Vocal Cord Dysfunction as Demonstrated by Impulse Oscillometry

Abstract

Background Vocal cord dysfunction (VCD) is a respiratory disorder characterized by inappropriate vocal cord adduction during inspiration. The diagnosis of VCD is challenging, as expected flow volume loop abnormalities are uncommonly noted and laryngoscopy must be timed to coincide with symptoms. Objective To determine the potential role of Impulse Oscillometry (IOS) in the diagnosis of VCD. Methods: We conducted an analysis of 6 patients in which the diagnosis of VCD was being considered as well as 7 normal subjects and five subjects with asthma. All were evaluated with IOS, spirometry and patients underwent laryngoscopy. Two patients with suspected VCD who did not exhibit symptoms or abnormal pulmonary function at baseline underwent exercise challenge and repeat studies. One patient with suspected VCD underwent an additional irritant challenge. Results VCD was diagnosed by laryngoscopy in 3 of the 6 patients where the diagnosis of VCD was entertained. These three patients as a group all exhibited higher amplitude (mean, 9.3 cm H20/L/sec) and more variable spikes (SD, 4.8) on IOS impedance during inspiration, while the 3 patients where the diagnosis was not confirmed by endoscopy did not show these findings (mean, 2.0, P<0.0002; SD, 0.8, P<0.0001). This pattern was also not observed in the normal volunteers (mean, 1.8; SD, 0.7) and asthmatics at baseline (mean, 4.2; SD, 1.2) or following exercise challenge (mean, 1.5; SD, 0.5). Conclusions These findings support the conclusion that IOS displays a characteristic pattern in patients with VCD and thus may offer a rapid and non-invasive adjunct to the assessment and diagnosis of patients suspected to have this disorder.

Vocal cord dysfunction: a review

“…Diagnosis of vocal cord dysfunction can be identified with the use of laryngoscopy, ideally performed after a bronchoprovocation challenge. It can also be suggested by the appearance of the flow-volume loop obtained through spirometry or pulmonary function testing as well as through impulse oscillometry, although the latter is not as readily available [40]. …”

“…This may offer a rapid, noninvasive adjunct to diagnose patients with VCD [40] The main drawback to this type of testing, however, is the impulse oscillometers are not readily available.…”

Breathing‐related changes of respiratory resistance in vocal cord dysfunction

“…A mechanical model of VCD suggested the strong potential of measuring the within‐breath respiratory resistance (Rrs) with its considerable increase during inspiration . Increases in the mean inspiratory impedance obtained with the impulse oscillation system were reported in subjects with laryngoscopy confirmed VCD . The forced oscillation technique using a single excitation frequency has been reported to be suitable to identify time variations of Rrs .…”

Vocal Cord Dysfunction after an Inhalation Exposure

“…We did not employ provocation testing to confirm abnormal vocal cords closure such as by using aerosolized methacholine, administering inhaled mannitol powder, performing strenuous exercise on a treadmill or bicycle ergometer, breathing in refrigerated cold air, or inhaling odorants/irritants, such as perfume or cleaning agents containing chlorine or ammonia [10,11]. Impulse oscillometry was not employed in any case [12]. Table 1 records the author's collective list of inhalation exposures ascribed to VCD.…”