Airway hyper-responsiveness and small airway function in children with well-controlled asthma

Abstract

Background: Airway hyper-responsiveness (AHR) and small airway function are critical to children with asthma. Little is known about the role of the small airway in well-controlled subjects with AHR. We aimed to evaluate AHR and small airway function in children with well-controlled asthma, and to investigate the association between them. Methods: We studied 116 cases of children with well-controlled asthma (group A), 46 cases healthy children as controls (group C). Spirometry, impulse oscillometry (IOS), and methacholine challenge test (MCT) were conducted on all the children. results: (i) Group A and group C had no differences in forced expiratory volume in 1 s (FEV 1 ) and FEV 1 /forced vital capacity (FVC) ratio (P > 0.05). Forced expiratory flow between 25 and 75% of vital capacity ) and reactance at 5 Hz (X5) in group A were significantly lower than those in group C. (ii) One hundred and five cases (90.5%) of group A proved positive to MCT. (iii) FEF in group A proved positive to MCT but were lower than those proved negative (P < 0.05). conclusion: AHR persisted in majority of children with well-controlled asthma. Among children with well-controlled asthma, small airway function was lower in those with AHR than those without AHR. a sthma is the most common chronic lower respiratory disease in childhood throughout the world. The newest Global Initiative for Asthma guidelines, as well as international consensus on pediatric asthma suggested that, after initial severity assessment, ongoing care should include continual assessment of the patient's asthma control in terms of real-life activities (1,2). This approach uses a cycle of detailed assessment and intervention to achieve and maintain asthma control. The level of control is defined by frequency of asthma symptoms, and the degree of lung function (forced expiratory volume in 1 s (FEV 1 ), peak expiratory flow). But in some cases called "well controlled asthma" with no disease activity and normal lung function, how can we evaluate and manage them? Airway hyper-responsiveness (AHR) is a clinical feature of asthma and is often in proportion to the underlying severity of the disease. AHR of children with well-controlled asthma can display condition of the disease. But, the evaluation of AHR is not popular in pediatric clinic. In areas without this means, how can we do next?Asthma is an inflammatory airway disorder that involves also the small airways (defined as the peripheral membranous bronchioles <2 mm in diameter) (3). Two decades ago, Wagner et al. (4) demonstrated a more than sevenfold increase in small airway resistance in asymptomatic asthma with normal spirometry (FEV 1 and forced vital capacity (FVC)). The contribution of the small airways to the development of the clinical features and functional impairment in asthma is incompletely understood (5). Study suggested that asthmatics with AHR have more severe small airways obstruction, but little is known about the role of the small airways in asymptomatic subjects with AHR. Therefore, the aim of our...

Impulse oscillometry for the evaluation and management of pediatric asthma

“…The AX value of 37.435 cmH 2 O/L (1 cmH 2 O = 0.098 kPa) at baseline turned out to be the best cut-off point to predict future loss of asthma control. In this study, FeNO did not predict the risk for persistent uncontrolled asthma [13]. Shi et al [12] also showed that school-age children with mild-to-moderate controlled asthma who had evidence of SAD, as measured by IOS (AX, R5-R20), were at high risk of uncontrolled asthma at the 8-to 12week follow-up visit.…”

“…A prospective study of 75 children (4-7 years of age) with intermittent asthma, showed that IOS (R5) was a better predictor of future asthma exacerbations than spirometry (FEV1) and methacholine challenge [9]. In another prospective study on 111 preschool children (age 3-6 years) with mild-to-moderate asthma using inhaled corticosteroids (ICS), IOS was shown to predict loss of asthma control at the 8-to 12-week follow-up visit [13]. Children who had persistent uncontrolled asthma at the follow-up showed significantly altered IOS parameters [R5, R5-R20, AX, and Zrs at 5 Hz (Z5)] compared with those in the controlled asthma group and those without asthma.…”

“…Surgical resection and autopsy analyses have shown small airway involvement in adults affected by asthma [6], with some data suggesting more inflammation and remodeling in small than in large airways [7]. Clinical studies have shown that SAD correlates with the risk of asthma development and exacerbations [8][9][10], worse asthma control [11][12][13], greater bronchial hyperresponsiveness [14], and loss of pulmonary function with age [15].…”

A Longitudinal Study of a Selected Pediatric Asthmatic Population with Normal and Abnormal Spirometry at Baseline: An Emphasis on Treatment Outcomes

“… 12 , 13 Previous studies have reported evidence of airway reversibility in children with asthma with good asthma control or normal lung function. 14 , 15 These controversial findings affect the role of spirometry and BDR testing in asthma management. However, because of the scarcity of pediatric studies, it is still unclear whether, besides symptom assessment, considering abnormal lung function or the presence of BDR as another marker for disease control can help physicians adjust asthma controllers in children.…”