Validity and reliability of anharmonic morphological ventilometry for the characterisation of human breathing

Diagnosing and monitoring respiratory disorders typically rely on pulmonary function testing, which requires full patient cooperation and trained personnel, limiting its applicability. Analysing natural breathing offers a valuable alternative but requires new methodological approaches. This study introduces anharmonic morphological analysis, a novel technique to characterise breathing cycles, and evaluates its reliability and ability to distinguish healthy individuals from patients with chronic obstructive pulmonary disease (COPD). Twenty healthy individuals (17 men; age 28 ± 5 years; body mass index 21 ± 2 kg/m²) and 119 COPD patients (covering all spirometric GOLD stages) were studied during natural breathing using a linear pneumotachograph. Ventilatory flow traces were analysed using anharmonic morphological analysis, enabling the reconstruction of an average ventilatory cycle for each individual (personal respiratory profile, PRP). Comparisons were performed by calculating Euclidean distances between PRPs. Anharmonic morphological analysis enabled precise and reproducible characterisation of ventilatory cycles. PRPs showed high temporal stability. Tessellation based on Euclidean distances distinguished healthy individuals from COPD patients with a sensitivity of 86 % and a specificity of 94 %. Exploratory analyses further suggested the potential of the method to identify COPD patients responsive to bronchodilator administration based on inspiratory capacity changes. Anharmonic morphological analysis offers a reproducible, physiologically meaningful description of natural breathing and shows promise for future development as a spontaneous-breathing-based tool to assist in diagnosing respiratory disorders without requiring patient cooperation.