Exhaled nitric oxide and other exhaled biomarkers in bronchial challenge with exercise in asthmatic children: current knowledge

Is there cardiac autonomic dysfunction in children and adolescents with exercise-induced bronchospasm?

BACKGROUND

The pulmonary impairment in patients with bronchoconstriction induced by eucapnic voluntary hyperpnea(EVH) goes beyond the respiratory system, also impairing autonomic nervous modulation. This study aimed to evaluate the behavior of cardiac autonomic modulation in young asthmatics with and without EIB after the EVH test.

RESEARCH DESIGN AND METHODS

A cross-sectional study design using 54 asthmatics(51.9% female), aged between 10 and 19 years, investigated with the EVH test. Forced expiratory volume in one second(FEV1) was measured at 5, 10, 15, and 30 min after EVH. Heart rate variability(HRV) measures of time were assessed pre and 30 min-post EVH. The diagnosis of Exercise-Induced bronchoconstriction with underlying clinical asthma(EIBA) was confirmed by a fall in FEV1 ≥10% compared to baseline.

RESULTS

Thirty(55.5%) asthmatics had EIBA. Subjects with EIBA have reduced mean of the R-R intervals in relation to baseline until 15 minutes after EVH. Individuals without EIBA had increased parasympathetic activity compared to baseline(rMSSD) from 5 min after EVH(p < 0.05). This parasympathetic activity increase in relation to baseline was seen in individuals with EIBA after 25 minutes (rMSSD = 49.9 ± 5.3 vs 63.5 ± 7.2, p < 0.05).

CONCLUSION

Young asthmatics with EIBA present a delay in the increase of the parasympathetic component after EVH when compared to asthmatics without EIBA.

Reproducibility of eucapnic voluntary hyperpnoea for exercise-induced bronchoconstriction diagnosis in asthmatic children and adolescents

BACKGROUND

Respiratory symptoms after exercise are frequently reported by asthmatic patients, and exercise-induced bronchoconstriction (EIB) is a frequent cause, which requires objective testing for diagnosis. Eucapnic voluntary hyperpnea (EVH) is recommended as a surrogate stimulus for this purpose. Its short-term reproducibility is not yet established in children and young adolescents with asthma.

OBJECTIVE

To evaluate the short-term test-retest agreement and reproducibility of FEV₁ changes after EVH in this population.

METHODS

Asthmatic patients aged between 10 and 20 years underwent EVH for EIB diagnosis on two occasions 2-4 days apart at a specialized university clinic. FEV₁ was measured at 5, 15, and 30 min after EVH with a target ventilation rate 21 times the baseline FEV₁ . EIB was diagnosed as a decrease ≥10% in FEV₁ from baseline.

RESULTS

A total of 26 of 62 recruited individuals tested positive for EIB on both visits (positive group) and 17 on one visit only (divergent group), while 19 tested negative on both visits (negative group). The overall agreement was 72.5% (95%CI 61.6%, 83.6%), and Cohen's kappa coefficient was 0.452. Low bias (0.87%) and high intra-class correlation coefficient (0.854, 95%CI 0.758,0.912; p < .001) for FEV₁ response between test days were found, but with wide limits of agreement (±20.72%). There were no differences in pre-challenge FEV₁ or achieved ventilation rate between visits either between groups (p = .097 and p = .461) or within groups (p = .828 and p = .780). There were no safety issues.

CONCLUSIONS

More than one EVH test should be performed in children and young adolescents with asthma to exclude EIB and minimize misdiagnosis and mistreatment.

Serum BPI as a novel biomarker in asthma

Background

Neutrophils, eosinophils and inflammatory cells contribute to asthmatic inflammation. The anti-bactericidal/permeability-increasing protein (BPI), produced by neutrophils, peripheral blood monocytes or epithelial cells, can neutralize lipopolysaccharide activity and enhance phagocytosis regulation function. This study aimed to assess the clinical significance of BPI in asthmatic patients.

Methods

We recruited 18 controlled asthma, 39 uncontrolled asthma and 35 healthy controls individuals. Clinical characteristics (age, gender, allergy history, body mass index (BMI) and smoking history), clinical indicators [whole blood count, forced expiratory volume in one second as percentage of predicted volume (FEV1% predicted), IgE level, high sensitivity C-reactive protein (hs-CRP) and fractional expiratory nitric oxide (FeNO)] and serum BPI levels were measured to compare among each group. We then evaluated the correlation between BPI, clinical characteristics and clinical indicators. Finally, linear regression analysis was performed to exclude the influence of other factors and to find the independent influencing factors of BPI.

Results

Our results showed that the serum BPI levels increased by twofold in the controlled asthma group (12.83 ± 6.04 ng/mL) and threefold in the uncontrolled asthma group (18.10 ± 13.48 ng/mL), compared to the healthy control group (6.00 ± 2.58 ng/mL) (p < 0.001). We further found that serum BPI levels were positively correlated with the hs-CRP (p = 0.002). There was no significant association among BPI, age, gender, BMI, allergy, blood eosinophils, blood neutrophils, IgE, FeNO or FEV1% predicted.

Conclusion

BPI levels were increased in asthma and positively correlated with hs-CRP. BPI as a potential asthma biomarker that still needs further research.

Urinary and exhaled biomarkers of exercise-induced bronchoconstriction in atopic asthmatic children

BACKGROUND

Exercise-induced bronchoconstriction (EIB) reflects poor asthma control. Assessing noninvasive biomarkers associated with EIB could help to monitor patients in the pediatric age.

AIMS

To test exhaled and urinary biomarkers for assessing EIB in atopic asthmatic children.

METHODS

In 45 atopic patients (11.1 ± 1.8 years, 25 males) we measured the fractional exhaled nitric oxide (FE_NO ), its alveolar (CaNO), and bronchial (J'awNO) components corrected for the trumpet shape of the airways and axial NO diffusion (TMAD), concentrations of urinary adenosine and 8-hydroxy-2'-deoxyguanosine (8-OxodG), blood eosinophils count, total immunoglobulin E , skin prick tests, and baseline spirometry before a treadmill exercise challenge. Forty healthy control subjects participated solely to baseline measurements.

RESULTS

Patients yielded higher FE_NO and urinary adenosine concentrations than healthy controls. After the challenge, 18 patients (40%) had EIB; these patients had higher levels of CaNO, CaNO TMAD, and urinary adenosine than patients without EIB. Baseline spirometry, FE _NO , JawNO, JawNO TMAD, urinary 8-OxodG, allergy, and blood eosinophil counts were found similar in both groups. In multiple linear regression, the fall in FEV ₁ was explained by CaNO TMAD, urinary adenosine and blood eosinophil count, whereas the fall in FEF _25-75 was explained by CaNO TMAD and blood eosinophil count. Both CaNO TMAD ≥10.5 ppb and urinary adenosine ≥406 nmol/mmol Cr predicted a fall in FEV ₁ ≥10%, while only CaNO TMAD ≥10.5 ppb predicted a fall in FEF _25-75 ≥26%.

CONCLUSION

Concentrations of peripheral airway NO are complementary with urinary adenosine for assessing EIB and promising tools of asthma control in pediatric patients with the atopic phenotype.

Oxidative Stress and Bronchial Asthma in Children-Causes or Consequences?

Bronchial asthma is one of the most common chronic inflammatory diseases of the airways. In the pathogenesis of this disease, the interplay among the genes, intrinsic, and extrinsic factors are crucial. Various combinations of the involved factors determine and modify the final clinical phenotype/endotype of asthma. Oxidative stress results from an imbalance between the production of reactive oxygen species and reactive nitrogen species and the capacity of antioxidant defense mechanisms. It was shown that oxidative damage of biomolecules is strongly involved in the asthmatic inflammation. It is evident that asthma is accompanied by oxidative stress in the airways and in the systemic circulation. The oxidative stress is more pronounced during the acute exacerbation or allergen challenge. On the other hand, the genetic variations in the genes for anti-oxidative and pro-oxidative enzymes are variably associated with various asthmatic subtypes. Whether oxidative stress is the consequence of, or the cause for, chronic changes in asthmatic airways is still being discussed. Contribution of oxidative stress to asthma pathology remains at least partially controversial, since antioxidant interventions have proven rather unsuccessful. According to current knowledge, the relationship between oxidative stress and asthmatic inflammation is bidirectional, and genetic predisposition could modify the balance between these two positions-oxidative stress as a cause for or consequence of asthmatic inflammation.

Exercise test using dry air in random adolescents: Temporal profile and predictors of bronchoconstriction

BACKGROUND AND OBJECTIVE

Guidelines recommend exercise tests using dry air to diagnose exercise-induced bronchoconstriction (EIB). Lung function changes subsequent to these tests have not been investigated in a general adolescent population, and it remains unknown whether signs of airway inflammation, measured using exhaled nitric oxide (FeNO), can predict a positive response. The aim of this study was to investigate the temporal aspect of decline in forced expiratory volume in 1 s (FEV1 ) after an exercise test using dry air, and to investigate predictors of EIB.

METHODS

From a cross-sectional study on adolescents aged 13-15 years (n = 3838), a random subsample of 146 adolescents (99 with and 47 without self-reported exercise-induced dyspnoea) underwent standardized treadmill exercise tests for EIB while breathing dry air.

RESULTS

Of the adolescents, 34% had a positive EIB test (decline of ≥10% in FEV1 from baseline) within 30 min. Of the subjects with EIB, 53% showed the greatest decline in FEV1 at 5 to 10 min (mean decline 18.5%), and the remaining 47% of the subjects showed the greatest decline at 15 to 30 min (mean decline 18.9%) after exercise. Increased FeNO (>20 ppb), female gender and self-reported exercise-induced dyspnoea were independently associated with a positive EIB test.

CONCLUSION

When assessing general adolescents for EIB with exercise test using dry air, there is a temporal variation in the greatest FEV1 decline after exercise. Therefore, lung function should be measured for at least 30 min after the exercise. Increased FeNO, female gender and self-reported exercise-induced dyspnoea can be predictors of a positive EIB test.

Ultrafine particle content in exhaled breath condensate in airways of asthmatic children

Air pollution triggers and exacerbates airway inflammation. Particulate material (PM) in ambient is characterized as being coarse (PM 10, aerodynamic diameter range 2.5-10 µm), fine (PM 2.5, 2.5-0.1 µm) and ultrafine (UFP, nano-sized, <0.1 µm). It is known that smaller inhaled PM produced more inflammation than larger ones. Most data on human exposure to PM are based on environmental monitoring. We evaluated the effect of individual exposure to UFP on functional respiratory parameters and airway inflammation in 52 children aged 6-18 years referred to the Pulmonary and Allergic Diseases Laboratory due to respiratory symptoms. Spirometry, bronchial provocation challenge, induced sputum (IS), exhaled breath condensate (EBC) and franctional exhaled nitric oxide evaluations were performed by conventional methods. UFP content in EBC was analyzed by using a NanoSight Light Microscope LM20. The total EBC UFP content correlated with wheezing (r = 0.28, p = 0.04), breath symptom score (r = 0.3, p = 0.03), and sputum eosinophilia (R = 0.64, p = 0.005). The percent of EBC particles in the nano-sized range also correlated with wheezing (r = 0.36, p = 0.007), breath symptom score (r = 0.33, p ≤ 0.02), and sputum eosinophilia (r = 0.72, p = 0.001). Respiratory symptoms and airway inflammation positively correlated to UFP content in EBC of symptomatic children.