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摘要
Objective Alveolar concentration (CANO) and bronchial flux (JawNO) of nitric oxide (NO) characterize the contributions of peripheral and proximal airways to exhaled NO. Both parameters can be estimated using a two-compartment model if the fraction of NO in orally exhaled air (FENO) is measured at multiple constant expiratory flow rates (V). The aim of this study was to evaluate how departures from linearity influence the estimates of CANO and JawNO obtained with the help of linear regression analysis of the relationships between FENO and 1/V (method P), and between the NO output (VNO?=?FENO?x?V) and V (method T). Furthermore, differences between patients with atopic asthma (AA) and allergic rhinitis (AR) and between methods P and T were assessed. Design Measurements of FENO were performed with a chemiluminiscence analyzer at five levels of V ranging from 50 to 250?ml/sec in school children and adolescents with mild to moderate-severe AA treated by inhaled corticosteroids (N?=?42) and AR (N?=?20). Results Violation of the linearity condition at V?=?100?ml/sec caused shifts between methods with regard to the partition of exhaled NO into alveolar (CANO: P?%26gt;?T) and bronchial (JawNO: T?%26gt;?P) components. Both methods gave similar results in the linear range of 150-250?ml/sec: The mean ratios P/T and limits of agreement calculated in AA and AR patients were 1.03 (0.49-1.56) and 1.07 (0.55-1.59) for CANO and 1.03 (0.73-1.33) and 0.99 (0.90-1.10) for JawNO, respectively. No significant differences between AA and AR were found in CANO and JawNO calculated in the linear range by the T method {medians (inter-quartile ranges): 1.7?ppb (0.93.9) vs. 2.3?ppb (0.83.7), P?=?0.91; 1,800?pl/sec (9503,560) vs. 1,180?pl/sec (6391,950), P?=?0.061}. However, the flow-dependency of the estimates was markedly higher in AA than in AR patients: CANO was decreased 2.8-fold vs. 1.5-fold and JawNO was increased 1.5-fold vs. 1.2-fold in the linear range as compared to the range of 50250?ml/sec. In both groups, the median standard errors (SE) of the JawNO estimates were similar for the metods P and T and small (%26lt;15%) regardless of the range for expiratory flows. The precision of CANO estimates was less in all ranges. For both methods, the SE of the estimates obtained in the range of 150-250?ml/sec exceeded 50% in asthmatics and 30% in AR patients, respectively. The results show that FENO has to be measured at several expiratory flows =100?ml/sec for the accurate estimation of CANO and JawNO using linear methods P and T in children and adolescents with AA and AR. A stepwise procedure for detecting nonlinearity and evaluating the quality of FENO measurements is suggested. Pediatr Pulmonol. 2012. 47:10701079.
- 出版日期2012-10
