• W R Addington, R E Stephens, and R E Goulding.
• Breyard Rehabilitation Medicine, Melbourne, FL 32901, USA.
• Arch Phys Med Rehabil. 1999 Dec 1;80(12):1584-6.

ObjectiveThe internal branch of the superior laryngeal nerve (ibSLN) conveys impulses for the laryngeal cough reflex, which protects the laryngeal aditus and prevents the development of aspiration pneumonia. The purpose of this study was to determine the effect of bilateral anesthesia of the ibSLN on the cough reflex after inhalation of a nebulized chemoirritant solution of tartaric acid.DesignProspective, clinical investigation.SettingOutpatient.ParticipantsNine healthy volunteers.InterventionsBilateral injections of 2% lidocaine solution without epinephrine into the paraglottic space containing the ibSLN.Main Outcome MeasuresThe tidal volume after inhalation of a nebulized 20% tartaric acid solution and forced vital capacity (FVC) were measured before and after injection. Data were analyzed using the Wilcoxon signed ranks, Mann-Whitney, and sign tests.ResultsComplete anesthesia of the ibSLN abolished the laryngeal cough reflex. Postinjection tidal volumes were significantly lower than preinjection volumes (p<.01). The decrease in tidal volumes for six subjects with complete bilateral anesthesia was significantly larger than the decrease in tidal volumes for three subjects with partial anesthesia (p<.05). FVC in both the six subjects with complete bilateral anesthesia and the three subjects with partial anesthesia did not significantly change from preinjection to postinjection. None of the subjects in this study had complications or adverse respiratory sequelae.ConclusionTartaric acid-induced cough may be useful in assessing the integrity of the laryngeal cough reflex after anesthesia or in patients with neurologic injury who are at risk of developing aspiration pneumonia. It may also be useful in making the decision whether to resume oral feeding.

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