Exhaled nitric oxide in children measured by tidal breathing method: Differences between asthmatics and nonasthmatic controls

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Abstract
The single‐breath maneuver used to measure nitric oxide (NO) in adults cannot be performed by young children. We, therefore, developed a method of measuring NO in mixed exhaled gas collected during tidal breathing. NO was measured in mixed exhaled gas during 5 min of tidal breathing in 113 children 4–14 years of age: 22 nonasthmatics, 21 asthmatic children not taking inhaled corticosteroids, and 70 asthmatic children using inhaled corticosteroids. Exhaled NO levels (median, range) were significantly lower in nonasthmatic controls (median, range: 7, 2–10 ppb) than in asthmatic children on inhaled corticosteroids (8, 3–25 ppb; 95% CI for difference in medians with those of controls, 0–4 ppb), and in those not on inhaled corticosteroids (13, 6–37, ppb; 95% CI for difference in medians, 5–17 ppb). Asthmatic children not using inhaled corticosteroids had significantly higher exhaled NO levels than asthmatic children using inhaled corticosteroids (95% CI for difference in medians, 3–10 ppb). The tidal breathing method is a useful and practical way of measuring exhaled NO levels in children regardless of their age. Pediatr Pulmonol. 2000; 29:434–437.