Submitted on April 4, 2008
Revised on July 14, 2008
Accepted on July 15, 2008
ORIGINS OF THE INHIBITING EFFECTS OF NASAL CPAP ON NON-NUTRITIVE SWALLOWING IN NEWBORN LAMBS
Nathalie Samson1, Bianca Roy1, Alain Ouimet1, Francois Moreau-Bussiere2, Dominique Dorion1, Sandeep Mayer1, and Jean-Paul Praud1*
1 University of Sherbrooke
2 Universite de Sherbrooke
* To whom correspondence should be addressed. E-mail: jean-paul.praud{at}usherbrooke.ca.
The present study investigated the mechanism by which CPAP suppresses non-nutritive swallowing (NNS) during quiet sleep (QS) in newborn lambs. Eighteen full-term lambs were chronically instrumented and evenly distributed into 3 separate groups to determine the extent to which modulation of NNS may be attributed to stimulation of upper airway and/or bronchopulmonary mechanoreceptors. Six lambs were tracheotomized, six other lambs underwent a 2-step bilateral intrathoracic vagotomy while the remaining 6 lambs underwent chronic laryngo-tracheal separation (isolated upper airway group). Forty-eight hours after surgery, each non-sedated lamb underwent polysomnographic recordings on 3 consecutive days. States of alertness, NNS and respiratory movements were recorded. Results demonstrate that a CPAP of 6 cm H2O inhibited NNS during QS while administered directly on the lower airways, and that bivagotomy prevented this inhibition. However, application of CPAP on the upper airways only also inhibited NNS during QS. Finally, the application of a CPAP of 6 cm H2O had no systematic effect on NNS-breathing coordination (assessed by the respiratory phase preceding and following NNS). In conclusion, our results suggest that bronchopulmonary receptors are implicated in the inhibiting effects of nasal CPAP 6 cm H2O on NNS in all our experimental conditions, whereas upper airway receptors are only implicated in certain conditions.
