Source: Annual Congress 2002 - The role of inflammatory markers in children with asthma
Disease area: Airway diseases, Paediatric lung diseases

Abstract

Background & Aims: Opinion varies as to the effect that ambient nitric oxide (NO) levels have on exhaled nitric oxide (ENO) measurement. It is usually recommended that NO free air be inhaled if the ambient NO level is >10 parts per billion (ppb). Offline bag techniques could be used for large-scale epidemiological studies, but ambient NO measurement and the use of NO free air in this context is impractical. The aim of this study was to use a simple zero air filter with various methods of ENO measurement and to examine the effect that ambient NO had on the ENO values obtained.
Methods: Children [n=264, 89 normals, 175 asthmatics, 143 males, aged 4 to 14 y (median 9 y)] were recruited. ENO was measured using an online restricted breath technique, a tidal breathing method and an offline ENO bag method. For the offline bag technique, a zero NO filter was always used, and if the ambient NO level was >20 ppb the filter was used for the other methods.
Results: Median (IQR) ENO values (ppb) for online, tidal and offline methods were 11.2 (6.5-27.0), 4.8 (1.8-9.8) and 11.1 (6.7-19.2) respectively. Median (IQR, range) ambient NO values (ppb) were 5.6 (3.0-10.8, 0-100). Ambient NO and ENO were not correlated when measured by the online (r=0.05, p=0.44), tidal breathing (r=-0.05, p=0.49) or offline technique (r=0.14, p=0.17).
Conclusions: Using a simple protocol involving a zero NO filter, ambient NO did not affect ENO levels as measured by 3 different methods. This calls into question the current recommendations regarding the need for inhalation of NO free air, which would be impractical for community epidemiological studies.
Support: RDO(NI); NAC(UK); MSD(Equipment grant).

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Citations should be made in the following way:
T. J. Warke, V. A. Mairs, J. Finnegan, P. S. Fitch, M. Ennis, M. D. Shields (Belfast, United Kingdom). The effect of ambient nitric oxide on exhaled nitric oxide measurement in children. Eur Respir J 2002; 20: Suppl. 38, 920

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