Cardiorespiratory responses to bidirectional tilts in infants

Prior research in newborns has shown that head-up and head-down tilting eli cits sustained increases and decreases in heart rate, respectively. Other s tudies in older infants have suggested that the pattern of heart rate respo nses to head-up tilting varies with risk for sudden infant death syndrome ( SIDS). In this study, heart and respiratory rate changes following bidirect ional tilting were recorded in sleeping infants on Day 1 or 2 of life, and during the period of maximum risk for SIDS, at 2 and 4 months of age. Newbo rns show increases in heart rate following 30 degrees head-up tilts and dec reases in heart rate to 300 head-down tilting. Respiratory rates decreased to head-up tilting but did not change significantly to head-down tilting. W hile respiratory rate changes at 2 and 4 months of age are comparable to th ose of newborns, and decreases in heart rate to head-down tilting are simil ar across ages, sustained elevations in heart rate following head-up tiltin g are no longer apparent at the older ages. These results are consistent wi th the hypothesis that, during the period of maximum risk for SIDS, infants may have reduced ability to compensate for challenges that lead to decreas es in blood pressure. (C) 1999 Elsevier Science Ireland Ltd. All rights res erved.