Some factors modifying airway defensive reflexes

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The first purpose of this study is to elucidate patterns of airway defensive reflexes elicited by a constant stimulation of airway mucosa in humans and the second purpose is to see the importance of various factors influencing airway reflexes in modification of airway defensive reflex responses. In this study we established the methidoiogy of elicitation and eveluation of airway defensive reflexes in humans. We also investigated the effects of an intravenous anesthetic agent (propofol) and a narcotic (fentanyl) on airway defensive reflexes. In addition, the effects of smoking habit and the influence of a voltile agent (sevoflurane) on airway defensive reflexes were investigated. The results were summarized as follows :1.Both laryngeal and tracheal stimulation caused protective responses, such as cough reflex, expiration reflex, and spasmodic panting whereas bronchial stimulation caused little or no such responses.2.An increase in depth of anesthesia shortened the response duration but did not affect the nature of the elicited responses.3.It was impossible to suppress the airway defensive reflexes by administration of propofol alone but an addition of a small amount of fentanyl effectively depressed the airway defensive reflexes.4.Smoking habit augmented the airway reflex responses but this was evident only with mechanical stimulation of the airway mucosa.5.Sevoflurane which possesses a very mild airway-irritation may elicit airway defensive responses through the stimulation of the nasal mucosa.