Comparative analysis of various types of exercise tests in evaluating the functional reserves of the oxygen transport system in cardiac surgery patients.

In 373 cardiac surgery patients and in 33 healthy persons, the authors compared the results of two (continuous and discontinuous) types of exercise tests designed to assess maximal (VO2max) and peak (VO2peak) oxygen uptake, anaerobic threshold (AT), threshold of decompensated metabolic acidosis (TDMA) and oxygen cost of exercise. The authors found that use of continuous tests is associated very rarely with "plateau" oxygen uptake (in less than 1%); it is present in 20.6% during discontinuous tests. Nevertheless, the values of VO2peak obtained in continuous tests and VO2max did not differ significantly. This makes VO2peak a fairly accurate indicator of VO2max if sufficiently exact criteria of maximal exertion have been defined. Both types of exercise tests provide close values of oxygen uptake at AT, TDMA and oxygen cost of physical exercise (up to 100 W). Therefore, both types of exercise tests can be employed in evaluating the functional state of the oxygen transport system in cardiac surgery patients.