Impaired small airway function in non‐asthmatic chronic rhinosinusitis with nasal polyps

Abstract Background There is clinical evidence for impaired lung function in chronic rhinosinusitis with nasal polyps (CRSwNP) patients, which may be due to a high incidence of asthma comorbidity. The lung function characteristics of non‐asthmatic CRSwNP patients are not known. Small airway dysfunction (SAD) is involved in the pathogenesis of asthma. However, whether SAD is detected in non‐asthmatic patients with CRSwNPs remains unclear. Objective This study analysed the lung function of non‐asthmatic patients with CRSwNPs and evaluated its clinical relevance in CRSwNPs. Methods The clinical data for 191 consecutive CRSwNP patients (73 asthmatic and 118 non‐asthmatic) and 30 control subjects were prospectively collected. The patients were followed up for at least 3 years (mean [standard deviation], 42.47 ± 8.38 months). Serum and tissue total IgE levels were measured in 95 and 93 patients, respectively. Tissue eosinophil counts were documented in 63 patients. Results Non‐asthmatic CRSwNP patients had decreased forced expiratory flow at 75% of the FVC (FEF 75 ) and FEF 50 compared to the control subjects, and this difference was related to the severity of CRSwNP. The risk factors for impaired lung function in asthmatic and non‐asthmatic patients were duration of asthma and smoking. A multivariate logistic analysis showed that decreased FEF 50 was associated with the recurrence of non‐asthmatic CRSwNPs. The lung function of CRSwNP patients negatively correlated with the degree of type‐2 inflammation, which was defined by the levels of Eos and IgE in polyp tissues and blood. The SAD of non‐asthmatic CRSwNP patients was related to serum IgE levels. Conclusions and clinical relevance This study provides evidence that non‐asthmatic CRSwNP patients may have SAD, which correlated with the severity and recurrence of CRSwNP. The decreased lung function of patients with CRSwNP was related to the degree of type‐2 inflammation.