Changes in breathing pattern upon 100% oxygen during N2MBW in children

Abstract

Background: Nitrogen multiple breath washout (N2MBW) with 100% oxygen (O2) is frequently used as diagnostic tool for abnormal lung function. However, it has been shown that the use of 100% O2 can influence breathing pattern in infants. It is unknown whether O2 influences breathing pattern in older children. We systematically compared normal breathing pattern (ambient air) and possible changes due to 100% O2 administration. Methods: We performed one tidal breathing and two N2MBW measurements in former preterm children and healthy controls using Exhalyzer D (Spiroware, Eco Medics) according to ERS/ATS consensus. The first 10 breaths of tidal breathing measurements were excluded for analysis. We compared tidal volume (VT) and coefficient of variation of VT (CVVT) between tidal breathing in room air vs. O2-exposure during N2MBW by paired t-test. Sensitivity analysis was performed by comparing the effect of different numbers of breaths (8, 10, and 12). Results: We measured 40 children (24=healthy; 16=former preterm) aged mean (sd) 6.8 (0.9) years. There was no difference in VT or in CVVT between tidal breathing in room air compared to breathing during the first or second N2MBW. These findings were consistent in both preterm and term children and confirmed by sensitivity analysis. There was no difference in the lung clearance index (LCI) between the first and the second O2-exposure. Conclusion: We did not find any difference in VT after administration of 100% O2 in healthy and former preterm children. CVVT did not differ between measurements but was generally high in this age group (mean: 25.8%). The known effect of 100% O2 in infancy seems to be outgrown at early school age.