A new tidal breathing measurement device detects bronchial obstruction during methacholine challenge test

Purpose: Bronchial hyperresponsiveness (BHR), a hallmark of bronchial asthma, is typically diagnosed through a methacholine inhalation test followed by spirometry, known as the methacholine challenge test (MCT). While spirometry relies on proper patients' cooperation and precise execution of forced breathing maneuvers, we conducted a comparative analysis with the portable nanomaterial-based sensing device, SenseGuard™, to non-intrusively assess tidal breathing parameters.

Materials and methods: In this prospective study, 37 adult participants with suspected asthma underwent sequential spirometry and SenseGuard™ measurements after inhaling increasing methacholine doses.

Results: Among the 37 participants, 18 were MCT responders, 17 were non-responders and 2 were excluded due to uninterpretable data. The MCT responders exhibited a significant lung function difference when comparing the change from baseline to maximum response. This was evident through a notable decrease in forced expiratory volume in 1 ​s (FEV₁) levels in spirometry, as well as in prominent changes in tidal breathing parameters as assessed by SenseGuard™, including the expiratory pause time (T_rest) to total breath time (T_tot) ratio, and the expiratory time (T_ex) to T_tot ratio. Notably, the ratios T_rest/T_tot (∗p ​= ​0.02), T_ex/T_tot (∗p ​= ​0.002), and inspiratory time (T_in) to T_ex (∗p ​= ​0.04) identified MCT responders distinctly, corresponding to spirometry (∗p ​< ​0.0001).

Conclusions: This study demonstrates that tidal breathing assessment using SenseGuard™ device reliably detects clinically relevant changes of respiratory parameter during the MCT. It effectively distinguishes between responders and non-responders, with strong agreement to conventional spirometry-measured FEV₁. This technology holds promise for monitoring clinical respiratory changes in bronchial asthma patients pending further studies.