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.

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.

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.

Lung function in children following empyema

Spirometry was performed and response to exercise was measured in 15 children following recovery from empyema to evaluate the impact of pleural infection on subsequent lung function. Seven children underwent chest tube drainage; eight did not. The two groups were similar in age (mean +/- SD, 6 +/- 5 years), sex distribution, bacterial pathogen-producing empyema, and age at follow-up evaluation (12 +/- 5 years). Only one child reported recurrent respiratory symptoms. No child had restrictive spirometric changes (total lung capacity, less than 80%; vital capacity, less than 80% predicted) but seven of 15 had a reduced forced expiratory volume in 1 second (less than 80% predicted) or forced expiratory flow during the middle half of the vital capacity (less than 75% predicted), suggesting mild airway obstruction. No child demonstrated reduced exercise tolerance due to restrictive ventilatory limitations. Mild obstructive abnormalities in lung function were identified with equal frequency in children treated with and without chest tube drainage.