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Accuracy and Dynamic Range of Optical-Surface-Imaging (OSI)-Based Spirometry

G Li

H Huang1 , J Wei2 , Q Chen1 , C Gaebler1 , J Zatcky1 , J Mechalakos1 , G Li1*, (1) Memorial Sloan Kettering Cancer Center, New York, NY, (2) City College of New York, New York, NY


SU-E-J-43 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall

To assess the accuracy of optical-surface-imaging (OSI)-based spirometry for tidal volume (TV) measurement using a conventional spirometer and the usability under different breathing conditions.

Video-based OSI with high-speed image capture (HSIC) and a Bernoulli-type spirometer were applied simultaneously to measure dynamic TVs of human subjects. Six healthy volunteers participated in an IRB protocol study. The subjects lied on 7.5°-10° upward-tilted breast board while breathe through the spirometer. The entire torso was imaged to capture all respiration-induced external motions. Five breathing exercises were performed, including free breathing (FB), belly breathing (BB), chest breathing (CB), deep breathing (DB), and breath holding (BH) with pseudo-breathing motions. The HSIC data were acquired at 5Hz and 3D surfaces were reconstructed retrospectively. The volume of interest was manually delineated and applied to all surface images for batch-mode computation. Dynamic TVs were calculated by subtracting the volume at full exhalation. The thorax and abdomen were separated and the breathing pattern (BPv=ΔVthorax/ΔVtorso) was calculated for each exercise. The spirometer was calibrated before experiments and baseline drifts were corrected by zeroing the background pressure initially and during involuntary breath hold, and resetting the baseline by linear regression of five consecutive full-exhalation points. The two TV datasets were compared.

For FB, the average difference among all subjects is -3.2±6.0%. From BB, CB to DB, the discrepancies increase to -3.8±6.0%, -6.4±4.3%, and -1.1±14.0%, respectively. A near full range of BP (0.1-1.0) was observed. During BH, a constant TV was obtained despite the torso motion, conforming to volume conservation and suggesting diaphragmatic motion at the same TV.

The accuracy and dynamic range of OSI-based spirometry has been assessed by using conventional spirometry as the reference among six healthy volunteers. The resultant discrepancy is acceptable (except DB), suggesting this new spirometry is of promising utility under common breathing conditions.

Funding Support, Disclosures, and Conflict of Interest: This study is in part supported by NIH (U54CA137788 and U54CA132378).

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