The circulation in sleep in newborn lambs.

Abstract

Interaction of the cardiovascular, homeothermic and behavioural systems has particular significance in early life as this period of development sees high cardiac output, limited circulatory reserves, a particular vulnerability to thermal stress, and long periods of rapid eye movement (REM) sleep during which thermal regulation may be suspended. In unstressed lambs, significant cardiovascular differences exist between behavioural states of sleep and wakefulness, with the REM sleep-state being outstanding. In REM sleep there is wide cardiac output variation, a low heart rate, and a high stroke volume. High levels of cardiac output occurring in combination with poorer oxygenation and respiratio..