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Flow dependency and off-line measurement of exhaled NO in children
J G C van Amsterdam1, P Zanen, S Somer
1Laboratory of Health Effects Research, National Institute of Public Health and the Environment, PO Box 1, 3720 BA Bilthoven, The Netherlands. JGC.van.Amsterdam@rivm.nl
Insights
High exhaled nitric oxide (eNO) flow rates, specifically 350 ml/s, are feasible for measuring eNO in children as young as 3.5 years. This method effectively detects allergic disease without compromising diagnostic accuracy.
Area of Science:
- Respiratory Medicine
- Pediatric Allergy
- Biomarker Measurement
Background:
- Exhaled nitric oxide (eNO) levels are flow-dependent, impacting measurement accuracy.
- Previous recommendations for eNO measurement flow rates are unsuitable for young children.
- Optimal flow rates for off-line and on-line eNO measurement remain debated.
Purpose of the Study:
- To evaluate the efficacy of different exhalation flow rates for off-line eNO measurement in children.
- To determine if high flow rates can reliably discriminate between atopic and non-atopic children.
- To assess the feasibility and reproducibility of high-flow eNO measurements in young children.
Main Methods:
- Comparison of off-line eNO measurements at 8.3 ml/s and 350 ml/s in children aged 8-12 years.
- Evaluation of eNO's discriminatory power between normal and atopic children using receiver operating characteristic curves.
- Assessment of feasibility and reproducibility of high-flow (>350 ml/s) eNO maneuvers in children aged 3.5-5 years.
Main Results:
- Children sensitive to house dust mite showed significantly higher eNO levels at both 8.3 ml/s and 350 ml/s (p < 0.001).
- The discriminatory power of eNO between atopic and non-atopic subjects was similar across tested flow rates (p = 0.89).
- Children aged 4.5-5 years could perform high-flow maneuvers, with good reproducibility (5.5% variation) in younger children (35-46 months).
Conclusions:
- An exhalation flow rate of 350 ml/s is feasible for off-line eNO determination in children from 3.5 years of age.
- High flow rates do not compromise the ability of eNO to detect allergic disease.
- High-flow eNO measurement offers a viable option for pediatric allergy assessment.
Abstract:
Levels of exhaled nitric oxide (eNO) are flow-dependent, and the choice of an optimal flow rate for off-line and on-line eNO measurement has raised much debate. Recently, a flow rate of 50 ml/s was recommended, but children younger than 5-6 years are not capable of stabilizing their expiratory flow at low flow rates. The power of off-line eNO values to discriminate between normal and atopic children was therefore evaluated at different exhalation flow rates. At flow rates of both 8.3 ml/s and of 350 ml/s, children (8-12 years) sensitive to house dust mite have two-fold higher eNO values (p < 0.001) as compared with children lacking such a sensitivity. The power of eNO to discriminate between normal and atopic subjects was similar at the two flow rates (no difference in AUC of receiver operation curves, p = 0.89). All children from 4.5 to 5 years of age (n = 29) could perform a single off-line exhalation manoeuvre at high (>350 ml/s) but not at low (8.3 ml/s) flow rates. At high exhalation flow rate, eNO was 7.1 +/- 2.4 (mean +/- SD) median, 6.5 p.p.b. with a mean variation coefficient of 5.5%. Depending on their developmental level, about half of the younger children (35-46 months of age) could perform an off-line exhalation manoeuvre at high flow rate with good reproducibility (mean variation coefficient of 6.6%). It is concluded that an exhalation flow rate of 350 ml/s is feasible to determine off-line eNO-values in children from 3.5 years of age, and that this high flow rate does not compromise the power of eNO to detect allergic disease.