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Sensors 2016, 16(3), 397; doi:10.3390/s16030397

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

1
Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA
2
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)
View Full-Text   |   Download PDF [2743 KB, uploaded 18 March 2016]   |  

Abstract

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
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

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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