{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T19:42:13Z","timestamp":1760211733874,"version":"build-2065373602"},"reference-count":25,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2016,3,18]],"date-time":"2016-03-18T00:00:00Z","timestamp":1458259200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"US Army Medical Research and Material Command","award":["W81XWH-12-1-0541"],"award-info":[{"award-number":["W81XWH-12-1-0541"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>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% \u00b1 5.171% (mean \u00b1 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 \u22120.051 L and a RMSE of 0.189 \u00b1 0.074 L corresponding to 18.559% \u00b1 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.<\/jats:p>","DOI":"10.3390\/s16030397","type":"journal-article","created":{"date-parts":[[2016,3,18]],"date-time":"2016-03-18T13:31:03Z","timestamp":1458307863000},"page":"397","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Employing an Incentive Spirometer to Calibrate Tidal Volumes Estimated from a Smartphone Camera"],"prefix":"10.3390","volume":"16","author":[{"given":"Bersain","family":"Reyes","sequence":"first","affiliation":[{"name":"Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Natasa","family":"Reljin","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Youngsun","family":"Kong","sequence":"additional","affiliation":[{"name":"Department of Computer Science and Engineering, Soonchunhyang University, Asan 336-745, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yunyoung","family":"Nam","sequence":"additional","affiliation":[{"name":"Department of Computer Science and Engineering, Soonchunhyang University, Asan 336-745, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sangho","family":"Ha","sequence":"additional","affiliation":[{"name":"Department of Computer Science and Engineering, Soonchunhyang University, Asan 336-745, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ki","family":"Chon","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2016,3,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Koeppen, B.M., and Stanton, B.A. (2009). 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