Effects of hypercapnia on non-nutritive swallowing in newborn lambs

The purpose of this study was to determine the effect of hypercapnia on non-nutritive swallowing (NNS) frequency and on NNS-breathing coordination in newborn lambs. Six lambs were chronically instrumented for recording electroencephalogram, eye movements, diaphragm and thyroarytenoid muscle activity, nasal airflow and electrocardiogram. Each lamb was placed in a Plexiglas chamber and exposed to a hypercapnic gas mixture (21% O2, 5% CO2). Polysomnographic recordings were conducted in non-sedated lambs using a custom-designed radiotelemetry system. Results show that hypercapnia increased NNS frequency in all three states of alertness (p < 0.0001 to 0.03), through a specific increase in ie-type NNS. Causal mechanisms and potential consequences of such observations on aspirations and apneas, as well as on swallowing maturation, will require further studies.