Cardiovascular responses to hypovolemic circulatory stress in women With special reference to venous compliance and capacitance

........................................................................................................................... 3 LIST OF PAPERS ........................................................................................................ 5 ABBREVIATIONS...................................................................................................... 6 INTRODUCTION....................................................................................................... 7 AIMS ........................................................................................................................... 13 MATERIALS.............................................................................................................. 14 Ethics..................................................................................................................... 14 Healthy volunteers (paper I‐IV)...................................................................... 14 Women prone to vaso‐vagal reaction (additional study) ........................... 15 METHODS................................................................................................................. 16 Lower body negative pressure (LBNP).......................................................... 16 Cardiovascular responses................................................................................. 17 Changes in calf volume .................................................................................... 19 Changes in upper arm volume during LBNP............................................... 22 Blood samples..................................................................................................... 23 Data recordings................................................................................................... 23 Statistics ............................................................................................................... 24 RESULTS .................................................................................................................... 25 Calf volumetric responses (paper I‐IV) ......................................................... 25 The effect of capillary fluid filtration on compliance calculations ......... 29 Total hypovolemic response (paper I‐IV) ..................................................... 30 Cardiovascular responses to acute hypovolemia (paper III‐IV)............... 30 Women prone to vaso‐vagal reaction during LBNP (additional study).. 37 Cardiovascular responses to hypovolemic circulatory stress in women DISCUSSION............................................................................................................ 40 Venous capacitance and compliance.............................................................. 40 Capillary fluid filtration in the calf and capillary filtration coefficient. 42 Cardiovascular responses to hypovolemic circulatory stress.................... 45 Cardiovascular responses in women prone to vaso‐vagal reaction ......... 49 Methodological considerations and limitations.......................................... 51 CONCLUSIONS ....................................................................................................... 53 POPULÄRVETENSKAPLIG SAMMANFATTNING....................................... 54 ACKNOWLEDGEMENTS...................................................................................... 58 REFERENCES ............................................................................................................ 60