Bronchial hyperresponsiveness plays a central role in the pathophysiology of asthma. This hyperresponsiveness is present in almost all patients with symptomatic asthma and can result from a variety of stimuli. One possible stimulus that may exacerbate asthma is chronic sinusitis. Approximately one half of children with asthma have radiographic evidence of sinusitis, and the incidence of chronic sinusitis ranges from 40 to 60 percent. In previous studies, treatment of sinusitis has been shown to decrease bronchial hyperresponsiveness, but the relationship between sinusitis and asthma remains unclear. Tsao and colleagues conducted a prospective study to determine whether aggressive treatment of sinusitis has a positive impact on asthma management and whether chronic sinusitis can induce bronchial hyperresponsiveness.

The trial design was a prospective, open-label study of children with asthma. The participants were seven to 12 years of age with a history of mild asthma and sensitivity to dust mites. The study also included a control group of children with no history of allergic rhinitis, chronic cough, sinusitis, or asthma. Participants with chronic sinusitis had to have persistent symptoms of nasal obstruction, headache, and postnasal drainage for more than 12 weeks and complete opacification or the appearance of fluid in one or both maxillary sinuses and ethmoid cells on plain sinus radiography.

All of the children with asthma had computed tomography of the sinuses. The children with chronic sinusitis were divided into two groups. The first group received six weeks of amoxicillin-clavulanate therapy, followed by six weeks of nasal saline irrigation. The second group received nasal saline irrigation for six weeks, followed by amoxicillin-clavulanate therapy. The children without chronic sinusitis were treated with 12 weeks of nasal saline irrigation. The outcomes measured were clinical symptoms of sinusitis, forced expiratory volume in one second (FEV₁), and bronchial hyperresponsiveness, measured by using a methacholine challenge test.

The clinical signs and symptoms of sinusitis improved in treated patients. However, no significant differences in the FEV₁ values were evident before or after sinusitis treatment. In addition, children with chronic sinusitis had significantly less nocturnal cough after treatment. With regard to bronchial hyperresponsiveness, children treated for sinusitis had significantly better results during the methacholine challenge test compared with the baseline measurements taken before treatment was started.

The authors conclude that there is an association between sinusitis and bronchial hyper-responsiveness in children with asthma. They add that all patients with asthma should be evaluated to determine if they have concomitant sinusitis. In addition, patients with asthma who have unpredictable responses to appropriate asthma management and also have sinusitis should receive aggressive treatment for sinusitis.