Impulse Oscillometry may help in diagnosing Vocal Cord Dysfunction

Published Online: July 2013

Vocal cord dysfunction (VCD) is a condition that is caused by paradoxical closure of the vocal cords during inspiration and patients often present with respiratory distress. The diagnosis of VCD is challenging because the symptoms are fleeting and it may be misdiagnosed as asthma, a more common condition. VCD is more prevalent in women; is often triggered by exercise, inhaled irritants, and respiratory infection; and may be associated with anxiety and social stress. The direct observation of vocal cord closure during inspiration using a laryngoscope confirms the diagnosis. Impulse oscillometry (IOS) is one less invasive methodology that may aid in diagnosing this condition.  IOS is a noninvasive and rapid technique that measures airway function through impedance in both children and adults and its usefulness has been well documented.

In a recent issue of The Journal of Allergy and Clinical Immunology: In Practice, Komarow et al studied six patients 12-60 years of age with a clinical history of VCD, as well as 7 normal subjects and 5 subjects with asthma. All participants were evaluated with IOS and spirometry, and in addition the patients suspected of VCD underwent laryngoscopy. Two patients with suspected VCD who were not symptomatic while in clinic and had normal baseline pulmonary function, underwent exercise challenge and repeat studies, and one patient completed an additional irritant challenge.  The results were analyzed and compared with spirometry and laryngoscopy.

VCD was diagnosed by laryngoscopy in 3 of the 6 patients where the diagnosis of VCD was entertained.  These three patients exhibited high amplitude and variable spikes on IOS impedance during inspiration, while the 3 patients where the diagnosis was not confirmed by endoscopy did not show these findings. This characteristic pattern on IOS was not observed in the normal volunteers and asthmatics at baseline or following exercise challenge. These results are consistent with the conclusion that IOS exhibits a characteristic impedance pattern in patients with VCD verified by laryngoscopy.

The authors suggest that IOS may serve as a valuable adjunct when evaluating individuals where the diagnosis of VCD is entertained.  

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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