[Continuous monitoring of mixed venous oxygen saturation during exercise using fiberoptic pulmonary artery catheter]

We measured the mixed venous oxygen saturation (SvO2) continuously using a fiberoptic thermodilution pulmonary artery catheter to analyze the time course of SvO2 during exercise, and evaluated the relationship between SvO2 and exercise load, SvO2 and cardiac output. Five patients with old myocardial infarction and one healthy man underwent pulmonary arterial catheterization and then performed an incremental steady state exercise test using a supine cycle ergometer. There was a rapid fall in SvO2 43.4 +/- 10.6 seconds after the start of exercise and new steady state were achieved 92.6 +/- 22.5 seconds after changing the exercise load. The value of SvO2 at exercise load 60 watts were 44.7 +/- 9.8% and this value was under the level of lactic acid accumulation. SvO2 correlates well with cardiac output by the thermodilution method in individual patients. We conclude that a fiberoptic thermodilution pulmonary artery catheter was useful to evaluate the dynamic changes of SvO2 during exercise.