Dysfunctional Breathing, in COPD: A Validation Study

Background/Objectives: The Nijmegen Questionnaire (NQ) has been a prevalent screening tool for dysfunctional breathing for the past 40 years. Until recently, the validity of the NQ has been established for the general population with hyperventilation syndrome (HVS) and for individuals with asthma, but not for people with COPD. The aim of the study was to examine the validity and reliability of the NQ in individuals with COPD. Methods: Construct, convergent, divergent and discriminant validity as well as internal consistency reliability were examined in a sample of 84 people with stable COPD. Results: A three-factor solution with 16 items and 74.70% of explained variability was extracted through principal component analysis. High internal consistency (Cronbach alpha = 0.94) of the 16 NQ items was found. Significant differences were found between COPD individuals with and without DB (p < 0.001) and among people of all COPD levels of severity (p < 0.001). The value ">23" was found to detect the presence of DB, with 95.92% sensitivity and 94.29% specificity. Significant correlations were found between the total NQ score with BODE index (r = 0.81), Borg dyspnea scale (r = 0.47) and CAT (r = 0.49). The prevalence of DB for the specific sample was found to be 58.3%. Conclusions: The present study provided the first validity and reliability evidence for the NQ for people with stable COPD.