, data management,
      reporting for adverse events are standardized. The results will be analyzed by scientists
      specializing in each field in order to better understand the dry immersion model, to compare
      its effects with those of the bedrest model and those of spaceflight. The clinical (adverse
      effects, comfort of subjects) and operational aspects are also part of the secondary
      objectives of the study.

      Twenty healthy female subjects will participate in the study. There is no published data on
      dry immersion with female participation to help calculation the sample size. Moreover, female
      spaceflight and bedrest data are scarce, and do not provide any insight into inter-individual
      variability. This prolonged DI protocol in women is conceived as a pilot, descriptive,
      explorative study, as well as an operational and methodological study. Power-based
      calculation of the number of subjects is not directly applicable for such explorative
      studies. However, based on effect sizes obtained with previous DI studies in men, a total of
      20 subjects was deemed necessary for this study.
    

Intervention name(s): Dry immersion
Intervention type(s): Other
Intervention description(s): Subjects are immersed up to the neck for 5 days in a specially designed bath filled with tap water.
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Simulated Microgravity; Weightlessness; Dry immersion; Supportlessness