Respiratory activity of the cricopharyngeus muscle in the neonatal period.

While phasic electrical activity of the cricopharyngeus muscle (EAcp)-the main component of the upper esophageal sphincter-occurs with inspiration and forceful expiration in adults, no such data is available for newborns. In addition, the effect of nasal respiratory support commonly used in newborns is unknown. We aimed to describe the phasic respiratory EAcp and to assess the potential effect of nasal CPAP (nCPAP, 6 cmH2O) or high-flow nasal cannula (HFNC, 7 L/min) in newborn lambs during 6-h recordings. Phasic EAcp was present in 11/17 lambs, including in 32 % (25, 81) [(median (Q1, Q3)] of respiratory cycles in wakefulness, 40 % (27, 70) in NREM sleep, and 10 % (0, 23) in REM sleep. In addition, EAcp was observed only during post-inspiration and/or expiration. Nasal CPAP or HFNC assessed in 7 of the 17 lambs did not have any effect. We conclude that phasic respiratory EAcp occurs in post-inspiration and expiration in newborn lambs.