Vocal cord dysfunction as demonstrated by impulse oscillometry.

BACKGROUND: Vocal cord dysfunction (VCD) is a respiratory disorder characterized by inappropriate vocal cord adduction during inspiration. The diagnosis of VCD is challenging, because expected flow volume loop abnormalities are uncommonly noted, and laryngoscopy must be timed to coincide with symptoms.

OBJECTIVE: We wanted to determine the potential role of impulse oscillometry (IOS) in the diagnosis of VCD.

METHODS: We conducted an analysis of six patients in which the diagnosis of VCD was being considered as well as seven healthy subjects and five subjects with asthma. All were evaluated with IOS and 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 three of the six patients in whom the diagnosis of VCD was entertained. These three patients as a group all exhibited higher amplitude (mean, 9.3 cm H20/L/second) and more variable spikes (SD, 4.8 cm H20/L/second) on IOS impedance during inspiration, whereas the three patients in whom the diagnosis was not confirmed by endoscopy did not show these findings (mean, 2.0 cm H20/L/second; P < .0002; SD, 0.8 cm H20/L/second; P < .0001). This pattern was also not observed in the healthy volunteers (mean ± SD, 1.8 ± 0.7 cm H20/L/second) and patients with asthma at baseline (mean, 4.2 ± 1.2 cm H20/L/second) or after exercise challenge (mean, 1.5 ± 0.5 cm H20/L/second).

CONCLUSIONS: These findings support the conclusion that IOS displays a characteristic pattern in patients with VCD and thus may offer a rapid and noninvasive adjunct to the assessment and diagnosis of patients suspected to have this disorder.