Space health requirements: the challenges.

This article explores the application of theoretical knowledge to clinical situations based on general systems theory and space health requirements to familiarize health care providers with requirements for the space environment. Preparation for extended periods of humans living in the space environment requires carefully planned delivery system that will promote and maintain health. Past, present, and future efforts for the establishment of'space health delivery systems are discussed. The National Aeronautics and Space Administration (NASA), Man-systems integration standards, NASA-STD-3000 Volume 1-MSIS, Revision B (1995, July), Houston, TX, National Aeronautics and Space Administration documents will be reviewed. Health care services will be supported by the available crew health care and emergency services systems. Providing health care in the extreme space environment with limited resources in which to carry out health practices offers challenges to health care providers.

Body volume changes during simulated microgravity: auditory changes, segmental fluid redistribution, and regional hemodynamics.

Space adaptation syndrome (SAS), manifested by cephalad fluid shifts, spacial disorientation, nausea, and vomiting, is of varied expression and uncertain etiology. One theory is that fluid shift to the upper body alters the function of the vestibular apparatus to create an entity similar to Meniere's disease. Since clinical vestibular dysfunction syndromes are mirrored by altered cochlear function, this experiment was undertaken to study the relation between fluid redistribution and the auditory effects of initial antiorthostatic bed rest. Manual and bone audiometry, impedance tympanometry, and brain-stem evoked potentials were used to monitor auditory changes prior to, during, and following short term exposure to -6 degrees head down tilt. Impedance plethysmography was performed to assess the segmental and intracranial fluid redistribution and hemodynamic changes during short-term head down tilt simulated microgravity. Even though significant cephalad fluid shift produced marked intracranial congestion and the subjects exhibited SAS symptoms, no clinically significant changes in the auditory system could be detected.

Sleep monitoring: the second manned Skylab mission.

The first objective measurements of man's ability to obtain adequate sleep during prolonged space flight were made during the three manned Skylab missions. EEG, EOG, and head-motion signals were acquired during sleep by use of an elastic recording cap containing sponge electrodes and an attached miniature preamplifier/accelerometer unit. A control-panel assembly, mounted in the sleep compartment, tested electrodes, preserved analog signals, and automatically analyzed data in real time (providing a telementered indication of sleep stage). One subject was studied during each manned mission and, while there was considerable variation among individuals, several characteristics were common to all three: stage 3 sleep increased during the flight and decreased in the postflight period; stage 4 was consistently decreased postflight, although this stage was variable during the flight; stage REM (rapid eye movement) was elevated, and REM latency decreased in the late postflight period (after day 3 postrecovery); and the number of awakenings during sleep either showed no change or decreased during the flight. In only the 28-d mission (Skylab 2) was there a significant decrease in total sleep time; in that case it was a result of voluntarily reduced rest time and was not due to difficulty in sleeping nor frequent awakening. The subject on the 84-d mission (Skylab 4) experienced more difficulty in the first half of the flight, showing a decreased total sleep time and increased sleep latency, but this resolved itself with time. Sleep latency presented no problem in the other flights. While many of the findings are statistically significant, in no case would they be expected to produce a noticeable decrement of performance capability. These findings suggest that men are able to obtain adequate sleep in regularly scheduled 8-h rest periods during extended space flights. It seems likely, based upon these results, that the problems encountered in earlier space flights did not arise from the zero-g environment per se but possibly were a result of more restricted living and working areas in the pre-Skylab spacecraft.

The Skylab sleep monitoring experiment: methodology and initial results.

The sleep monitoring experiment permitted an objective evaluation of sleep characteristics during the first two manned Skylab flights. Hardware located onboard the spacecraft accomplished data acquisition, analysis, and preservation, thereby permitting near-real-time evaluation of sleep during the flights and more detailed postmission analysis. The crewman studied during the 28-Day Mission showed some decrease in total sleep time an increase in the percentage of Stage 4 sleep, while the subject in the 59-Day Mission exhibited little change in total sleep time and a small decrease in Stage 4 and REM sleep. Some disruption of sleep characteristics was seen in the final days of both missions, and both subjects exhibited decreases in REM-onset latency in the immediate postflight period. The relatively minor changes seen were not of the type nor magnitude which might be expected to be associated with significant degradation of performance capability.