[Exercise-induced vocal cord dysfunction in asthma: a new diagnostic method].

OBJECTIVE: Vocal cord dysfunction (VCD) is an under-recognized cause of dyspnea and is difficult to diagnose. The symptoms caused by exercise-induced VCD (IEVCD) often falsely suggest asthma, but there is sometimes a real association between the two diseases. The objective of this study was to evaluate a new, simple method for analyzing vocal cord behavior in the diagnosis of IEVCD, and to clarify the prevalence of IEVCD in an uncontrolled asthma population with unexplained exertional dyspnea.

METHODS: This single-center study was conducted prospectively between April 2012 and March 2013. The main inclusion criterion was uncontrolled asthma with unexplained dyspnea. The assessment included cardiopulmonary exercise testing and supraglottal laryngoscopy during exercise with measurement of the vocal cord-opening angle (VCOA). Data from 15 asthmatic patients were compared with those from 10 non-asthmatic dyspneic patients (controls) to define specific criteria for the endoscopic diagnosis of IEVCD.

RESULTS: Endoscopy during bicycle exercising was well tolerated. Normal value of inspiratory VCOA (itVCOA) was>49°. Values for the itVCOA were lower for asthmatics than for controls when exercising at 50% maximal power (52.8°±13.3° and 64.5°±8.3°, respectively). Four of the 15 asthmatics (26%) demonstrated IEVCD characterized with itVCOApeak of less than 49°.

CONCLUSION: Measurement of VCOA represents a new, simple method for obtaining objective data in the exploration of VCD. The prevalence of IEVCD in uncontrolled asthmatic patients is important (26% in our small sample). IEVCD is probably an under-diagnosed aggravating factor in asthma, and its diagnosis and management could avoid the therapeutic climbing in asthma. This method of analysis may help to accurately and objectively assess vocal cord dysfunction.