Measuring venous oxygenation using the photoplethysmograph waveform
Tóm tắt
Objective. We investigate the hypothesis that the photoplethysmograph (PPG) waveform can be analyzed to infer regional venous oxygen saturation. Methods. Fundamental to the successful isolation of the venous saturation is the identification of PPG characteristics that are unique to the peripheral venous system. Two such characteristics have been identified. First, the peripheral venous waveform tends to reflect atrial contraction. Second, ventilation tends to move venous blood preferentially due to the low pressure and high compliance of the venous system. Red (660 nm) and IR (940 nm) PPG waveforms were collected from 10 cardiac surgery patients using an esophageal PPG probe. These waveforms were analyzed using algorithms written in Mathematica. Four time-domain saturation algorithms (ArtSat, VenSat, ArtInstSat, VenInstSat) and four frequency-domain saturation algorithms (RespDC, RespAC, Cardiac, and Harmonic) were applied to the data set. Results. Three of the algorithms for calculating venous saturation (VenSat, VenInstSat, and RespDC) demonstrate significant difference from ArtSat (the conventional time-domain algorithm for measuring arterial saturation) using the Wilcoxon signed-rank test with Bonferroni correction (p < 0.0071). Conclusions. This work introduces new algorithms for PPG analysis. Three algorithms (VenSat, VenInstSat, and RespDC) succeed in detecting lower saturation blood. The next step is to confirm the accuracy of the measurement by comparing them to a gold standard (i.e., venous blood gas).
Tài liệu tham khảo
Shelley KH, Dickstein M, Shulman SM. The detection of peripheral venous pulsation using the pulse oximeter as a plethysmograph. J Clin Monit 1993;9:283–287.
Shelley KH, Tamai D, Jablonka D, Gesquiere M, Stout RG, Silverman DG. The effect of venous pulsation on the forehead pulse oximeter wave form as a possible source of error in SpO2 calculation. Anesth Analg 2005;100:743–747.
Shelley KH, Shelley S. Pulse oximeter waveform: photoelectric plethysmography. In: Clinical monitoring: practical applications for anesthesia and critical care, Lake CL, Hines RL, Blitt CD, eds. Philadelphia PA: W.B. Saunders Company, 2001 420–428.
Allen J. Photoplethysmography and its application in clinical physiological measurement. Physiol Meas 2007;28:R1–39.
Yoxall CW, Weindling AM. Measurement of venous oxyhaemoglobin saturation in the adult human forearm by near infrared spectroscopy with venous occlusion. Med Biol Eng Comput 1997;35:331–336.
Nitzan M, Babchenko A, Khanokh B, Taitlebaum H. Measurement of oxygen saturation in venous blood by dynamic near infrared spectroscopy. J Biomed Opt 2000;5:155–162.
Echiadis AS, Crabtree VP, Bence J, et al. Non-invasive measurement of peripheral venous oxygen saturation using a new venous oximetry method: evaluation during bypass in heart surgery. Physiol Meas 2007;28:897–911.
Natalini G, Rosano A, Franceschetti ME, Facchetti P, Bernardini A. Variations in arterial blood pressure and photoplethysmography during mechanical ventilation. Anesth Analg 2006;103:1182–1188.
Wardhan R, Shelley K. Peripheral venous pressure waveform. Curr Opin Anaesthesiol 2009;22:814–821.
Kyriacou PA, Moye AR, Gregg A, Choi DM, Langford RM, Jones DP. A system for investigating oesophageal photoplethysmographic signals in anaesthetised patients. Med Biol Eng Comput 1999;37:639–643.
Kyriacou PA, Powell S, Langford RM, Jones DP. Investigation of oesophageal photoplethysmographic signals and blood oxygen saturation measurements in cardiothoracic surgery patients. Physiol Meas 2002;23:533–545.
Kyriacou PA, Powell SL, Jones DP, Langford RM. Evaluation of oesophageal pulse oximetry in patients undergoing cardiothoracic surgery. Anaesthesia 2003;58:422–427.
Kyriacou PA. Pulse oximetry in the oesophagus. Physiol Meas 2006;27:R1–R35.
Webster JG. Design of Pulse Oximeters. Bristol: Institute of Physics Publishing, 1997.
Reinhart K, Bloos F. The value of pulse oximetry. Curr Opin Crit Care 2005;11:259–263.