Comparison of online single-breath vs. online multiple-breath exhaled nitric oxide in school-age children

Evaluation of the Double-Tracer Gas Single-Breath Washout Test in a Pediatric Field Study

BACKGROUND

The early life origins of chronic pulmonary diseases are thought to arise in peripheral small airways. Predictors of ventilation inhomogeneity, a proxy of peripheral airway function, are understudied in schoolchildren.

RESEARCH QUESTION

Is the double-tracer gas single-breath washout (DTG-SBW) measurement feasible in a pediatric field study setting? What are the predictors of the DTG-SBW-derived ventilation inhomogeneity estimate in unselected schoolchildren?

STUDY DESIGN AND METHODS

In this prospective cross-sectional field study, a mobile lung function testing unit visited participating schools in Switzerland. We applied DTG-SBW, fraction of exhaled nitric oxide (Feno), and spirometry measurements. The DTG-SBW is based on tidal inhalation of helium and sulfur-hexafluoride, and the phase III slope (SIIIHe-SF6) is derived. We assessed feasibility, repeatability, and associations of SIIIHe-SF6 with the potential predictors of anthropometrics, presence of wheeze (ie, parental report of one or more episode of wheeze in the prior year), Feno, FEV1, and FEV1/FVC.

RESULTS

In 1,782 children, 5,223 DTG-SBW trials were obtained. The DTG-SBW was acceptable in 1,449 children (81.3%); the coefficient of variation was 39.8%. SIIIHe-SF6 was independently but weakly positively associated with age and BMI. In 276 children (21.2%), wheeze was reported. SIIIHe-SF6 was higher by 0.049 g.mol.L-1 in children with wheeze compared with those without and remained associated with wheeze after adjusting for age and BMI in a multivariable linear regression model. SIIIHe-SF6 was not associated with Feno, FEV1, and FEV1/FVC.

INTERPRETATION

The DTG-SBW is feasible in a pediatric field study setting. On the population level, age, body composition, and wheeze are independent predictors of peripheral airway function in unselected schoolchildren. The variation of the DTG-SBW possibly constrains its current applicability on the individual level.

TRIAL REGISTRATION

ClinicalTrials.gov; No.: NCT03659838; URL: www.

CLINICALTRIALS

gov.

Tidal breathing FeNO measurements: a new algorithm

OBJECTIVE

International guidelines recommend measuring fractional exhaled nitric oxide (FeNO) during a single slow exhalation with a constant flow of 50 ml/sec. We developed a new algorithm to compute FeNO at 50 ml/sec from tidal breathing measurements. The main objective is to assess the correlation and agreement of this algorithm with the conventional single breath FeNO measurements.

METHODS

We recruited children aged 6-18 years, who performed both a single breath and a tidal breathing FeNO measurement in random order. Both maneuvers were performed on the Eco Medics NO-analyser (Eco Physics AG, Duernten, Switzerland).

RESULTS

We included 109 patients between January 2011 and April 2011. Geometric mean (95% CI) FeNO values did not differ significantly between single breath and tidal breathing technique: 21.0 (17.7-24.8) ppb and 20.0 (17.0-23.6) ppb (P = 0.18), respectively. We found an excellent intraclass correlation coefficient of 0.96 (0.94-0.97) and moderate agreement with a mean difference of 4% (95% limits of agreement -43% and +90%).

CONCLUSION

Tidal breathing FeNO values could be transformed with a new algorithm to match single breath FeNO at a constant flow of 50 ml/sec. This algorithm opens the way to standardized FeNO measurements in preschool children and uncooperative patients.