Laurianne Coutier

Flow dependence of specific airway resistance and diagnostic of asthma in children.

Panting majors turbulent flow and contribution of larger airways to the measurement of specific airway resistance (sRaw). The hypothesis was tested that the difference between asthmatic and healthy children is enhanced by narrowing the flow interval to compute sRaw.

Specific airway resistance in children: Panting or tidal breathing?

The measurement of specific airway resistance during tidal breathing (sRawtb) has gained popularity in children, but methodological concerns have been raised regarding the electronic compensation for the thermal artifact. The panting method (sRawp) is efficient in minimizing the latter, but may be associated with a change in end expiratory lung volume if the effort is not properly balanced. The aim of the study was to compare sRawtb with sRawp in children.

What is chronic cough in children

The cough reflex is modulated throughout growth and development. Cough—but not expiration reflex—appears to be absent at birth, but increases with maturation. Thus, acute cough is the most frequent respiratory symptom during the first few years of life. Later on, the pubertal development seems to play a significant role in changing of the cough threshold during childhood and adolescence resulting in sex-related differences in cough reflex sensitivity in adulthood. Asthma is the major cause of chronic cough in children. Prolonged acute cough is usually related to the long-lasting effects of a previous viral airway infection or to the particular entity called protracted bacterial bronchitis. Cough pointers and type may orient toward specific etiologies, such as barking cough in croup or tracheomalacia, paroxystic whooping cough in Pertussis. Cough is productive in protracted bacterial bronchitis, sinusitis or bronchiectasis. Cough is usually associated with wheeze or dyspnea on exertion in asthma; however, it may be the sole symptom in cough variant asthma. Thus, pediatric cough has particularities differentiating it from adult cough, so the approach and management should be developmentally specific.

Real-life acute lung function changes after lumacaftor/ivacaftor first administration in pediatric patients with cystic fibrosis

The combination of lumacaftor and ivacaftor (LUM/IVA) has been reported to induce a mean acute absolute drop of -4.1% predicted forced expiratory volume in 1s (FEV1) after a unique administration in healthy subjects. The aim of the present study was to assess acute FEV1 changes after the first dose of LUM/IVA in CF patients. A total of 32 pediatric patients were included. Respiratory manifestations occurred in only 3 patients (9.4%), but FEV1 consistently decreased (-10.4±4.6%, range: -1.5; -21.8%). FEV1 only partially resumed after salbutamol inhalation. Patients with previously known significant reversible airway obstruction and low FEV1 were more at risk of FEV1 decrease.

Breathing‐related changes of respiratory resistance in vocal cord dysfunction

Vocal cord dysfunction induced by exercise in children with uncontrolled asthma was identified by laryngoscopy. The paradoxical adduction of the vocal cords was also indicated by the breathing‐related changes of the forced oscillation respiratory resistance showing prominent increase during inspiration and a large positive difference between inspiration and expiration. The breathing‐related changes of respiratory resistance offer thus a useful first‐line technique to diagnose vocal cord dysfunction.

Bronchial obstruction and reversibility in children: inspiratory or expiratory resistance?

To the Editor: Assessing bronchial obstruction and reversibility is of help in diagnosing asthma. The forced oscillation technique (FOT) has gained popularity in children since minimal cooperation is required. Owing to the fact that measurements are performed during tidal breathing, the upper airway may significantly impact on the respiratory resistance ( R rs) [1], [2]. The glottic aperture narrows during tidal expiration [3], contributing to R rs being larger than in inspiration [2], [4], [5]. Acute bronchial obstruction promotes further laryngeal narrowing [6]–[8], which is expected to impact the R rs measured during expiration. It is not known to what extent the mechanism is present in children with stable asthma, or whether the ability of R rs to diagnose bronchial obstruction and reversibility is impeded in expiration. With a single excitation frequency, R rs may be described along the respiratory cycle and computed in expiration ( R rs,e) and inspiration ( R rs,i). The aim of this study was to compare R rs,i and R rs,e, their response to salbutamol and respective ability to separate asthmatics from controls. The hypothesis was that the diagnostic value of R rs,e and its response to bronchodilator inhalation is impeded compared with R rs,i. Patients with asthma were diagnosed in the local paediatric pulmonology clinic (Hopital d’enfants, CHU de Nancy, Nancy, France). All had discontinued their bronchodilator therapy ≥12 h prior to the study. Age-matched healthy children served as controls. Written informed consent was obtained and the study was approved by the Ethics Committee (Comite de Protection des Personnes EST III, CHU de Nancy, …

An impulse oscillometry system is less efficient than spirometry in tracking lung function improvements after intravenous antibiotic therapy in pediatric patients with cystic fibrosis

A literature search identified one retrospective study on the responsiveness of impulse oscillometry (IOS) in pediatric patients with cystic fibrosis. The aim of this prospective observational study was to assess this property in an adequately powered study after intravenous antibiotic therapy (IVAT) administered for an acute episode of pulmonary exacerbation. Spirometry and IOS were done on the same day as the start and the end of IVAT. Data from 34 patients’ of mean age 11.9 years (range, 5–17 years) were studied. The mean FEV1 at the start and at the end of the IVAT was 73.1 ± 23.8% (range, 23.4–122%) and 88.3 ± 21.3% (range, 29.4–131%), respectively. The mean relative change (mean ± SD) was 20.2 ± 14.2% for FEV1 (ΔFEV1), −21.9 ± 23.8% for reactance at 5 Hz (ΔX5) and –13.4 ± 18.9% for resistance at 5 Hz (Δ R5) (all P‐values <0.05). There was a weak but significant correlation between ΔFEV1 and ΔX5 (r =–0.473; p = 0.01). The magnitude of improvement of ΔX5 was not statistically different between patients with normal versus abnormal lung function at the start of IVAT. Furthermore, using ΔX5 alone as an outcome measure of IVAT efficiency resulted in a significant improvement in 44% of the patients, while it was 79% with ΔFEV1. These results indicate that IOS may track changes after IVAT, but that this improvement may be insufficiently evaluated using IOS alone. Pediatr Pulmonol. 2015; 50:1073–1081.

Specific airway resistance in preschool children: why not panting after all?

Specific airway resistance (sRaw) is measured with minimal cooperation in the preschool child during tidal breathing [1]. Methodological difficulties have been encountered in modern plethysmographs when the warming and humidification of the inspired gas [2] are replaced by numerical algorithms to eliminate the thermo hygrometric artefact [1, 3, 4]. Measuring sRaw during panting [5] had been dismissed in preschool children based on the assumption that the ventilatory manoeuvre would be difficult to perform and standardise. The feasibility of such an assumption, however, has not been verified. Therefore, the aim of this study was to assess the feasibility of measuring sRaw during panting in preschool children with asthma and compare the outcome with the tidal breathing method. Specific airway resistance may be measured in preschool children during routine lung function http://ow.ly/pvxr3034Bo8

Neonatal hyperoxia up regulates cough reflex in young rabbits.

A link between cough in childhood and neonatal exposure to hyperoxia following preterm birth has been suggested. The hypothesis is tested that neonatal exposure to hyperoxia is associated with long term up regulation of cough. Airway hyperresponsiveness is also investigated because it is a frequent finding in children born preterm and may be linked to cough. Thirty nine young rabbits survived a 48 h neonatal exposure to 93% oxygen (H, n=26) or continued room air (A, n=13). Cough response to mechanical tracheal stimulation and airway responses to a mock exercise and to methacholine were studied under anaesthesia. Larger incidence of coughs and increased sensitivity to tracheal stimulation occurred in H vs A (p<0.01), while bronchial responses to exercise or methacholine were similar in both groups. Neonatal hyperoxia is associated with up regulation of cough in young rabbits. The lack of a parallel increase in airway responsiveness suggests up regulation may be of central origin.

More Relaxation by Deep Breath on Methacholine- Than on Exercise-Induced bronchoconstriction during the Routine Testing of Asthmatic Children

Deep inspiration (DI) dilates normal airway precontracted with methacholine. The fact that this effect is diminished or absent in asthma could be explained by the presence of bronchial inflammation. The hypothesis was tested that DI induces more relaxation in methacholine induced bronchoconstriction—solely determined by the smooth muscle contraction—than in exercise induced bronchoconstriction, which is contributed to by both smooth muscle contraction and airway wall inflammation. The respiratory conductance (Grs) response to DI was monitored in asthmatic children presenting a moderately positive airway response to challenge by methacholine (n = 36) or exercise (n = 37), and expressed as the post- to pre-DI Grs ratio (GrsDI). Both groups showed similar change in FEV1 after challenge and performed a DI of similar amplitude. GrsDI however was significantly larger in methacholine than in exercise induced bronchoconstriction (p < 0.02). The bronchodilatory effect of DI is thus less during exercise- than methacholine-induced bronchoconstriction. The observation is consistent with airway wall inflammation—that characterizes exercise induced bronchoconstriction—rendering the airways less responsive to DI. More generally, it is surmised that less relief of bronchoconstriction by DI is to be expected during indirect than direct airway challenge. The current suggestion that airway smooth muscle constriction and airway wall inflammation may result in opposing effects on the bronchomotor action of DI opens important perspective to the routine testing of asthmatic children. New crossover research protocols comparing the mechanical consequences of the DI maneuver are warranted during direct and indirect bronchial challenges.