Levels of exhaled nitric oxide in recurrently wheezy infants are decreasedfollowing inhaled steroid therapy

We investigated the variability of exhaled nitric oxide over both short (on e hour) and extended (four-week) periods of time using the single-breath te chnique with positive expiratory pressure (SBT-PEP) in a population of 16 h ealthy (n = 4) and wheezy (n = 12) infants. In addition, wheezy infants wit h high levels of exhaled nitric oxide and a positive parental history of as thma were randomised to untreated (n = 6) or treated (n = 6) groups. The tr eated group received nebulised budesonide twice daily for four weeks. Lung function was also assessed by the raised volume rapid thoracic compression technique (RVRTC). Levels of exhaled nitric oxide were obtained by the SBT- PEP technique. The infants' lungs are raised to a trans-respiratory pressur e of 20 cm H2O three times, after the third inflation a jacket surrounding the chest and abdomen of the infant is manually inflated and forced expirat ion is initiated against an expiratory resistance, resulting in constant fl ow and airway opening pressure. Exhaled nitric oxide was measured using a r apid response chemiluminiscence analyser and plateau values were reported. Mean values of exhaled nitric oxide were lower in healthy than in wheezy in fants (10.3 +/- 3.2 ppb and 38.2 +/- 6.9 ppb, p <0.001 respectively). Value s of exhaled nitric oxide determined one hour (n = 16) and four weeks (n = 10) apart showed good agreement (coefficient of repeatability 5.1 ppb and 7 .3 ppb respectively). Wheezy infants treated with inhaled steroids for a pe riod of four weeks had significantly reduced levels of exhaled nitric oxide and increased values of FEV0.5 (39.4 +/- 8.0 ppb and 15.2 +/- 1.2 ppb, p < 0.001; 161 +/- 31.5 and 210 +/- 28.8 mi, p <0.02), while the untreated grou p did not. We conclude that measurements of exhaled nitric oxide are highly reproducible over both short and extended periods of time in infants. Inha led steroids in infants with recurrent wheeze, high levels of exhaled nitri c oxide and a positive parental history of asthma reduced exhaled nitric ox ide to levels similar to that seen in healthy infants, suggesting that youn g infants with a history of recurrent wheeze may have underlying chronic ai rway inflammation.