Predominant symptoms of the syndrome are headache, depressed appetite, general malaise, lethargy, gastrointestinal discomfort, nausea, and vomiting. As in other forms of motion sickness, the syndrome may reduce self motivation and result in decreased ability to perform demanding tasks. The syndrome is self-limiting. Complete recovery from major symptomatology, or, in other words, adaptation to the space flight environment, occurs within two to four days. After complete adaptation occurs, crewmembers appear to be immune to the development of further symptomatology.
Because of the complexity and uniqueness of this biomedical problem, the researchers considered it essential that data be collected systematically on individuals who fly shuttle missions. Therefore, this experiment was developed to collect data on the first four Shuttle missions, with a primary purpose of conducting inflight observations supported by a series of preflight/postflight tests. The objectives of this study were to develop a set of predictors of SMS and countermeasures by determining whether ground-based tests that can cause motion sickness on Earth can predict susceptibility to SMS.
Three different laboratory test procedures were used to provide a ground-based data point against which in-flight susceptibility could be compared.
For the first nine Shuttle missions, which involved 29 different crewmembers, a standard Coriolis Sickness Susceptibility Index test (CSSI), was used. This procedure, which stimulates primarily the semicircular canals, requires the performance of head movements while rotating at a constant velocity in a servo-controlled chair. Prior to the start of the test, the crewmember was instructed on how to report his or her symptoms of motion sickness to an observer who was skilled in the recognition of signs and symptoms of motion sickness. The signs and symptoms were recorded and scored accordingly. The test was terminated when the blindfolded crewmember reached the Malaise III level of motion sickness or performed 150 head movements, whichever occurred first. The higher the score, the longer the subject continued the test, indicating a greater resistance to motion sickness. A majority of the crewmembers on the first nine Shuttle missions were tested at least one additional time with the CSSI procedure in order to evaluate the efficacy of an anti-motion sickness medication. The medication most frequently evaluated was oral scopolamine (.4 mg) plus dexedrine (5 mg).
The second motion sickness susceptibility procedure used was a modified version of an off-vertical rotation or OVR. The OVR produces a rotating linear acceleration and is essentially an otolith stimulus. During this procedure crewmembers were blindfolded and restrained in the rotating chair with lap, shoulder and leg straps. The head was also restrained. While in the vertical position the chair was accelerated to a velocity of 20 rpm and rotated for 5 minutes. Following stabilization of 0° tilt the angle of tilt of the chair was increased in 5° increments at 5 minute intervals until the crewmember reached the Malaise III levels of symptoms or the chair had been maintained at a 30° tilt for 5 minutes. The OVR test was performed on 29 individual astronauts most of whom flew subsequent to the ninth Shuttle flight.
The third procedure used was a modified version of an eyes open sudden-stop test. This test assessed susceptibility to a vestibulo-visual interaction stimulus. Visual stimulation was provided by a stationary optokinetic field which surrounded the chair in which the crewmember was restrained. The chair was accelerated to a velocity of 50 rpm and held at that velocity for 30 seconds. The chair was then decelerated at 150°/sec to a complete stop and maintained at zero velocity for 30 seconds, after which the sequence was repeated for a total of 20 clockwise and 20 counterclockwise stops or until the Malaise III level of symptoms was reached, whichever occurred first. Data were collected on only six crewmembers with this procedure.
In-flight data collection was limited to the use of a microcassette tape recorder and a motion sickness symptom checklist. The checklist allowed comparisons between the pattern of symptoms that occurred during the preflight tests and those that occurred in-flight. The checklist also required crewmembers to report on preventative measures used such as anti-motion sickness drugs and voluntary restriction of head and body movements. Each crewmember was required to use the recorder and checklist each mission day to report any symptoms or sensations that had been experienced during that day.
Questions pertaining to SMS, vestibular sensations, and performance were also asked of each crewmember on the day of landing and during postflight medical debriefings. Both the in-flight and postflight crew debriefing data were used to categorize crewmembers as susceptible or non-susceptible to SMS. Those who were defined as being susceptible were further classified into mild, moderate, and severe subgroups for subsequent data analysis.
There is a striking difference in the pattern of symptomatology generated in flight versus during the ground-based tests. Subjective warmth, sweating, and pallor, which were dominant ground-based test symptoms, were almost nonexistent inflight. In contrast, vomiting, anorexia, headache, malaise and lethargy were dominant in-flight symptoms.
The specific nature and time course of in-flight symptomatology tends to be highly variable. Some crewmembers reported that symptoms appeared within the first one to two hours of the mission. Others did not become aware of symptoms until the second day of flight. In general, however, symptoms began during the first day of flight, plateau between 24-48 hours and gradually diminished between approximately 48-96 hours. During this time the symptoms usually waxed and waned in severity. Unquestionably, head and body movements exacerbated the symptomatology.
Anti-motion sickness and/or anti-emetic medication was used by 40 of the 65 crewmembers included in this study. The oral scopolamine plus dexedrine combination was the most frequently used with 25 crewmembers taking one or more doses during the first few days of flight. Oral metoclopramide was used by 18 crewmembers in an effort to restore gastric motility and alleviate nausea and vomiting. Of the 31 crewmembers that experienced symptoms, 29 used medication during the course of their symptomatology.
The preflight questionnaire results did not correlate with the reported incidence of SMS. Differences between susceptible and non-susceptible crewmembers in results for each of the preflight tests were not significant, nor were correlations between susceptibility to motion sickness in the ground-based tests and susceptibility to SMS.
The results indicated that the use of a single ground-based parameter or test procedure is inadequate for predicting SMS susceptibility and that a composite index, which requires a larger number of cases, would be needed. Despite an inability to identify ground-based predictors of SMS susceptibility, one reasonably accurate predictor was identified, and that is space flight itself. Of 16 crewmembers who had flown two or more space missions, the response pattern of only 3 changed from one flight to the next.
Information archived for this experiment was provided by the William E.Thornton collection.
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