Primate body temperature and sleep responses to lower body positive pressure

Cephalic fluid shifts, induced by lower body positive pressure (LBPP) are known to influence various physiological systems (i.e. cardiovascular and renal). In earlier experiments, we observed an apparent change in the arousal state of primates in such LBPP conditions. This study was designed to examine the effects of LBPP on arousal state and body temperature level which is normally correlated with sleep. Chair restrained male squirrel monkeys were exposed to 40 mmHg LBPP for 90-100 minutes between the daytime hours of 13:00-15:00. Each monkey was placed in a specially modified restraint chair to which they were highly restrained [correction of trained]. Deep body temperature (DBT) was collected from 10 animals. Sleep parameters were obtained from 6 animals chronically implanted for sleep recording. A video camera was used to observe each animal's apparent state of arousal. LBPP resulted in an approximate 0.9 degree C decrease in DBT. During video observation some animals appeared drowsy during LBPP, however, sleep recording revealed no significant changes in the state of arousal. Thus, LBPP is capable of inducing a mild hypothermia [correction of hyperthermia]. Further, the mechanisms underlying the observed lowering of body temperature appear to be independent of arousal state.