Laryngeal and diaphragmatic activities with a single expiratory load in newborn lambs.
Expiratory resistive loads elicit compensatory reflexes in the neonate which regulate end-expiratory lung volume (EEV). This study investigated the coordination of laryngeal and diaphragmatic activities when awake neonatal lambs were exposed to a single breath expiratory resistive load. The lambs were chronically instrumented for recording trans-upper airway pressure and electromyographic signals from the posterior cricoarytenoid, thyroarytenoid, and diaphragm. The lambs breathed through a sealed face mask connected to a pneumotachograph and non-rebreathing valve with a loading manifold connected to the expiratory port. Single breath expiratory loads produced, decreased airflow; prolongations of PCA EMG activity and diaphragm EMG inhibition; decreased trans-upper airway resistance and increased EEV. In the post-load breath, inspiratory volume decreased, expired volume increased, and EEV returned towards control baseline. Thus, neonatal lambs compensate for a single breath expiratory load by dilating the larynx and prolonging expiratory time. In the post-load breath, integrated activities of laryngeal and diaphragmatic muscles, coupled with mechanical factors return EEV towards baseline.
Watts
T L
TL
Department of Pediatrics, JHMHC, Gainesville, FL 32610-0296, USA.
Wozniak
J A
JA
Davenport
P W
PW
Hutchison
A A
AA
D000403:Airway Resistance; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D003964:Diaphragm / Q000502:physiology*; D004576:Electromyography; D005105:Expiratory Reserve Volume / Q000502:physiology; D007830:Larynx / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology*; D012756:Sheep