Vocal cord dysfunction detected by a three-dimensional image of dynamic change in respiratory resistance in a patient with difficult-to-treat asthma: a case report

Vocal cord dysfunction (VCD) often coexists with asthma and exacerbates respiratory symptoms. A noninvasive method could be considered beneficial for the detection and follow-up of VCD complicated by asthma. Here, we report a case of VCD complicated by asthma, highlighting the effectiveness of colored three-dimensional (3-D) imaging of respiratory impedance using a broadband frequency forced oscillation technique (MostGraph).A 74-year-old woman with difficult-to-treat asthma, in whom mepolizumab treatment was ineffective, was referred to our hospital. Stridulous sounds were loudest over the anterior neck. Pulmonary function tests' results were normal; however, a flattening of the inspiratory flow-volume curve was detected.Remarkably, prominent spikes were observed in the inspiratory phase in the colored 3-D imaging of respiratory resistance, which was superimposed on increased respiratory resistance in the expiratory phase. Flexible laryngoscopy revealed the adduction of vocal cords on inspiration. The patient was diagnosed with asthma complicated by VCD. After successful treatment of VCD by speech therapy, inspiratory spikes of respiratory resistance disappeared, and normal vocal cord movement was observed on laryngoscopy.The present case report indicates the effectiveness of forced oscillometry in evaluating dynamic changes in respiratory resistance for detecting and monitoring VCD complicated by asthma.