Evaluating asthma in children

The Impact of Reactance Inversion on Lung Function in Asthmatic Children

Asthma is a chronic respiratory condition that affects millions of children worldwide. One aspect that has gained increasing attention is the phenomenon of reactance inversion (RI), which has been associated with impaired peripheral airway function in persistent asthma. However, little research has explored the differences between asthmatic children with and without RI. A recent study aimed to address this gap by examining the clinical and lung function differences in moderate-severe asthmatic children with and without RI.

The study, conducted between 2021 and 2022, involved school-age asthmatic children who underwent impulse oscillometry (IOS) and spirometry tests following ATS/ERS standards using the Vyntus system. The researchers divided the 62 participants, with a mean age of 8.4 years, into three groups: Group 1 (32%) with no RI, Group 2 (27.4%) with RI that disappeared after a bronchodilator test, and Group 3 (40.3%) with persistent RI even after the bronchodilator test.

The findings revealed some intriguing insights. Children in Groups 2 and 3, who exhibited RI, had significantly lower birth weights compared to those in Group 1. Additionally, Group 2 had a lower gestational age than Group 1. Lung function tests showed that FEV1 (forced expiratory volume in 1 second) and FEF25-75 (forced expiratory flow at 25-75% of the pulmonary volume) were significantly lower in Groups 2 and 3.

Notably, in Group 3, which had persistent RI after the bronchodilator test, the researchers observed significantly higher values for R5 (resistance at 5 Hz), AX (area of reactance), R5-20 (resistance at 5-20 Hz), and R5-R20/R5 ratios. Furthermore, bronchodilator responses in X5c, AX, and R5-R20 were significantly different between the groups, with Group 3 exhibiting the lowest response.

The study's conclusion highlights the high prevalence of RI in children with moderate-severe persistent asthma, particularly those with a history of prematurity or low birth weight. While RI may disappear after a bronchodilator test in some patients, it persists in those with the worst pulmonary function. The researchers suggest that RI could be a marker of small airway dysfunction in these children.

This research underscores the importance of understanding the role of RI in asthma management and its potential implications for identifying and addressing small airway impairment in children with persistent asthma. Further studies are needed to explore the long-term effects of RI and develop targeted interventions for this subgroup of asthmatic children.

Reference: Ramiro González Vera Dr. , Alberto Vidal Grell Dr. , José A Castro-Rodríguez Dr. , María A Palomino Montenegro Dra. & Alejandra Méndez Yarur (2024) Reactance inversion in moderate to severe persistent asthma: low birth weight, prematurity effect, and bronchodilator response, Journal of Asthma, DOI: 10.1080/02770903.2024.2324865