Head-to-head comparison of single-breath and tidal-breath exhaled nitric oxide measurements

Abstract

Background: exhaled nitric oxide (eNO) is an endogenous gas involved in airway pathophysiology and is determined in orally exhaled air by various techniques. however, traditional single-breath technique (eNO sB ) requires active cooperation and is not always easily practicable (especially in young children); simpler techniques including tidal breathing measurements (eNO TB ) are not standardized. The aim of this study was to evaluate the possible correlation and correspondence between eNO sB and eNO TB and the impact of potential confounders in children with chronic adenotonsillar disease. Methods: eighty-six children (mean age 8.7 ± 3.2 y) underwent eNO assessment by means of eNO sB and eNO TB . The correlation among eNO TB , eNO sB , and other potential confounders (i.e., gender, age, weight, height, BMI, and passive smoking exposure) were studied. results: The analyses showed a poor correspondence between eNO sB and eNO TB , with the latter underestimating (P < 0.001) mean eNO values: 6.4 parts per billion (ppb) (95% confidence interval (cI): 8.4-11.4 ppb) vs. 9.8 ppb (95% cI: 5.6-7.3 ppb). a greater correlation was found between eNO sB and eNO TB in children younger than 6 y. Only eNO sB and age predicted eNO TB (R 2 = 43.6%). conclusion: eNO TB is not a good predictor of eNO sB in children. constant-flow eNO sB is the technique of choice for eNO assessment in young children.

Measurement of Exhaled Nitric Oxide Using End Tidal Value during Normal Breathing

“…The ATS guidelines attempted to create a uniform method for measuring and reporting exhaled NO, however, investigators remain reluctant about the procedure, and have looked for other ways to measure exhaled NO [28][29][30]. Some studies compared the single breath measurement with measurement from mixed expired air during tidal breathing [15,29,31].…”

“…Some studies compared the single breath measurement with measurement from mixed expired air during tidal breathing [15,29,31]. Mixed expired samples may be highly affected by NO in dead space (physiological and anatomical) or contamination by NO derived from ambient or nasal NO.…”