Abstract Objective. Spirometry is the clinical gold standard for pulmonary function testing, but its reliance on mouthpiece-based airflow, trained supervision, and patient effort limits its use for frequent or home-based monitoring. This study investigates a single-point time-of-flight (TOF) sensor to capture abdominal wall displacement as a non-contact surrogate for spirometric indices. Approach. Displacement signals were recorded from 31 adult volunteers during quiet breathing, vital capacity (VC), and forced vital capacity (FVC) manoeuvres, with simultaneous spirometry as reference. A preprocessing framework with filtering, segmentation, and feature extraction was developed, and subject-specific two-point calibration mapped displacement to lung volume. TOF-derived measures were compared to spirometry using agreement analyses, with Bland–Altman plots used to quantify bias and limits of agreement for key indices. Main results. TOF signals accurately reproduced volume-related parameters: tidal volume, VC, and maximal voluntary ventilation (MVV) agreed well with spirometry after calibration, with mean differences within clinically acceptable ranges. Estimation of the FEV₁/FVC ratio showed greater variability. After exclusion of one artefactual TOF measurement, Bland–Altman analysis showed a small positive bias (~+0.05) with limits of agreement of approximately −0.1 to +0.2. All TOF-derived ratios exceeded the clinical threshold of 0.7, supporting correct classification of normal ventilatory function in this cohort. Significance. These results indicate that although single-point TOF sensing cannot replace spirometry, it offers a non-contact, subject-specific calibration-minimal method for estimating pulmonary function, with promising applications in longitudinal monitoring, telehealth, and early screening.
Wesam Bachir (Thu,) studied this question.