Estimating activity from heart rate in preterm infants

ESTIMATING ACTIVITY FROM HEART RATE IN PRETERM INFANTS R. Woodson Since heart rate and motor activity are each related to energy expenditure they should be related to one another. To determine whether their relationship is sufficiently strong to provide a prediction of motor activity from heart rate, 24 medically stable preterm infants were observed for two half hour periods during which their heart beats were counted. Average activity and heart rate values were calculated for comparison periods of five to 30 minutes' duration. Regardless of the duration of the comparison periods, the difference in heart rate between periods correlated positively and significantly with the concomitant difference in the infant's motor activity. When adjacent half hour periods were compared, eighty-five percent of the variation in activity could be accounted for by heart rate. Heart rate thus appears to be a strong positive linear correlate of change in motor activity in the preterm infant.