Abnormal vocal cord function in difficult-to-treat asthma.

RATIONALE

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 computerized tomography (CT), was used to examine laryngeal behavior in healthy individuals and individuals with asthma.

METHODS

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.

MEASUREMENTS AND 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%) patients with asthma and severe in 9 (19%) patients (abnormal > 50% of inspiration or expiration time). Imaging also revealed that laryngeal dysfunction characterized the movement abnormality rather than isolated vocal cord dysfunction.

CONCLUSIONS

Noninvasive quantification of laryngeal movement was achieved using 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.