Reproducibility of the alterations in circulation and cerebral oxygenationfrom supine rest to head-up tilt

Cardiovascular stability, as affected by several diseases, may be assessed by head-up tilt testing. Follow-up studies are essential in both evaluating interventions and assessing progression. However, data on the reproducibil ity of the changes in circulatory status and cerebral oxygenation provoked by head-up tilt testing are fundamental to follow-up studies. The aim of th is study was, therefore, to assess the reproducibility of the alterations i n stroke volume (SV), mean arterial pressure (MAP), as well as oxygenated ( [O(2)Hb]) and deoxygenated haemoglobin ([HHb]) concentration in cerebral ti ssue from supine rest (SW) to head-up tilt (HUT). SV was calculated by Mode lflow, a pulse contour method, from the finger arterial pressure wave measu red by Portapres, the portable version of Finapres. [O(2)Hb] and [HHb] were measured using near-infrared spectroscopy (NIRS). Ten healthy individuals visited the laboratory on two different days. On both days, they underwent 10 min SUP followed by 10 min 70 degrees HUT twice. SV decreased, which was (in part) compensated for by an increased heart rate, while MAP increased slightly during HUT compared with SUP. Although [HHb] increased during HUT, no presyncope symptoms were experienced. The circulatory variables (SV, HR and MAP) as well as [HHb] showed an acceptably small systematic and random error as well as reproducibility error compared with the observed differen ce between HUT and SUP and were similar between and within visits. Therefor e, it is concluded that MAP measured by Portapres and SV calculated by Mode lflow as well as HHb measured by NIRS seem to be reproducible and may there fore be used in follow-up studies.