The aim of the proposed research is to define the airflow- controlling mechanisms employed by neonates. To achieve this aim the PI has developed a unique lamb model of the human neonate, with electrodes implanted chronically in all of the major intrinsic laryngeal muscles and the diaphragm. Since anesthesia and the presence of a tracheostomy can profoundly affect laryngeal muscle function, we shall study the lambs unanesthetized, with intact airways. Thus, the model permits a comprehensive study of neonatal laryngeal and diaphragmatic function in the control of airflow-pattern and absolute lung volume under normal and abnormal circumstances. In the mammalian neonate, upper airway muscles and the diaphragm are thought to play crucial roles in the control of airflow and the establishment and maintenance of end-expiratory lung volume. However, no studies in neonates have determined the overall relationship between the co-ordinated activities of all the major intrinsic laryngeal muscles and the control of glottic function. Utilization of the lamb model will permit testing of the following hypothesis; 1. that co-ordinated action of both intrinsic laryngeal adductor and abductor muscles control neonatal glottic resistance during inspiration and expiration, and is a principal mechanism in determining airflow pattern and end-expiratory lung volume; 2. that the maintenance of normal airflow during changes in posture and sleep state and defense of end-expiratory lung volume during arousal depend upon adaptive changes of the intrinsic laryngeal muscle which affect glottic resistance; 3. that the intrinsic laryngeal muscles, in co-ordination with chest wall muscles, play a crucial role in the first breath at birth and in the establishment and later maintenance of absolute lung volume and 4. that compensatory changes in intrinsic laryngeal and diaphragmatic muscle activities, which defend end-expiratory lung volume, accompany endotracheal intubation and extubation in lambs and human neonates. The importance of this study is that it will determine the relationships between laryngeal muscle activities and their mechanical functions, providing information about laryngeal mechanisms crucial both in normal and abnormal neonatal respiration.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
First Independent Research Support & Transition (FIRST) Awards (R29)
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Respiratory and Applied Physiology Study Section (RAP)
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University of Florida
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Hutchison, Alastair A; Burchfield, David J; Wozniak, John A et al. (2002) Laryngeal muscle activities with cerebral hypoxia-ischemia in newborn lambs. Am J Respir Crit Care Med 166:85-91
Watts, T L; Wozniak, J A; Davenport, P W et al. (1997) Laryngeal and diaphragmatic activities with a single expiratory load in newborn lambs. Respir Physiol 107:27-35
Webb, B; Hutchison, A A; Davenport, P W (1996) Contribution of vagal afferents to the volume-timing response to expiratory loads in neonatal lambs. Neurosci Lett 207:147-50
Hutchison, A A; Wozniak, J A; Choi, H G et al. (1994) Respiratory muscle activities after birth in asphyxiated preterm lambs. Acta Paediatr 83:241-8
Choi, H G; Principe, J C; Hutchison, A A et al. (1994) Multiresolution segmentation of respiratory electromyographic signals. IEEE Trans Biomed Eng 41:257-66
Hutchison, A A; Wozniak, J A; Choi, H G et al. (1993) Laryngeal and diaphragmatic muscle activities and airflow patterns after birth in premature lambs. J Appl Physiol 75:121-31