Nonnutritive swallowing and respiration relationships in preterm lambs

The aim of the present study was to assess the effects of the different states of alertness on 1) nonnutritive swallowing (NNS) frequency, 2) the relationship between NNS and the respiratory cycle, and 3) the association of NNS with spontaneous apneas. Recordings of sleep states, diaphragm and laryngeal constrictor electrical activity, nasal flow, electrocardiogram, respiratory inductance plethysmography, and pulse oximetry were obtained from six preterm lambs without sedation. Analysis of 2,468 NNS showed that 1) NNS frequency was higher during quiet wakefulness and active sleep (AS) than in quiet sleep; 2) in all states of alertness, a greater number of NNS (38%) were preceded and followed by an inspiration; 3) although NNS and central apneas were rarely coincidental, AS appeared to favor their association; and 4) most obstructive apneas occurred in AS and were coincidental with bursts of NNS. Compared with results in full-term lambs, premature birth does not modify the NNS-respiratory coordination. However, AS in preterm lambs is characterized by a higher association of NNS bursts with obstructive apneas.