Methods and Materials
Equipment
The most recent versions of the three commercially available, FDA-approved in vivo oximetry systems (catheter, optical module, and computer) were obtained from their respective manufacturers. Three oximetry PA catheters were studied: (1) Oximetrix 3 P7110-EP-H 7.5 Fr; (2) Edwards Critical Care SAT-2 93-A-770H 7.5 Fr; and (3) Viggo-Spectramed HEMOPRO 7.5 Fr. The Oximetrix 3 system (Abbott Critical Care Systems, Hospital Products Division, Abbott Laboratories, North Chicago, 111) uses a dual fiberoptic bundle in the PA catheter. Three reference wavelengths are produced by the optical module and transmitted down one fiberoptic bundle.

The other fiberoptic bundle is used for detection of backscatter of light from the red blood cells. The SAT-2 system (Edwards Critical Care Division, Baxter Healthcare Corporation, Irvine, Calif) also uses a dual fiberoptic bundle in the PA catheter. Two reference wavelengths are used. The HEMOPRO, system (Viggo-Spectramed, Oxnard, Calif) uses a triple fiberoptic bundle in the PA catheter. One bundle is used for transmission of two reference wavelengths; the other two bundles are used for detection of backscatter.