Airway Response to Exercise by Forced Oscillations in Asthmatic Children

Abstract

Forced expiratory volume in 1 s (FEV 1 ) detection of exercise-induced bronchoconstriction (EIB) to identify asthma has good specificity but rather low sensitivity. The aim was to test whether sensitivity may be improved by measuring respiratory resistance (RRS) by the forced oscillation technique (FOT). Forty-seven asthmatic and 50 control children (5-12 y) were studied before and after running 6 min on a treadmill. RRS in inspiration (RRSi) and expiration (RRSe), FEV 1 and RRSi response to a deep inhalation (DI) were measured before and after exercise. In asthmatics versus controls, exercise induced significantly larger increases in RRSi (p Ͻ 0.001) and larger decreases in FEV 1 (p ϭ 0.004). Asthmatics but not controls showed more bronchodilation by DI after exercise (p ϭ 0.02). At specificity Ͼ0.90, sensitivity was 0.53 with 25% increase RRSi and 0.45 with 27% increase RRSe or 5% decrease FEV 1 . It is concluded that the FOT improves sensitivity of exercise challenge, and the RRSi response to DI may prove useful in identifying the mechanism of airway obstruction. (Pediatr Res 68: 537-541, 2010) E xercise-induced bronchoconstriction (EIB) is closely linked to airway inflammation and unlikely to develop in healthy children (1), so that detecting airway hyperresponsiveness to exercise in the lung function laboratory is considered highly specific of asthma, i.e. it is associated with low rate of false-positive responses. A limitation is the rather low sensitivity of the test (2,3). EIB has been identified in primary school children by changes in forced expiratory volume in 1 s (FEV 1 ) or peak expiratory flow, and decision levels were mostly based on the former parameter (3). Respiratory resistance (RRS) measured by the forced oscillation technique (FOT) offers an alternative assessment of airway caliber, the time variations of which may be characterized for instance using a single excitation frequency (4). Computing RRS separately in inspiration and expiration (RRSi and RRSe, respectively) rather than over the whole breathing cycle may be of interest because the upper airways, which may represent a confounding factor in assessing the intrathoracic airways, are known to contribute differently to airway mechanics in inspiration and expiration (5,6). Furthermore, the RRS change in relation to volume history, more specifically the bronchomotor alteration that follows a deep inhalation (DI), has potential relevance in identifying the mechanism of EIB (7-9). Indeed, stretching the acutely contracted bronchial smooth muscle promotes bronchial wall relaxation, which in turn could be taken as an indicator of the magnitude of the airway response (10). To the best of our knowledge, a systematic analysis of diagnostic value of single-frequency RRS has not been performed during case-control identification of EIB in the lung function laboratory at school age.Therefore, the aim of this study was to assess the value of the FOT in identifying EIB in asthmatic children. More specifically, RRSi and RRSe and the change in...

Exercise-induced bronchoconstriction in school-age children born extremely preterm

“…Nevertheless, former premature infants at school age in the current study appear to exhibit a pattern of response to exercise different from that reported in asthmatic children using the same protocol (13). Indeed, the magnitude of the FEV1 response to exercise observed in the latter was approximately two times larger, and the increase in Rrs was statistically significant (13). The transient bronchodilation occurring during hyperpnoea might in fact outlast the exercising period according to a shorter time course in asthmatics (14), in line with the attenuated bronchodilatory effect of a deep breath reported in these patients (15).…”

“…In addition, it is worth noting that, in one child born prematurely, the clinical respiratory response required salbutamol nebulization after exercise. Nevertheless, former premature infants at school age in the current study appear to exhibit a pattern of response to exercise different from that reported in asthmatic children using the same protocol (13). Indeed, the magnitude of the FEV1 response to exercise observed in the latter was approximately two times larger, and the increase in Rrs was statistically significant (13).…”

Assessment of murine lung mechanics outcome measures: alignment with those made in asthmatics

“…The other opinion is that additional mechanistic insight into airway structural changes can be generated by using complex mathematical modeling to examine how lung mechanics are influenced by frequency (Bates, 2007; Lundblad, 2012). Extension of this viewpoint claims that the FOT can provide (for both human and animal models) important physiological interpretations of disease progression and/or resolution associated with novel treatment strategies (Wagers et al, 2004, 2007; Lundblad et al, 2007; Schweitzer et al, 2010; Bates et al, 2011). Neither viewpoint is incorrect; as long as study designs embrace quantitative (and validated) measurements of lung mechanics as an outcome measure for murine models of inflammatory lung disease, then the methods employed largely reflect the goals of the investigator.…”

Within-breath respiratory impedance and airway obstruction in patients with chronic obstructive pulmonary disease

“…In recent years, strong evidence has emerged supporting the utility of within-breath FOT (WbFOT) measurements in several contexts. This method has been successfully applied to undertake difficult studies, including studies on sleep disorders 7 , 8 and studies evaluating pediatric 9 and elderly 10 subjects. A detailed analysis of the expiratory flow limitation (EFL) 11 , 12 and the response to salbutamol 13 in COPD patients was also recently performed.…”