{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T12:43:47Z","timestamp":1790772227345,"version":"4.1.0"},"reference-count":21,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2023,5,24]],"date-time":"2023-05-24T00:00:00Z","timestamp":1684886400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Speckle Plethysmography (SPG) and Photoplethysmography (PPG) are different biophotonics technologies that allow for measurement of haemodynamics. As the difference between SPG and PPG under low perfusion conditions is not fully understood, a Cold Pressor Test (CPT\u201460 s full hand immersion in ice water), was used to modulate blood pressure and peripheral circulation. A custom-built setup simultaneously derived SPG and PPG from the same video streams at two wavelengths (639 nm and 850 nm). SPG and PPG were measured at the right index finger location before and during the CPT using finger Arterial Pressure (fiAP) as a reference. The effect of the CPT on the Alternating Component amplitude (AC) and Signal-to-Noise Ratio (SNR) of dual-wavelength SPG and PPG signals was analysed across participants. Furthermore, waveform differences between SPG, PPG, and fiAP based on frequency harmonic ratios were analysed for each subject (n = 10). Both PPG and SPG at 850 nm show a significant reduction during the CPT in both AC and SNR. However, SPG showed significantly higher and more stable SNR than PPG in both study phases. Harmonic ratios were found substantially higher in SPG than PPG. Therefore, in low perfusion conditions, SPG seems to offer a more robust pulse wave monitoring with higher harmonic ratios than PPG.<\/jats:p>","DOI":"10.3390\/s23115016","type":"journal-article","created":{"date-parts":[[2023,5,24]],"date-time":"2023-05-24T01:29:26Z","timestamp":1684891766000},"page":"5016","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Comparison between Speckle Plethysmography and Photoplethysmography during Cold Pressor Test Referenced to Finger Arterial Pressure"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2347-401X","authenticated-orcid":false,"given":"Jorge","family":"Herranz Olazabal","sequence":"first","affiliation":[{"name":"IMEC NL, 5656 AE Eindhoven, The Netherlands"},{"name":"Faculty of Engineering Science, Katholieke Universiteit Leuven (KUL), 3000 Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1479-2446","authenticated-orcid":false,"given":"Ilde","family":"Lorato","sequence":"additional","affiliation":[{"name":"IMEC NL, 5656 AE Eindhoven, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jesse","family":"Kling","sequence":"additional","affiliation":[{"name":"IMEC NL, 5656 AE Eindhoven, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marc","family":"Verhoeven","sequence":"additional","affiliation":[{"name":"IMEC NL, 5656 AE Eindhoven, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7759-7816","authenticated-orcid":false,"given":"Fokko","family":"Wieringa","sequence":"additional","affiliation":[{"name":"IMEC NL, 5656 AE Eindhoven, The Netherlands"},{"name":"Division of Internal Medicine, Department of Nephrology, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chris","family":"Van Hoof","sequence":"additional","affiliation":[{"name":"IMEC NL, 5656 AE Eindhoven, The Netherlands"},{"name":"Faculty of Engineering Science, Katholieke Universiteit Leuven (KUL), 3000 Leuven, Belgium"},{"name":"IMEC, 3000 Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1381-2740","authenticated-orcid":false,"given":"Willem","family":"Verkruijsse","sequence":"additional","affiliation":[{"name":"Philips Research, 5656 AE Eindhoven, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Evelien","family":"Hermeling","sequence":"additional","affiliation":[{"name":"IMEC NL, 5656 AE Eindhoven, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,5,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"3937","DOI":"10.1364\/BOE.9.003937","article-title":"Wearable Speckle Plethysmography (SPG) for Characterizing Microvascular Flow and Resistance","volume":"9","author":"Ghijsen","year":"2018","journal-title":"Biomed. 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