Abstract des Autors

Using impedance cardiography, the effect of different body postures on stroke volume (SV), heart rate (HR) and left ventricular (LV) contractility in terms of pre-ejection-period (PEP) and LV ejection time (LVET), was studied beat by beat from the onset of exercise until attainment of steady state. Eleven healthy men aged 22 years volunteered for the study. Exercise was performed both in the supine and the seated posture on a bicycle ergometer for 5 min at 150 W. Both contractility and the hemodynamic adjustment were significantly affected by body position. In the seated posture, SV and contractility increased by 20-25% within the first seconds, while SV in the supine posture started rising slowly only after a delay of 30-40 seconds. The maximal rise of SV was 51% in the seated and 16% in the supine position. HR was 18% and 4% higher seated than supine at rest and during exercise respectively. Contractility in terms of PEP/LVET in the supine posture was 50% and 12% higher at rest and exercise respectively, than when seated. Final exercise SV and CO in the seated posture remained about 20-25% lower than in the supine posture. Under all conditions adjustment was accomplished within 60 to 90 sec. Verf.-Referat