To study the coordination of respiration and swallow rhythms we assessed feeding episodes in 20 preterm infants (gestational age range at birth 26–33wks; postmenstrual age [PMA] range when studied 32–40wks) and 16 term infants studied on days 1 to 4 (PMA range 37–41wks) and at 1 month (PMA range 41–45wks). A pharyngeal pressure transducer documented swallows and a thoracoabdominal strain gauge recorded respiratory efforts. Coefficients of variation (COVs) of breath–breath (BR–BR) and swallow–breath (SW–BR) intervals during swallow runs, percentage of apneic swallows (at least three swallows without interposed breaths), and phase of respiration relative to swallowing efforts were analyzed. Percentage of apneic swallows decreased with increasing PMA (16.6% [SE 4.7] in preterm infants [les ]35wks' PMA; 6.6% [SE 1.6] in preterms >35wks; 1.5% [SE 0.4] in term infants; p<0.001). Term infants had significantly lower BR–BR COV (0.405 [SE 0.016]) than preterm infants (0.641 [SE 0.052] at >35wks' PMA; 0.693 [SE 0.059] at [les ]35wks' PMA). Phase relation between swallowing and respiration stabilized with increasing PMA, with decreased apnea, and a significant increase in percentage of swallows occurring at end-inspiration. These data indicate that unlike the stabilization of suck and suck–swallow rhythms, which occur before about 36 weeks' PMA, improvement in coordination of respiration and swallow begins later. Coordination of swallow–respiration and suck–swallow rhythms may be predictive of feeding, respiratory, and neurodevelopmental abnormalities.
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