Effects of elevated sleeping postures on cardiac functions analyzing electrical bio-impedance and skin blood perfusion

This study investigated the effects of elevated sleeping postures on cardiac functions by analyzing electrical bio-impedance and skin blood perfusion in case of normal human subjects. Using different data acquisition units, the electrical bio-impedance based stroke volume and cardiac output were calculated in different elevated sleeping postures. Skin blood perfusion was measured also by laser Doppler flowmetry technique in all elevations to evaluate cardiac activity using frequency domain analysis. At first, data recordings were performed in supine sleeping (0° elevation) then sleeping elevations were changed sequentially from 0° to 15°, 15° to 30° and 30° to 45°. Data were recorded in all mentioned sleeping elevations for every subject. In most of the subjects, the parameters of cardiac functions were found highest in supine sleeping. When sleeping elevations were changed the cardiac functions were also changed in some significant level. Among all elevations except 0°, most significant improvements in cardiac functions were observed in 30° elevation only. It was highly recommended to sleep with an elevation around 30° to get best cardiac functions for those subjects only who prefer to sleep in elevation rather than supine.