Three-wavelength System Research Articles

Three-wavelength system for practical application in skin oximetry: simultaneous equations with prediction-correction approach

<p><span>This paper presented the use of a three-wavelength system coupled with a prediction-correction model for the measurement of a person’s tissue oxygen levels and in the efforts towards the development of a field-portable system. This study considered light wavelength of market-available emitters in the range 500 − 650 nm for its practical implementation. This approach required the use of light attenuation and hemoglobin absorptivity information of three different wavelengths in determining tissue oxygen saturation value, StO2. It was found through the analysis of results using Monte Carlo method that considerable improvement in the accuracy of the predictions was obtained using the corrective models (ρ =0.874). The low mean prediction errors of similar magnitude, not exceeding 4 %, given by two wavelength combinations 538, 560, 633 nm and 538, 560, 650 nm were observed for signals with signal-noise ratio (SNR) of down to 30 dB. A significant statistical difference was found between the prediction errors and the wavelength combination used under this noise condition (ρ =0.011). This work concluded that the findings of this study provide insights into technology implementation of skin oximetry and the possible impacts it might have in medical arena.</span></p>

Optical visualization of skin oxygen saturation for dermatological applications

The role of oxygen in skin care is well known for assisting in skin rejuvenation and repair. This work is an unprecedented scientific and clinical effort to understand changes in percent skin oxygen saturation level (StO2) with topical application of a range of oxygen therapeutic skin care products, and in a course of skin breakout, using a newly developed three-wavelength system in a trial involving a total of eight volunteers. This technology is able to provide measurable positive effects on facial StO2 of the recruited volunteers one week after the topical application of oxygen creams with mean (standard deviation, SD) relative change in StO2 of 5.8 (4.6) %. Meanwhile a case study using this system on an individual with untoward skin condition revealed a drastic change in the mapping of StO2 values from the formation of papule to pustule, and to its encrustation. This optical technology could be a significant breakthrough in the dermatology research by redefining pharma-cosmeceutical research design and process in the development of skin care products by evaluating the efficacy of these products in improving skin oxygen level. In the future, this system may have major applications in the translational research of human physiology and pharmacology.

Simultaneous in vivo comparison of two-versus three-wavelength mixed venous (Svo 2) oximetry catheters

Venous oximetry catheters provide useful realtime information about mixed venous hemoglobin saturation (Svo2). Currently available systems utilize either two or three wavelengths of light to obtain these measurements. Previous animal and clinical studies have attempted to compare the accuracy of these two devices under similar circumstances. However, the relative accuracy of the two-wavelength versus three-wavelength systems has never been assessed under identical conditions. For this purpose, we designed an animal model for simultaneous measurement of Svo2, over a wide range of physiologic and pathologic states. Seven anesthetized swine underwent simultaneous placement of two- and three-wavelength catheters. Paired data points consisted of values obtained from a reference oximeter and from each of the catheters. Observations were obtained every 15 min during the following manipulations: (1) eucarbic hypoxia induced by reducing FiO2 to 0.18, 0.15, and 0.12 for 15 min each; (2) stimulated surgical manipulation; and (3) hypovolemic shock produced by hemorrhage to a mean arterial pressure of 50 torr for 1 hr. Data were analyzed by calculation of mean error (bias) and precision for each system in comparison with the oximeter. The overall error of the two-wavelength system was +0.15%, with a precision of +/- 2.52%. The three-wavelength system had an overall error of +3.71%, with a precision of +/- 2.30%. Overall correlation between catheter Svo2 and oximeter values was the same for both devices (r = 0.99). Both currently available in vivo spectrophotometric systems are capable of producing satisfactory results over wide ranges of Svo2. In contradistinction to older reports, we found that the two-wavelength Svo2 system produced results equivalent to those obtained from the three-wavelength device. In this regard, there is no detectable advantage in accuracy to measuring in vivo Svo2 with three rather than with two wavelengths.

Three-color optical range finding

In the known three-wavelength distance-measuring systems two optical wavelengths are used and a microwave is added for air-humidity influence consideration. In our research, which proceeds from results obtained at the National Research Laboratory of Metrology (Japan), the possibility of constructing a three-optical-wavelength ranging system is discussed. We investigate different versions by using a CO(2) laser as the source of the third wavelength. Analysis shows that the three-wavelength system with two lasers (YAG:Nd(3+) laser, which yields first- and second-harmonic radiation, and a CO(2) laser) seems to be optimum. A possible schematic structure of the three-wavelength YAG-CO(2) laser system is given.

Clinical comparison of two- and three-wavelength systems for continuous measurement of venous oxygen saturation

To evaluate clinically the accuracy of continuous SvO2 systems to reflect reference SvO2 values over a 24-hour period. Randomized clinical trial. Six-bed cardiac surgical intensive care unit of a 540-bed federal facility. Sixty postoperative cardiac patients. Random assignment to a two- or three-wavelength continuous SvO2 catheter for postoperative SvO2 monitoring. At 4-hour intervals over a 24-hour period, mixed venous blood samples were analyzed with a reference cooximeter and compared with the monitor value of the SvO2 catheter. A reference cooximeter method to measure SvO2 in mixed venous blood; SvO2 as measured by the in-line, SvO2 catheter system. SvO2 measured by the three-wavelength system did not differ significantly from the reference SvO2 measurement. In contrast, SvO2 measured by the two-wavelength system was significantly lower than the reference SvO2 measurement within 4 hours of admission to the critical care unit and remained significantly lower throughout the 24-hour study period. The results of this clinical study confirmed a previous study in dogs, showing that SvO2 is measured more accurately by the three-wavelength continuous monitoring system.

Three Mixed Venous Saturation Catheters in Patients with Circulatory Shock and Respiratory Failure

Thirty-one critically ill patients with acute respiratory failure and circulatory shock were divided into three groups. Group 1 included 11 patients with an inserted mixed venous saturation (SvO2) catheter using three-reference wavelengths and characterized by one transmitting and one detecting fiberoptic filament (Oximetrix opticath catheter); group 2 included eight patients with an inserted SvO2 catheter using two-reference wavelengths and characterized by one transmitting and one detecting fiberoptic filament; (Edwards sat-one catheter); group 3 included 12 patients with an inserted SvO2 catheter using two-reference wavelengths and characterized by one transmitting and two detecting fiberoptic filaments. Once calibration procedures were performed, SvO2 measured by the catheter and by an hemoximeter OSM 3 (reference value) were compared following each therapeutic intervention. Over a period of 1.5 to 6 hours during which the hematocrit value remained unchanged, 119 measurements were obtained in group 1, 91 in group 2 and 181 in group 3. The dispersion of SvO2 values was much more pronounced with the two-reference wavelength systems using either one or two detecting fiber optic filaments, and the correlation coefficient was significantly higher with the three-reference wavelength system (r = 0.970 for the Oximetrix catheter vs r = 0.855 for the Edwards catheter and r = 0.826 for the Spectramed catheter, p less than 0.001). After 24 hours, the spontaneous drifts in the two-reference wavelength systems, using either one or two detecting fiber optic filaments (expressed as the SvO2 value measured by the catheter minus the reference SvO2 value) were significantly higher than the spontaneous drift in the three-reference wavelength system (9.3 +/- 7 percent for the Edwards catheter and +/- 6 +/- 4.1 percent for the Spectramed catheter vs 3.3 +/- 3.1 percent for the Oximetrix catheter, p less than 0.05). This study shows that a three-wavelength system is more accurate than a two-wavelength system for measuring acute changes in SvO2. The addition of a second detecting fiber optic filament does not seem to improve the accuracy of the system when SvO2 changes occur in conditions of stable hematocrit.

A comparison of two pulmonary artery mixed venous oxygen saturation catheters during the changing conditions of cardiac surgery

Continuous mixed venous oxygen saturation (Sv̄O 2), using modified pulmonary artery (PA) catheters, can assist in the management of cardiac surgery patients. Two FDA-approved catheters are available for Sv̄O 2 monitoring. One system uses two wavelengths of light and the other is a three-wavelength system. The present study was designed to determine the accuracy of the two catheters during cardiac surgery. Sixty-five consecutive patients were assigned to one of the two catheter groups. Data were collected pre- and post-induction, after sternotomy, and after extracorporeal circulation. An updated hematocrit was entered in the two-wavelength system preceding the last two measurements. Patient demographics, severity of preoperative cardiac disease, and intraoperative hemodynamics were comparable between groups. Two-wavelength determinations varied inconsistently from cooximeter values, while three-wavelength measurements did not differ significantly. Changes in hematocrit were responsible in part for the variability in two-wavelength measurements. In summary, three-wavelength measurements by the Shaw system were more accurate than two-wavelength measurements by the Edwards system.