This research proposes to investigate specifically the neural reflexes involved in regulation of the laryngeal aperture and of the pattern of breathing in awake humans with respect to adaptation to mechanical loads similar in size to those encountered normally due to changes in internal mechanics. A technique involving the application of mechanical loads at the body surface using a head-out body plethysmorgraph will be used in conjunction with traditional loading at the mouth to separate possible response contributions attibutable to receptors in the upper airway and degine the roles of such extra-thoracic receptors in both laryneal aperature regulation and breathing pattern control. The contribution of perceptual reactions to mechanical loading, an unavoidable and significant contamination of the neural reflex responses using traditional experimental techniques, will be eliminated by using a new loading procedure, which will permit the reliable assessment of larnygeal aperture and breathing pattern response to loads that are imperceptible to the subjects. The indication from initial experimental and modeling results is that immediate timing responses of the pattern reflect the action of unconscious reflexes. Measurement of the timing of the diaphragmatic electromyogram will be done to substantiate the basis for using the timing of airflow, a mechanical measure, as a reflection of neural responses to loading, free of mechanical artifact and from the influence of intrinsic muscle properties. A recently developed semi-automated analysis technique will be used to facilitate description of laryngeal aperture responses in the absenceof perceptual reaction to loading in order to reveal control stategies that may be used in regulating this accessory muscle of respiration. Elastic loading will be performed using larger loads to examine the role of the larynx in regulating expiratory flowrate and end-expieratory volume. The effect of sleep upon the immediate neural reflex responses to loading will be determined by comparing pattern responses to imperceptible loads between the awake and slow-wave sleep states. The importance of higher brain activity will be assessed by determining the influence of the level of alertness within the wakeful state upon such pattern responses to loading and the influenceof alterations in the baseline impedance upon pattern responses will indicate the importance of mechanical changes that may occur subsequent to disease.
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