Effect of prone sleeping on circulatory control in infants

Background-The mechanism of death in sudden infant death syndrome (SIDS) re mains unclear. Progressive bradycardia is the pre-eminent terminal event, s uggesting that circulatory failure might be a crucial factor. Vasomotor ton e regulates the circulatory system by controlling blood volume distribution while maintaining venous return and blood pressure. Aim-To examine whether prone sleeping, the most consistently identified ris k factor for SIDS, has a measurable influence on vasomotor/circulatory cont rol. Methods-44 full term infants (mean age, 7.9 weeks) were studied during an o vernight sleep. Recordings were made while the infants were horizontal and asleep in the supine and prone positions, and repeated after a head up tilt to 60 degrees, maintained for 30 minutes, while in both sleep positions. B lood pressure, heart rate, anterior shin, and anterior abdominal wall skin temperatures were measured. Results-Systolic blood pressure was lower, but peripheral skin temperature and heart rate were higher during sleep, while horizontal, in the prone rat her than the supine position. After tilting, there was a greater reduction in blood pressure and a greater increase in peripheral skin temperature and heart rate when in the prone position. Anterior abdominal wall skin temper ature did not vary in either sleeping positions while horizontal or tilted. Conclusion-Prone sleeping has a measurable effect on circulatory control, w ith a reduction in vasomotor tone resulting in peripheral vasodilatation, a higher peripheral skin temperature, a lower blood pressure, and a higher r esting heart rate. Because vasomotor tone is crucially important in circula tory control this could be a factor in increasing the risk of SIDS.