EXHALED NITRIC-OXIDE MEASUREMENTS IN NORMAL AND ASTHMATIC-CHILDREN

The aim of this study was to determine whether we could measure exhale d nitric oxide (NO) levels in children, and whether the same pattern o f exhaled NO concentrations was observed in asthmatic and normal child ren as had been seen in adults. Using a chemiluminescence NO analyzer, we measured NO in exhaled air both directly and through a T-piece all owing us to measure carbon dioxide (CO2), mouth pressure, and expirato ry flows. In 39 normal children the mean peak exhaled NO was 49.6 part s per billion (ppb) (SD 37.4) when all expired gas passed directly thr ough the NO analyzer, and 29.7 ppb (SD 27.1) when expiration occurred through a T-piece. The results were significantly higher in 15 asthmat ic subjects on bronchodilator therapy only [126.1 ppb (SD 77.1) direct (P < 0.001), and 109.5 ppb (SD 106.8) via T-piece (P < 0.001)]. In 16 asthmatics on regular inhaled corticosteroids the mean peak exhaled l evels were significantly lower 48.7 ppb (SD 43.3) direct(P < 0.001) an d 45.2 ppb (SD 45.9) via T-piece (P < 0.01). There was no difference b etween the normal children and the asthmatic children on regular inhal ed corticosteroids (P = 0.9 direct, P = 0.2 via T-piece). There were n o significant differences in carbon dioxide levels, mouth pressure, du ration of expiration and expiratory flows between the different groups , and no difference between carbon dioxide levels, mouth pressure and duration of expiration between the two methods (direct and T-piece). I n 6 asthmatic children mean peak exhaled levels on NO fell from a medi an peak level of 124.5 ppb to 48.6 ppb when measured before and 2 week s after commencement of inhaled corticosteroid treatment. The measurem ent of exhaled NO levels may be useful as a noninvasive means of monit oring children with asthma. (C) 1997 Wiley-Liss, Inc.