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Published in:
2020 | OriginalPaper | Chapter
Photoplethysmographic Signals Measured at the Nose
Authors : Pin-Lu Li, Shao-Hung Lu, Kang-Ping Lin, Cheng-Lun Tsai
Published in: Future Trends in Biomedical and Health Informatics and Cybersecurity in Medical Devices
Publisher: Springer International Publishing
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Abstract
Polysomnography is the main diagnostic instrument for sleep apnea, but it is not convenient for patient to take frequent measurements at home. An in-home sleep test is a solution to help physicians to collect more information. Sleep medicine societies suggest that a home sleep-apnea testing device should measure at least oxygen saturation and breathing signals. To reduce the discomfort of measurement during sleep, the device should be also as small as possible. One possible measuring site for both signals is at the nose. The accuracy of oxygen saturation measurement relies on the quality of photoplethysmographic signals (PPG). PPG signals of red and near-infrared light measured at the nasal septum and nasal wing were compared. PPG signals were also measured at different body postures includes standing, sitting and supine.
Although nasal septum and wing are both thin layer of tissue, the perfusion index is greater and has a larger variation at nasal septum than at nasal wing. Although the PPG at nasal wing is relatively stable and not greatly affected by the autonomic nervous regulation, the change in signals with oxygen saturation is also small. Therefore, the nasal septum is a better position for measuring oxygen saturation at the nose.