In this study, we investigated the feasibility and the accuracy of transtracheal mixed venous oxygen saturation (Svo(2)) monitoring. Ten patients undergoing thoracic surgery were included in this study. A single-use pediatric pulse oximetry sensor was attached to the double-lumen tube between the tracheal and bronchial cuff. After anesthesia was induced, the double-lumen tube was inserted into the trachea and adjusted to the proper position. During surgery, the pulmonary arterial blood was sampled every 3 min for 15 min to measure the Svo(2). The measurements made by the transtracheal pulmonary pulse oximeter (Sto(2)) were recorded at the same time that blood was sampled from the pulmonary artery for Svo(2) measurements. The levels of measurement agreement between the Sto(2) and the Svo(2) were analyzed using the Bland and Altman method. The mean +/- sd (range) oxygen saturation values during the data collecting period were 82.0% +/- 4.9% (72%-91%) for the Sto(2) and 82.2% +/- 5.5% (71%-91%) for the Svo(2), respectively. The linear correlation coefficient of the regression analysis between the Sto(2) and the Svo(2) was 0.934 (P < 0.05). A 95% confidence interval for absolute difference between the Sto(2) and the Svo(2) was 1.58%-2.09%. The mean +/- 2 sd difference between the Sto(2) and the Svo(2) was 0.12% +/- 3.97% on the Bland and Altman graph. We conclude that it is feasible to monitor the pulmonary artery oxygen saturation continuously by a transtracheal pulse oximetry technique and that it can be done so accurately.
Implications: Mixed venous oxygen saturation (Svo2) is a measure of the balance between oxygen supply and consumption throughout the whole body. Svo2 can be measured invasively by inserting a pulmonary artery catheter with the associated disadvantages of cost and potential for patient injury. In this study, we investigated the feasibility of noninvasive Svo2 measurement using a transtracheal pulse oximetry technique.