[Hemodynamic status of man in a graded orthostatic test].

Fourteen volunteers were exposed to a graded orthostatic test by a passive tilt from the horizontal position (0 degree) to an orthostatic posture (70 degrees) with intermediate angles of 10, 20, 30, 40, 50 and 60 degrees. Each position was maintained for 5 min. At the end of each step ECG, the first derivative of impedance cardiogram and auscultative blood pressure were registered. Stroke volume, cardiac output, Q-Z interval, thoracic impedance and diastole-systolic coefficient of impedance cardiogram (the parameter of pre-loading) were most markedly changed at the beginning of the test, when the tilt angle was less than 30 degrees. Its further increase was associated with moderate changes of the mentioned parameters. Diastolic arterial pressure began growing significantly from the tilt angle of 10 degrees and the cardiac rhythm became significantly more frequent starting from 30 degrees. Thus, the set of parameters registered becomes more informative if the test is performed in a graded manner since in this case it is possible to evaluate the order and magnitude of passive and active hemodynamic changes, and on the basis of their comparison to assess the adequacy of compensatory circulatory responses to orthostatic exposure.