Abstract
The diagnosis of vocal cord dysfunction (VCD) relies on laryngoscopy, a rather invasive procedure that may not be readily available in the lung function lab during attacks. An alternative identification of the paradoxical glottis adduction during inspiration could be provided by the forced oscillation technique at a single frequency, allowing to describe the time course of respiratory resistance (Rrs). Rrs is dependent on the glottis calibre which narrows during expiration in normal subjects. In VCD, Rrs should increase during inspiration. The hypothesis was tested that the Rrs difference between inspiration and expiration (Rrsi-e) is at variance between VCD and asthma.
Six VCD patients and 36 asthmatics underwent bronchial challenge. Rrsi-e was 0.51 ± 2 hPa.s/L in VCD vs -0.37 ± 1 hPa.s/L in controls (p<0.03) at baseline. A typical Rrs vs Flow relationship after challenge is shown.
The average Rrsi-e after challenge was 6 ± 5 hPa.s/L in VCD vs -0.5 ± 1 hPa.s/L in asthma (p<0.0001).
These measurements of Rrs are thus consistent with vocal cord adduction in inspiration in VCD but not asthma, a pattern exacerbated during the bronchial challenge.
- © 2014 ERS
