Prevalence of inducible laryngeal obstruction among patients diagnosed as bronchial asthma

Inducible laryngeal obstruction (ILO) is an important cause of a variety of respiratory symptoms and can mimic bronchial asthma (BA). This study was planned to measure the prevalence of ILO among patients diagnosed with BA and to detect its effect on BA control and severity.

Patients aged 18 years or older who were previously diagnosed with BA were enrolled. Laryngeal obstruction was induced using the patient's specific trigger (e.g. exercise). Visualization of vocal folds was accomplished using a 70-degree rigid laryngoscope (Karl Storz). A visual grade score was utilized to determine the severity of laryngeal obstruction.

Results showed that 38.3% (n = 46) of the patients had ILO with the majority being classified as grade 2 (80.4%) (n = 37). The most common subtype was glottic ILO (63%). Bronchial asthma duration, level of control, and severity were not associated with ILO (P values: 0.2, 0.3 and 0.8 respectively).

Asthma and ILO commonly co-exist. An accurate classification of patients is very important and must be considered in order to determine whether the symptoms are directly related to ILO or whether they are caused by BA. Ceasing inappropriate treatment may be necessary. Objective diagnostic modalities of ILO are essential.