What Does a Single Exhaled Nitric Oxide Measurement Tell us in Asthmatic Children?

Gender and age affect the levels of exhaled nitric oxide in healthy children

Asthma is a chronic inflammatory disorder of the lung and diagnosis is difficult in children. The measurement of fractional exhaled nitric oxide (FeNO) may be useful in the diagnosis and monitoring of treatments. A number of factors affect FeNO levels and their influence varies across countries and regions. This study included 300 healthy students, aged from 6 to 14 years, who participated voluntarily. A comprehensive medical survey was used and measurements of FeNO levels and spirometric parameters were recorded in Shenyang, China. We observed that the median FeNO was 11 ppb (range, 8–16 ppb) in children from the northern areas of China. For males, the median level was 13 ppb (range, 9–18 ppb) and the median level was 10 ppb (range, 8–14 ppb) for females. There was a significant difference between males and females (P= 0.007) and age was correlated with FeNO (R²= 0.6554), while weight, height, body mass index (BMI), forced vital capacity (FVC), forced expiratory volume (FEV1), FEV1/FVC and peak expiratory flow (PEF) had no correlation with FeNO. In conclusion, the median FeNO is 11 ppb (range, 8–16 ppb) in male and female healthy children from northern areas of China and is affected by gender and age.

[Physiological characteristics associated with previous control in asthmatic children]

OBJECTIVE

To analyze MEF(50%) (central airways), RV/TLC (distal airways), reversibility of FEV(1) (bronchial tone, REV(FEV1)) and FE(NO) (inflammation) in relation to clinical events in asthmatic children on the assumption that mild symptoms and severe exacerbations in the previous 3 months could be associated with distinct functional characteristics.

PATIENTS AND METHODS

A retrospective, single center, out-patient hospital study including all asthmatic children who had complete lung function testing (without and with bronchodilation) during a period of clinical stability, without treatment on the day of the test.

RESULTS

Two hundred and forty-five children (11.4±2.4 years) were included: 114 (46%) were asymptomatic, 87 (36%) had minor symptoms and 44 (18%) had had a severe exacerbation in the past 3 months. FEV(1), FEV(1)/FVC and MEF(50%) were not different in these three groups. REV(FEV1) was higher in the symptomatic than in the asymptomatic group (P=0.019), RV/TLC was greater in the exacerbation group than in the asymptomatic group (P=0.019), and FE(NO) was higher in the symptomatic group than in the asymptomatic and exacerbation groups (P=0.006).

CONCLUSIONS

In asthmatic children, minor symptoms and severe exacerbation in the previous 3 months are associated with distinct functional characteristics that are not detected by single baseline spirometry without treatment on the day of testing.

Exhaled nitric oxide and clinical phenotypes of childhood asthma

Whether exhaled NO helps to identify a specific phenotype of asthmatic patients remains debated. Our aims were to evaluate whether exhaled NO (FENO(0.05)) is independently associated (1) with underlying pathophysiological characteristics of asthma such as airway tone (bronchodilator response) and airway inflammation (inhaled corticosteroid [ICS]-dependant inflammation), and (2) with clinical phenotypes of asthma.We performed multivariate (exhaled NO as dependent variable) and k-means cluster analyses in a population of 169 asthmatic children (age ± SD: 10.5 ± 2.6 years) recruited in a monocenter cohort that was characterized in a cross-sectional design using 28 parameters describing potentially different asthma domains: atopy, environment (tobacco), control, exacerbations, treatment (inhaled corticosteroid and long-acting bronchodilator agonist), and lung function (airway architecture and tone). Two subject-related characteristics (height and atopy) and two disease-related characteristics (bronchodilator response and ICS dose > 200 μg/d) explained 36% of exhaled NO variance. Nine domains were isolated using principal component analysis. Four clusters were further identified: cluster 1 (47%): boys, unexposed to tobacco, with well-controlled asthma; cluster 2 (26%): girls, unexposed to tobacco, with well-controlled asthma; cluster 3 (6%): girls or boys, unexposed to tobacco, with uncontrolled asthma associated with increased airway tone, and cluster 4 (21%): girls or boys, exposed to parental smoking, with small airway to lung size ratio and uncontrolled asthma. FENO(0.05) was not different in these four clusters.In conclusion, FENO(0.05) is independently linked to two pathophysiological characteristics of asthma (ICS-dependant inflammation and bronchomotor tone) but does not help to identify a clinically relevant phenotype of asthmatic children.

Prediction of nosocomial infection acquisition in ventilated patients by nasal nitric oxide: proof-of-concept study

The development of biomarkers able to predict the occurrence of nosocomial infection could help manage preventive strategies, especially in medical patients whose degree of acquired immunosuppression may be variable. We hypothesized that the NO fraction present in the airways (upper and lower) of critically ill patients under mechanical ventilation could constitute such a biomarker. We conducted an observational proof-of-concept study in a medical intensive care unit of a teaching hospital. Forty-five patients (26 men; 72 [25th-75th percentiles] years [56-82]; Simplified Acute Physiology Score II, 63 [50-81], 14 infected) under mechanical ventilation (>3 days) underwent on day 1 and day 3 of their stay: nasal and exhaled (partitioned in bronchial and alveolar sources) bedside NO measurements, determination of urine NO end products and plasma cytokine (IL-6, IL-10) concentrations, and Sequential Organ Failure Assessment score calculation. Nosocomial infection incidence was recorded during the 15 subsequent days. Fifteen patients (33%) acquired a nosocomial infection (16 infections, 15 ventilator-associated pneumonia and 1 bacteremia). Nasal NO was the only marker significantly different between patients with and without subsequent infection (day 1, 52 ppb [20-142] vs. 134 [84-203], P = 0.038; day 3, 98 ppb [22-140] vs. 225 [89-288], P = 0.006, respectively). Nasal NO fraction 148 ppb or less at day 3 had an 80% sensitivity, a 70% specificity, and an odds ratio of 2.7 (95% confidence interval, 1.9-3.8) to predict acquisition of nosocomial infection. Nonsurvivors had a higher IL-6 concentration on day 3 (P = 0.014), whereas their nasal NO fractions were not significantly different. Nasal NO seems to be a relatively sensitive and specific biomarker of subsequent nosocomial infection acquisition (at least for ventilator-associated pneumonia), which warrants confirmation in a multicenter trial.

Influence of age on the risk of severe exacerbation and asthma control in childhood

BACKGROUND

Asthma is a heterogeneous disease but it is a common observation that children tend to "grow out of their asthma."

OBJECTIVE

The aim was to specifically assess the influence of age on the occurrence of a severe exacerbation (at least 3 days use of systemic corticosteroid--international 2009 definition) and of the achievement of control (GINA guidelines) in children treated for asthma. Our study was controlled for amount of therapy and for season.

METHODS

Children under inhaled corticosteroid (ICS) were enrolled over two 2-month periods (autumn, spring). Duration of oral steroid treatment and of symptoms, dose of ICS and long-acting beta-agonist were recorded for the past 3 months.

RESULTS

Three hundred and fifty-nine children (110 girls) were included (48 [<2 years], 116 [2-6 years], 107 [6-10 years], 88 [>10 years]) during autumn (n = 175) and spring (n = 184), all treated by ICS (mean daily dose ± SD = 378 ± 250 μg). Among the 359 children, 133 (37%) experienced at least one severe exacerbation, and control was observed in 111 (31%) children. A multivariate logistic regression model demonstrated that age, season, and ICS dose are independent risk factors for exacerbation, whereas age is the only predictor of control. The odds ratio of exacerbation and control are 0.85 (95% CI, 0.78-0.92, p < .0001) and 0.85 (95% CI, 0.79-0.91, p < .0001) per year of increase in age, respectively.

CONCLUSIONS

From infancy to adolescence, each year of life reduces per se the risk of a severe exacerbation by 15% and similarly increases the achievement of control in children treated for asthma.

Lung function impairment evidenced by sequential specific airway resistance in childhood persistent asthma: a longitudinal study

BACKGROUND

Specific airway resistance (sRaw) is virtually independent of lung growth, height, and gender, thus facilitating longitudinal follow-up.

OBJECTIVE

To assess whether a specific phenotype of asthmatic children with a decline in lung function can be evidenced using sRaw.

METHODS

The authors hypothesized that sequential sRaw measurements over a long period would detect subtle trends. Clinical and functional data of children with persistent asthma under inhaled corticosteroids, evaluated at least three times per year for at least 4 years, were retrieved from a database.

RESULTS

One hundred fourteen children (30 girls) were followed for (median [interquartile range]) 6.9 years [5.6-7.9]. Data from 1699 measurements of sRaw (median 14/child) allowed the calculation of individual slopes of sRaw plotted against time demonstrating stable values in the group as a whole between 4 and 18 years. A positive correlation between individual slopes and the degree of intraindividual variation of sRaw was observed (R(2) = .16; p < .0001). Children with more than one positive skin test showed larger intrasubject variation of sRaw (p = .011). In 19/114 children (17%), a significant increase in sRaw of 12.3% per year (median) was observed. As compared to children without, those with a significant increase in sRaw were boys (p < .0001), had a lower initial (p = .008) and a higher final resistance (p = .025) but did not differ in terms of inhaled corticosteroid dose.

CONCLUSION

This retrospective study identifies a specific phenotype of asthmatic children that develops an impairment of lung function, confirming the results of a post hoc analysis of the Childhood Asthma Management Program study.

Partitioning of exhaled NO in ventilated patients undergoing cardiac surgery

The change in exhaled NO after cardio-pulmonary bypass remains controversial. The aims were to determine whether exhaled NO sources (alveolar or bronchial) are modified after bypass, and whether mechanical ventilation (MV) settings during bypass modify exhaled NO changes. Thirty-two patients were divided into three groups: without MV during bypass and positive end-expiratory pressure (PEEP) (n=12), dead space MV without PEEP (n=10) and dead space MV with PEEP (n=10). Alveolar NO concentration and bronchial NO flux were calculated before and 1h after surgery using a two-compartment model of NO exchange developed in spontaneous breathing patients. Whereas a significant decrease in bronchial NO was found after bypass in the two groups without PEEP during bypass, this decrease was not observed in patients with dead space ventilation with PEEP. Alveolar NO was not significantly modified whatever the ventilation settings. In conclusion, the impairment of bronchial NO seemed related to airway closure since dead space mechanical ventilation with PEEP prevented its decrease.

The link between exhaled NO and bronchomotor tone depends on the dose of inhaled steroid in asthma

BACKGROUND

Exhaled NO (FE(NO)) is a steroid dose dependent eosinophilic inflammometer, but also a mediator of bronchomotor tone, but statistically significant relationships have infrequently been obtained with pulmonary function tests (PFT). The aim was to test the hypothesis that the relationships between FE(NO) and PFT could be uncovered by inhaled corticosteroid (ICS) treatment, namely that a link between FE(NO) and bronchodilator response (an index of bronchomotor tone) would appear under ICS.

METHODS

Exhaled NO, forced expiratory flows and lung volumes were measured in atopic asthmatic children without recent (one month) respiratory symptoms.

RESULTS

Two hundred and thirty children (mean + or - SD, age: 11.2 + or - 2.5 years, 69 girls) were included (% predicted, FEV(1): 100 + or - 14; FEF(50%): 76 + or - 23; RV: 107 + or - 29). The relationship between ICS dose (GINA classification) and FE(NO) plateaued in children with an ICS dose higher than 200 microg beclomethasone equipotent daily dose: FE(NO) (median [25th-75th percentiles]), 43 ppb [15-105] (no treatment, n=65), 33 ppb [15-77] (low dose, n=70), 23 ppb [12-57] (medium dose, n=57) and 26 ppb [9-49] (high dose, n=38). Statistically significant relationships between FE(NO) and PFT were only observed in children receiving more than 200 microg/day ICS: with FEV(1) (medium ICS dose: rho=0.43, p=0.001; high dose: rho=0.32, p=0.052) and bronchodilator (400 microg salbutamol) response (medium dose: rho=0.54, p=0.001; high dose: rho=0.65, p=0.002).

CONCLUSIONS

A positive correlation between FE(NO) and bronchomotor tone appears with increasing ICS doses in atopic children with clinically controlled asthma, which further suggests that children depicting the highest FE(NO) values may have lesser steroid sensitivity.