Effect of elevated exhaled nitric oxide levels on the risk of respiratory tract illness in preschool-aged children with moderate-to-severe intermittent wheezing

Exhaled Nitric Oxide in Wheezy Infants Predicts Persistent Atopic Asthma and Exacerbations at School Age

BACKGROUND

There are limited data assessing the predictive value of fraction of exhaled nitric oxide (FENO) in infants/toddlers with recurrent wheezing for asthma at school age.

OBJECTIVES

In a cohort of infants/toddlers with recurrent wheezing determine the predictive values of sedated single-breath FENO (SB-FENO) and awake tidal-breathing mixed-expired FENO (tidal-FENO) for active asthma, severe exacerbations, and lung function at age 6 years.

METHODS

In 44 infants/toddlers, SB-FENO was measured under sedation at 50 mL/sec in conjunction with forced expiratory flow and volume measurements, and tidal-FENO was measured during awake tidal breathing. Clinical outcomes and lung function were assessed at age 6 years in 36 subjects.

RESULTS

Enrollment SB-FENO was significantly higher among subjects with active asthma at age 6 years than among subjects without asthma (36.4 vs. 16.9 ppb, p < 0.0001), and the odds of asthma was 7.6 times greater (OR 7.6; 95% CI 1.8-31.6) for every 10 ppb increase in enrollment SB-FENO. A ROC analysis demonstrated that an enrollment SB-FENO > 31.5 ppb predicted active asthma at age 6 years with an area under the curve (AUC) of 0.92 (95% CI: 0.82-1). SB-FENO was also higher among subjects who experienced severe asthma exacerbations during the year preceding age of 6 years. SB-FENO at enrollment and lung function measures at age 6 years were modestly correlated (FEV1: r = -0.4; FEF25-75: r = -0.41; FEV1/FVC ratio: r=-0.46), and SB-FENO was significantly higher among subjects with bronchodilator responsiveness (BDR) at age 6 years. Tidal-FENO was not predictive of active asthma, exacerbations, or lung function at age 6 years.

CONCLUSION

In wheezy infants/toddlers, SB-FENO was predictive of school-age asthma and associated with lung function measures at age 6 years.

Management of Preschool Children with Recurrent Wheezing: Lessons from the NHLBI's Asthma Research Networks

Recurrent wheezing in the preschool children is a common clinical problem, often associated with significant morbidity related to acute episodes. The management of these children has been complicated by a paucity of high-quality clinical trials in this age group. To fill this knowledge gap, National Heart, Lung, and Blood Institute's asthma research networks have performed a series of clinical trials in an effort to provide practitioners with guidance on appropriate management strategies. These studies establish daily inhaled corticosteroid (ICS) therapy in toddlers at high risk for subsequent asthma as an effective approach for the prevention of exacerbations and symptom reduction, but without evidence of disease-modifying properties. Additional studies have confirmed substantial heterogeneity in ICS response, in terms of both efficacy and effect on linear growth. Treatment with intermittent high-dose ICS was demonstrated to be an alternative approach to daily low-dose ICS for preventing severe exacerbations in toddlers with intermittent but significant wheeze and a positive modified asthma predictive index. This review details the findings and clinical implications derived from these studies, discuss the utility of biomarkers and the role of oral corticosteroids during acute exacerbations, and summarizes ongoing clinical trials in this age group.

Association of recent exposure to ambient metals on fractional exhaled nitric oxide in 9-11 year old inner-city children

Exposure to ambient metals in urban environments has been associated with wheeze, and emergency room visits and hospitalizations due to respiratory illness. However, the effect of ambient metals exposure on airway inflammation, and how these associations may be modified by seroatopy, has not been determined. Fractional exhaled nitric oxide (FENO) is a reliable proxy marker of airway inflammation. We hypothesized that recent ambient concentrations of Ni, V, Zn and Fe would be associated differentially with proximal and distal fractions of exhaled NO, and that these associations would be modified by seroatopy. As part of the Columbia Center for Children's Environmental Health (CCCEH) birth cohort study, 9-11 year old children (n=192) were evaluated. Ambient measures of Ni, V, Zn and Fe were obtained from a local central monitoring site and averaged over 9 days based on three 24h measures every third day. Fractional exhaled nitric oxide (FENO) samples were obtained at constant flows of 50 (FENO50), 83 and 100mL/s, and used to determine surrogate measures for proximal (JNO) and alveolar (Calv) inflammation. Seroatopy was determined by specific IgE at age 7. Data were analyzed using multivariable linear regression. Ambient V and Fe concentrations were associated positively with FENO50 (p=0.018, p=0.027). Ambient Fe was associated positively with JNO (p=0.017). Ambient Ni and V concentrations were associated positively with Calv (p=0.004, p=0.018, respectively). A stronger association of Ni concentrations with Calv was observed among the children with seroatopy. These results suggest that ambient metals are associated differentially with different fractions of FENO production, and this relationship may be modified by seroatopy.

Exhaled nitric oxide predicts persistence of wheezing, exacerbations, and decline in lung function in wheezy infants and toddlers

BACKGROUND

There are limited data assessing the predictive value of fraction of exhaled nitric oxide (FENO ) for persistence of wheezing, exacerbations, or lung function change over time in infants/toddlers with recurrent wheezing.

OBJECTIVES

In an ongoing longitudinal cohort of infants and toddlers with recurrent wheezing, we compared predictive values of single-breath FENO (SB-FENO ), tidal-breathing mixed expired FENO (tidal-FENO ), bronchodilator responsiveness (BDR) and the Castro-Rodriquez Asthma Predictive Index (API) for persistence of wheezing, exacerbations and lung function change through age 3 years.

METHODS

Enrolment forced expiratory flows and volumes infant pulmonary function tests (iPFTs) were measured in 44 infants/toddlers using the raised volume rapid thoracoabdominal compression method. SB-FENO was measured at 50 mL/s, and tidal-FENO was measured during awake tidal breathing. Clinical outcomes were assessed at age 3 years in 42 infants. Follow-up iPFTs were completed between ages 2.5-3 years in 32 subjects.

RESULTS

An enrolment SB-FENO concentration ≥ 30 p.p.b. predicted persistence of wheezing at age 3 years with a sensitivity of 77%, a specificity of 94%, and an area under the curve (AUC) of 0.86 (95% CI: 0.74-0.98). The sensitivity, specificity, positive predictive, and negative predictive values of SB-FENO for persistence of wheezing and exacerbations were superior to tidal-FENO , BDR, and the API. SB-FENO ≥ 30 p.p.b. and tidal-FENO ≥ 7 p.p.b. measured at enrolment was associated with a decline in both FEV0.5 and FEF25-75 between enrolment and age 3 years.

CONCLUSIONS

In wheezy infants/toddlers, SB-FENO was superior to tidal-FENO , BDR, and the API in predicting future exacerbations and persistence of wheezing at age 3 years. Both SB-FENO and tidal-FENO were associated with lung function decline over time.

Guideline-recommended fractional exhaled nitric oxide is a poor predictor of health-care use among inner-city children and adolescents receiving usual asthma care

BACKGROUND

American Thoracic Society guidelines support using fractional exhaled nitric oxide (FENO) measurements in patients with asthma and highlight gaps in the evidence base. Little is known about the use of FENO levels to predict asthma exacerbations among high-risk, urban, minority populations receiving usual care.

METHODS

Children with persistent asthma (n = 138) were enrolled in a prospective, observational cohort study and skin tested at baseline (a wheal ≥ 3 mm indicated a positive skin-prick test). FENO levels, lung function, and asthma-related health-care use were assessed at baseline and every 3 months thereafter for 1 year. Relationships between FENO levels and health-care use in the subsequent 3 months were examined. Final models accounted for repeated outcome measures and were adjusted for age, sex, and lung function.

RESULTS

The mean age of the children was 11 years (range, 5-17 years), and most were male (57%), black (91%), and atopic (90%). At baseline, the median FENO level was 31.5 parts per billion (interquartile range, 16-61 ppb) and mean FEV1/FVC was 80.7% (SD, ± 9.6%). There were 237 acute asthma-related health-care visits, 105 unscheduled doctor visits, 125 ED visits, and seven hospitalizations during the follow-up period. FENO level was not a significant predictor of acute visits, ED visits, unscheduled doctor visits, or hospitalization in either unadjusted or adjusted analyses. Use of recommended cut points did not improve the predictive value of the FENO level (positive predictive value, 0.6%-32.8%) nor did application of the guideline-based algorithm to assess change over time.

CONCLUSIONS

FENO level may not be a clinically useful predictor of health-care use for asthma exacerbations in urban minority children with asthma.

Daily or intermittent budesonide in preschool children with recurrent wheezing

BACKGROUND

Daily inhaled glucocorticoids are recommended for young children at risk for asthma exacerbations, as indicated by a positive value on the modified asthma predictive index (API) and an exacerbation in the preceding year, but concern remains about daily adherence and effects on growth. We compared daily therapy with intermittent therapy.

METHODS

We studied 278 children between the ages of 12 and 53 months who had positive values on the modified API, recurrent wheezing episodes, and at least one exacerbation in the previous year but a low degree of impairment. Children were randomly assigned to receive a budesonide inhalation suspension for 1 year as either an intermittent high-dose regimen (1 mg twice daily for 7 days, starting early during a predefined respiratory tract illness) or a daily low-dose regimen (0.5 mg nightly) with corresponding placebos. The primary outcome was the frequency of exacerbations requiring oral glucocorticoid therapy.

RESULTS

The daily regimen of budesonide did not differ significantly from the intermittent regimen with respect to the frequency of exacerbations, with a rate per patient-year for the daily regimen of 0.97 (95% confidence interval [CI], 0.76 to 1.22) versus a rate of 0.95 (95% CI, 0.75 to 1.20) for the intermittent regimen (relative rate in the intermittent-regimen group, 0.99; 95% CI, 0.71 to 1.35; P=0.60). There were also no significant between-group differences in several other measures of asthma severity, including the time to the first exacerbation, or adverse events. The mean exposure to budesonide was 104 mg less with the intermittent regimen than with the daily regimen.

CONCLUSIONS

A daily low-dose regimen of budesonide was not superior to an intermittent high-dose regimen in reducing asthma exacerbations. Daily administration led to greater exposure to the drug at 1 year. (Funded by the National Heart, Lung, and Blood Institute and others; MIST ClinicalTrials.gov number, NCT00675584.).

The Asthma Predictive Index: a very useful tool for predicting asthma in young children

Recurrent wheezing is a common problem in young children: approximately 40% of children wheeze in their first year of life. However, only 30% of preschoolers with recurrent wheezing still have asthma at the age of 6 years. Nevertheless, asthma, the most prevalent chronic disease in children, is difficult to diagnose in infants and preschoolers. This article reviews the importance of determining at an early age which infants/preschoolers will have asthma later in life, analyzes the pros and cons of different predictive indices, and discusses the efficacy of the Asthma Predictive Index.

Exhaled nitric oxide, lung function, and exacerbations in wheezy infants and toddlers

BACKGROUND

There are limited data assessing the relationship between fraction of exhaled nitric oxide and lung function or exacerbations in infants with recurrent wheezing.

OBJECTIVES

In a longitudinal pilot study of children less than 2 years old, we assessed whether baseline fraction of exhaled nitric oxide was associated with lung function, bronchodilator responsiveness, changes in lung function, or subsequent exacerbations of wheezing.

METHODS

Forced expiratory flows and volumes using the raised-volume rapid thoracic compression method were measured in 44 infants and toddlers (mean age, 15.7 months) with recurrent wheezing. Single-breath exhaled nitric oxide (SB-eNO) was measured at 50 mL/s. Lung function was again measured 6 months after enrollment.

RESULTS

At enrollment, forced expiratory volume in 0.5 seconds (FEV(0.5)), forced expiratory flow at 25% to 75% of expiration (FEF(25-75)), and forced expiratory flow at 75% of expiration (FEF(75)) z scores for the cohort were significantly less than zero. There was no correlation between enrollment SB-eNO levels and enrollment lung function measures. SB-eNO levels were higher in infants with bronchodilator responsiveness (46.1 vs 23.6 ppb, P < .001) and was associated with a decrease in FEV(0.5) (r = -0.54, P = .001), FEF(25-75) (r = -0.6, P < .001), and FEF(75) (r = -0.55, P = .001) over 6 months. A 10-ppb increase in SB-eNO level was associated with a 0.4-point z score decrease in FEV(0.5), a 0.4-point z score decrease in FEF(25-75), and a 0.42-point z score decrease in FEF(75). SB-eNO level was superior to lung function and bronchodilator responsiveness in predicting subsequent wheezing treated with systemic steroids.

CONCLUSIONS

SB-eNO level might predict changes in lung function and risk of future wheezing and holds promise as a biomarker to predict asthma in wheezy infants and toddlers.