Markers of oxidative stress in exhaled breath condensate: prediction of one-year development of pulmonary function and nutritional status in cystic fibrosis

Abstract

Few studies have been published on airway resistance measurements using the interrupter technique (IT). We performed a cross-sectional study, evaluating 38 children and adolescents with Cystic Fibrosis (CF), followed at the outpatient CF clinic of Hospital Sao Lucas from Pontificia Universidade Catolica do Rio Grande do Sul. Airway resistance (Rint) was measured by the IT, followed by spirometry in all patients. Measurements were repeated after inhalation of salbutamol in order to evaluate bronchodilator response. There was a strong corelation between inverse Rint and forced expiratory volume in one second (FEV1) (r = 0.8, p< 0.001) and fair correlations between the inverse Rint and mid expiratory flow (MEF) (r = 0.74 p< 0.001) and between inverse Rint and body mass index (BMI) (r = 0.62 p< 0.001). The accuracy of bronchodilator response by the IT was tested through the ROC (reciever operating curve), comparing results with spirometry bronchodilator response. An area of 0.75 under the curve was obtained, for the cutoff point of −28% of Rint, achieving a sensitivity of 66% and a specificity of 82%. The findings suggest that Rint shows good correlation with spirometry parameters, although the IT is not sufficiently acurate to replace spirometry in the evaluation of bronchodilator response.