Increase in Alveolar Nitric Oxide in the Presence of Symptoms in Childhood Asthma. Part 5

All available measurements of FEno and V were used to compute these parameters. Several measurements at very low flow (< 40 mL/s) enhance the validity of the results concerning Dno and Cw,no.

In this model, the product (Dno X Cw,no) is the largest amount of NO that can be delivered by the nonexpansible compartment. The product (Dno X Cw,no) obtained by the nonlinear method reflects the same proximal airway ability to produce NO than Qbr,maxNO calculated by the linear method.

Lung Function Tests

Spirometry measurements and flow-volume curves were obtained using a spirometer (PF/DX 1085; SensorMedics; St. Paul, MN) after NO measurements. Pulmonary function tests were performed at least 12 h after discontinuation of long-acting P2-agonists (if possible). The highest values of three technically satisfactory forced expirations were taken and expressed as the percentages of predicted normal values. Maximal expiratory flow between 25% and 75% of FVC (MEF25_75) was used as an index of small-airway caliber. The children were classified into two subgroups according to whether their MEF25_75 value was < 50% of predicted or > 50% of predicted.

Statistical Analysis

Data are expressed as means ± SD. Comparison of the three groups (asymptomatic, recently symptomatic asthmatic children, and healthy children) was done using analysis of variance. When a significant difference was found, individual means were compared using the modified t test. Correlations between variables were analyzed using least-square regression techniques, and multiple regression analysis was also performed using NO measurement as the dependent variable and symptoms and/or peripheral obstruction as independent variables. For all comparisons, p < 0.05 was considered significant.


Forty-five consecutive children or adolescents with asthma were enrolled (mean age, 12.3 ± 2.7 years; mean height, 147 ± 15 cm). Thirty-eight participants (84%) had positive skin test results for one or more airborne allergens. All participants used inhaled corticosteroid therapy (beclomethasone, n = 23; budesonide, n = 8; fluticasone, n = 14). Fifteen patients had mild and recent symptoms; the others (n = 30) were asymptomatic. The average dose of inhaled steroids and their mean height were similar in these two groups of asthmatic patients (data not shown). Fifteen healthy children, with no significantly different mean height as compared to asthmatic groups (143.7 ± 10.1 cm), were also enrolled.

Technical Aspects of Multiple Flow Analysis of FEno in Children

All 60 subjects were able to perform at least one stable prolonged V rate maneuver in low, intermediate, and high V rate, allowing the determination of the parameters of the linear model. As expected, we observed in the 60 children a marked flow dependency of FEno.