Estimation of the bronchodilatory effect of deep inhalation after a free run in children

Vu, Lan T.T.; Nguyen, Yen Thi Minh; Choné, C.; Demoulin, Bruno; Marchal, François

doi:10.1183/09031936.06.00114705

Cited by 25 publications

(30 citation statements)

References 38 publications

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“…Altogether, the current findings on the effects of DI at baseline are consistent with significant airway smooth muscle tone in children, as indicated in other studies by the effect of beta-adrenergic agonists (32,33). Recently, asthmatic children were demonstrated to exhibit large bronchodilation by DI during mild EIB, an effect attributed to transient reversal of airway smooth muscle contraction (10). In contrast, in the current study, the significant Rrs decrease by DI was similar at E5 and baseline (Fig.…”

Section: Discussioncontrasting

confidence: 41%

“…Pressure was applied at 12 Hz around the child's head to minimize upper airway wall motion. One advantage of the head generator technique is that it allows using such range of excitation frequency without majoring the upper airway artifact (16), thereby improving the signal to noise ratio and the ability to track Rrs time course (10). Airflow, tidal volume (VT) and Rrs were displayed immediately after each acquisition to allow visual inspection and selection of data, which were stored on disk.…”

Section: Methodsmentioning

confidence: 99%

“…Forced spirometry was performed as previously described (10). An electronic flowmeter with computer animation programs (Masterscope Erich Jaeger GmbH, Wuertzburg, Germany) was used.…”

Section: Methodsmentioning

confidence: 99%

“…FEV0.5 could also prove useful in school children who are known to have higher FEV1 to forced vital capacity ratio than adults. In addition, the tracking of time variations of Rrs has the potential to identifying mechanisms of bronchoconstriction by assessing change induced by a deep inhalation (DI) (9,10). When acute bronchoconstriction has been pharmacologically induced in a context of normal baseline lung function, DI induces significant bronchial smooth muscle relaxation (11)(12)(13).…”

mentioning

confidence: 99%

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Post-Exercise Airway Narrowing in Healthy Primary School Children

Marchal

Werts

Vu³

et al. 2008

Pediatr Res

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Changes in lung function after exercise in healthy primary school children have mostly been described in field studies. More complete description and insight into relevant mechanisms may be provided in lung function laboratory. The aim was to describe airway caliber and response to deep inhalation (DI) after exercise in healthy primary school children. Respiratory resistance (Rrs) by the forced oscillation technique and spirometry were measured before and after exercise in 50 healthy primary school children. The Rrs response to DI was assessed in 31 subjects, assuming a significantly larger decrease in Rrs after exercise would attest relief of exerciseinduced airway smooth muscle contraction. Measurements were taken before, 5 min (E5) and 15 min (E15) after exercise. Significantly larger Rrs and lower forced expiratory volume in 0.5 s were observed at E5 versus baseline or E15 (p Ͻ 0.05). DI induced significant decrease in Rrs (p ϭ 0.01) that was not different between E5 and baseline. Healthy primary school children exhibit changes in Rrs and spirometry after exercise indicating small but significant airway narrowing. The response to DI similar at baseline and E5 suggests airway narrowing from hyperemia in the bronchial wall rather than airway smooth muscle constriction. T here is considerable interest in assessing the airway response to exercise in children because of the clinical impact of exercise triggered asthma attacks (1,2). Field studies in unselected primary school children have described the distribution of lung function changes after exercise (3,4) or tested prevalence of exercise induced bronchoconstriction (EIB) in relation with respiratory symptoms (5,6). In these studies, the response was expressed as largest fall in forced expiratory volume in 1 s (FEV1) within 10 -15 min of exercise cessation (3,4) or considered positive when peak expiratory flow decreased 15% or more (5,6). To the best of our knowledge, whether significant change in airway caliber occurs in healthy children during the recovery from exercise has not been documented. In the context of a lung function laboratory, the airway response to exercise may be characterized more thoroughly and indications obtained relative to potential mechanisms. The respiratory resistance (Rrs) measured by the forced oscillation technique (FOT) is considered a good proxy to airway caliber above a few herz (7). It is particularly relevant to pediatric studies, as it requires minimal cooperation. Forced expiratory volume in 0.5 s (FEV0.5) has been suggested more sensitive than FEV1 to airway caliber in young children because of their high rate of lung emptying (8). FEV0.5 could also prove useful in school children who are known to have higher FEV1 to forced vital capacity ratio than adults. In addition, the tracking of time variations of Rrs has the potential to identifying mechanisms of bronchoconstriction by assessing change induced by a deep inhalation (DI) (9,10). When acute bronchoconstriction has been pharmacologically induced in a context ...

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Section: Discussioncontrasting

confidence: 41%

Section: Methodsmentioning

confidence: 99%

“…Forced spirometry was performed as previously described (10). An electronic flowmeter with computer animation programs (Masterscope Erich Jaeger GmbH, Wuertzburg, Germany) was used.…”

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Post-Exercise Airway Narrowing in Healthy Primary School Children

Marchal

Werts

Vu³

et al. 2008

Pediatr Res

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“…Forced spirometry was performed using an electronic flowmeter with computer animation programs (Masterscope; Erich Jaeger GmbH, Wuertzburg, Germany) as previously described (15). The forced expiratory maneuver was explained to the child, and trials were performed.…”

Section: Effect Of DImentioning

confidence: 99%

Airway Response to Exercise by Forced Oscillations in Asthmatic Children

et al. 2010

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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...

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Oscillation Mechanics of the Respiratory System

Bates

Irvin

Farré

et al. 2011

Comprehensive Physiology

181

182

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The mechanical impedance of the respiratory system defines the pressure profile required to drive a unit of oscillatory flow into the lungs. Impedance is a function of oscillation frequency, and is measured using the forced oscillation technique. Digital signal processing methods, most notably the Fourier transform, are used to calculate impedance from measured oscillatory pressures and flows. Impedance is a complex function of frequency, having both real and imaginary parts that vary with frequency in ways that can be used empirically to distinguish normal lung function from a variety of different pathologies. The most useful diagnostic information is gained when anatomically based mathematical models are fit to measurements of impedance. The simplest such model consists of a single flow-resistive conduit connecting to a single elastic compartment. Models of greater complexity may have two or more compartments, and provide more accurate fits to impedance measurements over a variety of different frequency ranges. The model that currently enjoys the widest application in studies of animal models of lung disease consists of a single airway serving an alveolar compartment comprising tissue with a constant-phase impedance. This model has been shown to fit very accurately to a wide range of impedance data, yet contains only four free parameters, and as such is highly parsimonious. The measurement of impedance in human patients is also now rapidly gaining acceptance, and promises to provide a more comprehensible assessment of lung function than parameters derived from conventional spirometry.

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Estimation of the bronchodilatory effect of deep inhalation after a free run in children

Cited by 25 publications

References 38 publications

Post-Exercise Airway Narrowing in Healthy Primary School Children

Post-Exercise Airway Narrowing in Healthy Primary School Children

Airway Response to Exercise by Forced Oscillations in Asthmatic Children

Oscillation Mechanics of the Respiratory System

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