This measure of performance of the three catheter systems showed the greatest agreement among the three groups. The ESD for each group is also shown in Table 4. The 95 percent confidence limits based both on total variability and intrasubject variability are shown. The 95 percent confidence limits based on intrasubject variability are similar for the Oximetrix 3, SAT-2, and HEM0PR02 (±4.59, ±5.66, and ±6.56, respectively) while the 95 percent confidence limits based on total variability are more disparate (±6.03, ±6.86, and ±10.30, respectively).
Discussion
Techniques for monitoring mixed venous oxygen saturation (SvOa) were first described in 1962. Technologic advancements in the design and manufacture of fiberoptics and light-emitting diodes have led to the development of PA catheters capable of monitoring Sv02 continuously, using the principles of the Beer Lambert Law. In vivo measurement of blood oxygen saturation is possible because of the differential reflection and absorption of various wavelengths of red and infrared light by oxyhemoglobin and reduced hemoglobin. In theory, a solution containing a mixture of oxyhemoglobin and deoxyhemoglobin has absorption or reflection characteristics that can be quantified to yield the relative percentage of each species present.