ABSTRACT
Extravehicular activities (EVAs), better known as "spacewalks," involve exposures of individuals to the environmental conditions of space with a minimum of protective equipment. This environment includes many factors that threaten crew safety and health, such as thermal extremes, ionizing radiation, objects traveling at extraordinary relative velocities, and, of direct relevance to this book, extremely low ambient atmospheric pressures. This chapter focuses on the physiological consequences and limits of exposures to low ambient pressure, and the methods used to prevent violations of these physiological limits while still maintaining the capability for performing useful work. Additionally, because Earthbound training in water immersion facilities is an essential part of successful EVA programs, this aspect of space flight preparations will also be considered. Taken together, these environments represent ambient pressure extremes from near-vacuum to several atmospheres.
