8. Functional Neurological Assessment
   During spaceflight astronauts often experience motion sickness and problems with orientation. When they return to Earth, astronauts may experience problems with balance, orientation, standing, and walking. These changes may have a significant effect on astronauts during landing and extravehicular activity. These problems are called sensorimotor disturbances. Results from short-duration Shuttle missions indicated the initial astronaut performance decrement can be moderate to severe, and recovery of normal function requires 2 to 4 days after return. For longer-duration crew members, the time course of recovery has not been fully characterized; however, preliminary results from Mir station cosmonauts and ISS crew members suggest that the initial degradation of balance control is more severe than for Shuttle astronauts, and that recovery of normal function requires far longer after return.

   The purpose of the Functional Neurological Assessment is to monitor critical aspects of degradation and recovery of sensorimotor control following spaceflight and bed rest. Sensory-motor changes are performed with the Equitest computerized dynamic posturography system widely used for clinical assessment of balance disorders. One of the goals for NASA is to develop and test countermeasures that involve neurologic training and can be used before or after flight. Such countermeasures would enable astronauts to adjust more rapidly to weightlessness, to other gravitational environments and upon return to Earth. Results from these studies provide basic knowledge relating to balance disorders affecting more than 90 million Americans.

9. Cardiovascular Assessment
   Significant cardiovascular changes are associated with spaceflight and have shown:
   • Disturbances in cardiac rhythm
   • Postflight faintness upon standing, because of drop in blood pressure (orthostatic intolerance)
   • Reduced exercise tolerance
   • Reduced circulating blood volume
   • Changes in vascular function
   • Greater susceptibility to orthostatic intolerance in women than men
   Testing during the bed rest campaigns includes tilt tests, heart rate, arterial pressure, cardiac rhythm, cardiac function (ultrasound), blood volume, neuroendocrine levels, orthostatic intolerance, and changes in blood volume. Vascular function in the brachial and anterior tibial arteries is assessed. Echocardiography provides views of the heart and images of all valves and chambers. Calculations of systolic function include ejection fraction, stroke volume, velocity of circumferential shortening and left ventricular mass.

   The goal of these cardiovascular Standard Measures is to assess cardiovascular function in response to bed rest. These responses are compared to those following spaceflight so that the value of bed rest as a model for cardiovascular effects of spaceflight may be determined. Once a bed rest model is established, the effectiveness of specific countermeasures in preventing the negative effects of spaceflight may be determined.

10. Immune Function Assessments
    One of the critical risks identified by NASA to astronauts during long-duration spaceflight is the effect on the astronaut's immune system. Spaceflight factors that have an effect on the immune system include isolation, microgravity and radiation exposure. The increased radiation exposure is of particular concern to NASA due to the development of pre-malignant or malignant diseases. Data from previous spaceflight studies have shown evidence that the human immune system is compromised during spaceflight.

    Another area of interest is the potential development of disease conditions where the human immune system is compromised, such as with stress, infection, and chronic virus infections resulting from reactivation of latent viruses

    Image right: Sample analyzer with computer for data analysis.

    During bed rest campaigns, the immunology team conducted research to:
    • Assess stress levels using measures of biochemical and psychologic stress
    • Determine immune status or virus-specific T-lymphocyte immunocompetence
    The knowledge gained on bed rest is critical to the ongoing assessment of crew health issues during flight. These data provide future rationale to develop specific immunomodulatory therapies to minimize/eliminate the increased risk to crew members.

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