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Sensors 2016, 16(3), 397;

Employing an Incentive Spirometer to Calibrate Tidal Volumes Estimated from a Smartphone Camera

Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA
Department of Computer Science and Engineering, Soonchunhyang University, Asan 336-745, Korea
Author to whom correspondence should be addressed.
Academic Editor: Steffen Leonhardt
Received: 25 January 2016 / Revised: 24 February 2016 / Accepted: 14 March 2016 / Published: 18 March 2016
(This article belongs to the Special Issue Smartphone-Based Sensors for Non-Invasive Physiological Monitoring)
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A smartphone-based tidal volume (VT) 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 VT 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 VT 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. View Full-Text
Keywords: tidal volume; incentive spirometer; smartphone camera; calibration; breathing monitor tidal volume; incentive spirometer; smartphone camera; calibration; breathing monitor

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Reyes, B.A.; Reljin, N.; Kong, Y.; Nam, Y.; Ha, S.; Chon, K.H. Employing an Incentive Spirometer to Calibrate Tidal Volumes Estimated from a Smartphone Camera. Sensors 2016, 16, 397.

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