Nitrogen Single-breath Washout Test Research Articles

Cardiopulmonary exercise testing and second-line pulmonary function tests to detect obstructive pattern in symptomatic smokers with borderline spirometry

BackgroundThe need for additional research on symptomatic smokers with normal spirometry has been recently emphasized. Albeit not meeting criteria for Chronic obstructive pulmonary disease (COPD) diagnosis, symptomatic smokers may experience activity limitation, evidence of airway disease, and exacerbations. We, therefore, evaluated whether symptomatic smokers with borderline spirometry (post-bronchodilator FEV1/FVC ratio between 5th to 20th percentile of predicted values) have pulmonary function abnormalities at rest and ventilatory constraints during exercise. Methods48 subjects (aged 60 ± 8 years, mean ± SD, 73% males, 16 healthy, and 17 symptomatic smokers) underwent cardiopulmonary exercise testing (CPET), body plethysmography, nitrogen single-breath washout test (N2SBW), lung diffusion for carbon monoxide (DLCO), and forced oscillation technique (FOT). ResultsCompared to healthy subjects, symptomatic smokers showed: 1) reduced breathing reserve (36 ± 17 vs. 49 ± 12%, P = 0.050); 2) exercise induced dynamic hyperinflation (−0.20 ± 0.17 vs. −0.03 ± 0.21 L, P = 0.043); 3) higher residual volume (158 ± 22 vs. 112 ± 22%, P < 0.001); 4) phase 3 slope at N2SBW (4.7 ± 2.1 vs. 1.4 ± 0.6%, P < 0.001); 5) no significant differences in DLCO and FOT results. ConclusionsIn smokers with borderline spirometry, CPET and second-line pulmonary function tests may detect obstructive pattern. These subjects should be referred for second line testing, to obtain a diagnosis, or at least to clarify the mechanisms underlying symptoms. Whether the natural history of these patients is similar to COPD, and they deserve a similar therapeutic approach is worth investigating.

Lack of correlation between the grade of methacholine-induced bronchial hyperreactivity and ipratropium bronchodilation in asthmatics.

In 46 never-smoking randomly chosen patients with non-allergic asthma, 40 to 60 years old, a methacholine hyperreactivity test and lung function tests were performed after inhalation of different doses of ipratropium bromide (IB). The grade of hyperreactivity was measured as the cumulative dose of methacholine necessary to produce a decrease in the forced expiratory volume in one second of 20% of the lowest post-NaCl value (PD20). The following lung function tests were carried out: Lung volumes, ventilatory capacity including flow-volume curves, airway resistance and nitrogen single-breath wash-out test. The bronchodilator effect, measured as a change in the different lung function tests for different doses of IB given (0.08 mg, 0.15 mg and 0.25 mg), was correlated to the grade of hyperreactivity (PD20 dose). No or only a slight correlation was found between the grade of methacholine-induced hyperreactivity and the bronchodilator effects of the different doses of IB. These results indicate a lack of correlation between an anticholinergic bronchodilator effect and the grade of methacholine-induced bronchial hyperreactivity, or possibly an insensitivity of the above-mentioned methacholine test.