Noninvasive NIR measurement of tissue pH to assess hemorrhagic shock in swine

Babs R. Soller; Songbiao Zhang; Ronald H. Micheels; Juan Carlos Puyana

doi:10.1117/12.353018

13 July 1999 Noninvasive NIR measurement of tissue pH to assess hemorrhagic shock in swine

Babs R. Soller, Songbiao Zhang, Ronald H. Micheels, Juan Carlos Puyana

Proceedings Volume 3712, Battlefield Biomedical Technologies; (1999) https://doi.org/10.1117/12.353018
Event: AeroSense '99, 1999, Orlando, FL, United States

Abstract

Body-worn noninvasive physilogical sensors are needed to continuously monitor soldiers for hemorrhage and to provide real-time information for minimally skilled medics to treat the injured. In the hospital intramucosal pH_i of the gut is used to monitor shock and its treatment. We hypothesize that abdominal wall muscle (AWM) pH can be measured noninvasively using near infrared (NIR) spectroscopy and partial least squares analysis (PLS) and will correlate with pH_i. METHODS: AWM pH was measured with microelectrodes and gastric pH_i was measured with a tonometric catheter simultaneously while NIR spectra were collected using prototype LED spectrometers placed on the pig's flanks. Animals were subject to hemorrhagic shock at 45 mm Hg for 45 minutes, then resuscitated with blood and lactated ringers. Relationships between electrode pH, pH_i and NIR spectra were developed using PLS with cross validation. RESULTS: NIR spectral changes noninvasively acquired through the skin were shown to be from the muscle, not from changes in skin blood flow. Trending ability (R²) model accuracy (RMSD), and relative error were calculated for individual pigs. Using electrode pH as the reference, average R² was 0.88 with a predicted accuracy of 0.17 pH units, a 9.3% relative error. Slightly degraded results were observed when pH_i was used as a reference. CONCLUSIONS: NIR measurement of tissue pH can be used to noninvasively monitor for shock and guide its treatment in a swine model. These measurements correlate with gastric pH_i, a clinically accepted measure of shock, providing an approach to develop similar methodology for humans.

Citation Download Citation

Babs R. Soller, Songbiao Zhang, Ronald H. Micheels, and Juan Carlos Puyana "Noninvasive NIR measurement of tissue pH to assess hemorrhagic shock in swine", Proc. SPIE 3712, Battlefield Biomedical Technologies, (13 July 1999); https://doi.org/10.1117/12.353018

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