title: Cross time-frequency analysis for combining information of several sources: application to estimation of spontaneous respiratory rate from photoplethysmography.
abstract: A methodology that combines information from several nonstationary biological signals is presented. This methodology is based on time-frequency coherence, that quantifies the similarity of two signals in the time-frequency domain. A cross time-frequency analysis method, based on quadratic time-frequency distribution, has been used for combining information of several nonstationary biomedical signals. In order to evaluate this methodology, the respiratory rate from the photoplethysmographic (PPG) signal is estimated. The respiration provokes simultaneous changes in the pulse interval, amplitude, and width of the PPG signal. This suggests that the combination of information from these sources will improve the accuracy of the estimation of the respiratory rate. Another target of this paper is to implement an algorithm which provides a robust estimation. Therefore, respiratory rate was estimated only in those intervals where the features extracted from the PPG signals are linearly coupled. In 38 spontaneous breathing subjects, among which 7 were characterized by a respiratory rate lower than 0.15 Hz, this methodology provided accurate estimates, with the median error {0.00; 0.98} mHz ({0.00; 0.31}%) and the interquartile range error {4.88; 6.59} mHz ({1.60; 1.92}%). The estimation error of the presented methodology was largely lower than the estimation error obtained without combining different PPG features related to respiration.
authors.affiliation: Centro Universitario de la Defensa, Academia General Militar, Carreter de Huesca s/n, 50090 Zaragoza, Spain ; GTC, Aragón Institute of Engineering Research, IIS, Universidad de Zaragoza, C/Mariano Esquillor s/n, 50018 Zaragoza, Spain.
authors.forename: M D
authors.initials: MD
authors.lastname: Peláez-Coca
authors.affiliation: CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), c/Poeta Mariano Esquillor s/n, Edificio I+D, 50018 Zaragoza, Spain ; Institute of Cardiovascular Science, University College London, Gower Street, London WC1E 6BT, UK.
authors.forename: M
authors.initials: M
authors.lastname: Orini
authors.affiliation: GTC, Aragón Institute of Engineering Research, IIS, Universidad de Zaragoza, C/Mariano Esquillor s/n, 50018 Zaragoza, Spain ; CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), c/Poeta Mariano Esquillor s/n, Edificio I+D, 50018 Zaragoza, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Lázaro
authors.affiliation: GTC, Aragón Institute of Engineering Research, IIS, Universidad de Zaragoza, C/Mariano Esquillor s/n, 50018 Zaragoza, Spain ; CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), c/Poeta Mariano Esquillor s/n, Edificio I+D, 50018 Zaragoza, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Bailón
authors.affiliation: GTC, Aragón Institute of Engineering Research, IIS, Universidad de Zaragoza, C/Mariano Esquillor s/n, 50018 Zaragoza, Spain ; CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), c/Poeta Mariano Esquillor s/n, Edificio I+D, 50018 Zaragoza, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Gil
mesh_terms: D000328:Adult; D000465:Algorithms; D002648:Child; D002675:Child, Preschool; D016208:Databases, Factual; D005260:Female; D064368:Healthy Volunteers; D006339:Heart Rate; D006801:Humans; D008297:Male; D017156:Photoplethysmography; D012016:Reference Values; D012044:Regression Analysis; D015203:Reproducibility of Results; D012119:Respiration; D056152:Respiratory Rate; D012815:Signal Processing, Computer-Assisted