title: Employing an Incentive Spirometer to Calibrate Tidal Volumes Estimated from a Smartphone Camera.
abstract: A smartphone-based tidal volume (V(T)) estimator was recently introduced by our research group, where an Android application provides a chest movement signal whose peak-to-peak amplitude is highly correlated with reference V(T) measured by a spirometer. We found a Normalized Root Mean Squared Error (NRMSE) of 14.998% ± 5.171% (mean ± SD) when the smartphone measures were calibrated using spirometer data. However, the availability of a spirometer device for calibration is not realistic outside clinical or research environments. In order to be used by the general population on a daily basis, a simple calibration procedure not relying on specialized devices is required. In this study, we propose taking advantage of the linear correlation between smartphone measurements and V(T) to obtain a calibration model using information computed while the subject breathes through a commercially-available incentive spirometer (IS). Experiments were performed on twelve (N = 12) healthy subjects. In addition to corroborating findings from our previous study using a spirometer for calibration, we found that the calibration procedure using an IS resulted in a fixed bias of -0.051 L and a RMSE of 0.189 ± 0.074 L corresponding to 18.559% ± 6.579% when normalized. Although it has a small underestimation and slightly increased error, the proposed calibration procedure using an IS has the advantages of being simple, fast, and affordable. This study supports the feasibility of developing a portable smartphone-based breathing status monitor that provides information about breathing depth, in addition to the more commonly estimated respiratory rate, on a daily basis.
authors.affiliation: Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA. bersain.reyes@engineer.uconn.edu.
authors.forename: Bersain A
authors.initials: BA
authors.lastname: Reyes
authors.affiliation: Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA. reljin@engr.uconn.edu.
authors.forename: Natasa
authors.initials: N
authors.lastname: Reljin
authors.affiliation: Department of Computer Science and Engineering, Soonchunhyang University, Asan 336-745, Korea. vengeful224@gmail.com.
authors.forename: Youngsun
authors.initials: Y
authors.lastname: Kong
authors.affiliation: Department of Computer Science and Engineering, Soonchunhyang University, Asan 336-745, Korea. yynams@gmail.com.
authors.forename: Yunyoung
authors.initials: Y
authors.lastname: Nam
authors.affiliation: Department of Computer Science and Engineering, Soonchunhyang University, Asan 336-745, Korea. hsh.oopsla@gmail.com.
authors.forename: Sangho
authors.initials: S
authors.lastname: Ha
authors.affiliation: Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA. kchon@engr.uconn.edu.
authors.forename: Ki H
authors.initials: KH
authors.lastname: Chon
mesh_terms: D000328:Adult; D002138:Calibration; D005260:Female; D006801:Humans; D008297:Male; D008991:Monitoring, Physiologic / Q000295:instrumentation* / Q000379:methods; D012119:Respiration; D056152:Respiratory Rate / Q000502:physiology; D000068997:Smartphone; D013147:Spirometry / Q000295:instrumentation / Q000379:methods*; D013990:Tidal Volume / Q000502:physiology*
keywords: breathing monitor; calibration; incentive spirometer; smartphone camera; tidal volume