An investigation into the variability of stroke volume using non-invasive measurements

Beat-to-beat pulse contour stroke volume (SV) and Doppler stroke distance (SD) were determined in 13 healthy adults in supine and upright positions during spontaneous and controlled breathing. Our aim was to determine the reliability of the pulse contour method for assessing beat-to-beat changes and investigate the variability of stroke volume. Spectral analysis showed that these parameters have very similar power spectra comprising strong respiratory frequency fluctuations under all conditions and low frequency (LF, 0.05-0.15Hz) peaks in the upright position. Beat-to-beat values of SV and SD correlated well in most recordings (mean correlation coefficient 0.63±0.18). Coherence between SV or SD and other cardiovascular parameters (pulse interval, systolic pressure and respiration) was highly significant at respiratory frequencies for all conditions and in the LF band for the upright recordings