Radar-based inspiratory-to-expiratory time ratio estimation: a validation study

Respiration is a key indicator of health and wellbeing, with metrics such as respiratory rate (RR), inspiratory time (TI), expiratory time (TE), and the inspiratory-to-expiratory time (I:E) ratio offering insights into conditions ranging from acute life-threatening and chronic diseases to symptom management. While traditional methods already measure these parameters with high accuracy, they still require contact-based sensors, limiting their practicality for continuous monitoring. This study evaluates radar as a non-contact alternative by validating multiple radar-derived respiratory metrics against impedance pneumography measurements in 30 healthy volunteers at rest. Synchronous recordings from both modalities were analysed to assess agreement across methods using descriptive statistics, scatter plots, modified Bland-Altman plots, and equivalence testing (TI: ±0.3 s, TE: ±0.3 s, RR: ±2 brpm, I:E ratio: ±0.2). Equivalence testing indicated high correlation (p ≤ 0.001***) across all metrics, with 81.8% (TI), 77.6% (TE), 97.2% (RR), and 85.7% (I:E ratio) of values within predefined bounds. These findings highlight radar's potential for continuous respiratory monitoring, particularly in medical fields where minimizing patient burden is essential as in palliative, post anaesthesia, and intensive care settings.

Subjects

Biomarkers

Inspiratory-to-expiratory time ratio

Radar-based vital sign monitoring

Respiration

DDC Class

610: Medicine, Health

616: Diseases

621.38: Electronics, Communications Engineering

519: Applied Mathematics, Probabilities

Funding(s)

SFB 1483: Teilprojekt Kardiovaskuläres respiratorisches Mikrowelleninterferometer (A04)

Lizenz

https://creativecommons.org/licenses/by/4.0/

Publication version

publishedVersion

Name

s41598-026-42517-9.pdf

Type

Main Article

Size

3.68 MB

Format

Adobe PDF

Options

Radar-based inspiratory-to-expiratory time ratio estimation: a validation study