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.

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 (FEV) after a unique administration in healthy subjects. The aim of the present study was to assess acute FEV 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 FEV consistently decreased (-10.4±4.6%, range: -1.5; -21.8%). FEV only partially resumed after salbutamol inhalation. Patients with previously known significant reversible airway obstruction and low FEV were more at risk of FEV decrease.

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.

Diaphragmatic paralysis (DP) is a rare cause of respiratory distress in young children. In the first years of life, the main cause is phrenic nerve injury after cardiothoracic surgery or obstetrical trauma. DP usually presents as respiratory distress. Asymmetrical thorax elevation, difficulty weaning from mechanical ventilation, pulmonary atelectasis, and repeated pulmonary infections are other suggestive signs or complications. DP is usually suspected on chest X‐ray showing abnormal hemidiaphragm elevation. Although fluoroscopy was considered the gold standard for DP confirmation, it has gradually been replaced by ultrasound, which can be done at the bedside. Some electrophysiological tools may be useful for a better characterization of phrenic nerve injury and chance of recovery. The management of DP is mainly based on clinical severity. In mild asymptomatic cases, DP may only require close monitoring. In more severe cases, adequate ventilatory support and/or surgical diaphragmatic plication may be needed. Electrophysiological tools may help clinicians assess the ideal timing for diaphragmatic plication.

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.

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Tidal breathing is associated with an overestimation of sRaw compared with panting in children. Although the latter results in small increase throughout the panting maneuver, sRaw(p) is probably more trustful than sRaw(tb).

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