A matter of terminology. Alveolar-arterial oxygen gradient.

in accordance with the article of Fletcher et a13 who systematically tested the accuracy of this catheter system in humans. He also found a consistent underestimation of the fiberoptic pulmonary artery catheter SvO2 values below 50% compared with direct spectophotometry and proposed two equations to adjust the catheter measurements: (1) Catheter=-11.68+1.1892XCOOX (2) Catheter=COOX-210.997 exp (-0.099XCOOX) Catheter=SvO2-Opticath Spectrophotometry =SvO2-Spectrophotometer. Figure 1 shows the difference between catheter and spectrophotometry on the basis of equation 1. Concerning our measurements, this equation gave the best conformity in the range from 20 to 50%. SvO2 values readout from the fiberoptic pulmonary artery catheter from ranges 100 to 20%. Our method to evaluate the fiberoptic catheter and the results were already published in Japan in 1992. The illustration of experimental system and the figures of the result in this article are shown below.