Clinical implications of concentration of alveolar nitric oxide in asthmatic and non-asthmatic subacute cough

Background and objective: Asthma is one of the important causes of subacute cough. Concentration of alveolar nitric oxide (CANO) is a sensitive inflammatory indicator of peripheral airways, which has received much less attention than fraction of exhaled nitric oxide (FeNO50). The main objective of this study was to explore the correlation between CANO and clinical parameters in asthmatic and non-asthmatic subacute cough, which might promote understanding the clinical utility of CANO in these special patient population. Materials and methods: 155 patients with subacute cough were included consecutively, of which 25 were diagnosed as asthma. Data for demographic characteristics, FeNO50, CANO, baseline spirometry, bronchial provocation test (or bronchodilation test) and response dose ratio (RDR) was collected. Differences between asthmatic and non-asthmatic group were analyzed. Spearman’s correlation coefficient (rho) was used to evaluate the correlation between FeNO50, CANO and other clinical parameters. Results: In patients with subacute cough, baseline CANO values did not differ between asthmatic and non-asthmatic patients (4.4(1.3, 11.4) versus 4.0(2.1, 6.8) ppb, P>0.05). Besides, CANO exhibited stronger association with pulmonary function parameters when compared with FeNO50. For asthmatic subacute cough, CANO was inversely correlated with FEV1/FVC (rho=-0.69, P<0.01) and small airway parameters including MEF25 (rho=-0.47, P<0.05) and MMEF (rho=-0.45, P<0.05). For non-asthmatic subacute cough, CANO was inversely correlated with MEF25 (rho=-0.19, P<0.05) and RDR (rho=-0.21, P<0.05). Conclusion: In subacute cough, asthmatic and non-asthmatic patients had similar values of baseline CANO. In both asthmatic and non-asthmatic subacute cough, CANO exhibited stronger association with pulmonary function parameters when compared with FeNO50. A low CANO value in non-asthmatic subacute cough corresponded to a higher value of RDR, which implied stronger tendency towards airway responsiveness.

Bronchial provocation test measured by using the forced oscillation technique to assess airway responsiveness

Background: The bronchial provocation test (BPT) performed by using the forced oscillation technique (FOT) is cooperated without forced expiratory effort. However, a comparison of the application value and safety of BPTs measured by using the FOT and the standardized dosimeter method is lacking, which limits its clinical practice. Objective: We aimed to analyze the diagnostic value and safety of the BPT as measured by the FOT in patients with asthma and in healthy subjects. Methods: This was a randomized cross-over clinical study. Airway responsiveness was measured by using the FOT and the aerosol provocation system (APS) dosimeter method in all the participants. The between-test interval was 24 hours. The diagnostic value and safety of the two tests were analyzed. Results: Asthma control status was assessed based on ACT scores, and patients with asthma (including 27 uncontrolled, 34 partially controlled, and 32 controlled) were collected, and 69 healthy subjects were recruited. Receiver operating characteristic curves revealed slightly superior screening capability of cumulative dose of methacholine causing a 20% decrease (PD20)‐forced expiratory volume in the first second of expiration when measured by using the APS-dosimeter method (area under the curve [AUC] 0.981 [95% confidence interval {CI}, 0.952‐1.000]) over that of cumulative dose of inhaled methacholine at the inflection point when respiratory resistance began to increase continuously (Dmin) by using the FOT (AUC 0.959 [95% CI, 0.924‐0.994]). The sensitivity and specificity were 98.9% and 98.6%, respectively, with the APS-dosimeter method, and 100% and 87.0%, respectively, with the FOT. It took an average of 9.0 minutes (range, 6.0‐11.0 minutes) when using the FOT and an average of 17.0 minutes (range, 14.0‐25.0 minutes) when using APS-dosimeter method (p < 0.01) in all the participants. The measurement time for the FOT was reduced by 47.1% than the APS-dosimeter. The incidence rate of the adverse events with the FOT was slightly higher than that with the APS-dosimeter method (p < 0.05). Both tests were well tolerated. No serious adverse event was found. Conclusion: The FOT, characterized as being simple, safe, and time saving, could be used to assess airway hyperresponsiveness in patients with asthma and worthy of clinical application.

Does the asthma control test reflect inflammation?

The present issue of Multidisciplinary Respiratory Medicine includes a paper by Bora et al. [1] investigating the relationship between the asthma control test (ACT) and airway inflammation. In a group of stable asthmatic patients admitted to a pulmonary outpatient clinic, the authors carried out the ACT, pulmonary function tests, methacholine bronchial provocation test (MBPT), fractional exhaled nitric oxide level (FeNO), and induced sputum test. [...]