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An imbalance in autonomic nervous system (ANS) activity may play a role in asthma, but it is unclear whether this is associated with specific pathophysiology. This study assessed ANS activity by measuring heart rate variability (HRV) in eosinophilic (EA) and non-eosinophilic asthma (NEA) and people without asthma. HRV, combined hypertonic saline challenge/sputum induction, exhaled nitric oxide (FeNO), skin prick tests to measure atopy, and spirometry tests were conducted in teenagers and young adults (14–21 years) with (n = 96) and without (n = 72) generally well-controlled asthma. HRV parameters associated with sympathetic and parasympathetic ANS branches were analyzed. EA and NEA were defined using a 2.5% sputum eosinophil cut-point. Airway hyperreactivity (AHR) was defined as ≥15% reduction in FEV1 following saline challenge. HRV parameters did not differ between asthmatics and non-asthmatics or EA and NEA. They were also not associated with markers of inflammation, lung function or atopy. However, increased absolute low frequency (LFµs2; representing increased sympathetic nervous system (SNS) activity) was found in asthmatics who used β-agonist medication compared to those who did not (median: 1611, IQR 892–3036 vs 754, 565–1592; p < 0.05) and increased normalized low frequency (LF nu) was found in those with AHR compared to without AHR (64, 48–71 vs 53, 43–66; p < 0.05). ANS activity (as measured using HRV analysis) is not associated with pathophysiology or inflammatory phenotype in young asthmatics with generally well-controlled asthma. However, enhanced SNS activity can be detected in asthmatics with AHR or who use β-agonist medication. [ABSTRACT FROM AUTHOR]

Background and objective. Measuring the fraction of nitric oxide in exhaled breath (FENO) is increasingly utilized to assess airway inflammation in asthma. The primary aim of this study was to compare exhaled nitric oxide measurements obtained using two devices from different manufacturers, that is, the recently marketed portable and electrochemical-based Medisoft HypAir FENO and the well-established chemiluminescence-based Aerocrine NIOX analyzer, in an unselected population. Methods. FENO measurements were conducted in 106 subjects (86 healthy; 20 asthmatic; 56.6%% atopic). Atopy and health status were assessed by skin prick tests and questionnaire, respectively. Results. The two instruments showed strong correlation over a wide range of FENO measurements (8--261.3 ppb with the HypAir, 5.6--156.8 ppb with the NIOX; r == 0.98; p < .0001). This correlation was observed in the population as a whole, as well as in healthy non-atopics, healthy atopics, and atopic asthmatics when considered separately. The measurements on the HypAir FENO were consistently 1.6 times (95%% CI 1.11--2.05) higher than those obtained with the NIOX. Conclusions. FENO measurements obtained with the HypAir FENO correlated well with the NIOX, but were approximately 1.6 times higher. Therefore, a conversion factor is required if results are to be compared with the NIOX instrument. [ABSTRACT FROM AUTHOR]