Development and Validation of a Resting Respiratory Flow Analyzer as an Alternative to Spirometry

Pulmonary function tests are vital for assessing respiratory function with spirometry as the standard. However, its reliance on active patient participation limits its use in the elderly, children and patients with neuromuscular disorders. To address this, we developed a novel respiratory function test device that identifies and classifies ventilatory disorders using resting breathing pattern analysis without requiring patient effort. Resting breathing data from healthy individuals and patients (n=1969) with respiratory diseases were analyzed. Spirometry results were compared with VC, FEV1, FEV1/FVC, FEF75%, VTE, TE/TI, and F_Mid_E. Expiratory flow was analyzed using 4-segment (75% to 25%) and 8-segment (87.5% to 12.5%) divisions. Expiratory flow indices (FE_T2/4, FE_T3/8, FE_T4/8, FE_T5/8, Vd_E_3/8, Vd_E_4/8, Vd_E_5/8) were evaluated for correlation and agreement with spirometry. The device accurately classified ventilatory disorders, showing strong correlations (r > 0.5, P < 0.01) for VTE, TE/TI, F_Mid_E, FE_T2/4, FE_T4/8, FE_T5/8 and Vd_E_4/8 with agreement rates exceeding 95%. FE_T3/8, Vd_E_3/8, and Vd_E_5/8 had slightly lower agreement (93.5%). The coefficient of variation was below 0.5 for most parameters except VC and VTI (CV = 0.6). Comparison with spirometry showed strong correlations, though some indices had agreement rates below 95%, indicating minor variability. This study demonstrates that the device classifies ventilatory disorders with accuracy comparable to spirometry and suggests it as a simple, non-invasive alternative. It may enable reliable respiratory function assessment in various patients with respiratory disease unable to perform conventional pulmonary tests.