The Effects of Deuterium on Static Posture Control

A significant operational problem impacting upon the Space Shuttle program involves the astronaut's ability to safely egress from the Orbiter during an emergency situation. Following space flight, astronauts display significant movement problems. One variable which may contribute to increased movement ataxia is deuterium (D^O), an isotope of hydrogen/ Deuterium is present in low levels within the Orbiter's water supply but may accumulate to significant physiological levels during lengthy missions. Deuterium has-been linked to a number of negative physiological responses, including motion sickness, decreased metabolism and slowing of neural conduction velocity. The purpose of-the present study was to investigate the effects of D0 on static postural control in response to a range of dosage levels?\ Nine subjects were divided into three groups of three subjects each. The groups were divided in to a low, (50 g/70 Kg body water), medium (100 g/70 Kg body water), and a high (200 g/70 Kg body water) D0 dosage group. The subjects static posture was assessed with the use of the EquiTest system, a commercially available postural control evaluation system featuring movable force plates and a visual surround that can be servoed to the subject's sway. In addition to the force plate information, data about the degree of subject sway about the hips and shoulders was obtained. Additionally, surface electromyographic (EMG) data from the selected lower limb muscles was collected along with saliva samples used to determine the amount of deuterium enrichment following Do ingestion. Two baseline testing sessions were performed using the EquiTest testing protocol prior to ingestion of the D2Q. Thirty minutes after dosing, subjects again performed the test. Two more post-dosing tests were run with an intertest interval of one hour. Preliminary data analysis indicates that only subjects in the high dose group displayed any significant static postural problems. Future analyses of the sway and EMG is expected to reveal significant variations in the subjects's postural control strategy following D0 dosing. While functionally significant static postural problems were not commonly observed, subjects in both the medium and high dosage groups displayed significant, and in some cases, severe voluntary movement problems. These problems included locomotion and hand-eye coordination deficits.