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. 2026 Feb 27.
doi: 10.1186/s12938-026-01540-7. Online ahead of print.

Estimation of anaerobic threshold and peak oxygen uptake from tracheal sound during cycle ergometer cardiopulmonary exercise test

Qi Zhang #  1   2 , Nasim Montazeri Ghahjaverestan #  1   3 , Cristina de Oliveira Francisco  1 , Muammar Muhammad Kabir  1   4 , Md Saiful Hoque  1   4 , Shahram Kharabian Masouleh  5 , Paul Oh  1 , Susan Marzolini  1   6 , Azadeh Yadollahi  7   8
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Free article

Estimation of anaerobic threshold and peak oxygen uptake from tracheal sound during cycle ergometer cardiopulmonary exercise test

Qi Zhang et al. Biomed Eng Online. .
Free article

Abstract

Cardiopulmonary exercise test (CPET) is widely used for assessing exercise capacity of individuals through ventilatory anaerobic threshold (AT) and peak oxygen uptake (VO2peak). However, CPET requires specialized equipment, resources, time, and trained personnel. In this study, we investigated the feasibility of estimating ventilatory AT and submaximal VO2peak using tracheal respiratory sounds recording with a wearable sensor (The Patch) during incremental cycle ergometer testing. Twenty-four healthy adults (18 females, age: 31.0 ± 9.1 years, body mass index: 23.5 ± 3.3 kg/m2) underwent CPET with simultaneous tracheal sounds recording. Acoustic features (sound energy, sound intensity, respiratory rate, and ventilation) were extracted. AT was identified from breakpoints in acoustic features and compared with reference AT from ventilatory gas analysis. VO2peak was estimated using random forest regression models with subject-specific and subject-independent training models. Agreement with CPET was investigated using Bland-Altman analysis. Ventilatory AT was detected in 84% (sound energy) and 96% (sound intensity) of participants using The Patch. Workload stage agreement with CPET was 88% and 100% for sound energy and intensity, respectively, with AT timing within 20 s in 62% and 92% of cases. The subject specific model estimated VO2peak with minimal bias [confidence intervals] of - 1.01 [- 3.04 to 1.02] (mL/kg/min), while the subject-independent validation model exhibited wider variability of - 1.28 [- 12.39 to 9.82] (mL/kg/min). Our results shows that tracheal sound analysis can estimate ventilatory AT and provides a promising approach for non-invasive exercise capacity assessment. On the other hand, the estimation of VO2peak shows promise but requires further validation in maximal effort protocols.

Keywords: Acoustics; Anaerobic threshold; Cardiopulmonary exercise test; Oxygen uptake; Signal processing; Tracheal sound.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: Research was carried out in accordance with the declaration of Helsinki. All participants were informed of the protocols and signed a consent form approved by University Health Network, Canada’s Research Ethics Board (ID#16-5167). Consent for publication: All participants signed and informed consent form approved by University Health Network’s Ethics Board which indicated their de-identified data could be used in publications. Competing interests: The authors declare no competing interests.

References

    1. Prabhakaran D, et al. Cardiovascular, respiratory, and related disorders: key messages from disease control priorities. The Lancet. 2018;391:1224–36.
    1. Leon AS, et al. Cardiac rehabilitation and secondary prevention of coronary heart disease. Circulation. 2005;111:369–76.
    1. Fletcher GF, Balady G, Blair SN, Blumenthal J, Caspersen C, Chaitman B. Statement on exercise: benefits and recommendations for physical activity programs for all Americans. Circulation. 1996. https://doi.org/10.1161/01.CIR.94.4.857.
    1. Wasserman K, Hansen JE, Sue DY, Whipp BJ, Froelicher VF. Principles of exercise testing and interpretation. J Cardiopulm Rehabil Prev. 1987;7:189.
    1. Mark DB, Lauer MS. Exercise capacity: the prognostic variable that doesnt get enough respect. Circulation. 2003. https://doi.org/10.1161/01.CIR.0000094408.38603.7E.

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