Abnormal Vocal Cord Function in Difficult-to-Treat Asthma

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Am J Respir Crit Care Med. 2011 Mar 31. [Epub ahead of print]Abnormal Vocal Cord Function in Difficult-to-Treat Asthma.Low K, Lau KK, Holmes P, Crossett M, Vallance N, Phyland D, Hamza K, Hamilton G, Bardin PG.Respiratory and Sleep Medicine, Monash University and Medical Centre, Melbourne, , Australia.AbstractRATIONALE: Upper airway dysfunction may complicate asthma, but has been largely ignored as an etiological factor. Diagnosis using endoscopic evaluation of vocal cord function is difficult to quantify with limited clinical application.OBJECTIVES: A novel imaging technique, dynamic 320-slice computerised tomography (CT), was used to examine laryngeal behaviour in healthy and asthmatic individuals.METHODS AND MEASUREMENTS: Vocal cord movement was imaged using 320-slice CT larynx. Healthy volunteers were studied to develop and validate an analysis algorithm for quantification of normal vocal cord function. Further studies were then conducted in 46 patients with difficult-to-treat asthma.MAIN RESULTS: Vocal cord movement was quantified over the breathing cycle by CT using the ratio of vocal cord diameter to tracheal diameter. Normal limits were calculated, validated and applied to evaluate difficult-to-treat asthma. Vocal cord movement was abnormal with excessive narrowing in 23 of 46 (50%) asthmatics and severe in nine (19%) patients (abnormal >50% of inspiration or expiration time). Imaging also revealed that laryngeal dysfunction characterised the movement abnormality, rather than isolated vocal cord abnormality.CONCLUSIONS: Non-invasive CT larynx quantification of laryngeal movement was achieved employing CT larynx. Significant numbers of patients with difficult-to-treat asthma had excessive narrowing of the vocal cords. This new approach has identified frequent upper airway dysfunction in asthma with potential implications for disease control and treatment.