Interaction between nonnutritive sucking and respiration in preterm infants.

The effect of nonnutritive sucking bursts (NNSBs) on respiratory frequency was sequentially evaluated in 12 healthy preterm infants. Studies were performed during active sleep in infants between 32 and 37 weeks postconceptional age. The duration of NNSBs was classified as follows: (a) less than 3 s, (b) between 3 and 6 s, and (c) greater than 6 s. NNSBs of each duration were found at all ages, although NNSBs greater than 6 s were the least frequently observed. Respiratory rate increased significantly during NNSBs of less than 3 s, and also in those of 3-6 s duration. There was no significant effect on respiratory frequency of sucking bursts longer than 6 s. Our results document an early interaction between these two motor rhythms, which is influenced by the length of the NNSB. Moreover, they indicate that the decrease in respiratory frequency reported in a similar group of preterm infants during feeding should not be interpreted as an effect of sucking per se.