Usefulness of sRtot and Rint in bronchodilator testing in the diagnosis of asthma in children

Introduction
The usefulness of total specific resistance (sRtot) and interrupter resistance (Rint) as a bronchodilator reversibility test (BT) alternative to forced expiratory volume in 1 s (FEV1) in asthma diagnosis in children has not been established.

Aim
To compare different applied definitions of airflow obstruction in children measuring response to the bronchodilator by spirometry, plethysmography and the interrupter technique in asthmatic children.

Material and methods
Material and methods: It was a prospective, real-life, non-interventional study. Children, aged 6–18 with newly diagnosed asthma, able to perform lung function tests were included into the study. Subjects underwent a history taking, physical examination, reversibility test in spirometry, plethysmography, and the interrupter technique. A standard cut-off of 12% from the initial value for reversibility in FEV1 was employed. Improvement in the pre-bronchodilator sRtot and Rint ≥ 25% and ≥ 35% was assessed after administration of salbutamol (400 µg) as well as allergen sensitization were measured.

Results
We included 135 children diagnosed with asthma into the analysis. All investigated parameters changed statistically significantly due to the bronchodilator administration in the examined patients. The FEV1 was not as useful in diagnostics of asthma as the sRtot and Rint, taking into consideration the fait accompli that all the study participants had aptly been diagnosed as having asthma (p < 0.001). The differences between the sRtot and Rint were not statistically significant (p = 0.215).

Conclusions
Our results suggest that sRtot and Rint may be useful parameters in BT in clinical practice in the asthma diagnostic process in children.