RELIABILITY OF RESPIRATORY SINUS ARRHYTHMIA IN R-R INTERVALS IN 14-WEEK-OLD, 20-WEEK-OLD, AND 26-WEEK-OLD INFANTS

Measures of respiratory sinus arrhythmia (RSA) in R-R intervals were c alculated from a 5-min recording of 3- to 6-month-old full-term infant s. The reliability of the measures was estimated with Cronbach's alpha for sampling durations of 5, 15, 25, or 60 s, for single or multiple samples from each of the five baseline periods. Reliability of RSA was good (>.8) for samples of 25 s or greater but decreased with smaller sampling durations. The sensitivity of the measures in detecting an ag e effect between 14-, 20-, and 26 week-old infants correlated positive ly with the reliability of the measure. This study suggests that relia bility of RSA measures in young infants is acceptable.